The Technical Hub
O-Ring Calculator
This interactive calculator assists engineers with selection of O-ring and hardware dimensions, and to form the basis of an O-ring installation.
Chemical Compatibility Checker
This interactive guide will help you choose a seal material based on existing compatibility test results of known chemicals and elastomers.
Interactive Engineering Calculators
Click here for volume, mass and compression set values for O-rings and rotary seal and hydraulic cylinder calculations.
Unit Converter
Our interactive conversion tools allow engineers to switch between units of measurement when preparing engineering calculations.
Engineering Tables
Our reference tables provide cross reference information for surface finish, metal hardness and polymer hardness measurement units.
Precision Sealing for Naval Radar Slip RingPrecision Sealing for Naval Radar Slip Ring
The application
Our customer is a globally recognised leader in the design and manufacture of advanced slip ring systems and contactless rotary joints. Their technology ensures the reliable transmission of power, data, and media across a wide range of rotating interfaces. Read more about how our engineers developed a custom spring-energised seal for this application. For this project, the application was as demanding as they come: a naval radar system operating in some of the harshest conditions on the planet. Mounted on a naval vessel, the slip ring assembly needed to operate continuously and flawlessly, protecting the electrical components whilst exposed to the elements (seawater, rain and wide temperature fluctuations). The challenges
As well as these demanding conditions, the application itself had several challenges. A compact seal envelope meant design and installation had to be carefully considered. The seal needed to be durable as it was expected to withstand over 6 million cycles across a 10-year service life. The seal required minimal breakout friction to avoid wear and conserve energy consumption. This application required a rotary seal with low temperature capability and excellent resistance to oil-based fuels. A design was required to replace the existing seal in the available housing between the rotating metal faces. Therefore a standard spring energised rotary seal would not work in the application; a bespoke design was required.
Our sealing solution Our engineers developed a custom spring-energised seal, tailored precisely to the application’s needs. We adapted the Parker Praedifa NLO profile and optimised it with a low-load spring for reduced friction, and a high-performance material formulation offering exceptional wear resistance. An additional design feature were heel slots allowing for dowel pin integration within the hardware to provide enhanced application stability.
Results
The final design delivered excellent sealing performance, passed all endurance tests, and met the full 10-year lifecycle requirement. It also maintained low friction throughout, ensuring energy efficiency and minimal wear - exactly what’s needed for a radar system where reliability is non-negotiable. Learn more about our rotary seals HERE.
Using Finite Element Analysis (FEA) in seal designUsing Finite Element Analysis (FEA) in seal design Finite Element Analysis (FEA) is a computerised modelling method for predicting how an object reacts to forces, whether directly applied or generated by pressure, temperature effects or vibration. FEA provides data to help predict how a product will function under those applied conditions. Additionally, it identifies areas where the design can be optimised and improved, without having to test multiple prototypes. Our specialist software uses mathematical models to understand and quantify the effects of real-world conditions on a part or assembly. It can be used to identify potential causes where sub-optimal sealing performance has been witnessed and can also be used to guide the design of surrounding parts. Importantly for products such as diaphragms and boots where contact with adjacent parts may need to be avoided. The software also allows force data to be extracted . For example, compressive forces for static seals and friction forces for dynamic seals can be accurately predicted to help our customers in the final design of their products.
Why do we use Finite Element Analysis (FEA)?
Our engineers encounter many sealing applications that are critical and have many complicating influences. Envelope size, housing limitations, shaft speeds, pressure/temperature ratings and chemical media are all application parameters that our engineers must consider when designing a seal. In isolation, the impact of these application parameters is reasonably straightforward to predict when designing a sealing solution. However, when you compound a number of these factors (whilst often pushing some of them to their upper limit when sealing) it is crucial to predict what will happen in real application conditions. Using FEA as an iterative tool, our engineers can confidently design and then manufacture robust, reliable and cost-effective engineered sealing solutions for our customers. Starting with a 2D or 3D model of the initial design concept, produced within our advanced CAD system, we then apply the boundary conditions and constraints supplied by the customer, including pressure, force, temperatures, and any applied displacements. A suitable finite element mesh is overlaid onto the seal design, ensuring that areas of most interest have the necessary mesh size to ensure accurate results are returned for these regions whilst utilising larger mesh sizes in areas with less relevance or lower levels of displacement to minimise the computing time required to solve the model. Material properties are then assigned to the seal and hardware components. Most sealing materials are non-linear, whereby the amount they deflect under an increase in force varies depending on how large that force is, unlike the straight-line relationship for most metals and rigid plastics, at least over the displacement range relevant to sealing applications. This complicates the material model, and extends the processing time, but we use in-house tensile test facilities to accurately produce the stress-strain material models for our compounds to ensure the analysis is as representative of real-world performance as possible. What happens with the FEA data?
The analysis itself can take minutes or even hours of computing time, depending on the complexity of the part and the range of operating conditions being modelled; behind the scenes in the software, many hundreds of thousands of differential equations are being solved. The results are then analysed by our experienced seal designers to identify areas where the design can be optimised to match the specific requirements of the application; such requirements may be for sealing at very low temperatures, a need to minimise friction levels with a dynamic seal, withstand very large pressures without extruding, or whatever sealing system properties are most important to the customer and the application. Results for the finalised proposal can be presented to the customer as force/temperature/stress/time plots, numerical data or animations showing how a seal behaves throughout the analysis, as appropriate to their needs, and can be used as validation data in their system design process. Project 1 case study
Faced with very tight packaging constraints, a customer requested a diaphragm component from us for a valve application. Using FEA, we were able to optimise the design not only of the elastomer diaphragm itself, but also propose modifications to the customers hardware components that interfaced with it in order to increase the available space for the diaphragm, keeping material stress levels low to remove any possibility of fatigue failure of the diaphragm over the life of the valve. Project 2 case study
A customer approached us to design a PTFE rotary lip seal that had to meet tight maximum torque requirements as their system was driven by a size-limited low power motor with modest levels of torque available. At the same time, high seal tightness was required as leakage of the media would have caused significant problems. By using an iterative FEA process, we produced a seal design that optimised the sealing lip geometries to provide the lowest levels of rotational friction drag whilst ensuring sufficient contact force to maintain a tight seal, and went on to provide seals that successfully passed customer validation testing.
With the increased confidence in a proposed sealing solution that FEA provides, our customers can plan lower levels of physical testing and remove contingency for re-design steps, reducing their project lead times and costs, facilitating a faster and more cost-effective time to market for their new products.
Surface finish requirements for static and dynamic sealingWhat is hardware surface finish? Any surface can look (and even feel) perfectly smooth. However, look closely enough with high magnification and all surfaces will have a degree of fluctuation. The topography will look similar to a mountain range or the surface of the moon!The roughness of a surface is often linked to the way a surface is produced or machined, and any subsequent processes such as coating or platings.Just a couple of decades ago, the standard approach to assessing surface finish was to use comparison plates. These are small specimen sections of material produced by turning, grinding or milling. A fingernail comparison test with the finished part would then be used to determine which came closest.Historically, seal catalogues typically recommended a surface finish using just the Ra (metric) or CLA (Centre Line Average, inches) parameter. Little regard was given to what the seal was being expected to do.Ra simply, is the mean roughness. The average calculated from the peak heights and valley depths. A surface that is mostly spiked can have the same Ra value as one that is mostly troughed. However, each could have a very different impact on seal performance. Today, surface finish measuring equipment is more sophisticated and capable of tracing a surface finish using a diamond tipped stylus, or non-contact 3D laser scanning.These devices are now reasonably affordable and provide a sophisticated level of results from essentially a portable machine. These instruments can now analyse the surface roughness profile, trace and calculate a large range of parameters that define that profile. This includes Ra, Rt, Rz, Rmax, Rmr (bearing ratio) and even skewness parameters. What these are, and how they should be measured, have generally been well captured in standards such as ASME B46.1, ISO 4287, ISO 4288 and the upcoming ISO 21920. Why is surface finish important for sealing systems? To ensure seal effectiveness, a common assumption for specifying a hardware surface finish is the smoother the finish the better. However, this is not always the case. If the seal application is static and is sealing a low molecular size gas such as helium; then a very smooth surface would be preferable.This is often referred to as a “closed” surface (with no peaks and very few, shallow valleys). The seal mates tightly against the hardware, ensuring the leak path for the gas is reduced as much as possible. Even in this scenario, the required surface roughness can be influenced by other factors. These include the hardness (or rather, softness) of the seal material and the pressure being applied, both by the initial seal squeeze and the applied gas pressure.It’s important the interface between the seal and the hardware is well lubricated. This is critical for some dynamic applications for either seal friction (and hence noise, vibration and heat) or wear life.This is partly achieved by ensuring that the surface is more “open”, with small valleys or troughs to trap the lubricant -but no sharp peaks that would abrade the seal material. In these application cases, if the dynamic hardware surface (rod, shaft or piston bore) is too smooth, then the seal can wear prematurely. This can cause juddering, squeal and excessive heat build-up. Tribological performance consideration As a result, for dynamic applications it is important to consider all the factors affecting the tribological performance. These include the seal (design, material), the dynamic hardware (hardness, material type) and the fluid (viscosity, lubricity, contamination). The hardness of the dynamic hardware can also be a significant factor. Hardened or chromed steels at around the 50 Rockwell C level or less can often be polished by the seal itself. This means that even if the initial roughness is sub-optimal, good sealing performance is achieved after a brief period of bedding in.With the use of high hardness coatings such as HVOF and DLCs, the much softer seal material is very likely to be abraded by the hardware. In these cases, it’s essential to ensure that the optimal surface finish is met. This often requires a finer finish prior to the coating process (as the coatings can be rougher than the substrate material and post-process polishing is very difficult with such hard coatings). Any other factors to consider? Yes! Another thing to consider is the direction (or lay) of a particular surface finish. Machining marks, scratches, dents or other hardware damage that cut across a sealing contact face are likely to result in leakage. This is compared to (for example) concentric machining marks in the base of an axial face-seal O-ring groove. It is important to consider specifying a lay direction when applying surface finish requirements to the hardware design specifications and drawings. What hardware surface finish should you specify? Despite complexities involved in hardware surface topography, the sealing industry has developed a comprehensive set of recommendations. These can vary a little between different manufacturers and suppliers. Given the specificity of the seal design and material, they’re best found within the specific literature for the products considered for the application.This is a good starting point, but for each individual application it's worth considering whether these specifications should be addressed. For example, specifications could be tightened, or perhaps even loosened to ensure that performance targets can be met. This would reduce the need to over-specify the surface finish - because this can add unnecessary processing cost to a part.The practicalities involved in accessing the surface to measure also need consideration. It’s notoriously difficult to check the sidewalls of an O-ring groove, especially in a rod/ID sealing configuration. Cylinder bores are often less tightly defined due to stylus/probe access issues compared to rods and shafts.Importantly, whoever is required to produce and check a particular surface finish has both the equipment and understanding to do so. This is very important if using relatively modern and less well known parameters such as Rmr (or Tp, bearing ratio).Further detail can also be found in the ISO and ASME standards regarding measuring settings. For example, filtering/cut-off values, stylus tip radius, measuring, evaluation and tracing lengths. When validating a supplier’s measurements, it’s important these machine settings are identical. Failure to do so will result in differing surface finish values obtained on the same part. Those standards are not specific to sealing applications. Generally, we’d recommend a cut-off filter (λc) of 0.8, unless measuring very fine (< 0.1 µm Ra) surface finishes where 0.25 would be more suitable, with a 2 micron stylus tip in all cases.Specifying the right surface finish for the hardware components that contact a seal can be complex and daunting. Ensuring an optimum finish and right-first-time seal performance, will be achieved. This is with core understanding, and consideration of relevant parameters for the given application.
Are all elastomers the same?Are all elastomers the same? Material hardness This is often the least considered property when selecting a material. In sealing applications, elastomer material hardness can impact assembly loads, seal friction and extrusion resistance. Softer rubber can better accommodate surface imperfections (especially when sealing low pressure gas). This means softer seal compounds can be used effectively against rough hardware surface finishes. Harder compounds will have greater wear resistance in dynamic applications.Most of the common base elastomers are produced in 60 to 80 Shore hardness range. These tend to be produced in increments of 5 hardness points. It's important to remember the hardness tolerance of a material is typically +/-5 points, therefore 70 and 80 hard nominal materials could both legitimately have a hardness of 75 Shore A.With possible hardness down to 30 Shore A (or even lower), silicone rubber lends itself to applications requiring very soft seals. An example of which is where seal compression forces need to be low to enable easy manual assembly of components. NBR, HNBR and FKM materials can be formulated up to 95 Shore A hardness for highly demanding high pressure and temperature applications; for example applications found in the Oil & Gas industry. Chemical compatibility Unlike PTFE seals (given very few chemicals that will attack and breakdown the material) elastomer seal materials must be carefully selected. This is so the properties are not affected by any fluids or gasses that the seals come into contact with. This includes the main media that the seal is retaining or excluding, additionally any contaminants (such as cleaning fluids or bi-products of reactions between any of these fluids, the seal material or the surrounding hardware).Even a seemingly straightforward application often involves a long list of chemicals and compatibility must be checked with the elastomer. Most seal suppliers publish compatibility tables or like us, have interactive tools to help check this. Even then, it’s often not the brand name oil that’s listed. For example, often at the more basic chemical level, so some knowledge of what’s actually in the fluid is required. Recent developments in health, safety and environmental requirements have made this a little easier. However, some fluid manufacturers can still be a little reluctant to declare the full list of chemicals in their products.Manufacturers sometimes give guidance on general compatibility with elastomer groups, but this can be a little generic. Additionally, not all grades in a specific group will have the same resistance to a particular fluid. Again, this can be especially relevant to NBRs and HNBRs with a variable ACN content. Sometimes the reactions can be dramatic and swift, with the rubber shrinking or swelling in a matter of hours when exposed to a non-compatible fluid and especially at elevated temperatures where the chemical reaction is accelerated. Reactions in chemicals In other cases, the reaction could be slower, but still causes sealing issues resulting in earlier system failure compared to using more capable elastomers. This is often the case with FFKM seals in applications where the cost of replacement or downtime is very high. The outstanding chemical resistance of these materials gives considerably longer service life compared to lesser grades, and it justifies the higher initial cost of the seal. In other cases, some reactions can be beneficial, for example where a small amount of elastomer seal swell in an oil over time can help to offset wear in dynamic O-ring energized PTFE slipper seals. Temperature range Outwardly, this material property seems straightforward, but elastomer technology is rarely that cooperative. All elastomer compounds will have a low temperature property stated on their datasheet. Either the TR10 (temperature at which a stretched and frozen sample recovers by 10% of its length) or the Tg (the glass transition temperature, at which all flexibility is fully lost).However, applied pressure increases the Tg by approximately 1°C for every 5 MPa. This is significant for even moderately high-pressure applications. Additionally, the flexibility required for successful sealing will vary between applications, making the correct material selection critical. At the other end of the spectrum, elastomers respond poorly when exposed to temperatures above their capability. This results in the material suffering irreversible degradation that reduces seal performance.Whilst guidance is given on maximum temperature capability for any specific elastomer grade, this is often in a benign air environment. Therefore the chemical impact of being exposed to hot fluids in the sealing application should be considered.Material groups tend to have well published temperature ranges. For example, the silicone family is able to reach -100°C (or even lower with special grades), and perfluoroelastomer (FFKM) grades are able to withstand 320°C (or even higher for short durations).Confusingly though, considerable variations can exist even within the same material families; especially with FKM where the more modern grades can now reach down to -50°C, with older technology grades only capable of -15°C. There are many NBR and HNBR grades where the acrylonitrile (ACN) content can be varied so that the low temperature limits can be between -30°C and -60°C, depending on the specific recipe formulation.This is just a short summary of three properties of elastomer materials. It’s clear that selecting the correct grade of material for a specific application is a difficult task, yet one that is absolutely critical to achieving the seal performance and lifetime required.
The importance of engineering tolerancesThe importance of engineering tolerances What tolerances are we concerned with?
We can start with the seal itself, and specifically the seal material, as almost all polymer seal materials contain multiple ingredients. For PTFE and polyurethanes this is typically 2 or 3 different elements. However, for an elastomer material as many as 30 different ingredients can be used in the recipe. Each ingredient is weighed or measured before being added to the mixing machine, with a tolerance on the mass or volume of the solid or liquid ingredient. Digital advances in weighing and dosing equipment have improved tolerance ranges since synthetic rubbers were first commercially produced in the 1930’s. However, it’s important to remember that a small variation in material mix from batch to batch is inevitable. The mixing process (also now digitised to help reduce variation) is controlled by parameters which also have a tolerance. Pressures, temperatures, speeds and times are kept within certain limits and determined by the sophistication of the mixer and its control systems. To produce the finished seal, mould tools for polyurethane and elastomer seals are manufactured using CNC or electrical discharge machining techniques. These hold incredibly tight tolerances on the metal form. However, are will be variations in moulding pressure and temperature, combined with slight variations in material shrinkage rates. This results in tolerances on the finished parts that are significantly wider than the metal tool it was produced from. For machined seals, polymer seal materials tend to have high rates of thermal expansion. Together with their relative softness makes it difficult to maintain the same level of tolerance that can be achieved when machining metal components.
Hardware tolerances
When designing hardware for seal installation, tolerances are perhaps more obvious, and certainly where engineers can focus some attention. Plastic housings (whether injection moulded or machined), together with metal castings or pressings can pose tolerance challenges. Even for relatively straightforward machined metal housings, selecting the correct tolerance to apply is key. For many applications, a stack-up of tolerances is to be considered. This is together with tolerances of the assembly such as concentricity or misalignment (especially for dynamic sealing applications). Other considerations include bearing wear and the resulting increase in misalignment or runout as the equipment approaches the end of its target life.
Why are tolerances important for sealing systems?
A combination of theory and experience over decades, seal designers have developed an ideal set of installation conditions for many applications. From static flange or face sealing, through linear hydraulic cylinder seals and to rotary shaft sealing and more. Some of these applications have adopted standardised recommendations (such as ISO 3601 for O-rings and DIN 3760 for elastomer shaft seals). However, because no two applications are truly identical, many are based on the experience and preferences of the seal designer. Regardless, every application starts from a nominal condition, and the maximum and minimum tolerance conditions should always be considered. This is even in seemingly straightforward applications to ensure the seal is continuing to operate within it’s ideal set of conditions. Sometimes it’s assumed that tolerances only really come into play when looking at very small applications, with so-called “micro O-rings”.
This is not the case - and we can illustrate this with a hypothetical application:
A device containing a 25 mm rod, static, with an FKM O-ring sealing gas, whilst installed for 10 years untouched in the Arctic circle. However, it also needs to seal oil whilst installed in direct sun at the equator for 10 years, but with the rod removed and re-fitted several times a year. The device designer would prefer not to make two different variants. O-ring calculators working to ISO 3601 would recommend a 25.12 mm x 1. 78 mm O-ring fitted in a 27.8mm groove with f7 tolerance on the rod and H9 on the groove. However, in the cold application the worst-case squeeze is looking a little light to ensure long term gas sealing. Whilst in the high temperature location, the compression and groove fill are reaching levels that could accelerate compression set of the material and cause issues when the rod is disturbed and re-fitted. Moving the nominal sizes would help one installation but adversely impact the other. However, by tightening the tolerance on the rod and the groove, the concerns at the extreme conditions can be lessened. Approaching the seal supplier for tighter tolerance O-rings can improve the robustness of the design even further, as could incorporating a custom bonded seal-rod component which would remove one dimension and its tolerance completely. Such a hypothetical application rarely exists of course, but the approach is applicable to a surprisingly large number of applications which appear “standard” at first glance. What hardware tolerances should be specified?
There is not a definitive answer to this question, but more of a recommendation that the tolerances for each component within an application are considered. Both the technical and financial impacts being evaluated. Sometimes applying a tighter tolerance can be achieved without any cost implications. In other cases it might slow the manufacturing process, or potentially require a different and more costly process (for example, grinding a rod in place of turning). Tolerances should be evaluated by the consequences of the complete sealing system not performing as intended at the absolute extremes of potential tolerance conditions. In applications where the impact of non-optimal performance may be less severe, a paper based, or theoretical tolerance evaluation is carried out. This could provide enough confidence the risk and impact of the problem arising is acceptable compared to the costs of preventing the risk further. In some safety critical applications in Life Sciences & Medical, Aerospace or Vehicle Control systems markets, testing of parts at the most extreme sizes may be required. This is to be certain that any combination of components from anywhere within their minimum or maximum range of tolerance sizes would still produce an assembly product which performs successfully in the application.
Elastomer manufacturing moulding processesElastomer manufacturing moulding processes Compression moulding This is the simplest method of converting a piece of rubber into a finished seal product. The rubber compound is first mixed and prepared, and depending on the recipe can require up to 30 different individual ingredients. At this stage the curing (or vulcanization) of the rubber hasn’t yet taken place, therefore, the material has a stiff and non-elastic consistency (a little like thick dough). From this dough we produce a rubber blank (also known as a pre-form) by either cutting, punching or extruding cord. These blanks are normally a little bigger than the finished part (normally based on weight) and are placed into a metal moulding tool. The tool (in its simple form) is in two halves with the final product shape cut into the metal. This is known as the mould cavity.This “sandwich” of the bottom tool/rubber blank/top tool is placed into a hydraulic compression press with heated platens. This transfers the heat into the rubber via the metal tool. The press closes. The rubber is then squeezed into every part of the cavity, and any extra material that extrudes from the mould join becomes become overflow, or flash. Next comes curing of the material. This takes place through a chemical reaction between the ingredients, and is controlled by pressure, temperature and time. These parameters are pre-set according to the recipe of the material and the curing system. At the end of the specified cure time, the press is opened. The tool is then removed and split apart, and the cured (elastic) component is removed. Through a variety of methods, the excess flash is then detached, and the part may undergo a post-cure process. This fully completes the vulcanization reaction. Finally, the rubber seal is inspected, packaged and ready for application. The compression moulding process Compression moulding is sometimes a relatively slow and labour-intensive process. Some tools will have multiple cavities into the hundreds and use presses ranging in size and capacity from 20 tons to over 500 tons. This will increase throughput of seals, but the key limiting factor is the speed of heat transfer from the platens into the rubber via the mould tool. In-press cure times can be measured in minutes, but for large parts sometimes over 10 minutes or more. Removing the parts and loading the next set of rubber blanks can also be time consuming.Compression tools are quick and easy to produce, and changeover times from one component to another can be rapid. As a result, this manufacturing method is ideally suited to parts that are required in low quantities, or as prototypes. The tools are designed to ensure that the split/flash line is not located on a sealing contact surface. Therefore, high-quality parts will be produced.For some very hard rubber compounds that do not flow readily, compression moulding is sometimes the only manufacturing option. Injection moulding This manufacturing process is often used to produce plastic components, but for rubbers, the temperatures are switched. A warmed rubber is injected into a hot tool. This is because the force required to inject uncured rubber is much greater compared to pushing molten plastic into a chilled mould. Otherwise, the equipment and principles remain similar.Uncured rubber feedstock is fed into the screw of the injection machine (normally in the form of long coiled strip). The screw rotates and is forced upwards to generate a precise volume (or shot) of rubber at the front of the screw. Once the tool is closed in the press, the screw is pushed downwards to inject the rubber through the sprues and gates, and into the cavity in the tool. The tool always remains in contact with the heated platens of the press and therefore retains the necessary heat for the curing reaction. The temperature of the shot prior to injection is tightly controlled. This is to allow the rubber to flow easily. Additional to prevent the vulcanisation process to the point where the material is too elastic to properly fill the cavity. Alongside automated de-moulding of the parts (via brushes or robots) this reduces the press open time. The entire moulding cycle can be very fast; potentially under 60 seconds with small cross section parts.Elastomer materials need to be specifically formulated for injection moulding to give them the required flow characteristics. The tooling is also significantly more complex compared to compression or transfer tools, especially with multi-cavity tools and cold runner blocks to reduce the waste in the sprue and runner system. Set-up times somewhat longer. Machinery In terms of machinery, injection presses are also more complex and costly than hydraulic compression presses, but the injection moulding process can be highly automated. This, in conjunction with fast cycle times can result in very attractive manufacturing costs for parts produced in high volumes. As with the transfer process, the flow of the rubber into the cavity can be designed to reduce the risk of air trapping and give consistent material properties in the finished part. Transfer moulding This is a variation on compression moulding. It uses the same hydraulic compression presses, but this tooling is a little more sophisticated (and consequently a little more expensive).Rather than loading the rubber blank direct into the cavity it’s held in a “well”, and the top tool part contains a plunger which squeezes the rubber though feed ports/gates into the cavity below. By using this approach, the cavity is closed before the rubber enters. This reduces the amount of flash left remaining on the part, and allows accurate positioning of metal or plastic inserts for two-part bonded components.The material may need to be specifically formulated to allow it to flow through the feed gates. The result can be a more uniform part using this flow of rubber, compared to a compression moulded part where some of the rubber has not had to flow very far during the tool closure. The part and tool can be designed so that the direction of this flow acts to expel the air from the tool and prevent it becoming trapped by the rubber in the middle of the part (which can sometimes be an issue with compression moulding).Tolerances, accuracy and consistency are improved compared to compression moulded parts but the cycle time, or throughput, is broadly the same.There are other ways to manufacture rubber parts, including extrusion, calendaring and even 3D printing, but from comparing the three most common methods of producing an elastomer seal, we can see that considering how the part is going to be made at the start of the project is key to ensuring the technical and commercial success of the seal in the application.
Polyurethane as a seal materialThe foam in your armchair. The strap on your wristwatch. The wheels on a supermarket shopping trolley and beyond; Polyurethane certainly has a diverse range of uses since its invention almost 85 years ago. Aside from day-to-day products; it is also a highly capable and versatile sealing material - and an option that is often overlooked.
What is Polyurethane?
This material is rubber, plastic, rigid and flexible. Polyurethane covers a group of materials; plastic polymers produced by the combination (or synthesis) of di-isocyanates with polyols and a chain extender. This makes Polyurethane an excellent seal material.
How are Polyurethane materials manufactured?
There is a one and two-step process to manufacturing polyurethane.
One-step process
This is when a compound containing multiple hydroxyl groups (called a polyol), is mixed with highly reactive low molecular weight chemicals (isocyanate), and a chain extender (low molecular weight diols or diamines). Consequently, the result is a random copolymer with a physically cross-linked irregular molecular structure.
Two-step process
In a two-step process, the polyol and isocyanate are mixed first to produce a pre-polymer. This is mixed with the chain extender to produce a block copolymer with more regular molecular structure. Although this often results in improved and more consistent material properties, there is a slightly higher production cost.
Why is Polyurethane a good seal material?
Evidently, when formulated appropriately, Polyurethane does produce an impressive set of material properties that make it an ideal material for sealing products. Consequently, its flexible, with very high abrasion resistance, tensile strength and stiffness. The tensile and tear strengths are typically 3-5 times higher compared to rubber seal materials. Although it lacks the chemical resistance and temperature capability of PTFE, it is compatible with mineral oils. There is more information on polyurethane as a seal material HERE You will learn more about our range of materials HERE
Diaphragms for precise control in critical applicationsIn applications that require precise and rapid pressure responses, our diaphragms offer an engineered sealing solution for high performance valves and actuators. Why use diaphragms? Diaphragms provide excellent sealing results in multiple applications. For example: Valves, actuators, pumps, pressure & flow control, pressure switches/sensors, dispensing, metering, ventilation, and media separation applications. Valves and actuators controlling the flow of liquids or gases frequently utilise diaphragms for fast responses to small pressure changes. The sensitivity to signal pressure changes will give reliable valve positioning (with very low hysteresis, for example). Additionally, successful sealing in large diameter, high pressure and long stroke applications can all be achieved with the right design. Large diameter & long stroke engineered diaphragms We supply diaphragms in a wide selection of materials including elastomers, fabric reinforced and thermoplastics. Additionally, our range of diaphragms are an excellent seal of choice for a variety of hydraulic and pneumatic applications. Are diaphragms suitable for your application? Our experienced team of application engineers will design your seals and use the latest developments for each individual application. Additionally, we provide a complete seal design service from start to finish. As well as optimal sealing performance in an application, we will assist with hardware design to provide the most cost-effective sealing package. We will optimize the tooling in key areas to produce complex geometries. This is achieved by using modelling and specialist FEA technologies to predict the performance of fibre & fabric reinforced materials. Manufactured in a range of materials with industry specific approvals, our diaphragms are used in applications across many different markets. These industries include oil & gas, process control, potable water management, LPG & natural gas, life sciences and food & beverage. Learn more about diaphragms on this link HERE
Rotary seals for heavy duty transportationSupply Plus Ltd designs, manufactures, supplies and distributes safety and fuel delivery equipment, with brands including AS Fire & Safety, Bayley and Collins Youldon. The application Our customer, Supply Plus approached us with a requirement for their 2” Swing joint power spindle. The outlet pipe from the fuel tank on delivery vehicles is fed into the centre of a rotating hose reel. This is located between the tank and cab of the vehicle. This is powered by an electric motor and pumped through at relatively low pressure. The current design experienced issues of leakage from the hose fitting in low temperatures especially at -25°C, and particularly when vehicles are parked overnight. Therefore we recommended a rotary seal for this heavy duty transportation. The challenges This application required a rotary seal with low temperature capability and excellent resistance to oil-based fuels. A design was required to replace the existing seal in the available housing between the rotating metal faces. Therefore a standard spring energised rotary seal would not work in the application; a bespoke design was required. Leakage at night when vehicles are not in use often means the issue worsens because the seal is cold and not energised. Therefore, we designed a rotary seal for heavy duty transportation that would remain energised at low temperatures and low pressure. Our sealing solution Our engineers designed a simple but effective seal, incorporating a large heel in the base of the housing. This energised a lip sealing on a rotating metal face. The volume of rubber in the heel of the seal, combined with the 170° angled base, created sufficient force to maintain a seal at low pressure. We used a low temperature Viton ensuring the seal retained elastomeric properties and applied the sealing force at low energising pressures and very low temperatures. This also provided excellent resistance to fuel oils, diesel and aviation fuel. We tested prototypes at both an in-house test unit and in the field over four winter months. Results showed no issues during dispense of fuel and a complete cessation of leakage. The seal was approved and production orders placed, and the design has been incorporated across additional sizes of hose reels. Learn more about our rotary seals HERE
Special coated O-rings for renewable energy applicationOur customer manufactures wind sensors for a variety of applications in different environments. This seal application was within ultrasonic wind sensors designed for wind turbine control. The Application For optimal performance wind turbines need critical, consistent and reliable data on wind speed and wind direction measurements. Therefore we recommended special coated O-rings for this renewable energy application. The sensors that provide this must be able to operate continuously for many years, sometimes in the harshest of weather. Operating conditions are extremely challenging as the wind turbine sensors (and accompanying electronics) are exposed to fluctuating, extreme environmental changes over the years. Depending on the location of the turbines, temperatures can range from -40°C to +90° C. Additionally, humidity changes from 0-100%, and turbines are subject to rain, hail, snow, ice, lightning, vibration, sand, corrosion and altitude. Our Sealing Solution For this application, the required life cycle of the sensors is10+ years. Therefore, to achieve this, a robust protective housing for the electronics and sensors requires a series of reliable, consistent, high-quality seals. These will perform without compromise in challenging conditions. Each size of sensor requires a set of environmental seals in the separated top and bottom sections. Together with our customer’s intensive testing program, we specified EPDM O-rings (which offered exceptional ozone resistance) with a special coating. The coatings are colour coded for identification purposes according to the size of sensor. Therefore, this creates a fool-proof assembly process with no risk of error by operators. Customer Satisfaction Our range of seals have been cycle tested and approved by our customer. Furthermore, these have been built into nearly half of wind turbine projects globally. Read this link for more on our range of O-rings HERE One of our key industries is Hydrogen and Renewable Energy, learn more about our work HERE
Moulded gaskets for an automotive applicationAn existing customer (an automotive manufacturer) approached our engineers with an application where they were experiencing failures of a seal designed and manufactured by another rubber seal provider.
The application
This moulded gasket is used within a valve housing in an automotive application. The competitor gasket experienced failure at the “T-junction” areas of the seal. Our customer had experienced chronic failures of their existing moulded gasket design at high temperatures and high pressures. The seal is required to perform under pulsating pressure of up to 50 Bar and temperatures of up to 150°C. Our engineers reviewed the existing gasket design and application conditions and recommended an increase in height of 0.40 mm. This was to increase the compression and improve the sealing function. Additional beads were also added to further stabilise the gasket in the groove.
The challenges
Prototype parts were manufactured from a single cavity soft tool and sent to the customer for in-house testing and validation. The prototype gaskets very nearly passed testing but did not quite reach the 50 Bar pressure requirement at 150° C (42 Bar reached). This was still a great improvement on the performance of the customer’s original gasket. Analysis of the customers test data and images of the tested parts, determined there were areas where the gasket was sliding in the groove and then shearing as the pressure pulsed. We resolved this issue by our engineers adding beads to the rear of the T-intersections of the gasket. This provided additional support and further stabilised the gasket at the high-pressure stress points in the groove, and reduced movement within the housing. The number of additional beads added needed to be balanced carefully with calculations on groove fill. Further development captured the cleanliness requirements and altered radii on the beads.
Customer satisfaction
The new design was approved, and the customer moved to production tooling stage and sample parts were produced to PPAP Level 3 for production. More information about our mouldings & gaskets on the link HERE
Special O-rings for an automotive applicationOur customer manufactures high performance oil and vacuum pump solutions, and approached our engineers with a new O-ring application for review.
The application
Our customer required an FKM (Viton™) 60 shore special O-ring. This is to meet Porsche material specification PN707 Class 2 (Oil), Class 5 (Fuel/FAME mix) and Class 12 (Blowby gas). This proved to be a very cost sensitive project with a short lead time. Additionally, we did not have an existing grade in our materials portfolio to meet this specialised O-ring specification.
The challenges
Our engineers reviewed the application and we provided two material options. The first is a lower cost grade of FKM (Viton™) A grade, and would possibly meet the Porsche specification required. The second material, a medium to higher cost FKM (Viton™) B grade that will definitely meet the specification. We supplied a quotation for the two material types. Additionally, the quotation included production tooling, PPAP Level 3 submission, testing for both materials and a pre-production batch of O-rings. The project was urgent and we were able to accommodate PPAP Level 3 grade O-rings for both materials to be manufactured from the same tool. Also, to save time we conducted material testing in tandem with the manufacture and preparation of the the production tool. The choice of compound to be used in the tool would be made on review of the results of material testing. On completion of the material testing, the customer reviewed the results with Porsche. The decision to produce O-rings from the FKM B grade was made.
Customer satisfaction
By this stage of testing, production tooling was complete, allowing manufacture of PPAP 3 samples and the pre-production batch to commence. Pre-production O-rings were supplied to the customer in the promised 12-week lead time together with PPAP Level 3 and PPAP 3 samples. See this link for more on our O-ring range and expertise: HERE
High speed Rotary seals for electric vehiclesThe electric vehicle industry is growing; global manufacturing and registrations of electric vehicles is increasing exponentially each year. Our engineers have extensive experience in designing seals for automotive applications, but we still find new challenges involved in sealing components within hybrid, hydrogen fuel and full battery powered electric vehicles.
The Application
Our customer has 30 years’ experience of providing pioneering technologies globally to the mobility industry. This established organisation is a supplier of powertrain solutions for electric and hybrid vehicles and traditional internal combustion power engines. The team of powertrain development experts approached our engineers for a high speed rotary seal. This is for the gearbox within an electric vehicle. The position of the rotary seal is needed between the wet transmission and dry e-motor, and pressed into a bulkhead housing. The sealing lip runs on the surface of the transmission rotor shaft. It is pressed radially by a tension spring onto the shaft, and requires a dust lip to provide protection against dirt and debris from the environment on the dry motor side. The shaft and housing dimensions, are all fixed and provided by the customer. These include full dimensional, surface finish, pressure, temperature and media specification for our engineers to review and propose a bespoke seal design.
Our sealing solution
The application media was a synthetic oil. This is relatively standard for an automotive application. However, because of the maximum working temperature, FKM (Viton) was the elastomer material to meet the required range. As with many applications within electric vehicle gearboxes, the shaft speed is particularly high at 8500 RPM. Typically with these high speeds, seal design needs to ensure minimal friction to ensure the service life required. Our application engineers designed a bespoke, double lipped spring energised seal. On the dry e-motor side, the rubber lip has been designed to act as a dirt and dust excluder. There is a slight clearance from the shaft to avoid friction which prevents damage to the seal, additionally any unnecessary wear to the rotary system as a whole. In the wet transmission side it is imperative that the oil is kept away from the e-motor with the same minimal friction requirements. Consequently, our engineers designed the seal with an inlaid PTFE lip with 15% graphite fill. It is energised with spring to ensure force to achieve ultimate shaft sealing performance. Read more about our rotary seals HERE
Silicone O-rings for De Soutter EcoPulse™ lavage systemDe Soutter Medical Ltd specialises in the development, production and worldwide distribution of high performance orthopaedic tools for surgical procedures, offering their customers a comprehensive range of technically innovative and high quality products.
The application
De Soutter Medical recently launched their new EcoPulse™ lavage system for use in orthopaedic surgery. The company approached us to manufacture two different sized Silicone O-rings for the ECO Pulse upgraded design. The EcoPulse™ connects onto the front of a reusable De Soutter handpiece, and allows surgeons to lavage the surgical site using saline water. It can simultaneously be connected to a suction device to remove waste from the surgical site. The EcoPulse™ is supplied as a single use sterile packed product. It has a range of nozzles available for specific surgical procedures. The new EcoPulse™ has a pared back functional design to eliminate superfluous plastic. Additionally, instead of using disposable batteries (and the associated single use wiring and motors), it connects onto a reusable power tool that is already being used to perform the surgical procedure. This eliminates a large amount of clinical and WEEE waste (more information HERE). Furthermore, compared to other products in the market, reduces clinical waste by up to 60%.
Our sealing solution
The seal application is located within the disposable pump/irrigation attachments to ensure that no saline water leaked, and there is no loss of suction during use. This is a relatively straightforward application in terms of mechanical sealing. However, due to the nature of the product there are critical demands on the material and during the manufacturing process. Our engineers specified a USP Class VI translucent silicone; suitable for medical devices due to its biocompatibility features and resistance to bacterial growth. The (bespoke and dedicated) moulding tool was coated in titanium nitride. Therefore the use of release agents during the manufacture process of the silicone O-rings is not necessary. This is to mitigate the risk of any cross contamination with the O-rings. Additionally this is important when producing seals used within devices where there is any risk of patient fluids crossover. Cleanroom manufacturing and the silicone O-rings are double bagged packaging in order to avoid any cross contamination. These parts are manufactured and packaged at our ISO13485 approved manufacturing site to achieve these requirements.
Customer satisfaction
We work in conjunction with our valued customer De Soutter Medical. We assist with design support and technical recommendations on the development and manufacture of sealing products for use within their medical devices. For more on our full range of O-rings see this page: HERE Read more about our Life Sciences & Medical expertise: HERE
Gold plated metal seals for Oil & Gas couplingsOur customer designs and manufactures hydraulic distribution products and systems used to control subsea production systems for the offshore energy industry globally.
The application
This seal application is for a range of dual resistant hydraulic couplings, designed to be suitable for make and break under full system pressure. There were three different sizes in the same design of coupling. We recommended a gold plated metal seal for this type of application. Read on to find out more about this project. The customer had been using a back-to-back elastomer O-ring arrangement, but wanted to develop a superior sealing solution in order to achieve a greater number of connect/disconnects per coupling (therefore improving the lifespan). The application itself was high pressure at 15,000 psi. The temperature range wasn’t particularly demanding compared to other Oil & Gas applications. However, because the couplings were for subsea equipment, there could be contact with well fluids and control fluids. As result the seals required NACE approval.
Our sealing solution
Our engineers recommended a metal seal for this application because of pressure and compatibility requirements with the various hydraulic fluids. The action of mating/de-mating the coupling meant this seal had to perform under a slightly dynamic movement. The seal base alloy was NACE MR0175 heat treated to obtain the standard desired properties for oil and gas specific application service; (when a material that does not comply with the NACE MR0175 heat treatment requirement is exposed to H2S, catastrophic failure can take place). Gold plating of the seal was recommended due to its malleability and suitability for slightly dynamic operation. Our metal seal solution was extensively cycle tested and the customer confirmed that the new concept metal seal solution performed under the required conditions with no leakage.
Customer Satisfaction
This sealing arrangement extended the life of the couplings by achieving 100 connect/disconnect cycles before the seals needed changing. This was substantially higher than the original sealing solution and gold plated metal seals are now supplied in production quantities. For more on our expertise in the oil & gas industry, read HERE
PTFE Rotary Seal for Oil & Gas drilling toolOur customer designs and manufactures a leading range of unique downhole technology and drilling solutions that contribute to a net zero energy industry.
The Application
A seal was required for the rod of a downhole drilling tool - a hydraulic dynamic (rotary) application. Our solution is a PTFE rotary seal. Read on to find out about more. The application has a normal operating pressure of 500 PSI at 60 RPM, but maximum pressure can reach 6,500 PSI in static operation. Reverse pressure was unlikely in this application but the engineers wanted to ensure some level of resistance. Two single acting seals were considered, but groove space is limited. Keeping the grooves closed is preferable for bearing strength. The maximum operating temperature reaches 200°C and the application media drills mud and completion fluids (with wiper arrangement already installed).
Our Sealing Solution
Due to the pressure, temperature and chemical media parameters of this application, an elastomer seal selection was not suitable. Our engineers selected our standard FTOR profile PTFE seal This is a double acting slipper seal ideally suited to hydraulic applications and capable of sealing under alternating pressure directions. It’s ideal for sealing high pressure loads with slow to moderate rotational speeds. The PTFE rotary seal has side wall notches equally spaced, so the part can be fitted symmetrically either way. The initial sealing force is provided by the elastomer O-ring. This is seated within a machined saddle and activated by system pressure to perform under high pressure demands. The central lubricating channel design ensures low friction and wear. Additionally, the sealing set has been designed with a scarf cut PEEK back-up ring. This is to ensure stability and seal performance at maximum working pressure of 6,500 PSI.
Customer Satisfaction
Our customer tested the sealing arrangement at higher pressure (up to 10,000 PSI). Consequently, our customer is pleased it seals successfully over and above the application requirements. They have adopted this seal design for other sizes of parts in similar equipment. Read more about our rotary seals HERE
Why the focus on PFAS?PFAS is a blanket term used to describe Poly- and Per- fluoroalkyl substances. There are currently around 10,000 substances in existence that fit this description, with potentially more variants still yet to be produced. Some are already known to be harmful to human and animal health and the environment (such as PFOA and PFOS), and these specific PFAS are already controlled under legal restrictions. But in February 2023, The European Chemical Agency (ECHA) published a regulatory proposal to further restrict the manufacture, placing on the market, and use of all PFAS within the EU.
What are the consequences for seal manufacturers?
A broad ban on all PFAS would have a significant and direct impact on European industries and businesses that manufacture products using these substances. This will have consequences globally. One particular concern is the fluoropolymers material group. These elastomers could be caught in any blanket ban of PFAS without any exemption. These materials are essential in a wide variety of applications in many industries. These include food, medical, pharmaceutical, clean energy, semiconductor, electronics, oil & gas, chemical, automotive and electric vehicle industries. These fluoropolymers include materials used in high performance sealing solutions, such as PTFE and PVDF plastics, and FKM, FFKM and FVMQ elastomers.
What's the problem?
There is substantial scientific evidence showing fluoropolymers demonstrate unique characteristics that mean they do not pose significant risk to the environment. Additionally, no risk to human health as they’re not bio-available, toxic or mobile. They do not dissolve in or contaminate water, or generate microplastics, therefore cannot enter or accumulate in a person’s bloodstream. They meet the criteria specified by the Organisation for Economic Cooperation and Development (OECD) as “polymers of low concern” as they present no significant toxicity concerns, and do not degrade into other PFAS chemicals. Fluoropolymers far outperform other sealing materials in countless applications. To put it simply; they seal tighter, last longer and survive harsher application environments considerably better than any other available materials. Fluoropolymers add irreplaceable value to society, and contribute significantly to environmental sustainability
What do we do?
We fully support restricting the use of PFAS chemicals that are known to be harmful to our health or our environment; but we believe grouping all PFAS within a restriction would be a mistake. Fluoropolymers do not have the toxicological and environmental profiles of other PFAS. Additionally, prolonged existence alone is not justification to restrict a substance under REACH. We already work proactively to ensure the products we put to market are safe, compliant with legislation, and utilise the latest sustainability developments. This is to minimise our impact on the environment – during manufacture, in use and at end-of-life. As a company with high environmental, social and governance standards we will continue to do so, whenever and whatever new legislation comes into force. However, we believe the sealing industry, it’s many customers, end users and society as a whole, need specific derogations and exemptions for fluoropolymers (free of any time limitations) to be included in any legislation covering PFAS substances. As we have done, we strongly encouraged any individual or organisation that may be impacted by a ban to engage with ECHA. This would be during their consultation period on this proposed restriction (which ended on 25th September 2023). To learn more about our key industries and our sealing solutions, read HERE
Seals for cryogenic applicationsCryogenic sealing means controlling or sealing a media at very low temperatures. This process can be complex and advanced, and spans a range of markets; from pharmaceutical, chemical and refrigeration, to automotive and electronics.
What are low temperatures for seals?
A typical industrial sealing system operates in the realms of a stable temperature rating. This is often sufficient for elastomer seals to cope with most of the time. For example, a general pump application running at -20°C to +80°C in air or water would be perfectly suitable for a sealing solution manufactured in nitrile (NBR) elastomer. However, if that temperature specification dropped to -196°C in liquid Nitrogen, the overall sealing solution would need adapting dramatically. Therefore, a more advanced polymer solution is needed. This is because general elastomer groups such as NBR, FKM, & VMQ are not suitable to perform at very low temperatures. This is due to the chemistry of the elastomers at a molecular level. All elastomers need a particular chemical makeup to be able to withstand a temperature range of the application required. However, many global elastomers on the market are not rated much more below -70°C. This means they’re not a viable choice for cryogenic applications with temperatures way below -70°C (often requirements reach below -196°C).
Types of cryogenic sealing solutions
Specialised sealing solutions are required for cryogenics conditions. Our engineers utilise a range of more advanced seal polymers to solve the most demanding and critical application setups. PTFE has an outstanding temperature rating of -260°C to +260°C and low friction characteristics. It is also regularly used in conjunction with a metal spring energiser. The spring energiser acts to maximise the sealing force at the seal contact points and to maintain a tight seal. This is the case even when the very low temperature conditions are attempting to contract the seal away from the mating surfaces. Other common polymers suitable are UHMPWE and PTCFE for more specific applications.
Our seals for cryogenic applications
We offer a range of cryogenic sealing solutions for various markets and applications including; pumps, engines, couplings, cylinders and many more. Read about our full range of engineered materials HERE
Why use 2-Shot moulded seals?2-Shot moulding is a manufacturing process that allows the co-polymerisation of hard (or soft) plastics and thermoplastic elastomers (TPE’s). We use the 2-Shot manufacturing approach to deliver engineered parts that perform a critical sealing function.
What is 2-Shot moulding?
A 2-Shot mould is designed with a top and bottom cavity. During the moulding process the first material is injected into the top cavity and the mould opens and rotates. The first material is then injected into the top cavity again, while the second material is injected into the bottom cavity simultaneously. The mould then opens and the parts are ejected from the bottom cavity; the mould rotates again and the whole process is repeated. 2-Shot moulding is not considered a brand new method of manufacturing. In fact it has been used for years to produce items that we see and use every day. Toothbrushes, tools, kitchen utensils and toys are but a few examples of multi-shot moulding being used to produce relatively cheap items in large production quantities.
Why do we use 2-Shot Moulding?
Previously, manufacturers of high volume metal or plastic- to- rubber component assemblies have processed them via chemical or mechanical bonding, and by using adhesives or over-moulding. Examples of the types of markets that lend themselves to these types of sealing products are Automotive, Life Sciences and Aerospace & Defence. Although these production methods may achieve the final assembly requirement, the many different processes involved are lengthy, costly, and can be fraught with problem areas that require stringent controls. A failure in any of these areas will result in poor quality parts, therefore often deeming these methods unsuitable for critically engineered components.
Why do we use 2-Shot Moulding?
When designing a new 2-Shot moulded product (or replacing an existing assembly part) our engineers review each application parameter carefully, and utilise years of sealing experience and materials expertise alongside the latest 3D modelling technologies and FEA simulation programs before presenting a seal proposal. This allows us to anticipate and analyse the finest details of mould performance, and means we can adjust our seal design to ensure our customers receive the highest level of performance possible from our engineered 2-Shot seal solution. The result means we supply our customers with high integrity parts with a powerful molecular bond, reduced production cycle times (as many additional processes are removed from the production line) and comprehensive cost reductions as all parts are produced in a single manufacturing tool (meaning reduced running costs and the removal of pre and post moulding processes).
2-Shot moulding is not just a way of manufacturing simple, high volume parts. Our application engineers are always breaking norms and pushing design limits to consider more creative ways of producing high performance engineered sealing solutions to meet our customer requirements.
Read more about our 2 shot mouldings HERE
Why use PTFE seals?Polytetrafluoroethylene (PTFE) is a thermoplastic polymer that can be used in a variety of sealing applications; it is particularly suitable where the application conditions exceed the parameters of elastomeric seal use, but are not as highly demanding as applications that require the use of metal seals.
What is PTFE?
Discovered accidentally in the DuPont™ laboratory in Jackson, New Jersey, USA in in 1938. The molecular structure of PTFE is based on a linear chain of carbon atoms which are completely surrounded by fluorine atoms. The carbon-fluorine bonds are among the strongest occurring in organic compounds. As a result PTFE has thermal stability across a wide temperature range. It’s high melting point (342 °C) and morphological characteristics allow seal components made from virgin PTFE to be used continuously at service temperatures of up to 260 °C, and with the addition of fillers – up to 300°C. It has the unique ability to resist material degradation, heat-aging and alteration in its physical properties during temperature cycling. Alongside this rare combination of material characteristics PTFE also has unlimited shelf life.
Why use PTFE seals?
Notably PTFE demonstrates extraordinary chemical resistance: the intrapolymer chain bond strengths preclude reactions with most chemicals, thereby making it chemically inert at elevated temperatures and pressures with virtually all industrial chemicals and solvents. Only a few media (some molten alkalis) are known to react with PTFE seals making them the perfect sealing solution for highly aggressive chemical applications. PTFE also has the lowest friction coefficient of any known solid; it has self-lubricating capabilities which offers continuous dry running ability in dynamic sealing applications and has superb stick/slip capabilities.
Focus on dry coatings
The advantages of using PTFE in sealing applications are; functionality at high and low temperatures, dynamic sealing with high wear capabilities, high pressure sealing (using combinations of PEEK back-up rings) and compatibility with highly aggressive chemical combinations. Our range of PTFE seal products include back-up rings, rod and piston seals, slipper seals and spring energised seals in a wide variety of sizes. Materials depend on application requirements but we offer a wide range from Virgin PTFE or including filler combinations of MoS2, glass, carbon, carbon fibre, graphite, and bronze. These characteristics make PTFE seals perfect for the demanding applications involved in Oil & Gas, Aerospace, Automotive and Chemical Process markets (to name but a few) and Ceetak’s engineering team are experienced in the design of PTFE sealing solutions to meet the complex specifications these types of application demand. Read our overview and more detail about PTFE seals HERE
Why use metal seals?The use of metal seals as an engineered sealing solution is appropriate where it is not possible to use elastomeric or polymer seals due to extremely demanding application requirements. For example, these could include applications with extremely high temperatures (300°C upwards) and pressures, intense radiation, cryogenic conditions or highly aggressive chemicals.
How do metal seals work?
The metal seal concept is based on plastic and elastic deformation of the seal during compression which creates a sealing interface. The metal seal is compressed in the cavity on average about 20% of its original free height. The force generated through compression of the ring produces a high contact stress at the seal/cavity interface. This force is then supplemented by the pressure-energisation force which rises in proportion to the increase in differential pressure inside the seal cavity.
What types of metal seal are there?
There are three types of seal energisation; self, spring and pressure energisation. By design metal C-rings are self-energising due to the good spring back characteristic of the C-shaped profile. Additionally, they can be used in internal, external and axial pressure conditions. The different base material characteristics and heat treatments, along with material thickness, and cross section of the seal also determine the compressive load. This is directly related to the sealing level achieved and is known as “self-energisation”. Spring energised seals have excellent spring back properties and are typically used to improve leakage rates by increasing the load on the sealing interface. All metal seals can use system pressure to generate a hydrostatic load to obtain the highest level of sealing possible; this is known as pressure energisation. At high pressures this becomes an advantage and allows the design of metal seals for applications of 25,000 PSI and above.
Ultimate seal performance
Once the metal seal profile and material has been selected depending on the application, there are a variety of platings and coatings available. These can modify the surface properties of the seal to create a malleable outer surface layer. Typically precious metals such as gold and silver are used for plating, but many other options are available with two common ones also being Tin or PTFE. This layer ensures optimum sealing despite any mating surface imperfections. The plated or coated layer also reduces coefficient of friction so the seal can slide and bed down during initial compression. Consequently, this prevents galling. As well as providing better physical properties to the seal, coatings and platings are chosen to withstand high temperatures and aggressive (often corrosive or oxidizing) environments. There are ever changing industry demands and fast paced technology developments – particularly from customers in the Oil & Gas, Aerospace & Defence and Automotive markets. Therefore, we are challenged daily with applications where the boundaries are being pushed to the absolute limit. We have designed metal seals into F1 car exhaust systems, subsea repeaters, oil and gas production valves as a few examples; the capabilities of high performance metal seals is endless. Working with the latest developments in materials, platings and manufacturing technology; our engineering team design the sealing solutions to meet the complex specifications these types of application demand. Learn more about metal seals HERE
Why use Push-in-Place gaskets?Where a seal groove follows an irregular path or profile, a common sealing solution is to design a custom Push-In-Place (PIP) gasket that has the same profile as the centre line of the groove, simply drops into place and is retained by the features of its own design.
Gasket sealing overview
There are many ways to seal the static join between two components. This could be to keep fluids inside a cavity or to keep fluids or contaminants out of a device or assembly. The options can vary from simple O-rings, moulded elastomer gaskets and flat sheet style materials, to liquid gaskets (or RTV’s). As with all sealing applications, the optimal sealing solution is designed by first reviewing the application conditions. These include temperature, pressure, fluid exposure etc; and other variables such as life requirement, equipment serviceability and seal compression set should all be considered. Arguably though, compared to other sealing applications, when designing face, cover or flange sealing solutions it is imperative to consider the packaging requirements and assembly issues of gasket sealing options. The need to avoid or seal around bolt holes (or other retaining/clamping devices), together with optimizing hardware wall sections or depths can play a very important part in choosing the most suitable gasket sealing technique.
What are Push-in-Place gaskets?
With the right combination of application conditions, an o-ring style approach to sealing may be the most appropriate. O-rings tend to require relatively shallow grooves compared to their cross section in one half of the assembly, and in cases where the groove is round in plan view – they can be a good solution. However, in cases where the groove follows a more irregular path or profile (frequently referred to as a “racetrack”) the O-ring can sometimes pop out in places – often where the two housing parts are being brought together. A common solution is to design a custom moulding that has the same profile as the centre line of the racetrack groove and simply drops into place. A similar approach is used when the application or hardware constraints steer the design towards a gasket that has a greater cross section depth compared to the width; this would typically be designed so the centre line of the gasket matches the centre line of the groove plan profile – again so that it drops easily into place. An inherent problem with gaskets that can drop into place is that often, they easily drop out of place too. If the component needs to be inverted, or has the potential for rough handling during assembly then the gasket may become partially or fully dislodged from the groove, which results in a badly sealed interface. The best solution to this issue is to incorporate retention pips or bumps in the gasket design, a solution known as Push-In-Place (PIP) gaskets. These require a distinct force to put them into the groove, and as a result require more than just gravity to get them out of the groove.
Why use Push-in-Place gaskets?
There are other less effective solutions for tricky groove sealing, such as the use of a sticky grease, or the use of an adhesive. These can bring compatibility and health and safety issues to consider. Additionally, it carries the risk that any contaminant could keep the gasket off the surface that it is supposed to be sealing against. Therefore, the integrity of the seal can be severely compromised as a result. Neither of these approaches can be recommended, and instead the use of retention pips is a safe and secure way of ensuring the gasket remains in the groove. To determine the optimum number, size and position of the retention bumps, Finite Element Analysis (FEA) is used. This ensures they provide sufficient squeeze to prevent the gasket being easily dislodged. Additionally, it is important there’s no overfilling the groove space with seal material or interfering with the seal compression footprint against the hardware faces. The bumps can be strategically positioned to control any distortion of the gasket under pressure or temperature conditions. For example, low temperature conditions can shrink the gasket and tighten the radius it adopts around a bend in the racetrack profile. This can reduce the seal compression locally and potentially create a leak path.
Correct positioning
By positioning retention bumps at either end of the bend, the thermal contraction can be controlled to minimize the risk of leakage. Effective retention ensures that if the part needs to be inverted (which could be the preferred assembly method for practical reasons) or is subject to rough handling – the gasket remains correctly located in the groove. For large gaskets this is normally the most effective solution. On smaller gaskets (particularly those located well inside the periphery of the assembly), there is a significant risk of a dislodged gasket being totally undetected unless using a PIP gasket design. It’s possible to include tell-tale signs on a gasket design. For example, if a part of the elastomer gasket protrudes sideways through a gap in the housing wall, the presence of the gasket can be checked. This would be either with the human eye or an automated vision system. However, this does not ensure correct seating all around the gasket length, and cannot be used for internal gasket locations. In these cases a missing or badly fitted gasket would only be discovered during post-build testing, or even worse with a machine failure at a customer.
Further considerations
If included at the design stage, the small additional tooling and material costs associated with a PIP gasket are negligible compared to the costs of an impossible assembly scenario, strip and re-build costs on the assembly line, or the consequential costs associated with failure of an assembly once delivered to a customer. More information on PIPs and gaskets can be found HERE
Perfluoroelastomers in valvesIs it time to re-visit using perfluoroelastomer seals in your valves? First developed by DuPont™ in the late 1960s, perfluoroelastomers (or FFKMs), are now widely known and understood in a variety of markets. But for those that may be less familiar with these high performance materials, here is a quick recap...
What are perfluoroelastomers (FFKMs)?
They are essentially highly or fully fluorinated compounds with a fluorine content above 75%, and they offer outstanding chemical resistance. Generally better than all other elastomer types, FFKMs are often referred to as having the resistance of PTFE but in elastomer form. The term “universal” chemical resistance is commonly used; although it’s not strictly true as we will learn shortly. Unlike PTFE, the molecular make-up of FFKM includes crosslinks (or spring-like elements). This is contrast to just a backbone of carbon-carbon atoms surrounded by protective fluorine atoms. These crosslinks are what give the FFKMs their crucial elastic behaviour (in other words returning quickly to their original shape after being deformed). But the crosslinks are also a drawback as they can be a weak point for a chemical attack. Different crosslinking systems can be used when developing FFKMs and the choice will determine the high and low-temperature capabilities. Compounds developed for extreme high-temperatures (up to around 325oC) generally have a less broad chemical resistance. This is in comparison to the lower temperature grades (up to 225oC). Similarly, FFKMs developed to have excellent resistance to specific fluids (such as amines or high-temperature steam) can have limitations of low-temperature capability or compression set. As a result, there is no universal material that covers all application criteria bases.
A variety of grades
Previously the number of perfluoroelastomer grades was less prolific than other elastomer types such as FKM, EPDM, and NBR. However more than 50 years of technical developments have created a range of FFKM grades for specific and challenging applications. These are particularly in chemical process, oil and gas, semiconductor, and aerospace industries. Additionly, options with a hardness range of 65 to 90 durometer, and versions that meet international standards or specifications for food, medical, CPI, and oil & gas applications means the portfolio of FFKM-based compounds available to engineers is now substantial. In addition to technical developments, manufacturers and compounders have also been addressing the only real drawback of FFKM materials; the cost. They are difficult and time-consuming base polymers to manufacture. With a relatively low volume production base and sometimes lengthy processing times, FFKM seals carry a high financial premium over FKM seals. Even several times greater than FKM itself has over NBR. In recent years, there’s been more focus on making general-purpose grade FFKMs with broader temperature and chemical resistance capabilities more financially attainable. The initial procurement costs remain high compared to less capable elastomer bases. The overall cost of ownership may now be more appealing than it was twenty or even ten years ago. The ability of FFKM seals to survive for much longer in applications where exposure to a variety of fluids (perhaps wider than originally specified) is possible. This considerably reduces unplanned costs associated with maintenance and downtime.
Focus on dry coatings
The cost of unscheduled maintenance and repair in pump and valve equipment can be high in any industry, but exceptionally so in petrochemical, oil & gas, and semiconductor. When these costs are fully considered in the overall lifetime of a product, the initial price of seals in a valve is considered relatively minor, but it can still be a barrier in the material selection process. With both technical and commercial developments in recent times FFKM materials now compare more favourably against other materials for static, or low-duty dynamic applications in valves. In applications where persistent and sporadic issues keep coming back to cause problems, they are now a more financially attainable choice of material to avoid re-work, overhaul, downtime, customer dissatisfaction, and ultimately, more costs. Read more about FFKM as a suitable sealing material HERE
Seals for electric vehiclesPropelled by one or more electric motors and using energy stored in rechargeable batteries, electric vehicles are quieter, have zero exhaust emissions and lower emissions in general compared to internal combustion engines. The number of electric vehicles on the road grows exponentially every year globally, and our engineers support manufacturers with innovative sealing solutions in these specialist areas of application.
Hybrid and hydrogen vehicles
Hybrid vehicles have a petrol (or diesel) engine combined with an electric motor and relatively small battery. They feature all the traditional areas of automotive applications that require seals including oil, steering, suspension and braking systems. They also require seals for environmental and RFI/EMI (Radio Frequency Interference /Electro Magnetic Interference) applications. These are normally gaskets required for many electronic control, junction and connection boxes (for power invertors, charging electronics, motor and battery enclosures). These are generally placed around the vehicle, but batteries tend to be under or behind the back seat. Sometimes the fuel tank is smaller and the battery sits in a similar place. Application characteristics also include high speed rotary sealing requirements around the output shaft of the motor. Additionally, possibly in the gearbox that links in with the combustion engine drivetrain. Plug-in hybrid vehicles have gaskets or seals (environmental and/or shielded) associated with the cable charging connection.
Hydrogen Fuel Cell
These vehicles have no combustion engine, and the fuel cell is often located where the petrol engine would be. Electrical power is produced by passing hydrogen and oxygen gasses through a “battery” (the cell). Anodes and cathodes produce electricity that drives the motors and is also stored in more conventional hybrid style. Waste product is water and warm air; this is very environmentally friendly (more so than pure battery power which uses electricity often generated in a “non-green” way and which also consumes rare earth minerals such as lithium). There are traditional automotive seals in areas of applications such as steering, cooling, suspension, and braking systems. In addition to environmental and RFI/EMI shielding gaskets and high speed rotary seals requirements. Hydrogen gas is normally stored in a tank at up to 700 bar pressure. Again, is usually situated just behind or under the back seat, and requires sensors, valves and pressure regulators to operate. There are seals and gaskets required within the fuel cell itself, these require H2 resistance. Some fuel cells have small compressors which force the gasses through the fuel cell at higher pressure for improved efficiency, and then expanders which recover energy from this gas flow at the exhaust of the fuel cell. These often require high speed rotary seals (generally PTFE materials) and they run unlubricated.
Battery applications
Full battery electric
These vehicles have large batteries that typically take up the entire floor area underneath all of the seating compartment of a car. As with other EV’s there are the traditional seals in automotive areas; no oil system, but the steering and cooling systems, for the battery itself and the suspension and brakes. There are also environmental and EMI/RFI shielding gaskets and high speed rotary sealing requirements. The plug in charging ports also present a sealing application.
Filling and charging
There are many different applications for filling and charging. Home charging points are normally smaller and wall mounted for domestic use. Commercial and forecourt charging will encompass hydrogen filing. There are all similar application types as already mentioned including shielded and environmental gaskets for the electric applications and hydrogen sealing for the H2 filling applications.
Design & Development for Electric Vehicle applications
Our engineering team understand the demands associated with automotive applications, and we support vehicle manufacturers by designing innovative sealing solutions for electric vehicle applications. We use the latest in 2D/3D CAD and FEA simulation software to design and replicate automotive seal performance before finalising each individual seal design, incorporating significant feature and critical function elements for integration with customer mating parts. We offer material development and testing, and a component endurance testing service. Learn more about our expertise in the Automotive & EV industry HERE
Seals for valve applicationsValves are imperative for isolation and control functions, and can be found in a broad range of industries such as Oil & Gas, Water & Wastewater, Food & Beverage and Hydraulics & Pneumatics. We supply seal products into valve applications in a variety of styles including ball, gate, flap, plug, butterfly, spool, check and solenoid valves.
Characteristics of valve sealing
There are many challenges involved in valve application sealing. Conditions and application parameters can vary with temperature extremes from cryogenic up to 325°C, and pressures up to 1000+ bar. We need to carefully consider the materials to suit all fluid compatibility required. Often the seal design requires low breakout friction and offers no stick-slip following prolonged static periods when the valve is not used. Alongside this, customers require long service life and minimal maintenance. Valve styles include ball, gate, flap, butterfly, spool, check and solenoid valves. Also different types of actuation include manual, pneumatic, hydraulic and electro-mechanical. Different areas of the valve demonstrate different sealing requirements.
Valve sealing areas Actuation
There are a range of sealing solutions to suit the variety of actuation types employed with valves. This includes diaphragms for pneumatic actuation, rotary and linear hydraulic and pneumatic seals, and gaskets and O-rings. Seal materials are available to suit all ranges of temperatures and media associated with the actuator and any external contaminants it encounters.
Body bonnet joint
This is a static sealing location that can often be sealed with an O-ring (a wide range of materials are available to satisfy fluid compatibility). However dependent on the fluid, pressures and temperatures, metal seals can be more suited to the application. Additionally, housing deflection under pulsating system pressures may worsen compression set sealing issues. Therefore, a custom gasket design could be potentially more suitable than an O-ring. For subsea valves, a sealing solution capable of handling alternating pressure regimes and multiple media types may be required.
Stem
A critical and dynamic sealing location with often demanding requirements. Depending on the application of the valve, the seals used here may see frequent dynamic operation and will require a long wear life. In other cases, the valve may be static for long periods and then require operation with minimal break-out friction forces. In all cases, reliable sealing is paramount.
Seat body
Valve seats are often mounted in a housing or carrier which has a sealed interface within the valve body and in these cases it can be a critical location to seal correctly. Dependent on the design, the seal location may be subject to upstream or downstream pressures at various points. In some cases fluid flow through the valve can pull or wash-out seals from their grooves if they are not designed to prevent this. As pressure conditions change with valve operation, the seals here may be required to withstand small (but sometimes frequent) movements of the carrier without sticking or wearing.
Valve Seat
A wide variety of elastomers and engineered polymer materials can be moulded or machined to suit valve seat components. Bonded rubber to metal or rubber to plastic seals can provide bespoke solutions. These offer benefits in terms of space envelope, component count or ease of assembly.
Design & Development for valve sealing applications
Our engineering team understand the application demands associated with valve sealing and can support our customers with the design of seals for every position within the valves. We provide a complete design service; from initial seal geometry and profile choice, to material selection and prototyping, through to final production. This is utilised with our seal design experience and materials expertise, alongside technology such as 2D/3D CAD and FEA analysis. These simulate performance before finalising each individual seal design. We are familiar with the requirements of individual markets and their valve applications. Our seals are manufactured in materials with approval requirements such as NORSOK M-710, ISO23936-2, NACE, WRAS and FDA. For more on our design and engineering service, see our dedicated page HERE
Seals for Oil & Gas applicationsWith diverse applications in harsh environments, the Oil & Gas industry presents some of the most challenging demands on engineered sealing solutions. Our collaboration with Parker Seal Group allows us to integrate their materials and sealing expertise to meet our customer demands.
Characteristics of Oil & Gas sealing
Regardless of where seals are used in oil & gas applications, they are without doubt critical to the safe, reliable and efficient operation of a huge range of onshore and offshore equipment. There are many challenges involved in oil & gas application sealing; conditions typically include low and high temperature extremes, very high pressure conditions and most seals need to withstand aggressive fluids and media such as sour gas, salt water and super-heated steam. There are three main sectors within the Oil & Gas industry, with different processes and equipment requiring sealing solutions. Upstream; commonly known as exploration and production – this refers to the recovery of hydrocarbon reserves in the form of natural gas and crude oil. Midstream; refers to the processes involved in the transportation and storage of natural gas and crude oil, from production site to refinery location. Downstream; includes the processing of natural gas and crude oil at oil plants and petrochemical plants.
Well Drilling
This is the process of extracting oil and gas from beneath the ground, in both onshore and offshore environments. Seals used in these applications have to cope with increasingly harsh environments (with wells becoming deeper and deeper). System pressures up to 30,000 PSI and operating temperatures between -50°C and +220°C are common, and seals have to demonstrate excellent fluid compatibility and resistance against aggressive media – all with longer service life expectations. Applications include; drilling and tool bits, blow-out preventers, drilling mud systems, LWD and MWD test equipment, casing and pipe connections, subsea risers and connector systems, control valves, compressors and pumps. Seals need; high temperature and high pressure capabilities, sour gas and abrasive drilling fluids resistance, extrusion resistance and compatibility with well bore fluids.
Well Completion
This is the process of making a well ready for production after drilling. Similiar to well drilling, seals used in well completion must withstand increasingly harsh condition such as deeper wells and more diverse geographical areas with extreme hot and cold weather conditions. System pressures up to 30,000 PSI and operating temperatures between -45°C and +220°C are common, and seals have to demonstrate excellent fluid compatibility and resistance against aggressive media. Applications include; tubing heads and hangars, packer assemblies, well controls, Christmas trees, cementing equipment, well head completion assemblies, well service. Seals need; high temperature and high pressure capabilities, chemical compatibility (including H2S resistance), RGD & extrusion resistance and steam resistance.
Distribution
Following on from the production stage, petroleum products are transported to processing facilities and to end users in pipelines. Seals used in midstream distribution sector applications often operate in low temperatures, down to -196°C (required to liquify gas) as well as high temperatures of 480°C (to meet fire test requirements). System pressures can be as high as 10,000 PSI. Applications include; marine and offshore loading swivels and turrets, railcar loading systems, pipeline service equipment (pigs and spheres), pipeline valves & actuators, pumps & compressors, tank & loading systems. Seals need; Extrusion, corrosion and abrasion resistance, extreme temperature and pressure capabilities, chemical compatibility (including H2S), RGD resistance, compliance with NORSOK, ISO and API specifications.
API 6A, NORSOK M-710, ISO 23936-2 and TOTAL material qualifications
The Oil & Gas industry has specific testing and qualification standards to ensure that materials used in harsh drilling and production environments meet the critical demands of these applications. ISO 23936-2:2011 describes the requirements and procedures for the qualification of elastomeric materials in accordance with media related to oil and gas production. H2S testing in accordance with this specification enables the lifetime prediction of compounds. NORSOK M-710 defines the requirements for critical non-metallic (polymer) sealing, seat and anti-extrusion ring materials for permanent subsea use. This includes well completion, christmas trees, control systems and valves as well as topside valves in critical gas systems.
API 6A is the specification for drilling and production, wellhead and christmas tree equipment. Total GS EP PVV142 defines the requirements for non-metallic sealing materials concerning elastomers within pipeline valve applications. In conjunction with Parker Seals we offer a range of products in materials that are qualified to these specifications. We work closely with our oil & gas customers, read more HERE
Seals for Life Sciences & Medical ApplicationsWhen designing and manufacturing sealing solutions for applications within critical devices and equipment, the strictest demands in product integrity and the highest specifications of hygiene and cleanliness must be met. Characteristics of Life Sciences & Medical sealing The Life Sciences & Medical industry is one of the most demanding and stringently regulated. There are a variety of areas of product development and manufacture where seals for Life Sciences & Medical Applications are required.
Diagnostics
Because of technology changes, there are now many ways of supporting patients with accurate results for the safe management of health conditions. This includes at home and within a clinical setting. It’s vital that diagnostic devices and systems are developed with the accuracy and speed of response to enable targeted analysis and therapy.
Patient management and care
Repeatable and reliable control of the equipment used in patient management and care is paramount. Applications include seals for ventilators, anaesthesia pumps, respiratory therapy and monitoring equipment. Minimally invasive surgery equipment and metered dose aerosols (such as inhalers) also need Life Sciences & Medical seals. Optimised working friction and wear life are demands on seals. The critical feature’s function & tolerance control are also pressures on the seal, coupled with management of gas, liquids, or solid media at accurate rates.
Biotech and pharmaceutical processing
There's continued development of complex and expensive drugs and research control media. Therefore, demand for high performance interactive components within the biotechnology process industry is crucial. Typical applications include seals for analytical equipment, pumps, valves & actuators, monitoring & control equipment. In addition to storage equipment & transportation vessels. We support engineers on recommending Ultra High Purity (UHP) materials for application working extremes correspondingly with sensitive chemical media, and seal design recommendations for dead space and entrapment elimination within these applications.
Ultra High Purity (UHP) materials
Silicone based rubbers are a common choice of elastomer materials for seals used within medical devices. This is because of their biocompatibility features and resistance to bacterial growth. Commonly they’re platinum cured for injection moulded liquid silicone rubbers (LSR’s) and platinum and peroxide cured for compression moulded heat cured silicones (HCR’s). There’s a diverse range of silicone rubbers currently available in varying shore hardness’s that are already approved, making them a go to choice if the specification allows. An application could need a seal material to have better mechanical properties or more temperature versatility or media compatibility. Therefore EPDM and FKM rubbers are also a good choice. Many of our materials are fully compliant and therefore have the required industry approvals, read more HERE
Cleanroom Manufacturing
Life Science and Medical sealing products are produced in a cleanroom environment. Especially this is essential for manufacturing and packaging of products. Equally, external particulates such as dust, dirt, airborne microbes, and aerosol particles should not come into contact or contaminate the surface/the area. A cleanroom is created by removing air, circulating through a filtering system and distributing (the filtered) back into the cleanroom. This is achieved at varying levels of cleanliness depending on what is specified for each individual manufacturing environment, or the finished product requirements. Different cleanliness levels are classified by the concentration of airborne particles within a measured space. We provide a complete cleanroom production process. This includes material blank production through to inspection and packaging using controlled materials within state-of-the-art cleanrooms. Read more about our Life Sciences & Medical industry expertise HERE
Seals for Renewable Energy ApplicationsRenewable energy is derived from our planet's natural resources such as sunlight, wind, rain, tides, waves, biomass and thermal energy stored in the earth’s crust. With increasing fossil fuel prices, and the very real threat of global warming and climate change to our planet; the development of renewable energy production sources is more important than ever. In this article, we take a deeper look into seals for renewable energy applications and the different types of power the natural world provides.
Geothermal energy and Hydro power
Geothermal energy is generated from heat from the sub-surface of the earth. Heat is produced by the decay of elements known as radioactive isotopes. This is a constant process in the earth’s core, and as a result temperatures reach in excess of 5,000˚C. Wells of up to a mile deep or more are drilled into underground reservoirs to tap into the geothermal resources. Steam from these reservoirs is harnessed and used to rotate turbines that activate a generator, consequently producing electricity. There are different designs of geothermal power plants. A dry stream plant extracts steam directly from the ground and into a turbine, driving a generator to produce electricity. The most common type are flash plants; where high pressure hot water is pumped to the surface and mixed with cooler, lower pressure water. This causes the fluid to rapidly vaporise, and the resulting steam drives a turbine. Binary power generation plants will differ from the other systems. The water and steam from the geothermal reservoir never comes in contact with the turbine units. A low-moderately heated geothermal fluid, and a secondary “binary” fluid (with a much lower boiling point than water) pass through a heat exchanger. The heat from the geothermal fluid causes the secondary fluid to flash to vapour. This drives the turbines to power the generator.
Sealing in Geothermal applications
Application conditions to consider are high temperature requirements (up to 320°C) and high pressure requirements (up to 1400 BAR). Steam is present in working turbines and drilling fluids is present downhole (which may sharply change in viscosity during operational stages). The ability to seal drilling bores with large radial gaps is required. To suit application needs, there are various materials available. For example, EPDM with steam, FKM/FFKM for high temp, NBR has high expansion capabilities to seal large radial gaps. Spring energised seals offer exceptional pressure and temperature compatibility and can be offered in NACE approved springs which are corrosion resistant. Packer elements can also assist bore alignment and offer a dense sealing arrangement which prevents cross contamination of fluids.
Hydro Power
All forms of hydropower convert energy from water flow into electricity through the operation of a turbine and generator. There are different methods of hydropower production. Three of the main techniques are Impoundment, Diversion and Pumped Storage. Impoundment uses a dam to store river water in high reservoir. The water in the reservoir is manually released and the kinetic energy of its flow (as a result of gravity) is converted to electricity through a turbine and a generator. A diversion facility channels a portion of a flowing river through a separate channel. The channel will direct the water to a turbine and turn it before it re-enters the river at a lower point. The principle behind a pumped storage facility is that water is pumped to a higher elevation, and then manually released back to the original lower reservoir. The energy that was used to originally pump the water up can be extracted by a turbine and generator for use as electricity. The idea of pumped storage is to store the energy like a battery and use this in times of demand.
Sealing in Hydro Power applications
This technology provides a range of application environments, with varying water conditions and sources. Hydro power stations contain large and heavy duty mechanisms when dictating the flow of water, and high rotational speeds will be achieved on some turbines. Wear and abrasion resistance must be considered with potential for higher load impacts from initial water release and seals in a comprehensive range of elastomer compounds must be considered to ensure compatibility between varying water conditions. Heavy duty application rotary seal designs are suitable (in some cases with metal casings, and PTFE seals are suitable for applications that require abrasion and wear resistance.
Wind Energy
This is the process of converting the kinetic energy of wind into electricity through a wind turbine. Most wind turbines have three blades, and the shape of the blades are similar to the design of an aircraft wing so that the air flow around them provides lift. The force of the lift is much stronger than the wind’s force against the front side of the blade (which is called drag). The combination of lift and drag causes the rotor to spin like a propeller. This, in turn causes rotation of a shaft at the blades’ axis. The shaft is attached to a generator, which produces electricity from the torque of the shaft. A streamlined enclosure called the nacelle houses the key components of the turbine; including the gears, rotors, braking system and generator. There is a pitch control mechanism (comprising of hydraulic cylinders) to ensure that the blades are rotated at an angle to receive the wind and encourage lift most efficiently, and a yaw mechanism (located at the base of the nacelle) which rotates the entire body so that the front of the hub faces the direction of the wind. The shaft is incorporated into a gear system which has another higher speed shaft attached to the end. The high-speed shaft provides torque to a generator which converts this force into electricity. Application conditions for seals will vary depending where in the turbine they are located. General environmental factors include varying weather conditions, vibration, contaminants, corrosion, altitude and diverse (and often fluctuating) temperature ranges (-40˚C to 85 ˚C). Often long-life cycle and ease of installation are considered important (as downtime and maintenance are extremely costly). Areas of application are broken down below.
Gearboxes
There are a range of rotational shaft speeds to consider here. Typical high-speed shafts can reach approximately 2,000 RPM so require high wear resistant seals and shaft misalignment often needs to be considered. In low speed shaft applications, contamination from outside elements must be prevented. Rotary V-Seals reduce contact pressure as RPM increases (due to centrifugal force) which allows operation at a variety of speeds and reduces the chance of heat friction/friction loss. They also offer flexible lip arrangement to compensate for shaft misalignment. Oils and grease are used to lubricate systems so multiple compounds are available for compatibility.
Braking Systems
A wide range of pressure requirements are seen; low working pressure until brakes are applied, and then high and uni-directional pressures activated. Material compatibility is considered, therefore a range of brake fluids and oils are used. O-ring energised Polypak® seals, step seals and slipper seals will seal at a flexible tolerance range and offer sealing capability at low and higher pressures. PTFE seals offer a very consistent and strong chemical resistance. Scraper seals will contain fluids in brake system compartments and prevent components running dry.
Pitch & Yaw Systems
These present both static and dynamic sealing applications, but inconsistent dynamic operation (as it depends upon wind conditions). Both low and high pressure will be seen (for example, accumulators within pitching system present up to 250 BAR). Shaft offset/misalignment must be considered in heavy duty yaw systems. Hydraulic fluids and diverse lubricants will require material compatibility choices. O-ring energised PTFE step seals will seal at a flexible tolerance range and offer sealing capability at low pressures. Sealing assemblies comprising of other products can be designed to be used in conjunction to seal against high pressures. For example, products like back up rings, wear rings and slipper seals. Polypak® seals also offer sealing when high pressure is applied and also when under ambient conditions. O-ring energisers and wear rings help to contain shaft run out.
Seals for Renewable Energy Applications
In summary, seals are a vital part of the critical function of components in renewable energy power generation. They are required to provide long term functionality and provide durability in harsh environmental conditions. Our range of engineered sealing materials are designed to withstand critical sealing characteristics in these applications, including wear resistance, high pressure and high temperature conditions. Hydrogen and renewable energy is one of our key industries. Read more HERE
Seals for Semiconductor ApplicationsSemiconductor and electronics manufacturers are facing greater demands for more complex and powerful devices to fulfil applications across all industry segments. High performance seals and ultra high purity elastomer materials are crucial for these critical applications.
Characteristics of Semiconductor sealing
The technology push for more complex devices requires semiconductor companies to research and design new methods of processing within their manufacturing cells. Consequently, there’s an increase in challenging technical conditions. These include complex chemistry, increased temperatures and stringent cleanliness within manufacturing process and the surrounding tools. The need for high performance seals for semiconductor applications is greater than ever. Component and material suppliers are challenged with these complexities. They must adhere to the same rules, ensuring all the criteria for these new processes are met. Including the combined effects of the outlined above conditions. Our world demands modern performance materials for the semiconductor industry. It is therefore apparent materials previously formulated for older generation tools may not be technically capable in new and future applications. Therefore, it’s paramount to investigate and formulate new performance materials that meet each specific application.
Wet Cleaning and ECD
Wet cleaning is a method used in semiconductor manufacturing to remove any contaminants from each layer of the wafer surface, usually by using chemicals and pure water. ECD is a method of laying down the bulk of the copper wiring within a semiconductor device. Compounds for wet cleaning are engineered for static and dynamic applications with minimal metallic ion contamination.
Thermal applications
Compounds for these applications are required to have excellent thermal stability and maintain integrity at elevated temperatures. These are often found in processes such as Oxidation, Diffusion, Annealing, and RTP. These processes are extremely challenging for seal materials. High thermal load at 300°C with temperature cycling can encourage compression set. Additionally, they must be manufactured to limit out-gassing at high temperature to prevent contamination within the process area and offer superior physical properties.
Thin Film and Dry Etch
Thin film deposition is the process of creating and depositing thin film coatings onto a substrate material. These coatings can be made of many different materials, from metals to oxides to compounds. Dry etch is a process for material removal. Thin Film applications such as HDPCVD, PECVD, SACVD, PVD and ALD, along with Dry Etch and Ashing processes present harsh plasma and gas environments, often at elevated temperatures. Whereas traditional seals might deteriorate and fail in these conditions, our next-generation compounds have excellent chemical and thermal resistance. Consequently, they are virtually impervious to extreme fabrication processes, therefore excellent for semiconductor seals. Plasma processes are a very hostile and aggressive environment for seal materials. The corrosive chemistry at temperatures up to 250°C means that compounds must be chemically and thermal stable across the operating range and must include low-outgassing and low particle count features. These applications are varied; from window and door seals, chamber lid seals, valve seals, exhaust flange seals- each requires application knowledge to ensure all technical parameters are met before materials are recommended.
Ultra High Purity (UHP) materials
Perfluoroelastomer materials
FFKM’s contain fully fluorinated polymer chains. Subsequently, offer the ultimate performance from an elastomer for applications where the seals are exposed to high temperatures and aggressive chemicals for plasma, wet and dry, semiconductor process applications. There is an extensive range of FFKM materials available; the challenge is choosing the correct material grade for an individual application as one perfluoroelastomer will not cover the broad spectrum of requirements across all semiconductor process conditions. For example, some materials are better than others at high temperatures, some demonstrate better chemical resistance and some are poor at thermal expansion. Several compounds within our range of PERFREZ® perfluoroelastomer materials offer the best performance characteristics based on high thermal values, excellent low out-gassing and low particle count. We also offer a hybrid material which is an excellent “all-rounder” as it’s chemical formulation falls between FKM and FFKM. This means it performs consistently under slightly less demanding application conditions and with the added benefit of lower cost of purchase versus ultra-high grade FFKM’s. Other compounds within our range are very specific to semiconductor process applications such as CVD, PVD, Plasma Etch (oxide & metal), fluorine and oxygen compatibility with a high temperature threshold material for sub-fab NW /ISO exhaust line environments. As new challenging processes emerge within the semiconductor industry, further progress in high temperature materials above 300° C will be developed; we expect to add a new generation material for plasma applications to our portfolio of materials by the end of 2022.
Cleanroom Manufacturing
When producing seals for semiconductor applications, cleanroom manufacturing is essential. Semiconductor cleanrooms must be designed to control static, out-gassing, and any contamination from external particulates. For example dust, dirt, airborne microbes, and aerosol particles. Just a single particle of dust or debris on a wafer or component is enough to cause a catastrophic defect (that will ultimately lead to failure of a device). It is created and maintained by removing the air, circulating it through a filtering system and distributing (the clean and filtered) air back into the cleanroom environment. This can be achieved at varying levels of cleanliness, depending on specifications for the individual manufacturing environment or the finished product requirements. Different cleanliness levels are classified by the concentration of airborne particles within a measured space. Additional factors to consider are the manufacturing environment for the semiconductor itself. Furthermore, it’s important to ensure any auxiliary products (such as seals) brought into the environment also maintain the same levels of cleanliness. We provide a complete cleanroom production process; from material blank production through to inspection and packaging using controlled materials within state-of-the-art cleanrooms. Our clean room manufacturing facilities are Class 7 (10,000) manufacturing and Class 5 (100) inspection, cleaning, & packaging. Read more about our expertise in the semiconductor industry and how we can help you with your seals for semiconductor applications HERE
3D printing for seals3D printing has developed significantly and now performs a crucial role in many applications. 3D printed products vary from fully functional to purely aesthetic applications; with the most common application being for manufacturing. Here we discuss how our engineers use 3D printing to demonstrate a seal concept.
What is 3D printing?
3D printing is typically the more common name used for additive manufacturing. This process involves the construction of a three dimensional shape that is designed and generated from a computer aided design program (or CAD). The most typical process used for 3D printing is FFF (Fused Filament Fabrication) or FDM (Fused Deposition Modelling). The FDM process uses a continuous filament of a thermoplastic material that is then deposited onto the 3D print bed, creating layer by layer and gradually building up the structure of the 3D model. This is the process we commonly use to create our design and development range of 3D printed models and seal prototypes.
What material is suitable for 3D printing?
The materials used for 3D printing must of course be compatible with the process – these include a range of thermoplastic grades. Typical suitable material grades include; Polylactic acid (PLA), Acrylonitrile Butadiene Styrene (ABS), Thermoplastic Polyurethane (TPU), Nylon and Polypropylene (PP). The most common grade we use for 3D printing is PLA – for its great strength and stability. We’ve also adapted our design process to use more TPU based material grades, as it loosely demonstrates the same properties as elastomer grades and is better for using in prototype programmes where mechanical fit in groove is tested.
Why use 3D printing for seals?
3D printing can be used for a variety of designs and seal types; from O-rings, gaskets and lip seals – to grommets, multi shot mouldings and large seal assemblies. There are many benefits of using 3D printing during the initial design stages of a project. The rapid turnaround means that a simple seal design can be produced in around 15 minutes, and even more complicated parts can be manufactured in the same day. We can even print the application housings and it’s the perfect way to demonstrate to an engineer what they can expect from a seal part in terms of shape and fit for hardware without the lead time and cost of cutting a prototype tool for moulded parts. One example of this is by quick turnaround of gasket designs typically to suit automotive applications or similar critical markets. Our engineers can design the concept and then 3D print a rapid prototype of a gasket to suit a 3D printed gauge groove. This further demonstrates to the customer that the seal has been fit checked for installation and builds further confidence in the design recommendation. Our engineers combine the 3D print with FEA simulation reports to offer a fully engineered sealing solution. Learn more about our design and simulation service HERE
O-rings with special coatingsAll seals require some form of installation into application hardware and often this may seem to be a simple push in place function. However, without consideration of certain conditions this can potentially create sealing problems further into the life cycle of the seal. Once installation is achieved a seal can often sit in the housing hardware for many months - which potentially allows it to stick to the housing material and cause further issues. This is where O-rings with special coatings can make a difference.
Why use special coatings for seals?
The main function of coatings is to improve installation into the hardware and to lower friction within an application; but there are many other benefits too. They often mean that lower assembly forces are required and by not using grease lubricants seal parts don’t stick together in packaging for transit. Special coatings for O-rings can be manufactured in different colours. This is so seals and O-rings for specific applications can be easily identified. This is without the need to reformulate the elastomer compound with colour additives. All of these reasons make them easier to handle for users during installation.
What types of coatings are there?
There are a variety of coatings and lubricants available for the surface area of seals. They’re mainly divided into two common categories; wet coating/lubrication or dry micro film coating. Historically, coating technology was limited to just using wet type coatings. For example these may include silicone oils and greases and mineral oil based greases. The coating process would involve simply dipping the seals in the oil or grease during manufacture, or during installation on site. This is often a messy process, and although a relatively low-cost method, wet coating is less common. This is because more applications demand higher levels of cleanliness and control of products. Low contamination has become a key factor. Alongside the typical wet coatings traditionally used, there is an extensive range of what is often referred to as dry coatings. Common offerings are silicone dry coating, PTFE coating, PFPE coating, special polymer coating and MoS2 dry powder coating. These are applied during the manufacturing process and bagged in a clean and efficient process, delivered and ready to be installed into application straight from the bag.
Focus on dry coatings
Dry coatings are fast becoming the coating of choice for many customers, with PTFE dry coating being one of the most popular. Commonly applied to O-rings, the process involves the PTFE polymer being spray applied to the O-ring elastomer surface area. Therefore creating a microscopic thin film layer. At molecular level the PTFE then creates a covalent like bond to the surface ensure a high quality finish. The low friction properties of PTFE gives the advantage of low assembly forces. For example an O-ring assembled to a piston can be installed easier into the bore hardware housing mating part. Consequently, this significantly reduces the chance of installation damage (like pinching of the O-ring elastomer material). PTFE coatings can also be used as a short term dynamic improvement to a sealing solution, as many seals suffer from the phenomenon called stick slip. This can occur where a seal has remained in the application hardware bore for a medium to long period of time. It then starts to adhere between the surface of the elastomer and the mating metal material, causing sticking. When a PTFE coating is applied between the elastomer and the metal hardware it creates a low friction barrier. This provides a significant advantage over uncoated parts. This is because the PTFE coating generates a low friction layer. This greatly reduces breakout friction and resolves the stick slip issue therefore greatly improving the performance of the application.
Coating colours
Because the PTFE is a thin polymer layer, coatings can be manufactured in a range of colours by adding pigment to the recipe. Typical colours include, green, blue, red, yellow and orange. By adding these colours the customer benefits from easy identification and production line inspection. Furthermore allowing seals to be easily identified even once installed. Find out more about our range of O-rings with special coatings and the different materials O-rings are available in HERE
E1244-70 seals in Life Sciences & Medical applicationsPacked with multiple benefits, and recommended for pharmaceutical manufacturing, biopharmaceutical processing and disposable medical devices, E1244-70 is an internally lubricated compound, eliminating the need for an external lubricant.
What is E1244-70?
E1244-70 is a 70 durometer internally lubricated, black EPDM (Ethylene Propylene Diene Monomer Rubber) material. E1244-70 possesses an internal lubricant, which reduces installation force and dynamic friction. Additionally, E1244-70 is compatible with all water-soluble chemistries and has excellent resistance to repeated conditions. For example steam, gamma, ozone and ethylene oxide sterilization. Here we take a closer look at the use of E1244-70 seals in Life Sciences & Medical applications. Adding external lubricants can be problematic; the risk of leaking into flow paths and migrating into areas where they are not needed. Additionally, even ‘clean’ lubricants like USP silicone, which can trap dirt and dust, can compromise patient health. Removing the need for an external lubricant by using E1244-70 is clean and safe with no risk of leakage.
Benefits, application and use
E1244-70 has a temperature range of -54°C to 121°C (-65 to 250°F). Consequently, E1244-70 has a low compression set, and is suitable for both dynamic and static seal applications. Because this material does not need an additional lubricant, it prevents issues associated with non-lubricated seals. For example, mismanagement by not using a lubricant when needed, can lead to friction and heat build-up, resulting in erosion and potential leakage and failure of the application. Fully compliant with USP Class VI biocompatibility and USP cytotoxicity standards for life sciences applications. The internal lubricant derives from the fatty acid family, significantly reducing patient reactions. This means it is safe for medical devices and pharmaceutical applications. In summary, it is suitable for: Dynamic applications & difficult installations
• Surgical instruments
• Pharmaceutical manufacturing
• Biopharmaceutical processing
• Disposable medical devices
• Repeated device sterilization Our Life Sciences & Medical expertise
We have clean room manufacturing facilities which are Class 7 (10,000) manufacturing and Class 5 (100) inspection, cleaning, and packaging. Our application engineers utilise the latest in 2D/3D CAD and FEA simulation software to design and replicate seal performance before finalising each individual seal design, incorporating significant feature and critical function elements for integration with customer mating parts. We offer material development and testing, and a component endurance testing service. Learn more about how we support our customers in the Life Science and Medical Industries HERE
Seals for Hydrogen ApplicationsHydrogen is the most common element in our universe, and is becoming an increasingly vital part in decarbonisation and a global sustainable energy future for our planet.
How is hydrogen produced?
Hydrogen is a clean energy solution to parts of the economy that are difficult to decarbonise. These include industrial processes, domestic and industrial heating, and hard-to-electrify transport. For example heavy-duty vehicles, ships and aircraft (where battery solutions are much less practical than they are for passenger cars). The majority of natural hydrogen is not easily obtainable and is locked away as either hydrocarbons (in fossil fuels) or water. Here we detail how seals are used for hydrogen applications. Extracting hydrogen from either of these sources takes energy (and a lot of it!) but hydrogen becomes emission-free at the point of use. Today, 96% of the world’s hydrogen is produced using grey and brown processes, consequently, in reality it’s not very environmentally friendly at all. It is widely accepted that we need to switch to and expand green hydrogen production. However, the electricity sources for green hydrogen (solar, wind, etc) are not always located where the hydrogen needs to be used. Consequently, cannot be turned on and off as energy demand fluctuates.
How is hydrogen obtained?
Hydrogen can be obtained in a variety of different ways, and each of these methods is generally categorised by a different colour. Grey hydrogen is produced by reforming natural gas (methane). Brown hydrogen is produced by converting carbon rich materials (such as coal) into hydrogen and carbon dioxide. These are common processed, but both result in substantial carbon emissions. Turquoise hydrogen is produced by the pyrolysis of methane at temperatures over 1000°C. Solid carbon is a by-product which can then be used or buried without emitting greenhouse gases or causing groundwater pollution. Blue hydrogen is generated by the steam methane reforming of natural gas. This generates large amounts of CO2 which must then be captured and safely stored. Pink hydrogen is created where large amounts of electricity is used to chemically split water into hydrogen and oxygen. Manufactured from a nuclear power plant, it’s free from ongoing emissions (other than those emissions produced in building the nuclear power station). The oxygen can be used by industry or vented to the atmosphere, with no negative effects to the environment. Green hydrogen is also produced by electrolysis of water. However, the electricity required is taken purely from renewable sources such as solar, wind, tidal and geothermal processes. This is widely regarded as the ONLY totally clean hydrogen extraction method. Today, 96% of the world’s hydrogen is produced using grey and brown processes. This means in reality it’s not very environmentally friendly at all. It is widely accepted that we need to switch to, and expand green hydrogen production. However, the electricity sources for green hydrogen (solar, wind, etc) are not always located where the hydrogen needs to be used. Consequently, cannot be turned on and off as energy demand fluctuates.
Engineered seals for hydrogen applications
Sealing hydrogen presents challenges and we need to consider the following parameters when designing a sealing solution. Gas permeability of the sealing materials with pressures of 700 bar or more.
Tightness of the static or dynamic sealing surfaces – including surface finish requirements for the mating components. Hydrogen can be within a carrier. Therefore the chemical compatibility requirements of the carrier medium (e.g. ammonia or liquid organic hydrogen carriers) need to match the sealing materials specified. EPDM elastomer based solutions are often the most cost effective for seal applications in hydrogen with no particularly high demands in any one area. For permeation resistance, we offer chlorobutyl elastomer or polyurethane seals. In high pressure applications, alternatives are available. For example, elastomers or polyurethanes with high extrusion resistance and resistance to rapid gas decompression, or PTFE which is not affected by RGD. In electrolysers and fuel cells, the purity and cleanliness requirements can be met with materials and treatments we frequently use within the semiconductor market. In applications below -60°C, elastomers become hard and brittle, but PTFE, PCTFE and metal sealing solutions can be used down to cryogenic temperatures. For high temperature applications, some FKM or even FFKM elastomers can be used up to 220°C or even 300°C. However, the normal preference here would be PTFE sealing solutions. Metal seals are capable of even higher temperatures up to around 870°C. Metal seals can also have soft coatings such as tin or indium to achieve gas tight sealing, or gold or silver to reduce the risk of hydrogen embrittlement.
The evolving hydrogen industry
The hydrogen industry is technically vast and challenging for sealing applications. Extremes of temperature, alongside demanding pressure and chemical resistance requirements are challenges. Additionally, stringent leakage limits and associated safety requirements. Applications typically demand long service life and in certain cases require parts with high levels of technical cleanliness and purity. There are requirements for elastomer, polyurethane, PTFE and metal sealing solutions. It is important full consideration of the application to select the most appropriate seal design and materials. Learn more about how we serve customers in the Hydrogen & Renewable Energy Industry HERE
Tools
O-Ring Calculator
This interactive calculator assists engineers with selection of O-ring and hardware dimensions, and to form the basis of an O-ring installation.
Chemical Compatibility Checker
This interactive guide will help you choose a seal material based on existing compatibility test results of known chemicals and elastomers.
Interactive Engineering Calculators
Click here for volume, mass and compression set values for O-rings and rotary seal and hydraulic cylinder calculations.
Unit Converter
Our interactive conversion tools allow engineers to switch between units of measurement when preparing engineering calculations.
Engineering Tables
Our reference tables provide cross reference information for surface finish, metal hardness and polymer hardness measurement units.
Articles
Precision Sealing for Naval Radar Slip RingPrecision Sealing for Naval Radar Slip Ring
The application
Our customer is a globally recognised leader in the design and manufacture of advanced slip ring systems and contactless rotary joints. Their technology ensures the reliable transmission of power, data, and media across a wide range of rotating interfaces. Read more about how our engineers developed a custom spring-energised seal for this application. For this project, the application was as demanding as they come: a naval radar system operating in some of the harshest conditions on the planet. Mounted on a naval vessel, the slip ring assembly needed to operate continuously and flawlessly, protecting the electrical components whilst exposed to the elements (seawater, rain and wide temperature fluctuations). The challenges
As well as these demanding conditions, the application itself had several challenges. A compact seal envelope meant design and installation had to be carefully considered. The seal needed to be durable as it was expected to withstand over 6 million cycles across a 10-year service life. The seal required minimal breakout friction to avoid wear and conserve energy consumption. This application required a rotary seal with low temperature capability and excellent resistance to oil-based fuels. A design was required to replace the existing seal in the available housing between the rotating metal faces. Therefore a standard spring energised rotary seal would not work in the application; a bespoke design was required.
Our sealing solution Our engineers developed a custom spring-energised seal, tailored precisely to the application’s needs. We adapted the Parker Praedifa NLO profile and optimised it with a low-load spring for reduced friction, and a high-performance material formulation offering exceptional wear resistance. An additional design feature were heel slots allowing for dowel pin integration within the hardware to provide enhanced application stability.
Results
The final design delivered excellent sealing performance, passed all endurance tests, and met the full 10-year lifecycle requirement. It also maintained low friction throughout, ensuring energy efficiency and minimal wear - exactly what’s needed for a radar system where reliability is non-negotiable. Learn more about our rotary seals HERE.
Using Finite Element Analysis (FEA) in seal designUsing Finite Element Analysis (FEA) in seal design Finite Element Analysis (FEA) is a computerised modelling method for predicting how an object reacts to forces, whether directly applied or generated by pressure, temperature effects or vibration. FEA provides data to help predict how a product will function under those applied conditions. Additionally, it identifies areas where the design can be optimised and improved, without having to test multiple prototypes. Our specialist software uses mathematical models to understand and quantify the effects of real-world conditions on a part or assembly. It can be used to identify potential causes where sub-optimal sealing performance has been witnessed and can also be used to guide the design of surrounding parts. Importantly for products such as diaphragms and boots where contact with adjacent parts may need to be avoided. The software also allows force data to be extracted . For example, compressive forces for static seals and friction forces for dynamic seals can be accurately predicted to help our customers in the final design of their products.
Why do we use Finite Element Analysis (FEA)?
Our engineers encounter many sealing applications that are critical and have many complicating influences. Envelope size, housing limitations, shaft speeds, pressure/temperature ratings and chemical media are all application parameters that our engineers must consider when designing a seal. In isolation, the impact of these application parameters is reasonably straightforward to predict when designing a sealing solution. However, when you compound a number of these factors (whilst often pushing some of them to their upper limit when sealing) it is crucial to predict what will happen in real application conditions. Using FEA as an iterative tool, our engineers can confidently design and then manufacture robust, reliable and cost-effective engineered sealing solutions for our customers. Starting with a 2D or 3D model of the initial design concept, produced within our advanced CAD system, we then apply the boundary conditions and constraints supplied by the customer, including pressure, force, temperatures, and any applied displacements. A suitable finite element mesh is overlaid onto the seal design, ensuring that areas of most interest have the necessary mesh size to ensure accurate results are returned for these regions whilst utilising larger mesh sizes in areas with less relevance or lower levels of displacement to minimise the computing time required to solve the model. Material properties are then assigned to the seal and hardware components. Most sealing materials are non-linear, whereby the amount they deflect under an increase in force varies depending on how large that force is, unlike the straight-line relationship for most metals and rigid plastics, at least over the displacement range relevant to sealing applications. This complicates the material model, and extends the processing time, but we use in-house tensile test facilities to accurately produce the stress-strain material models for our compounds to ensure the analysis is as representative of real-world performance as possible. What happens with the FEA data?
The analysis itself can take minutes or even hours of computing time, depending on the complexity of the part and the range of operating conditions being modelled; behind the scenes in the software, many hundreds of thousands of differential equations are being solved. The results are then analysed by our experienced seal designers to identify areas where the design can be optimised to match the specific requirements of the application; such requirements may be for sealing at very low temperatures, a need to minimise friction levels with a dynamic seal, withstand very large pressures without extruding, or whatever sealing system properties are most important to the customer and the application. Results for the finalised proposal can be presented to the customer as force/temperature/stress/time plots, numerical data or animations showing how a seal behaves throughout the analysis, as appropriate to their needs, and can be used as validation data in their system design process. Project 1 case study
Faced with very tight packaging constraints, a customer requested a diaphragm component from us for a valve application. Using FEA, we were able to optimise the design not only of the elastomer diaphragm itself, but also propose modifications to the customers hardware components that interfaced with it in order to increase the available space for the diaphragm, keeping material stress levels low to remove any possibility of fatigue failure of the diaphragm over the life of the valve. Project 2 case study
A customer approached us to design a PTFE rotary lip seal that had to meet tight maximum torque requirements as their system was driven by a size-limited low power motor with modest levels of torque available. At the same time, high seal tightness was required as leakage of the media would have caused significant problems. By using an iterative FEA process, we produced a seal design that optimised the sealing lip geometries to provide the lowest levels of rotational friction drag whilst ensuring sufficient contact force to maintain a tight seal, and went on to provide seals that successfully passed customer validation testing.
With the increased confidence in a proposed sealing solution that FEA provides, our customers can plan lower levels of physical testing and remove contingency for re-design steps, reducing their project lead times and costs, facilitating a faster and more cost-effective time to market for their new products.
Surface finish requirements for static and dynamic sealingWhat is hardware surface finish? Any surface can look (and even feel) perfectly smooth. However, look closely enough with high magnification and all surfaces will have a degree of fluctuation. The topography will look similar to a mountain range or the surface of the moon!The roughness of a surface is often linked to the way a surface is produced or machined, and any subsequent processes such as coating or platings.Just a couple of decades ago, the standard approach to assessing surface finish was to use comparison plates. These are small specimen sections of material produced by turning, grinding or milling. A fingernail comparison test with the finished part would then be used to determine which came closest.Historically, seal catalogues typically recommended a surface finish using just the Ra (metric) or CLA (Centre Line Average, inches) parameter. Little regard was given to what the seal was being expected to do.Ra simply, is the mean roughness. The average calculated from the peak heights and valley depths. A surface that is mostly spiked can have the same Ra value as one that is mostly troughed. However, each could have a very different impact on seal performance. Today, surface finish measuring equipment is more sophisticated and capable of tracing a surface finish using a diamond tipped stylus, or non-contact 3D laser scanning.These devices are now reasonably affordable and provide a sophisticated level of results from essentially a portable machine. These instruments can now analyse the surface roughness profile, trace and calculate a large range of parameters that define that profile. This includes Ra, Rt, Rz, Rmax, Rmr (bearing ratio) and even skewness parameters. What these are, and how they should be measured, have generally been well captured in standards such as ASME B46.1, ISO 4287, ISO 4288 and the upcoming ISO 21920. Why is surface finish important for sealing systems? To ensure seal effectiveness, a common assumption for specifying a hardware surface finish is the smoother the finish the better. However, this is not always the case. If the seal application is static and is sealing a low molecular size gas such as helium; then a very smooth surface would be preferable.This is often referred to as a “closed” surface (with no peaks and very few, shallow valleys). The seal mates tightly against the hardware, ensuring the leak path for the gas is reduced as much as possible. Even in this scenario, the required surface roughness can be influenced by other factors. These include the hardness (or rather, softness) of the seal material and the pressure being applied, both by the initial seal squeeze and the applied gas pressure.It’s important the interface between the seal and the hardware is well lubricated. This is critical for some dynamic applications for either seal friction (and hence noise, vibration and heat) or wear life.This is partly achieved by ensuring that the surface is more “open”, with small valleys or troughs to trap the lubricant -but no sharp peaks that would abrade the seal material. In these application cases, if the dynamic hardware surface (rod, shaft or piston bore) is too smooth, then the seal can wear prematurely. This can cause juddering, squeal and excessive heat build-up. Tribological performance consideration As a result, for dynamic applications it is important to consider all the factors affecting the tribological performance. These include the seal (design, material), the dynamic hardware (hardness, material type) and the fluid (viscosity, lubricity, contamination). The hardness of the dynamic hardware can also be a significant factor. Hardened or chromed steels at around the 50 Rockwell C level or less can often be polished by the seal itself. This means that even if the initial roughness is sub-optimal, good sealing performance is achieved after a brief period of bedding in.With the use of high hardness coatings such as HVOF and DLCs, the much softer seal material is very likely to be abraded by the hardware. In these cases, it’s essential to ensure that the optimal surface finish is met. This often requires a finer finish prior to the coating process (as the coatings can be rougher than the substrate material and post-process polishing is very difficult with such hard coatings). Any other factors to consider? Yes! Another thing to consider is the direction (or lay) of a particular surface finish. Machining marks, scratches, dents or other hardware damage that cut across a sealing contact face are likely to result in leakage. This is compared to (for example) concentric machining marks in the base of an axial face-seal O-ring groove. It is important to consider specifying a lay direction when applying surface finish requirements to the hardware design specifications and drawings. What hardware surface finish should you specify? Despite complexities involved in hardware surface topography, the sealing industry has developed a comprehensive set of recommendations. These can vary a little between different manufacturers and suppliers. Given the specificity of the seal design and material, they’re best found within the specific literature for the products considered for the application.This is a good starting point, but for each individual application it's worth considering whether these specifications should be addressed. For example, specifications could be tightened, or perhaps even loosened to ensure that performance targets can be met. This would reduce the need to over-specify the surface finish - because this can add unnecessary processing cost to a part.The practicalities involved in accessing the surface to measure also need consideration. It’s notoriously difficult to check the sidewalls of an O-ring groove, especially in a rod/ID sealing configuration. Cylinder bores are often less tightly defined due to stylus/probe access issues compared to rods and shafts.Importantly, whoever is required to produce and check a particular surface finish has both the equipment and understanding to do so. This is very important if using relatively modern and less well known parameters such as Rmr (or Tp, bearing ratio).Further detail can also be found in the ISO and ASME standards regarding measuring settings. For example, filtering/cut-off values, stylus tip radius, measuring, evaluation and tracing lengths. When validating a supplier’s measurements, it’s important these machine settings are identical. Failure to do so will result in differing surface finish values obtained on the same part. Those standards are not specific to sealing applications. Generally, we’d recommend a cut-off filter (λc) of 0.8, unless measuring very fine (< 0.1 µm Ra) surface finishes where 0.25 would be more suitable, with a 2 micron stylus tip in all cases.Specifying the right surface finish for the hardware components that contact a seal can be complex and daunting. Ensuring an optimum finish and right-first-time seal performance, will be achieved. This is with core understanding, and consideration of relevant parameters for the given application.
Are all elastomers the same?Are all elastomers the same? Material hardness This is often the least considered property when selecting a material. In sealing applications, elastomer material hardness can impact assembly loads, seal friction and extrusion resistance. Softer rubber can better accommodate surface imperfections (especially when sealing low pressure gas). This means softer seal compounds can be used effectively against rough hardware surface finishes. Harder compounds will have greater wear resistance in dynamic applications.Most of the common base elastomers are produced in 60 to 80 Shore hardness range. These tend to be produced in increments of 5 hardness points. It's important to remember the hardness tolerance of a material is typically +/-5 points, therefore 70 and 80 hard nominal materials could both legitimately have a hardness of 75 Shore A.With possible hardness down to 30 Shore A (or even lower), silicone rubber lends itself to applications requiring very soft seals. An example of which is where seal compression forces need to be low to enable easy manual assembly of components. NBR, HNBR and FKM materials can be formulated up to 95 Shore A hardness for highly demanding high pressure and temperature applications; for example applications found in the Oil & Gas industry. Chemical compatibility Unlike PTFE seals (given very few chemicals that will attack and breakdown the material) elastomer seal materials must be carefully selected. This is so the properties are not affected by any fluids or gasses that the seals come into contact with. This includes the main media that the seal is retaining or excluding, additionally any contaminants (such as cleaning fluids or bi-products of reactions between any of these fluids, the seal material or the surrounding hardware).Even a seemingly straightforward application often involves a long list of chemicals and compatibility must be checked with the elastomer. Most seal suppliers publish compatibility tables or like us, have interactive tools to help check this. Even then, it’s often not the brand name oil that’s listed. For example, often at the more basic chemical level, so some knowledge of what’s actually in the fluid is required. Recent developments in health, safety and environmental requirements have made this a little easier. However, some fluid manufacturers can still be a little reluctant to declare the full list of chemicals in their products.Manufacturers sometimes give guidance on general compatibility with elastomer groups, but this can be a little generic. Additionally, not all grades in a specific group will have the same resistance to a particular fluid. Again, this can be especially relevant to NBRs and HNBRs with a variable ACN content. Sometimes the reactions can be dramatic and swift, with the rubber shrinking or swelling in a matter of hours when exposed to a non-compatible fluid and especially at elevated temperatures where the chemical reaction is accelerated. Reactions in chemicals In other cases, the reaction could be slower, but still causes sealing issues resulting in earlier system failure compared to using more capable elastomers. This is often the case with FFKM seals in applications where the cost of replacement or downtime is very high. The outstanding chemical resistance of these materials gives considerably longer service life compared to lesser grades, and it justifies the higher initial cost of the seal. In other cases, some reactions can be beneficial, for example where a small amount of elastomer seal swell in an oil over time can help to offset wear in dynamic O-ring energized PTFE slipper seals. Temperature range Outwardly, this material property seems straightforward, but elastomer technology is rarely that cooperative. All elastomer compounds will have a low temperature property stated on their datasheet. Either the TR10 (temperature at which a stretched and frozen sample recovers by 10% of its length) or the Tg (the glass transition temperature, at which all flexibility is fully lost).However, applied pressure increases the Tg by approximately 1°C for every 5 MPa. This is significant for even moderately high-pressure applications. Additionally, the flexibility required for successful sealing will vary between applications, making the correct material selection critical. At the other end of the spectrum, elastomers respond poorly when exposed to temperatures above their capability. This results in the material suffering irreversible degradation that reduces seal performance.Whilst guidance is given on maximum temperature capability for any specific elastomer grade, this is often in a benign air environment. Therefore the chemical impact of being exposed to hot fluids in the sealing application should be considered.Material groups tend to have well published temperature ranges. For example, the silicone family is able to reach -100°C (or even lower with special grades), and perfluoroelastomer (FFKM) grades are able to withstand 320°C (or even higher for short durations).Confusingly though, considerable variations can exist even within the same material families; especially with FKM where the more modern grades can now reach down to -50°C, with older technology grades only capable of -15°C. There are many NBR and HNBR grades where the acrylonitrile (ACN) content can be varied so that the low temperature limits can be between -30°C and -60°C, depending on the specific recipe formulation.This is just a short summary of three properties of elastomer materials. It’s clear that selecting the correct grade of material for a specific application is a difficult task, yet one that is absolutely critical to achieving the seal performance and lifetime required.
The importance of engineering tolerancesThe importance of engineering tolerances What tolerances are we concerned with?
We can start with the seal itself, and specifically the seal material, as almost all polymer seal materials contain multiple ingredients. For PTFE and polyurethanes this is typically 2 or 3 different elements. However, for an elastomer material as many as 30 different ingredients can be used in the recipe. Each ingredient is weighed or measured before being added to the mixing machine, with a tolerance on the mass or volume of the solid or liquid ingredient. Digital advances in weighing and dosing equipment have improved tolerance ranges since synthetic rubbers were first commercially produced in the 1930’s. However, it’s important to remember that a small variation in material mix from batch to batch is inevitable. The mixing process (also now digitised to help reduce variation) is controlled by parameters which also have a tolerance. Pressures, temperatures, speeds and times are kept within certain limits and determined by the sophistication of the mixer and its control systems. To produce the finished seal, mould tools for polyurethane and elastomer seals are manufactured using CNC or electrical discharge machining techniques. These hold incredibly tight tolerances on the metal form. However, are will be variations in moulding pressure and temperature, combined with slight variations in material shrinkage rates. This results in tolerances on the finished parts that are significantly wider than the metal tool it was produced from. For machined seals, polymer seal materials tend to have high rates of thermal expansion. Together with their relative softness makes it difficult to maintain the same level of tolerance that can be achieved when machining metal components.
Hardware tolerances
When designing hardware for seal installation, tolerances are perhaps more obvious, and certainly where engineers can focus some attention. Plastic housings (whether injection moulded or machined), together with metal castings or pressings can pose tolerance challenges. Even for relatively straightforward machined metal housings, selecting the correct tolerance to apply is key. For many applications, a stack-up of tolerances is to be considered. This is together with tolerances of the assembly such as concentricity or misalignment (especially for dynamic sealing applications). Other considerations include bearing wear and the resulting increase in misalignment or runout as the equipment approaches the end of its target life.
Why are tolerances important for sealing systems?
A combination of theory and experience over decades, seal designers have developed an ideal set of installation conditions for many applications. From static flange or face sealing, through linear hydraulic cylinder seals and to rotary shaft sealing and more. Some of these applications have adopted standardised recommendations (such as ISO 3601 for O-rings and DIN 3760 for elastomer shaft seals). However, because no two applications are truly identical, many are based on the experience and preferences of the seal designer. Regardless, every application starts from a nominal condition, and the maximum and minimum tolerance conditions should always be considered. This is even in seemingly straightforward applications to ensure the seal is continuing to operate within it’s ideal set of conditions. Sometimes it’s assumed that tolerances only really come into play when looking at very small applications, with so-called “micro O-rings”.
This is not the case - and we can illustrate this with a hypothetical application:
A device containing a 25 mm rod, static, with an FKM O-ring sealing gas, whilst installed for 10 years untouched in the Arctic circle. However, it also needs to seal oil whilst installed in direct sun at the equator for 10 years, but with the rod removed and re-fitted several times a year. The device designer would prefer not to make two different variants. O-ring calculators working to ISO 3601 would recommend a 25.12 mm x 1. 78 mm O-ring fitted in a 27.8mm groove with f7 tolerance on the rod and H9 on the groove. However, in the cold application the worst-case squeeze is looking a little light to ensure long term gas sealing. Whilst in the high temperature location, the compression and groove fill are reaching levels that could accelerate compression set of the material and cause issues when the rod is disturbed and re-fitted. Moving the nominal sizes would help one installation but adversely impact the other. However, by tightening the tolerance on the rod and the groove, the concerns at the extreme conditions can be lessened. Approaching the seal supplier for tighter tolerance O-rings can improve the robustness of the design even further, as could incorporating a custom bonded seal-rod component which would remove one dimension and its tolerance completely. Such a hypothetical application rarely exists of course, but the approach is applicable to a surprisingly large number of applications which appear “standard” at first glance. What hardware tolerances should be specified?
There is not a definitive answer to this question, but more of a recommendation that the tolerances for each component within an application are considered. Both the technical and financial impacts being evaluated. Sometimes applying a tighter tolerance can be achieved without any cost implications. In other cases it might slow the manufacturing process, or potentially require a different and more costly process (for example, grinding a rod in place of turning). Tolerances should be evaluated by the consequences of the complete sealing system not performing as intended at the absolute extremes of potential tolerance conditions. In applications where the impact of non-optimal performance may be less severe, a paper based, or theoretical tolerance evaluation is carried out. This could provide enough confidence the risk and impact of the problem arising is acceptable compared to the costs of preventing the risk further. In some safety critical applications in Life Sciences & Medical, Aerospace or Vehicle Control systems markets, testing of parts at the most extreme sizes may be required. This is to be certain that any combination of components from anywhere within their minimum or maximum range of tolerance sizes would still produce an assembly product which performs successfully in the application.
Elastomer manufacturing moulding processesElastomer manufacturing moulding processes Compression moulding This is the simplest method of converting a piece of rubber into a finished seal product. The rubber compound is first mixed and prepared, and depending on the recipe can require up to 30 different individual ingredients. At this stage the curing (or vulcanization) of the rubber hasn’t yet taken place, therefore, the material has a stiff and non-elastic consistency (a little like thick dough). From this dough we produce a rubber blank (also known as a pre-form) by either cutting, punching or extruding cord. These blanks are normally a little bigger than the finished part (normally based on weight) and are placed into a metal moulding tool. The tool (in its simple form) is in two halves with the final product shape cut into the metal. This is known as the mould cavity.This “sandwich” of the bottom tool/rubber blank/top tool is placed into a hydraulic compression press with heated platens. This transfers the heat into the rubber via the metal tool. The press closes. The rubber is then squeezed into every part of the cavity, and any extra material that extrudes from the mould join becomes become overflow, or flash. Next comes curing of the material. This takes place through a chemical reaction between the ingredients, and is controlled by pressure, temperature and time. These parameters are pre-set according to the recipe of the material and the curing system. At the end of the specified cure time, the press is opened. The tool is then removed and split apart, and the cured (elastic) component is removed. Through a variety of methods, the excess flash is then detached, and the part may undergo a post-cure process. This fully completes the vulcanization reaction. Finally, the rubber seal is inspected, packaged and ready for application. The compression moulding process Compression moulding is sometimes a relatively slow and labour-intensive process. Some tools will have multiple cavities into the hundreds and use presses ranging in size and capacity from 20 tons to over 500 tons. This will increase throughput of seals, but the key limiting factor is the speed of heat transfer from the platens into the rubber via the mould tool. In-press cure times can be measured in minutes, but for large parts sometimes over 10 minutes or more. Removing the parts and loading the next set of rubber blanks can also be time consuming.Compression tools are quick and easy to produce, and changeover times from one component to another can be rapid. As a result, this manufacturing method is ideally suited to parts that are required in low quantities, or as prototypes. The tools are designed to ensure that the split/flash line is not located on a sealing contact surface. Therefore, high-quality parts will be produced.For some very hard rubber compounds that do not flow readily, compression moulding is sometimes the only manufacturing option. Injection moulding This manufacturing process is often used to produce plastic components, but for rubbers, the temperatures are switched. A warmed rubber is injected into a hot tool. This is because the force required to inject uncured rubber is much greater compared to pushing molten plastic into a chilled mould. Otherwise, the equipment and principles remain similar.Uncured rubber feedstock is fed into the screw of the injection machine (normally in the form of long coiled strip). The screw rotates and is forced upwards to generate a precise volume (or shot) of rubber at the front of the screw. Once the tool is closed in the press, the screw is pushed downwards to inject the rubber through the sprues and gates, and into the cavity in the tool. The tool always remains in contact with the heated platens of the press and therefore retains the necessary heat for the curing reaction. The temperature of the shot prior to injection is tightly controlled. This is to allow the rubber to flow easily. Additional to prevent the vulcanisation process to the point where the material is too elastic to properly fill the cavity. Alongside automated de-moulding of the parts (via brushes or robots) this reduces the press open time. The entire moulding cycle can be very fast; potentially under 60 seconds with small cross section parts.Elastomer materials need to be specifically formulated for injection moulding to give them the required flow characteristics. The tooling is also significantly more complex compared to compression or transfer tools, especially with multi-cavity tools and cold runner blocks to reduce the waste in the sprue and runner system. Set-up times somewhat longer. Machinery In terms of machinery, injection presses are also more complex and costly than hydraulic compression presses, but the injection moulding process can be highly automated. This, in conjunction with fast cycle times can result in very attractive manufacturing costs for parts produced in high volumes. As with the transfer process, the flow of the rubber into the cavity can be designed to reduce the risk of air trapping and give consistent material properties in the finished part. Transfer moulding This is a variation on compression moulding. It uses the same hydraulic compression presses, but this tooling is a little more sophisticated (and consequently a little more expensive).Rather than loading the rubber blank direct into the cavity it’s held in a “well”, and the top tool part contains a plunger which squeezes the rubber though feed ports/gates into the cavity below. By using this approach, the cavity is closed before the rubber enters. This reduces the amount of flash left remaining on the part, and allows accurate positioning of metal or plastic inserts for two-part bonded components.The material may need to be specifically formulated to allow it to flow through the feed gates. The result can be a more uniform part using this flow of rubber, compared to a compression moulded part where some of the rubber has not had to flow very far during the tool closure. The part and tool can be designed so that the direction of this flow acts to expel the air from the tool and prevent it becoming trapped by the rubber in the middle of the part (which can sometimes be an issue with compression moulding).Tolerances, accuracy and consistency are improved compared to compression moulded parts but the cycle time, or throughput, is broadly the same.There are other ways to manufacture rubber parts, including extrusion, calendaring and even 3D printing, but from comparing the three most common methods of producing an elastomer seal, we can see that considering how the part is going to be made at the start of the project is key to ensuring the technical and commercial success of the seal in the application.
Polyurethane as a seal materialThe foam in your armchair. The strap on your wristwatch. The wheels on a supermarket shopping trolley and beyond; Polyurethane certainly has a diverse range of uses since its invention almost 85 years ago. Aside from day-to-day products; it is also a highly capable and versatile sealing material - and an option that is often overlooked.
What is Polyurethane?
This material is rubber, plastic, rigid and flexible. Polyurethane covers a group of materials; plastic polymers produced by the combination (or synthesis) of di-isocyanates with polyols and a chain extender. This makes Polyurethane an excellent seal material.
How are Polyurethane materials manufactured?
There is a one and two-step process to manufacturing polyurethane.
One-step process
This is when a compound containing multiple hydroxyl groups (called a polyol), is mixed with highly reactive low molecular weight chemicals (isocyanate), and a chain extender (low molecular weight diols or diamines). Consequently, the result is a random copolymer with a physically cross-linked irregular molecular structure.
Two-step process
In a two-step process, the polyol and isocyanate are mixed first to produce a pre-polymer. This is mixed with the chain extender to produce a block copolymer with more regular molecular structure. Although this often results in improved and more consistent material properties, there is a slightly higher production cost.
Why is Polyurethane a good seal material?
Evidently, when formulated appropriately, Polyurethane does produce an impressive set of material properties that make it an ideal material for sealing products. Consequently, its flexible, with very high abrasion resistance, tensile strength and stiffness. The tensile and tear strengths are typically 3-5 times higher compared to rubber seal materials. Although it lacks the chemical resistance and temperature capability of PTFE, it is compatible with mineral oils. There is more information on polyurethane as a seal material HERE You will learn more about our range of materials HERE
Diaphragms for precise control in critical applicationsIn applications that require precise and rapid pressure responses, our diaphragms offer an engineered sealing solution for high performance valves and actuators. Why use diaphragms? Diaphragms provide excellent sealing results in multiple applications. For example: Valves, actuators, pumps, pressure & flow control, pressure switches/sensors, dispensing, metering, ventilation, and media separation applications. Valves and actuators controlling the flow of liquids or gases frequently utilise diaphragms for fast responses to small pressure changes. The sensitivity to signal pressure changes will give reliable valve positioning (with very low hysteresis, for example). Additionally, successful sealing in large diameter, high pressure and long stroke applications can all be achieved with the right design. Large diameter & long stroke engineered diaphragms We supply diaphragms in a wide selection of materials including elastomers, fabric reinforced and thermoplastics. Additionally, our range of diaphragms are an excellent seal of choice for a variety of hydraulic and pneumatic applications. Are diaphragms suitable for your application? Our experienced team of application engineers will design your seals and use the latest developments for each individual application. Additionally, we provide a complete seal design service from start to finish. As well as optimal sealing performance in an application, we will assist with hardware design to provide the most cost-effective sealing package. We will optimize the tooling in key areas to produce complex geometries. This is achieved by using modelling and specialist FEA technologies to predict the performance of fibre & fabric reinforced materials. Manufactured in a range of materials with industry specific approvals, our diaphragms are used in applications across many different markets. These industries include oil & gas, process control, potable water management, LPG & natural gas, life sciences and food & beverage. Learn more about diaphragms on this link HERE
Rotary seals for heavy duty transportationSupply Plus Ltd designs, manufactures, supplies and distributes safety and fuel delivery equipment, with brands including AS Fire & Safety, Bayley and Collins Youldon. The application Our customer, Supply Plus approached us with a requirement for their 2” Swing joint power spindle. The outlet pipe from the fuel tank on delivery vehicles is fed into the centre of a rotating hose reel. This is located between the tank and cab of the vehicle. This is powered by an electric motor and pumped through at relatively low pressure. The current design experienced issues of leakage from the hose fitting in low temperatures especially at -25°C, and particularly when vehicles are parked overnight. Therefore we recommended a rotary seal for this heavy duty transportation. The challenges This application required a rotary seal with low temperature capability and excellent resistance to oil-based fuels. A design was required to replace the existing seal in the available housing between the rotating metal faces. Therefore a standard spring energised rotary seal would not work in the application; a bespoke design was required. Leakage at night when vehicles are not in use often means the issue worsens because the seal is cold and not energised. Therefore, we designed a rotary seal for heavy duty transportation that would remain energised at low temperatures and low pressure. Our sealing solution Our engineers designed a simple but effective seal, incorporating a large heel in the base of the housing. This energised a lip sealing on a rotating metal face. The volume of rubber in the heel of the seal, combined with the 170° angled base, created sufficient force to maintain a seal at low pressure. We used a low temperature Viton ensuring the seal retained elastomeric properties and applied the sealing force at low energising pressures and very low temperatures. This also provided excellent resistance to fuel oils, diesel and aviation fuel. We tested prototypes at both an in-house test unit and in the field over four winter months. Results showed no issues during dispense of fuel and a complete cessation of leakage. The seal was approved and production orders placed, and the design has been incorporated across additional sizes of hose reels. Learn more about our rotary seals HERE
Special coated O-rings for renewable energy applicationOur customer manufactures wind sensors for a variety of applications in different environments. This seal application was within ultrasonic wind sensors designed for wind turbine control. The Application For optimal performance wind turbines need critical, consistent and reliable data on wind speed and wind direction measurements. Therefore we recommended special coated O-rings for this renewable energy application. The sensors that provide this must be able to operate continuously for many years, sometimes in the harshest of weather. Operating conditions are extremely challenging as the wind turbine sensors (and accompanying electronics) are exposed to fluctuating, extreme environmental changes over the years. Depending on the location of the turbines, temperatures can range from -40°C to +90° C. Additionally, humidity changes from 0-100%, and turbines are subject to rain, hail, snow, ice, lightning, vibration, sand, corrosion and altitude. Our Sealing Solution For this application, the required life cycle of the sensors is10+ years. Therefore, to achieve this, a robust protective housing for the electronics and sensors requires a series of reliable, consistent, high-quality seals. These will perform without compromise in challenging conditions. Each size of sensor requires a set of environmental seals in the separated top and bottom sections. Together with our customer’s intensive testing program, we specified EPDM O-rings (which offered exceptional ozone resistance) with a special coating. The coatings are colour coded for identification purposes according to the size of sensor. Therefore, this creates a fool-proof assembly process with no risk of error by operators. Customer Satisfaction Our range of seals have been cycle tested and approved by our customer. Furthermore, these have been built into nearly half of wind turbine projects globally. Read this link for more on our range of O-rings HERE One of our key industries is Hydrogen and Renewable Energy, learn more about our work HERE
Moulded gaskets for an automotive applicationAn existing customer (an automotive manufacturer) approached our engineers with an application where they were experiencing failures of a seal designed and manufactured by another rubber seal provider.
The application
This moulded gasket is used within a valve housing in an automotive application. The competitor gasket experienced failure at the “T-junction” areas of the seal. Our customer had experienced chronic failures of their existing moulded gasket design at high temperatures and high pressures. The seal is required to perform under pulsating pressure of up to 50 Bar and temperatures of up to 150°C. Our engineers reviewed the existing gasket design and application conditions and recommended an increase in height of 0.40 mm. This was to increase the compression and improve the sealing function. Additional beads were also added to further stabilise the gasket in the groove.
The challenges
Prototype parts were manufactured from a single cavity soft tool and sent to the customer for in-house testing and validation. The prototype gaskets very nearly passed testing but did not quite reach the 50 Bar pressure requirement at 150° C (42 Bar reached). This was still a great improvement on the performance of the customer’s original gasket. Analysis of the customers test data and images of the tested parts, determined there were areas where the gasket was sliding in the groove and then shearing as the pressure pulsed. We resolved this issue by our engineers adding beads to the rear of the T-intersections of the gasket. This provided additional support and further stabilised the gasket at the high-pressure stress points in the groove, and reduced movement within the housing. The number of additional beads added needed to be balanced carefully with calculations on groove fill. Further development captured the cleanliness requirements and altered radii on the beads.
Customer satisfaction
The new design was approved, and the customer moved to production tooling stage and sample parts were produced to PPAP Level 3 for production. More information about our mouldings & gaskets on the link HERE
Special O-rings for an automotive applicationOur customer manufactures high performance oil and vacuum pump solutions, and approached our engineers with a new O-ring application for review.
The application
Our customer required an FKM (Viton™) 60 shore special O-ring. This is to meet Porsche material specification PN707 Class 2 (Oil), Class 5 (Fuel/FAME mix) and Class 12 (Blowby gas). This proved to be a very cost sensitive project with a short lead time. Additionally, we did not have an existing grade in our materials portfolio to meet this specialised O-ring specification.
The challenges
Our engineers reviewed the application and we provided two material options. The first is a lower cost grade of FKM (Viton™) A grade, and would possibly meet the Porsche specification required. The second material, a medium to higher cost FKM (Viton™) B grade that will definitely meet the specification. We supplied a quotation for the two material types. Additionally, the quotation included production tooling, PPAP Level 3 submission, testing for both materials and a pre-production batch of O-rings. The project was urgent and we were able to accommodate PPAP Level 3 grade O-rings for both materials to be manufactured from the same tool. Also, to save time we conducted material testing in tandem with the manufacture and preparation of the the production tool. The choice of compound to be used in the tool would be made on review of the results of material testing. On completion of the material testing, the customer reviewed the results with Porsche. The decision to produce O-rings from the FKM B grade was made.
Customer satisfaction
By this stage of testing, production tooling was complete, allowing manufacture of PPAP 3 samples and the pre-production batch to commence. Pre-production O-rings were supplied to the customer in the promised 12-week lead time together with PPAP Level 3 and PPAP 3 samples. See this link for more on our O-ring range and expertise: HERE
High speed Rotary seals for electric vehiclesThe electric vehicle industry is growing; global manufacturing and registrations of electric vehicles is increasing exponentially each year. Our engineers have extensive experience in designing seals for automotive applications, but we still find new challenges involved in sealing components within hybrid, hydrogen fuel and full battery powered electric vehicles.
The Application
Our customer has 30 years’ experience of providing pioneering technologies globally to the mobility industry. This established organisation is a supplier of powertrain solutions for electric and hybrid vehicles and traditional internal combustion power engines. The team of powertrain development experts approached our engineers for a high speed rotary seal. This is for the gearbox within an electric vehicle. The position of the rotary seal is needed between the wet transmission and dry e-motor, and pressed into a bulkhead housing. The sealing lip runs on the surface of the transmission rotor shaft. It is pressed radially by a tension spring onto the shaft, and requires a dust lip to provide protection against dirt and debris from the environment on the dry motor side. The shaft and housing dimensions, are all fixed and provided by the customer. These include full dimensional, surface finish, pressure, temperature and media specification for our engineers to review and propose a bespoke seal design.
Our sealing solution
The application media was a synthetic oil. This is relatively standard for an automotive application. However, because of the maximum working temperature, FKM (Viton) was the elastomer material to meet the required range. As with many applications within electric vehicle gearboxes, the shaft speed is particularly high at 8500 RPM. Typically with these high speeds, seal design needs to ensure minimal friction to ensure the service life required. Our application engineers designed a bespoke, double lipped spring energised seal. On the dry e-motor side, the rubber lip has been designed to act as a dirt and dust excluder. There is a slight clearance from the shaft to avoid friction which prevents damage to the seal, additionally any unnecessary wear to the rotary system as a whole. In the wet transmission side it is imperative that the oil is kept away from the e-motor with the same minimal friction requirements. Consequently, our engineers designed the seal with an inlaid PTFE lip with 15% graphite fill. It is energised with spring to ensure force to achieve ultimate shaft sealing performance. Read more about our rotary seals HERE
Silicone O-rings for De Soutter EcoPulse™ lavage systemDe Soutter Medical Ltd specialises in the development, production and worldwide distribution of high performance orthopaedic tools for surgical procedures, offering their customers a comprehensive range of technically innovative and high quality products.
The application
De Soutter Medical recently launched their new EcoPulse™ lavage system for use in orthopaedic surgery. The company approached us to manufacture two different sized Silicone O-rings for the ECO Pulse upgraded design. The EcoPulse™ connects onto the front of a reusable De Soutter handpiece, and allows surgeons to lavage the surgical site using saline water. It can simultaneously be connected to a suction device to remove waste from the surgical site. The EcoPulse™ is supplied as a single use sterile packed product. It has a range of nozzles available for specific surgical procedures. The new EcoPulse™ has a pared back functional design to eliminate superfluous plastic. Additionally, instead of using disposable batteries (and the associated single use wiring and motors), it connects onto a reusable power tool that is already being used to perform the surgical procedure. This eliminates a large amount of clinical and WEEE waste (more information HERE). Furthermore, compared to other products in the market, reduces clinical waste by up to 60%.
Our sealing solution
The seal application is located within the disposable pump/irrigation attachments to ensure that no saline water leaked, and there is no loss of suction during use. This is a relatively straightforward application in terms of mechanical sealing. However, due to the nature of the product there are critical demands on the material and during the manufacturing process. Our engineers specified a USP Class VI translucent silicone; suitable for medical devices due to its biocompatibility features and resistance to bacterial growth. The (bespoke and dedicated) moulding tool was coated in titanium nitride. Therefore the use of release agents during the manufacture process of the silicone O-rings is not necessary. This is to mitigate the risk of any cross contamination with the O-rings. Additionally this is important when producing seals used within devices where there is any risk of patient fluids crossover. Cleanroom manufacturing and the silicone O-rings are double bagged packaging in order to avoid any cross contamination. These parts are manufactured and packaged at our ISO13485 approved manufacturing site to achieve these requirements.
Customer satisfaction
We work in conjunction with our valued customer De Soutter Medical. We assist with design support and technical recommendations on the development and manufacture of sealing products for use within their medical devices. For more on our full range of O-rings see this page: HERE Read more about our Life Sciences & Medical expertise: HERE
Gold plated metal seals for Oil & Gas couplingsOur customer designs and manufactures hydraulic distribution products and systems used to control subsea production systems for the offshore energy industry globally.
The application
This seal application is for a range of dual resistant hydraulic couplings, designed to be suitable for make and break under full system pressure. There were three different sizes in the same design of coupling. We recommended a gold plated metal seal for this type of application. Read on to find out more about this project. The customer had been using a back-to-back elastomer O-ring arrangement, but wanted to develop a superior sealing solution in order to achieve a greater number of connect/disconnects per coupling (therefore improving the lifespan). The application itself was high pressure at 15,000 psi. The temperature range wasn’t particularly demanding compared to other Oil & Gas applications. However, because the couplings were for subsea equipment, there could be contact with well fluids and control fluids. As result the seals required NACE approval.
Our sealing solution
Our engineers recommended a metal seal for this application because of pressure and compatibility requirements with the various hydraulic fluids. The action of mating/de-mating the coupling meant this seal had to perform under a slightly dynamic movement. The seal base alloy was NACE MR0175 heat treated to obtain the standard desired properties for oil and gas specific application service; (when a material that does not comply with the NACE MR0175 heat treatment requirement is exposed to H2S, catastrophic failure can take place). Gold plating of the seal was recommended due to its malleability and suitability for slightly dynamic operation. Our metal seal solution was extensively cycle tested and the customer confirmed that the new concept metal seal solution performed under the required conditions with no leakage.
Customer Satisfaction
This sealing arrangement extended the life of the couplings by achieving 100 connect/disconnect cycles before the seals needed changing. This was substantially higher than the original sealing solution and gold plated metal seals are now supplied in production quantities. For more on our expertise in the oil & gas industry, read HERE
PTFE Rotary Seal for Oil & Gas drilling toolOur customer designs and manufactures a leading range of unique downhole technology and drilling solutions that contribute to a net zero energy industry.
The Application
A seal was required for the rod of a downhole drilling tool - a hydraulic dynamic (rotary) application. Our solution is a PTFE rotary seal. Read on to find out about more. The application has a normal operating pressure of 500 PSI at 60 RPM, but maximum pressure can reach 6,500 PSI in static operation. Reverse pressure was unlikely in this application but the engineers wanted to ensure some level of resistance. Two single acting seals were considered, but groove space is limited. Keeping the grooves closed is preferable for bearing strength. The maximum operating temperature reaches 200°C and the application media drills mud and completion fluids (with wiper arrangement already installed).
Our Sealing Solution
Due to the pressure, temperature and chemical media parameters of this application, an elastomer seal selection was not suitable. Our engineers selected our standard FTOR profile PTFE seal This is a double acting slipper seal ideally suited to hydraulic applications and capable of sealing under alternating pressure directions. It’s ideal for sealing high pressure loads with slow to moderate rotational speeds. The PTFE rotary seal has side wall notches equally spaced, so the part can be fitted symmetrically either way. The initial sealing force is provided by the elastomer O-ring. This is seated within a machined saddle and activated by system pressure to perform under high pressure demands. The central lubricating channel design ensures low friction and wear. Additionally, the sealing set has been designed with a scarf cut PEEK back-up ring. This is to ensure stability and seal performance at maximum working pressure of 6,500 PSI.
Customer Satisfaction
Our customer tested the sealing arrangement at higher pressure (up to 10,000 PSI). Consequently, our customer is pleased it seals successfully over and above the application requirements. They have adopted this seal design for other sizes of parts in similar equipment. Read more about our rotary seals HERE
Why the focus on PFAS?PFAS is a blanket term used to describe Poly- and Per- fluoroalkyl substances. There are currently around 10,000 substances in existence that fit this description, with potentially more variants still yet to be produced. Some are already known to be harmful to human and animal health and the environment (such as PFOA and PFOS), and these specific PFAS are already controlled under legal restrictions. But in February 2023, The European Chemical Agency (ECHA) published a regulatory proposal to further restrict the manufacture, placing on the market, and use of all PFAS within the EU.
What are the consequences for seal manufacturers?
A broad ban on all PFAS would have a significant and direct impact on European industries and businesses that manufacture products using these substances. This will have consequences globally. One particular concern is the fluoropolymers material group. These elastomers could be caught in any blanket ban of PFAS without any exemption. These materials are essential in a wide variety of applications in many industries. These include food, medical, pharmaceutical, clean energy, semiconductor, electronics, oil & gas, chemical, automotive and electric vehicle industries. These fluoropolymers include materials used in high performance sealing solutions, such as PTFE and PVDF plastics, and FKM, FFKM and FVMQ elastomers.
What's the problem?
There is substantial scientific evidence showing fluoropolymers demonstrate unique characteristics that mean they do not pose significant risk to the environment. Additionally, no risk to human health as they’re not bio-available, toxic or mobile. They do not dissolve in or contaminate water, or generate microplastics, therefore cannot enter or accumulate in a person’s bloodstream. They meet the criteria specified by the Organisation for Economic Cooperation and Development (OECD) as “polymers of low concern” as they present no significant toxicity concerns, and do not degrade into other PFAS chemicals. Fluoropolymers far outperform other sealing materials in countless applications. To put it simply; they seal tighter, last longer and survive harsher application environments considerably better than any other available materials. Fluoropolymers add irreplaceable value to society, and contribute significantly to environmental sustainability
What do we do?
We fully support restricting the use of PFAS chemicals that are known to be harmful to our health or our environment; but we believe grouping all PFAS within a restriction would be a mistake. Fluoropolymers do not have the toxicological and environmental profiles of other PFAS. Additionally, prolonged existence alone is not justification to restrict a substance under REACH. We already work proactively to ensure the products we put to market are safe, compliant with legislation, and utilise the latest sustainability developments. This is to minimise our impact on the environment – during manufacture, in use and at end-of-life. As a company with high environmental, social and governance standards we will continue to do so, whenever and whatever new legislation comes into force. However, we believe the sealing industry, it’s many customers, end users and society as a whole, need specific derogations and exemptions for fluoropolymers (free of any time limitations) to be included in any legislation covering PFAS substances. As we have done, we strongly encouraged any individual or organisation that may be impacted by a ban to engage with ECHA. This would be during their consultation period on this proposed restriction (which ended on 25th September 2023). To learn more about our key industries and our sealing solutions, read HERE
Seals for cryogenic applicationsCryogenic sealing means controlling or sealing a media at very low temperatures. This process can be complex and advanced, and spans a range of markets; from pharmaceutical, chemical and refrigeration, to automotive and electronics.
What are low temperatures for seals?
A typical industrial sealing system operates in the realms of a stable temperature rating. This is often sufficient for elastomer seals to cope with most of the time. For example, a general pump application running at -20°C to +80°C in air or water would be perfectly suitable for a sealing solution manufactured in nitrile (NBR) elastomer. However, if that temperature specification dropped to -196°C in liquid Nitrogen, the overall sealing solution would need adapting dramatically. Therefore, a more advanced polymer solution is needed. This is because general elastomer groups such as NBR, FKM, & VMQ are not suitable to perform at very low temperatures. This is due to the chemistry of the elastomers at a molecular level. All elastomers need a particular chemical makeup to be able to withstand a temperature range of the application required. However, many global elastomers on the market are not rated much more below -70°C. This means they’re not a viable choice for cryogenic applications with temperatures way below -70°C (often requirements reach below -196°C).
Types of cryogenic sealing solutions
Specialised sealing solutions are required for cryogenics conditions. Our engineers utilise a range of more advanced seal polymers to solve the most demanding and critical application setups. PTFE has an outstanding temperature rating of -260°C to +260°C and low friction characteristics. It is also regularly used in conjunction with a metal spring energiser. The spring energiser acts to maximise the sealing force at the seal contact points and to maintain a tight seal. This is the case even when the very low temperature conditions are attempting to contract the seal away from the mating surfaces. Other common polymers suitable are UHMPWE and PTCFE for more specific applications.
Our seals for cryogenic applications
We offer a range of cryogenic sealing solutions for various markets and applications including; pumps, engines, couplings, cylinders and many more. Read about our full range of engineered materials HERE
Why use 2-Shot moulded seals?2-Shot moulding is a manufacturing process that allows the co-polymerisation of hard (or soft) plastics and thermoplastic elastomers (TPE’s). We use the 2-Shot manufacturing approach to deliver engineered parts that perform a critical sealing function.
What is 2-Shot moulding?
A 2-Shot mould is designed with a top and bottom cavity. During the moulding process the first material is injected into the top cavity and the mould opens and rotates. The first material is then injected into the top cavity again, while the second material is injected into the bottom cavity simultaneously. The mould then opens and the parts are ejected from the bottom cavity; the mould rotates again and the whole process is repeated. 2-Shot moulding is not considered a brand new method of manufacturing. In fact it has been used for years to produce items that we see and use every day. Toothbrushes, tools, kitchen utensils and toys are but a few examples of multi-shot moulding being used to produce relatively cheap items in large production quantities.
Why do we use 2-Shot Moulding?
Previously, manufacturers of high volume metal or plastic- to- rubber component assemblies have processed them via chemical or mechanical bonding, and by using adhesives or over-moulding. Examples of the types of markets that lend themselves to these types of sealing products are Automotive, Life Sciences and Aerospace & Defence. Although these production methods may achieve the final assembly requirement, the many different processes involved are lengthy, costly, and can be fraught with problem areas that require stringent controls. A failure in any of these areas will result in poor quality parts, therefore often deeming these methods unsuitable for critically engineered components.
Why do we use 2-Shot Moulding?
When designing a new 2-Shot moulded product (or replacing an existing assembly part) our engineers review each application parameter carefully, and utilise years of sealing experience and materials expertise alongside the latest 3D modelling technologies and FEA simulation programs before presenting a seal proposal. This allows us to anticipate and analyse the finest details of mould performance, and means we can adjust our seal design to ensure our customers receive the highest level of performance possible from our engineered 2-Shot seal solution. The result means we supply our customers with high integrity parts with a powerful molecular bond, reduced production cycle times (as many additional processes are removed from the production line) and comprehensive cost reductions as all parts are produced in a single manufacturing tool (meaning reduced running costs and the removal of pre and post moulding processes).
2-Shot moulding is not just a way of manufacturing simple, high volume parts. Our application engineers are always breaking norms and pushing design limits to consider more creative ways of producing high performance engineered sealing solutions to meet our customer requirements.
Read more about our 2 shot mouldings HERE
Why use PTFE seals?Polytetrafluoroethylene (PTFE) is a thermoplastic polymer that can be used in a variety of sealing applications; it is particularly suitable where the application conditions exceed the parameters of elastomeric seal use, but are not as highly demanding as applications that require the use of metal seals.
What is PTFE?
Discovered accidentally in the DuPont™ laboratory in Jackson, New Jersey, USA in in 1938. The molecular structure of PTFE is based on a linear chain of carbon atoms which are completely surrounded by fluorine atoms. The carbon-fluorine bonds are among the strongest occurring in organic compounds. As a result PTFE has thermal stability across a wide temperature range. It’s high melting point (342 °C) and morphological characteristics allow seal components made from virgin PTFE to be used continuously at service temperatures of up to 260 °C, and with the addition of fillers – up to 300°C. It has the unique ability to resist material degradation, heat-aging and alteration in its physical properties during temperature cycling. Alongside this rare combination of material characteristics PTFE also has unlimited shelf life.
Why use PTFE seals?
Notably PTFE demonstrates extraordinary chemical resistance: the intrapolymer chain bond strengths preclude reactions with most chemicals, thereby making it chemically inert at elevated temperatures and pressures with virtually all industrial chemicals and solvents. Only a few media (some molten alkalis) are known to react with PTFE seals making them the perfect sealing solution for highly aggressive chemical applications. PTFE also has the lowest friction coefficient of any known solid; it has self-lubricating capabilities which offers continuous dry running ability in dynamic sealing applications and has superb stick/slip capabilities.
Focus on dry coatings
The advantages of using PTFE in sealing applications are; functionality at high and low temperatures, dynamic sealing with high wear capabilities, high pressure sealing (using combinations of PEEK back-up rings) and compatibility with highly aggressive chemical combinations. Our range of PTFE seal products include back-up rings, rod and piston seals, slipper seals and spring energised seals in a wide variety of sizes. Materials depend on application requirements but we offer a wide range from Virgin PTFE or including filler combinations of MoS2, glass, carbon, carbon fibre, graphite, and bronze. These characteristics make PTFE seals perfect for the demanding applications involved in Oil & Gas, Aerospace, Automotive and Chemical Process markets (to name but a few) and Ceetak’s engineering team are experienced in the design of PTFE sealing solutions to meet the complex specifications these types of application demand. Read our overview and more detail about PTFE seals HERE
Why use metal seals?The use of metal seals as an engineered sealing solution is appropriate where it is not possible to use elastomeric or polymer seals due to extremely demanding application requirements. For example, these could include applications with extremely high temperatures (300°C upwards) and pressures, intense radiation, cryogenic conditions or highly aggressive chemicals.
How do metal seals work?
The metal seal concept is based on plastic and elastic deformation of the seal during compression which creates a sealing interface. The metal seal is compressed in the cavity on average about 20% of its original free height. The force generated through compression of the ring produces a high contact stress at the seal/cavity interface. This force is then supplemented by the pressure-energisation force which rises in proportion to the increase in differential pressure inside the seal cavity.
What types of metal seal are there?
There are three types of seal energisation; self, spring and pressure energisation. By design metal C-rings are self-energising due to the good spring back characteristic of the C-shaped profile. Additionally, they can be used in internal, external and axial pressure conditions. The different base material characteristics and heat treatments, along with material thickness, and cross section of the seal also determine the compressive load. This is directly related to the sealing level achieved and is known as “self-energisation”. Spring energised seals have excellent spring back properties and are typically used to improve leakage rates by increasing the load on the sealing interface. All metal seals can use system pressure to generate a hydrostatic load to obtain the highest level of sealing possible; this is known as pressure energisation. At high pressures this becomes an advantage and allows the design of metal seals for applications of 25,000 PSI and above.
Ultimate seal performance
Once the metal seal profile and material has been selected depending on the application, there are a variety of platings and coatings available. These can modify the surface properties of the seal to create a malleable outer surface layer. Typically precious metals such as gold and silver are used for plating, but many other options are available with two common ones also being Tin or PTFE. This layer ensures optimum sealing despite any mating surface imperfections. The plated or coated layer also reduces coefficient of friction so the seal can slide and bed down during initial compression. Consequently, this prevents galling. As well as providing better physical properties to the seal, coatings and platings are chosen to withstand high temperatures and aggressive (often corrosive or oxidizing) environments. There are ever changing industry demands and fast paced technology developments – particularly from customers in the Oil & Gas, Aerospace & Defence and Automotive markets. Therefore, we are challenged daily with applications where the boundaries are being pushed to the absolute limit. We have designed metal seals into F1 car exhaust systems, subsea repeaters, oil and gas production valves as a few examples; the capabilities of high performance metal seals is endless. Working with the latest developments in materials, platings and manufacturing technology; our engineering team design the sealing solutions to meet the complex specifications these types of application demand. Learn more about metal seals HERE
Why use Push-in-Place gaskets?Where a seal groove follows an irregular path or profile, a common sealing solution is to design a custom Push-In-Place (PIP) gasket that has the same profile as the centre line of the groove, simply drops into place and is retained by the features of its own design.
Gasket sealing overview
There are many ways to seal the static join between two components. This could be to keep fluids inside a cavity or to keep fluids or contaminants out of a device or assembly. The options can vary from simple O-rings, moulded elastomer gaskets and flat sheet style materials, to liquid gaskets (or RTV’s). As with all sealing applications, the optimal sealing solution is designed by first reviewing the application conditions. These include temperature, pressure, fluid exposure etc; and other variables such as life requirement, equipment serviceability and seal compression set should all be considered. Arguably though, compared to other sealing applications, when designing face, cover or flange sealing solutions it is imperative to consider the packaging requirements and assembly issues of gasket sealing options. The need to avoid or seal around bolt holes (or other retaining/clamping devices), together with optimizing hardware wall sections or depths can play a very important part in choosing the most suitable gasket sealing technique.
What are Push-in-Place gaskets?
With the right combination of application conditions, an o-ring style approach to sealing may be the most appropriate. O-rings tend to require relatively shallow grooves compared to their cross section in one half of the assembly, and in cases where the groove is round in plan view – they can be a good solution. However, in cases where the groove follows a more irregular path or profile (frequently referred to as a “racetrack”) the O-ring can sometimes pop out in places – often where the two housing parts are being brought together. A common solution is to design a custom moulding that has the same profile as the centre line of the racetrack groove and simply drops into place. A similar approach is used when the application or hardware constraints steer the design towards a gasket that has a greater cross section depth compared to the width; this would typically be designed so the centre line of the gasket matches the centre line of the groove plan profile – again so that it drops easily into place. An inherent problem with gaskets that can drop into place is that often, they easily drop out of place too. If the component needs to be inverted, or has the potential for rough handling during assembly then the gasket may become partially or fully dislodged from the groove, which results in a badly sealed interface. The best solution to this issue is to incorporate retention pips or bumps in the gasket design, a solution known as Push-In-Place (PIP) gaskets. These require a distinct force to put them into the groove, and as a result require more than just gravity to get them out of the groove.
Why use Push-in-Place gaskets?
There are other less effective solutions for tricky groove sealing, such as the use of a sticky grease, or the use of an adhesive. These can bring compatibility and health and safety issues to consider. Additionally, it carries the risk that any contaminant could keep the gasket off the surface that it is supposed to be sealing against. Therefore, the integrity of the seal can be severely compromised as a result. Neither of these approaches can be recommended, and instead the use of retention pips is a safe and secure way of ensuring the gasket remains in the groove. To determine the optimum number, size and position of the retention bumps, Finite Element Analysis (FEA) is used. This ensures they provide sufficient squeeze to prevent the gasket being easily dislodged. Additionally, it is important there’s no overfilling the groove space with seal material or interfering with the seal compression footprint against the hardware faces. The bumps can be strategically positioned to control any distortion of the gasket under pressure or temperature conditions. For example, low temperature conditions can shrink the gasket and tighten the radius it adopts around a bend in the racetrack profile. This can reduce the seal compression locally and potentially create a leak path.
Correct positioning
By positioning retention bumps at either end of the bend, the thermal contraction can be controlled to minimize the risk of leakage. Effective retention ensures that if the part needs to be inverted (which could be the preferred assembly method for practical reasons) or is subject to rough handling – the gasket remains correctly located in the groove. For large gaskets this is normally the most effective solution. On smaller gaskets (particularly those located well inside the periphery of the assembly), there is a significant risk of a dislodged gasket being totally undetected unless using a PIP gasket design. It’s possible to include tell-tale signs on a gasket design. For example, if a part of the elastomer gasket protrudes sideways through a gap in the housing wall, the presence of the gasket can be checked. This would be either with the human eye or an automated vision system. However, this does not ensure correct seating all around the gasket length, and cannot be used for internal gasket locations. In these cases a missing or badly fitted gasket would only be discovered during post-build testing, or even worse with a machine failure at a customer.
Further considerations
If included at the design stage, the small additional tooling and material costs associated with a PIP gasket are negligible compared to the costs of an impossible assembly scenario, strip and re-build costs on the assembly line, or the consequential costs associated with failure of an assembly once delivered to a customer. More information on PIPs and gaskets can be found HERE
Perfluoroelastomers in valvesIs it time to re-visit using perfluoroelastomer seals in your valves? First developed by DuPont™ in the late 1960s, perfluoroelastomers (or FFKMs), are now widely known and understood in a variety of markets. But for those that may be less familiar with these high performance materials, here is a quick recap...
What are perfluoroelastomers (FFKMs)?
They are essentially highly or fully fluorinated compounds with a fluorine content above 75%, and they offer outstanding chemical resistance. Generally better than all other elastomer types, FFKMs are often referred to as having the resistance of PTFE but in elastomer form. The term “universal” chemical resistance is commonly used; although it’s not strictly true as we will learn shortly. Unlike PTFE, the molecular make-up of FFKM includes crosslinks (or spring-like elements). This is contrast to just a backbone of carbon-carbon atoms surrounded by protective fluorine atoms. These crosslinks are what give the FFKMs their crucial elastic behaviour (in other words returning quickly to their original shape after being deformed). But the crosslinks are also a drawback as they can be a weak point for a chemical attack. Different crosslinking systems can be used when developing FFKMs and the choice will determine the high and low-temperature capabilities. Compounds developed for extreme high-temperatures (up to around 325oC) generally have a less broad chemical resistance. This is in comparison to the lower temperature grades (up to 225oC). Similarly, FFKMs developed to have excellent resistance to specific fluids (such as amines or high-temperature steam) can have limitations of low-temperature capability or compression set. As a result, there is no universal material that covers all application criteria bases.
A variety of grades
Previously the number of perfluoroelastomer grades was less prolific than other elastomer types such as FKM, EPDM, and NBR. However more than 50 years of technical developments have created a range of FFKM grades for specific and challenging applications. These are particularly in chemical process, oil and gas, semiconductor, and aerospace industries. Additionly, options with a hardness range of 65 to 90 durometer, and versions that meet international standards or specifications for food, medical, CPI, and oil & gas applications means the portfolio of FFKM-based compounds available to engineers is now substantial. In addition to technical developments, manufacturers and compounders have also been addressing the only real drawback of FFKM materials; the cost. They are difficult and time-consuming base polymers to manufacture. With a relatively low volume production base and sometimes lengthy processing times, FFKM seals carry a high financial premium over FKM seals. Even several times greater than FKM itself has over NBR. In recent years, there’s been more focus on making general-purpose grade FFKMs with broader temperature and chemical resistance capabilities more financially attainable. The initial procurement costs remain high compared to less capable elastomer bases. The overall cost of ownership may now be more appealing than it was twenty or even ten years ago. The ability of FFKM seals to survive for much longer in applications where exposure to a variety of fluids (perhaps wider than originally specified) is possible. This considerably reduces unplanned costs associated with maintenance and downtime.
Focus on dry coatings
The cost of unscheduled maintenance and repair in pump and valve equipment can be high in any industry, but exceptionally so in petrochemical, oil & gas, and semiconductor. When these costs are fully considered in the overall lifetime of a product, the initial price of seals in a valve is considered relatively minor, but it can still be a barrier in the material selection process. With both technical and commercial developments in recent times FFKM materials now compare more favourably against other materials for static, or low-duty dynamic applications in valves. In applications where persistent and sporadic issues keep coming back to cause problems, they are now a more financially attainable choice of material to avoid re-work, overhaul, downtime, customer dissatisfaction, and ultimately, more costs. Read more about FFKM as a suitable sealing material HERE
Seals for electric vehiclesPropelled by one or more electric motors and using energy stored in rechargeable batteries, electric vehicles are quieter, have zero exhaust emissions and lower emissions in general compared to internal combustion engines. The number of electric vehicles on the road grows exponentially every year globally, and our engineers support manufacturers with innovative sealing solutions in these specialist areas of application.
Hybrid and hydrogen vehicles
Hybrid vehicles have a petrol (or diesel) engine combined with an electric motor and relatively small battery. They feature all the traditional areas of automotive applications that require seals including oil, steering, suspension and braking systems. They also require seals for environmental and RFI/EMI (Radio Frequency Interference /Electro Magnetic Interference) applications. These are normally gaskets required for many electronic control, junction and connection boxes (for power invertors, charging electronics, motor and battery enclosures). These are generally placed around the vehicle, but batteries tend to be under or behind the back seat. Sometimes the fuel tank is smaller and the battery sits in a similar place. Application characteristics also include high speed rotary sealing requirements around the output shaft of the motor. Additionally, possibly in the gearbox that links in with the combustion engine drivetrain. Plug-in hybrid vehicles have gaskets or seals (environmental and/or shielded) associated with the cable charging connection.
Hydrogen Fuel Cell
These vehicles have no combustion engine, and the fuel cell is often located where the petrol engine would be. Electrical power is produced by passing hydrogen and oxygen gasses through a “battery” (the cell). Anodes and cathodes produce electricity that drives the motors and is also stored in more conventional hybrid style. Waste product is water and warm air; this is very environmentally friendly (more so than pure battery power which uses electricity often generated in a “non-green” way and which also consumes rare earth minerals such as lithium). There are traditional automotive seals in areas of applications such as steering, cooling, suspension, and braking systems. In addition to environmental and RFI/EMI shielding gaskets and high speed rotary seals requirements. Hydrogen gas is normally stored in a tank at up to 700 bar pressure. Again, is usually situated just behind or under the back seat, and requires sensors, valves and pressure regulators to operate. There are seals and gaskets required within the fuel cell itself, these require H2 resistance. Some fuel cells have small compressors which force the gasses through the fuel cell at higher pressure for improved efficiency, and then expanders which recover energy from this gas flow at the exhaust of the fuel cell. These often require high speed rotary seals (generally PTFE materials) and they run unlubricated.
Battery applications
Full battery electric
These vehicles have large batteries that typically take up the entire floor area underneath all of the seating compartment of a car. As with other EV’s there are the traditional seals in automotive areas; no oil system, but the steering and cooling systems, for the battery itself and the suspension and brakes. There are also environmental and EMI/RFI shielding gaskets and high speed rotary sealing requirements. The plug in charging ports also present a sealing application.
Filling and charging
There are many different applications for filling and charging. Home charging points are normally smaller and wall mounted for domestic use. Commercial and forecourt charging will encompass hydrogen filing. There are all similar application types as already mentioned including shielded and environmental gaskets for the electric applications and hydrogen sealing for the H2 filling applications.
Design & Development for Electric Vehicle applications
Our engineering team understand the demands associated with automotive applications, and we support vehicle manufacturers by designing innovative sealing solutions for electric vehicle applications. We use the latest in 2D/3D CAD and FEA simulation software to design and replicate automotive seal performance before finalising each individual seal design, incorporating significant feature and critical function elements for integration with customer mating parts. We offer material development and testing, and a component endurance testing service. Learn more about our expertise in the Automotive & EV industry HERE
Seals for valve applicationsValves are imperative for isolation and control functions, and can be found in a broad range of industries such as Oil & Gas, Water & Wastewater, Food & Beverage and Hydraulics & Pneumatics. We supply seal products into valve applications in a variety of styles including ball, gate, flap, plug, butterfly, spool, check and solenoid valves.
Characteristics of valve sealing
There are many challenges involved in valve application sealing. Conditions and application parameters can vary with temperature extremes from cryogenic up to 325°C, and pressures up to 1000+ bar. We need to carefully consider the materials to suit all fluid compatibility required. Often the seal design requires low breakout friction and offers no stick-slip following prolonged static periods when the valve is not used. Alongside this, customers require long service life and minimal maintenance. Valve styles include ball, gate, flap, butterfly, spool, check and solenoid valves. Also different types of actuation include manual, pneumatic, hydraulic and electro-mechanical. Different areas of the valve demonstrate different sealing requirements.
Valve sealing areas Actuation
There are a range of sealing solutions to suit the variety of actuation types employed with valves. This includes diaphragms for pneumatic actuation, rotary and linear hydraulic and pneumatic seals, and gaskets and O-rings. Seal materials are available to suit all ranges of temperatures and media associated with the actuator and any external contaminants it encounters.
Body bonnet joint
This is a static sealing location that can often be sealed with an O-ring (a wide range of materials are available to satisfy fluid compatibility). However dependent on the fluid, pressures and temperatures, metal seals can be more suited to the application. Additionally, housing deflection under pulsating system pressures may worsen compression set sealing issues. Therefore, a custom gasket design could be potentially more suitable than an O-ring. For subsea valves, a sealing solution capable of handling alternating pressure regimes and multiple media types may be required.
Stem
A critical and dynamic sealing location with often demanding requirements. Depending on the application of the valve, the seals used here may see frequent dynamic operation and will require a long wear life. In other cases, the valve may be static for long periods and then require operation with minimal break-out friction forces. In all cases, reliable sealing is paramount.
Seat body
Valve seats are often mounted in a housing or carrier which has a sealed interface within the valve body and in these cases it can be a critical location to seal correctly. Dependent on the design, the seal location may be subject to upstream or downstream pressures at various points. In some cases fluid flow through the valve can pull or wash-out seals from their grooves if they are not designed to prevent this. As pressure conditions change with valve operation, the seals here may be required to withstand small (but sometimes frequent) movements of the carrier without sticking or wearing.
Valve Seat
A wide variety of elastomers and engineered polymer materials can be moulded or machined to suit valve seat components. Bonded rubber to metal or rubber to plastic seals can provide bespoke solutions. These offer benefits in terms of space envelope, component count or ease of assembly.
Design & Development for valve sealing applications
Our engineering team understand the application demands associated with valve sealing and can support our customers with the design of seals for every position within the valves. We provide a complete design service; from initial seal geometry and profile choice, to material selection and prototyping, through to final production. This is utilised with our seal design experience and materials expertise, alongside technology such as 2D/3D CAD and FEA analysis. These simulate performance before finalising each individual seal design. We are familiar with the requirements of individual markets and their valve applications. Our seals are manufactured in materials with approval requirements such as NORSOK M-710, ISO23936-2, NACE, WRAS and FDA. For more on our design and engineering service, see our dedicated page HERE
Seals for Oil & Gas applicationsWith diverse applications in harsh environments, the Oil & Gas industry presents some of the most challenging demands on engineered sealing solutions. Our collaboration with Parker Seal Group allows us to integrate their materials and sealing expertise to meet our customer demands.
Characteristics of Oil & Gas sealing
Regardless of where seals are used in oil & gas applications, they are without doubt critical to the safe, reliable and efficient operation of a huge range of onshore and offshore equipment. There are many challenges involved in oil & gas application sealing; conditions typically include low and high temperature extremes, very high pressure conditions and most seals need to withstand aggressive fluids and media such as sour gas, salt water and super-heated steam. There are three main sectors within the Oil & Gas industry, with different processes and equipment requiring sealing solutions. Upstream; commonly known as exploration and production – this refers to the recovery of hydrocarbon reserves in the form of natural gas and crude oil. Midstream; refers to the processes involved in the transportation and storage of natural gas and crude oil, from production site to refinery location. Downstream; includes the processing of natural gas and crude oil at oil plants and petrochemical plants.
Well Drilling
This is the process of extracting oil and gas from beneath the ground, in both onshore and offshore environments. Seals used in these applications have to cope with increasingly harsh environments (with wells becoming deeper and deeper). System pressures up to 30,000 PSI and operating temperatures between -50°C and +220°C are common, and seals have to demonstrate excellent fluid compatibility and resistance against aggressive media – all with longer service life expectations. Applications include; drilling and tool bits, blow-out preventers, drilling mud systems, LWD and MWD test equipment, casing and pipe connections, subsea risers and connector systems, control valves, compressors and pumps. Seals need; high temperature and high pressure capabilities, sour gas and abrasive drilling fluids resistance, extrusion resistance and compatibility with well bore fluids.
Well Completion
This is the process of making a well ready for production after drilling. Similiar to well drilling, seals used in well completion must withstand increasingly harsh condition such as deeper wells and more diverse geographical areas with extreme hot and cold weather conditions. System pressures up to 30,000 PSI and operating temperatures between -45°C and +220°C are common, and seals have to demonstrate excellent fluid compatibility and resistance against aggressive media. Applications include; tubing heads and hangars, packer assemblies, well controls, Christmas trees, cementing equipment, well head completion assemblies, well service. Seals need; high temperature and high pressure capabilities, chemical compatibility (including H2S resistance), RGD & extrusion resistance and steam resistance.
Distribution
Following on from the production stage, petroleum products are transported to processing facilities and to end users in pipelines. Seals used in midstream distribution sector applications often operate in low temperatures, down to -196°C (required to liquify gas) as well as high temperatures of 480°C (to meet fire test requirements). System pressures can be as high as 10,000 PSI. Applications include; marine and offshore loading swivels and turrets, railcar loading systems, pipeline service equipment (pigs and spheres), pipeline valves & actuators, pumps & compressors, tank & loading systems. Seals need; Extrusion, corrosion and abrasion resistance, extreme temperature and pressure capabilities, chemical compatibility (including H2S), RGD resistance, compliance with NORSOK, ISO and API specifications.
API 6A, NORSOK M-710, ISO 23936-2 and TOTAL material qualifications
The Oil & Gas industry has specific testing and qualification standards to ensure that materials used in harsh drilling and production environments meet the critical demands of these applications. ISO 23936-2:2011 describes the requirements and procedures for the qualification of elastomeric materials in accordance with media related to oil and gas production. H2S testing in accordance with this specification enables the lifetime prediction of compounds. NORSOK M-710 defines the requirements for critical non-metallic (polymer) sealing, seat and anti-extrusion ring materials for permanent subsea use. This includes well completion, christmas trees, control systems and valves as well as topside valves in critical gas systems.
API 6A is the specification for drilling and production, wellhead and christmas tree equipment. Total GS EP PVV142 defines the requirements for non-metallic sealing materials concerning elastomers within pipeline valve applications. In conjunction with Parker Seals we offer a range of products in materials that are qualified to these specifications. We work closely with our oil & gas customers, read more HERE
Seals for Life Sciences & Medical ApplicationsWhen designing and manufacturing sealing solutions for applications within critical devices and equipment, the strictest demands in product integrity and the highest specifications of hygiene and cleanliness must be met. Characteristics of Life Sciences & Medical sealing The Life Sciences & Medical industry is one of the most demanding and stringently regulated. There are a variety of areas of product development and manufacture where seals for Life Sciences & Medical Applications are required.
Diagnostics
Because of technology changes, there are now many ways of supporting patients with accurate results for the safe management of health conditions. This includes at home and within a clinical setting. It’s vital that diagnostic devices and systems are developed with the accuracy and speed of response to enable targeted analysis and therapy.
Patient management and care
Repeatable and reliable control of the equipment used in patient management and care is paramount. Applications include seals for ventilators, anaesthesia pumps, respiratory therapy and monitoring equipment. Minimally invasive surgery equipment and metered dose aerosols (such as inhalers) also need Life Sciences & Medical seals. Optimised working friction and wear life are demands on seals. The critical feature’s function & tolerance control are also pressures on the seal, coupled with management of gas, liquids, or solid media at accurate rates.
Biotech and pharmaceutical processing
There's continued development of complex and expensive drugs and research control media. Therefore, demand for high performance interactive components within the biotechnology process industry is crucial. Typical applications include seals for analytical equipment, pumps, valves & actuators, monitoring & control equipment. In addition to storage equipment & transportation vessels. We support engineers on recommending Ultra High Purity (UHP) materials for application working extremes correspondingly with sensitive chemical media, and seal design recommendations for dead space and entrapment elimination within these applications.
Ultra High Purity (UHP) materials
Silicone based rubbers are a common choice of elastomer materials for seals used within medical devices. This is because of their biocompatibility features and resistance to bacterial growth. Commonly they’re platinum cured for injection moulded liquid silicone rubbers (LSR’s) and platinum and peroxide cured for compression moulded heat cured silicones (HCR’s). There’s a diverse range of silicone rubbers currently available in varying shore hardness’s that are already approved, making them a go to choice if the specification allows. An application could need a seal material to have better mechanical properties or more temperature versatility or media compatibility. Therefore EPDM and FKM rubbers are also a good choice. Many of our materials are fully compliant and therefore have the required industry approvals, read more HERE
Cleanroom Manufacturing
Life Science and Medical sealing products are produced in a cleanroom environment. Especially this is essential for manufacturing and packaging of products. Equally, external particulates such as dust, dirt, airborne microbes, and aerosol particles should not come into contact or contaminate the surface/the area. A cleanroom is created by removing air, circulating through a filtering system and distributing (the filtered) back into the cleanroom. This is achieved at varying levels of cleanliness depending on what is specified for each individual manufacturing environment, or the finished product requirements. Different cleanliness levels are classified by the concentration of airborne particles within a measured space. We provide a complete cleanroom production process. This includes material blank production through to inspection and packaging using controlled materials within state-of-the-art cleanrooms. Read more about our Life Sciences & Medical industry expertise HERE
Seals for Renewable Energy ApplicationsRenewable energy is derived from our planet's natural resources such as sunlight, wind, rain, tides, waves, biomass and thermal energy stored in the earth’s crust. With increasing fossil fuel prices, and the very real threat of global warming and climate change to our planet; the development of renewable energy production sources is more important than ever. In this article, we take a deeper look into seals for renewable energy applications and the different types of power the natural world provides.
Geothermal energy and Hydro power
Geothermal energy is generated from heat from the sub-surface of the earth. Heat is produced by the decay of elements known as radioactive isotopes. This is a constant process in the earth’s core, and as a result temperatures reach in excess of 5,000˚C. Wells of up to a mile deep or more are drilled into underground reservoirs to tap into the geothermal resources. Steam from these reservoirs is harnessed and used to rotate turbines that activate a generator, consequently producing electricity. There are different designs of geothermal power plants. A dry stream plant extracts steam directly from the ground and into a turbine, driving a generator to produce electricity. The most common type are flash plants; where high pressure hot water is pumped to the surface and mixed with cooler, lower pressure water. This causes the fluid to rapidly vaporise, and the resulting steam drives a turbine. Binary power generation plants will differ from the other systems. The water and steam from the geothermal reservoir never comes in contact with the turbine units. A low-moderately heated geothermal fluid, and a secondary “binary” fluid (with a much lower boiling point than water) pass through a heat exchanger. The heat from the geothermal fluid causes the secondary fluid to flash to vapour. This drives the turbines to power the generator.
Sealing in Geothermal applications
Application conditions to consider are high temperature requirements (up to 320°C) and high pressure requirements (up to 1400 BAR). Steam is present in working turbines and drilling fluids is present downhole (which may sharply change in viscosity during operational stages). The ability to seal drilling bores with large radial gaps is required. To suit application needs, there are various materials available. For example, EPDM with steam, FKM/FFKM for high temp, NBR has high expansion capabilities to seal large radial gaps. Spring energised seals offer exceptional pressure and temperature compatibility and can be offered in NACE approved springs which are corrosion resistant. Packer elements can also assist bore alignment and offer a dense sealing arrangement which prevents cross contamination of fluids.
Hydro Power
All forms of hydropower convert energy from water flow into electricity through the operation of a turbine and generator. There are different methods of hydropower production. Three of the main techniques are Impoundment, Diversion and Pumped Storage. Impoundment uses a dam to store river water in high reservoir. The water in the reservoir is manually released and the kinetic energy of its flow (as a result of gravity) is converted to electricity through a turbine and a generator. A diversion facility channels a portion of a flowing river through a separate channel. The channel will direct the water to a turbine and turn it before it re-enters the river at a lower point. The principle behind a pumped storage facility is that water is pumped to a higher elevation, and then manually released back to the original lower reservoir. The energy that was used to originally pump the water up can be extracted by a turbine and generator for use as electricity. The idea of pumped storage is to store the energy like a battery and use this in times of demand.
Sealing in Hydro Power applications
This technology provides a range of application environments, with varying water conditions and sources. Hydro power stations contain large and heavy duty mechanisms when dictating the flow of water, and high rotational speeds will be achieved on some turbines. Wear and abrasion resistance must be considered with potential for higher load impacts from initial water release and seals in a comprehensive range of elastomer compounds must be considered to ensure compatibility between varying water conditions. Heavy duty application rotary seal designs are suitable (in some cases with metal casings, and PTFE seals are suitable for applications that require abrasion and wear resistance.
Wind Energy
This is the process of converting the kinetic energy of wind into electricity through a wind turbine. Most wind turbines have three blades, and the shape of the blades are similar to the design of an aircraft wing so that the air flow around them provides lift. The force of the lift is much stronger than the wind’s force against the front side of the blade (which is called drag). The combination of lift and drag causes the rotor to spin like a propeller. This, in turn causes rotation of a shaft at the blades’ axis. The shaft is attached to a generator, which produces electricity from the torque of the shaft. A streamlined enclosure called the nacelle houses the key components of the turbine; including the gears, rotors, braking system and generator. There is a pitch control mechanism (comprising of hydraulic cylinders) to ensure that the blades are rotated at an angle to receive the wind and encourage lift most efficiently, and a yaw mechanism (located at the base of the nacelle) which rotates the entire body so that the front of the hub faces the direction of the wind. The shaft is incorporated into a gear system which has another higher speed shaft attached to the end. The high-speed shaft provides torque to a generator which converts this force into electricity. Application conditions for seals will vary depending where in the turbine they are located. General environmental factors include varying weather conditions, vibration, contaminants, corrosion, altitude and diverse (and often fluctuating) temperature ranges (-40˚C to 85 ˚C). Often long-life cycle and ease of installation are considered important (as downtime and maintenance are extremely costly). Areas of application are broken down below.
Gearboxes
There are a range of rotational shaft speeds to consider here. Typical high-speed shafts can reach approximately 2,000 RPM so require high wear resistant seals and shaft misalignment often needs to be considered. In low speed shaft applications, contamination from outside elements must be prevented. Rotary V-Seals reduce contact pressure as RPM increases (due to centrifugal force) which allows operation at a variety of speeds and reduces the chance of heat friction/friction loss. They also offer flexible lip arrangement to compensate for shaft misalignment. Oils and grease are used to lubricate systems so multiple compounds are available for compatibility.
Braking Systems
A wide range of pressure requirements are seen; low working pressure until brakes are applied, and then high and uni-directional pressures activated. Material compatibility is considered, therefore a range of brake fluids and oils are used. O-ring energised Polypak® seals, step seals and slipper seals will seal at a flexible tolerance range and offer sealing capability at low and higher pressures. PTFE seals offer a very consistent and strong chemical resistance. Scraper seals will contain fluids in brake system compartments and prevent components running dry.
Pitch & Yaw Systems
These present both static and dynamic sealing applications, but inconsistent dynamic operation (as it depends upon wind conditions). Both low and high pressure will be seen (for example, accumulators within pitching system present up to 250 BAR). Shaft offset/misalignment must be considered in heavy duty yaw systems. Hydraulic fluids and diverse lubricants will require material compatibility choices. O-ring energised PTFE step seals will seal at a flexible tolerance range and offer sealing capability at low pressures. Sealing assemblies comprising of other products can be designed to be used in conjunction to seal against high pressures. For example, products like back up rings, wear rings and slipper seals. Polypak® seals also offer sealing when high pressure is applied and also when under ambient conditions. O-ring energisers and wear rings help to contain shaft run out.
Seals for Renewable Energy Applications
In summary, seals are a vital part of the critical function of components in renewable energy power generation. They are required to provide long term functionality and provide durability in harsh environmental conditions. Our range of engineered sealing materials are designed to withstand critical sealing characteristics in these applications, including wear resistance, high pressure and high temperature conditions. Hydrogen and renewable energy is one of our key industries. Read more HERE
Seals for Semiconductor ApplicationsSemiconductor and electronics manufacturers are facing greater demands for more complex and powerful devices to fulfil applications across all industry segments. High performance seals and ultra high purity elastomer materials are crucial for these critical applications.
Characteristics of Semiconductor sealing
The technology push for more complex devices requires semiconductor companies to research and design new methods of processing within their manufacturing cells. Consequently, there’s an increase in challenging technical conditions. These include complex chemistry, increased temperatures and stringent cleanliness within manufacturing process and the surrounding tools. The need for high performance seals for semiconductor applications is greater than ever. Component and material suppliers are challenged with these complexities. They must adhere to the same rules, ensuring all the criteria for these new processes are met. Including the combined effects of the outlined above conditions. Our world demands modern performance materials for the semiconductor industry. It is therefore apparent materials previously formulated for older generation tools may not be technically capable in new and future applications. Therefore, it’s paramount to investigate and formulate new performance materials that meet each specific application.
Wet Cleaning and ECD
Wet cleaning is a method used in semiconductor manufacturing to remove any contaminants from each layer of the wafer surface, usually by using chemicals and pure water. ECD is a method of laying down the bulk of the copper wiring within a semiconductor device. Compounds for wet cleaning are engineered for static and dynamic applications with minimal metallic ion contamination.
Thermal applications
Compounds for these applications are required to have excellent thermal stability and maintain integrity at elevated temperatures. These are often found in processes such as Oxidation, Diffusion, Annealing, and RTP. These processes are extremely challenging for seal materials. High thermal load at 300°C with temperature cycling can encourage compression set. Additionally, they must be manufactured to limit out-gassing at high temperature to prevent contamination within the process area and offer superior physical properties.
Thin Film and Dry Etch
Thin film deposition is the process of creating and depositing thin film coatings onto a substrate material. These coatings can be made of many different materials, from metals to oxides to compounds. Dry etch is a process for material removal. Thin Film applications such as HDPCVD, PECVD, SACVD, PVD and ALD, along with Dry Etch and Ashing processes present harsh plasma and gas environments, often at elevated temperatures. Whereas traditional seals might deteriorate and fail in these conditions, our next-generation compounds have excellent chemical and thermal resistance. Consequently, they are virtually impervious to extreme fabrication processes, therefore excellent for semiconductor seals. Plasma processes are a very hostile and aggressive environment for seal materials. The corrosive chemistry at temperatures up to 250°C means that compounds must be chemically and thermal stable across the operating range and must include low-outgassing and low particle count features. These applications are varied; from window and door seals, chamber lid seals, valve seals, exhaust flange seals- each requires application knowledge to ensure all technical parameters are met before materials are recommended.
Ultra High Purity (UHP) materials
Perfluoroelastomer materials
FFKM’s contain fully fluorinated polymer chains. Subsequently, offer the ultimate performance from an elastomer for applications where the seals are exposed to high temperatures and aggressive chemicals for plasma, wet and dry, semiconductor process applications. There is an extensive range of FFKM materials available; the challenge is choosing the correct material grade for an individual application as one perfluoroelastomer will not cover the broad spectrum of requirements across all semiconductor process conditions. For example, some materials are better than others at high temperatures, some demonstrate better chemical resistance and some are poor at thermal expansion. Several compounds within our range of PERFREZ® perfluoroelastomer materials offer the best performance characteristics based on high thermal values, excellent low out-gassing and low particle count. We also offer a hybrid material which is an excellent “all-rounder” as it’s chemical formulation falls between FKM and FFKM. This means it performs consistently under slightly less demanding application conditions and with the added benefit of lower cost of purchase versus ultra-high grade FFKM’s. Other compounds within our range are very specific to semiconductor process applications such as CVD, PVD, Plasma Etch (oxide & metal), fluorine and oxygen compatibility with a high temperature threshold material for sub-fab NW /ISO exhaust line environments. As new challenging processes emerge within the semiconductor industry, further progress in high temperature materials above 300° C will be developed; we expect to add a new generation material for plasma applications to our portfolio of materials by the end of 2022.
Cleanroom Manufacturing
When producing seals for semiconductor applications, cleanroom manufacturing is essential. Semiconductor cleanrooms must be designed to control static, out-gassing, and any contamination from external particulates. For example dust, dirt, airborne microbes, and aerosol particles. Just a single particle of dust or debris on a wafer or component is enough to cause a catastrophic defect (that will ultimately lead to failure of a device). It is created and maintained by removing the air, circulating it through a filtering system and distributing (the clean and filtered) air back into the cleanroom environment. This can be achieved at varying levels of cleanliness, depending on specifications for the individual manufacturing environment or the finished product requirements. Different cleanliness levels are classified by the concentration of airborne particles within a measured space. Additional factors to consider are the manufacturing environment for the semiconductor itself. Furthermore, it’s important to ensure any auxiliary products (such as seals) brought into the environment also maintain the same levels of cleanliness. We provide a complete cleanroom production process; from material blank production through to inspection and packaging using controlled materials within state-of-the-art cleanrooms. Our clean room manufacturing facilities are Class 7 (10,000) manufacturing and Class 5 (100) inspection, cleaning, & packaging. Read more about our expertise in the semiconductor industry and how we can help you with your seals for semiconductor applications HERE
3D printing for seals3D printing has developed significantly and now performs a crucial role in many applications. 3D printed products vary from fully functional to purely aesthetic applications; with the most common application being for manufacturing. Here we discuss how our engineers use 3D printing to demonstrate a seal concept.
What is 3D printing?
3D printing is typically the more common name used for additive manufacturing. This process involves the construction of a three dimensional shape that is designed and generated from a computer aided design program (or CAD). The most typical process used for 3D printing is FFF (Fused Filament Fabrication) or FDM (Fused Deposition Modelling). The FDM process uses a continuous filament of a thermoplastic material that is then deposited onto the 3D print bed, creating layer by layer and gradually building up the structure of the 3D model. This is the process we commonly use to create our design and development range of 3D printed models and seal prototypes.
What material is suitable for 3D printing?
The materials used for 3D printing must of course be compatible with the process – these include a range of thermoplastic grades. Typical suitable material grades include; Polylactic acid (PLA), Acrylonitrile Butadiene Styrene (ABS), Thermoplastic Polyurethane (TPU), Nylon and Polypropylene (PP). The most common grade we use for 3D printing is PLA – for its great strength and stability. We’ve also adapted our design process to use more TPU based material grades, as it loosely demonstrates the same properties as elastomer grades and is better for using in prototype programmes where mechanical fit in groove is tested.
Why use 3D printing for seals?
3D printing can be used for a variety of designs and seal types; from O-rings, gaskets and lip seals – to grommets, multi shot mouldings and large seal assemblies. There are many benefits of using 3D printing during the initial design stages of a project. The rapid turnaround means that a simple seal design can be produced in around 15 minutes, and even more complicated parts can be manufactured in the same day. We can even print the application housings and it’s the perfect way to demonstrate to an engineer what they can expect from a seal part in terms of shape and fit for hardware without the lead time and cost of cutting a prototype tool for moulded parts. One example of this is by quick turnaround of gasket designs typically to suit automotive applications or similar critical markets. Our engineers can design the concept and then 3D print a rapid prototype of a gasket to suit a 3D printed gauge groove. This further demonstrates to the customer that the seal has been fit checked for installation and builds further confidence in the design recommendation. Our engineers combine the 3D print with FEA simulation reports to offer a fully engineered sealing solution. Learn more about our design and simulation service HERE
O-rings with special coatingsAll seals require some form of installation into application hardware and often this may seem to be a simple push in place function. However, without consideration of certain conditions this can potentially create sealing problems further into the life cycle of the seal. Once installation is achieved a seal can often sit in the housing hardware for many months - which potentially allows it to stick to the housing material and cause further issues. This is where O-rings with special coatings can make a difference.
Why use special coatings for seals?
The main function of coatings is to improve installation into the hardware and to lower friction within an application; but there are many other benefits too. They often mean that lower assembly forces are required and by not using grease lubricants seal parts don’t stick together in packaging for transit. Special coatings for O-rings can be manufactured in different colours. This is so seals and O-rings for specific applications can be easily identified. This is without the need to reformulate the elastomer compound with colour additives. All of these reasons make them easier to handle for users during installation.
What types of coatings are there?
There are a variety of coatings and lubricants available for the surface area of seals. They’re mainly divided into two common categories; wet coating/lubrication or dry micro film coating. Historically, coating technology was limited to just using wet type coatings. For example these may include silicone oils and greases and mineral oil based greases. The coating process would involve simply dipping the seals in the oil or grease during manufacture, or during installation on site. This is often a messy process, and although a relatively low-cost method, wet coating is less common. This is because more applications demand higher levels of cleanliness and control of products. Low contamination has become a key factor. Alongside the typical wet coatings traditionally used, there is an extensive range of what is often referred to as dry coatings. Common offerings are silicone dry coating, PTFE coating, PFPE coating, special polymer coating and MoS2 dry powder coating. These are applied during the manufacturing process and bagged in a clean and efficient process, delivered and ready to be installed into application straight from the bag.
Focus on dry coatings
Dry coatings are fast becoming the coating of choice for many customers, with PTFE dry coating being one of the most popular. Commonly applied to O-rings, the process involves the PTFE polymer being spray applied to the O-ring elastomer surface area. Therefore creating a microscopic thin film layer. At molecular level the PTFE then creates a covalent like bond to the surface ensure a high quality finish. The low friction properties of PTFE gives the advantage of low assembly forces. For example an O-ring assembled to a piston can be installed easier into the bore hardware housing mating part. Consequently, this significantly reduces the chance of installation damage (like pinching of the O-ring elastomer material). PTFE coatings can also be used as a short term dynamic improvement to a sealing solution, as many seals suffer from the phenomenon called stick slip. This can occur where a seal has remained in the application hardware bore for a medium to long period of time. It then starts to adhere between the surface of the elastomer and the mating metal material, causing sticking. When a PTFE coating is applied between the elastomer and the metal hardware it creates a low friction barrier. This provides a significant advantage over uncoated parts. This is because the PTFE coating generates a low friction layer. This greatly reduces breakout friction and resolves the stick slip issue therefore greatly improving the performance of the application.
Coating colours
Because the PTFE is a thin polymer layer, coatings can be manufactured in a range of colours by adding pigment to the recipe. Typical colours include, green, blue, red, yellow and orange. By adding these colours the customer benefits from easy identification and production line inspection. Furthermore allowing seals to be easily identified even once installed. Find out more about our range of O-rings with special coatings and the different materials O-rings are available in HERE
E1244-70 seals in Life Sciences & Medical applicationsPacked with multiple benefits, and recommended for pharmaceutical manufacturing, biopharmaceutical processing and disposable medical devices, E1244-70 is an internally lubricated compound, eliminating the need for an external lubricant.
What is E1244-70?
E1244-70 is a 70 durometer internally lubricated, black EPDM (Ethylene Propylene Diene Monomer Rubber) material. E1244-70 possesses an internal lubricant, which reduces installation force and dynamic friction. Additionally, E1244-70 is compatible with all water-soluble chemistries and has excellent resistance to repeated conditions. For example steam, gamma, ozone and ethylene oxide sterilization. Here we take a closer look at the use of E1244-70 seals in Life Sciences & Medical applications. Adding external lubricants can be problematic; the risk of leaking into flow paths and migrating into areas where they are not needed. Additionally, even ‘clean’ lubricants like USP silicone, which can trap dirt and dust, can compromise patient health. Removing the need for an external lubricant by using E1244-70 is clean and safe with no risk of leakage.
Benefits, application and use
E1244-70 has a temperature range of -54°C to 121°C (-65 to 250°F). Consequently, E1244-70 has a low compression set, and is suitable for both dynamic and static seal applications. Because this material does not need an additional lubricant, it prevents issues associated with non-lubricated seals. For example, mismanagement by not using a lubricant when needed, can lead to friction and heat build-up, resulting in erosion and potential leakage and failure of the application. Fully compliant with USP Class VI biocompatibility and USP cytotoxicity standards for life sciences applications. The internal lubricant derives from the fatty acid family, significantly reducing patient reactions. This means it is safe for medical devices and pharmaceutical applications. In summary, it is suitable for: Dynamic applications & difficult installations
• Surgical instruments
• Pharmaceutical manufacturing
• Biopharmaceutical processing
• Disposable medical devices
• Repeated device sterilization Our Life Sciences & Medical expertise
We have clean room manufacturing facilities which are Class 7 (10,000) manufacturing and Class 5 (100) inspection, cleaning, and packaging. Our application engineers utilise the latest in 2D/3D CAD and FEA simulation software to design and replicate seal performance before finalising each individual seal design, incorporating significant feature and critical function elements for integration with customer mating parts. We offer material development and testing, and a component endurance testing service. Learn more about how we support our customers in the Life Science and Medical Industries HERE
Seals for Hydrogen ApplicationsHydrogen is the most common element in our universe, and is becoming an increasingly vital part in decarbonisation and a global sustainable energy future for our planet.
How is hydrogen produced?
Hydrogen is a clean energy solution to parts of the economy that are difficult to decarbonise. These include industrial processes, domestic and industrial heating, and hard-to-electrify transport. For example heavy-duty vehicles, ships and aircraft (where battery solutions are much less practical than they are for passenger cars). The majority of natural hydrogen is not easily obtainable and is locked away as either hydrocarbons (in fossil fuels) or water. Here we detail how seals are used for hydrogen applications. Extracting hydrogen from either of these sources takes energy (and a lot of it!) but hydrogen becomes emission-free at the point of use. Today, 96% of the world’s hydrogen is produced using grey and brown processes, consequently, in reality it’s not very environmentally friendly at all. It is widely accepted that we need to switch to and expand green hydrogen production. However, the electricity sources for green hydrogen (solar, wind, etc) are not always located where the hydrogen needs to be used. Consequently, cannot be turned on and off as energy demand fluctuates.
How is hydrogen obtained?
Hydrogen can be obtained in a variety of different ways, and each of these methods is generally categorised by a different colour. Grey hydrogen is produced by reforming natural gas (methane). Brown hydrogen is produced by converting carbon rich materials (such as coal) into hydrogen and carbon dioxide. These are common processed, but both result in substantial carbon emissions. Turquoise hydrogen is produced by the pyrolysis of methane at temperatures over 1000°C. Solid carbon is a by-product which can then be used or buried without emitting greenhouse gases or causing groundwater pollution. Blue hydrogen is generated by the steam methane reforming of natural gas. This generates large amounts of CO2 which must then be captured and safely stored. Pink hydrogen is created where large amounts of electricity is used to chemically split water into hydrogen and oxygen. Manufactured from a nuclear power plant, it’s free from ongoing emissions (other than those emissions produced in building the nuclear power station). The oxygen can be used by industry or vented to the atmosphere, with no negative effects to the environment. Green hydrogen is also produced by electrolysis of water. However, the electricity required is taken purely from renewable sources such as solar, wind, tidal and geothermal processes. This is widely regarded as the ONLY totally clean hydrogen extraction method. Today, 96% of the world’s hydrogen is produced using grey and brown processes. This means in reality it’s not very environmentally friendly at all. It is widely accepted that we need to switch to, and expand green hydrogen production. However, the electricity sources for green hydrogen (solar, wind, etc) are not always located where the hydrogen needs to be used. Consequently, cannot be turned on and off as energy demand fluctuates.
Engineered seals for hydrogen applications
Sealing hydrogen presents challenges and we need to consider the following parameters when designing a sealing solution. Gas permeability of the sealing materials with pressures of 700 bar or more.
Tightness of the static or dynamic sealing surfaces – including surface finish requirements for the mating components. Hydrogen can be within a carrier. Therefore the chemical compatibility requirements of the carrier medium (e.g. ammonia or liquid organic hydrogen carriers) need to match the sealing materials specified. EPDM elastomer based solutions are often the most cost effective for seal applications in hydrogen with no particularly high demands in any one area. For permeation resistance, we offer chlorobutyl elastomer or polyurethane seals. In high pressure applications, alternatives are available. For example, elastomers or polyurethanes with high extrusion resistance and resistance to rapid gas decompression, or PTFE which is not affected by RGD. In electrolysers and fuel cells, the purity and cleanliness requirements can be met with materials and treatments we frequently use within the semiconductor market. In applications below -60°C, elastomers become hard and brittle, but PTFE, PCTFE and metal sealing solutions can be used down to cryogenic temperatures. For high temperature applications, some FKM or even FFKM elastomers can be used up to 220°C or even 300°C. However, the normal preference here would be PTFE sealing solutions. Metal seals are capable of even higher temperatures up to around 870°C. Metal seals can also have soft coatings such as tin or indium to achieve gas tight sealing, or gold or silver to reduce the risk of hydrogen embrittlement.
The evolving hydrogen industry
The hydrogen industry is technically vast and challenging for sealing applications. Extremes of temperature, alongside demanding pressure and chemical resistance requirements are challenges. Additionally, stringent leakage limits and associated safety requirements. Applications typically demand long service life and in certain cases require parts with high levels of technical cleanliness and purity. There are requirements for elastomer, polyurethane, PTFE and metal sealing solutions. It is important full consideration of the application to select the most appropriate seal design and materials. Learn more about how we serve customers in the Hydrogen & Renewable Energy Industry HERE
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Product Range
Our seal products range from simple static O-rings to complex and bespoke seal designs in specialist materials. Whatever your application, we have the seal product for you.
