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.
Moulded gaskets for an automotive applicationMoulded gaskets for an automotive application An 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. Here we explore more about our solution for a moulded gasket for this automotive application. The application This gasket is used within a valve housing in an automotive application. The original competitor gasket was experiencing failure at the "T-junction" areas of the seal. Therefore, our customer had experienced chronic failures of their existing design at high temperatures and high pressures.A pulsating pressure of up to 50 Bar and temperatures up to 150°C provide an extreme environment for the seal. Consequently, 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 We manufactured prototype parts using a single-cavity soft tool and sent them to the customer for in-house testing and validation. The prototype gaskets nearly passed testing but fell just short of the 50 Bar pressure requirement at 150°C, achieving 42 Bar instead. Even so, they significantly improved on the performance of the customer’s original gasket.Upon analysis of customer test data and furthermore by reviewing images of the tested parts, improvements were needed. We determined there were areas where the gasket was sliding in the groove and then shearing as the pressure pulsed. To resolve this issue, our engineers added beads to the rear of the T-intersections of the gasket. This provided additional support, further stabilising the gasket at the high-pressure stress points in the groove. This reduced the amount of movement within the housing.Furthermore, 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 With the new design approved, the customer moved to production tooling stage and sample parts were produced to PPAP Level 3. These parts have since been approved and full production quantities have been ordered manufacturing builds in 2022.For more about our mouldings & gaskets, see our dedicated page HERE.
Special O-rings for an automotive applicationSpecial O-rings for an automotive application Our customer manufactures high performance oil and vacuum pump solutions, and approached our engineers with a new O-ring for their automotive application. The application Our customer required an FKM (Viton™) 60 shore O-ring to meet Porsche material specification PN707 Class 2 (Oil), Class 5 (Fuel/FAME mix) and Class 12 (Blowby gas).This was a very cost sensitive project and the lead time required was very tight; especially as we did not have an existing grade in our materials portfolio to meet this specification. The challenges Our engineers reviewed the application, and we provided two material options. The first was a lower cost grade of FKM (Viton™) A grade. This possibly meets the Porsche specification required. The second material to be offered was a medium to higher cost FKM (Viton™) B grade. This solution determined the best fit for the specification.We supplied a quotation for both material options. These included production tooling, PPAP Level 3 submission (with samples), testing programme for both material variants and a pre-production batch of O-rings. This was an urgent project. Consequently, we could accommodate PPAP Level 3 grade O-rings for both materials to be manufactured from the same tool. Additionally, to save time we would conduct material testing in tandem with the manufacture and preparation of the production tool. The choice of compound 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. As a result, 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 vehiclesHigh speed Rotary seals for electric vehicles The 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 over 30 years’ experience of providing pioneering technologies globally to the mobility industry. This established company is a supplier of powertrain solutions for electric and hybrid vehicles, additionally traditional internal combustion power engines.Their team of powertrain development experts approached our engineers for a rotary shaft sealing solution for the gearbox within an electric vehicle. The position of the seal was required 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 and pressed radially by a tension spring onto the shaft. Additionally, it required a dust lip to provide protection against environmental dirt and debris on the dry motor side.The shaft and housing dimensions were all fixed by the customer. However, they provided a full dimensional, surface finish, pressure, temperature and media specification. This enabled 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 was 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 was designed to act as a dirt and dust excluder, with slight clearance from the shaft to avoid friction. This prevents damage to the seal and unnecessary wear to the rotary system as a whole.In the wet transmission side, it was imperative that the oil was kept away from the e-motor with the same minimal friction requirements. As a result, our engineers have designed the seal with an inlaid PTFE lip with 15% graphite fill. It was energised with spring to ensure force which achieves ultimate shaft sealing performance.Read more about our rotary seals HERE
Why use PTFE seals?Why use PTFE seals? Polytetrafluoroethylene (PTFE) is a thermoplastic polymer. PTFE seals can be used in a variety of sealing applications. It’s suitable when application conditions exceed parameters of elastomeric seal use but not to the extent of a metal seal. What is PTFE? It has a high melting point (342 °C) and morphological characteristics. These allow seal components made from virgin PTFE to be used continuously at service temperatures of up to 260 °C. 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 multiple:Functionality at high and low temperaturesDynamic sealing with high wear capabilitiesHigh pressure sealing (using combinations of PEEK back-up rings)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. However, 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). 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?Why use metal seals? Using metal seals as an engineered sealing solution is appropriate when it’s not possible to use elastomeric or polymer seals. This will be because of 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 and 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 seals 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. They can be used in internal, external and axial pressure conditions. There are different base material characteristics and heat treatments, along with material thickness and cross section of the seal. These all determine the compressive load and 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 have been selected (depending on the application), a variety of platings and coatings are available. This is to 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. However, 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, therefore preventing 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.With ever changing industry demands and fast paced technology developments – particularly from our customers in the Oil & Gas, Aerospace & Defence and Automotive markets – we are challenged daily with applications where the boundaries are being pushed to the absolute limit. We’ve 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 are 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?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. This will have the same profile as the centre line of the groove, and simply drops into place, 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 will 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. Other variables such as life requirement, equipment serviceability and seal compression set will all be considered. Arguably though, compared to other sealing applications there are considerations when designing face, cover or flange sealing solutions. It is imperative to consider the packaging requirements and assembly issues of gasket sealing options. For example, if there is a need to avoid or seal around bolt holes (or other retaining/clamping devices). Additionally, consideration around optimizing hardware wall sections or depths can play an 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. 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. This will be often where the two housing parts are being brought together. A common solution is designing a custom moulding with the same profile as the centre line of the racetrack groove. This will simply drop 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. This can occur when the component needs to be inverted or has the potential for rough handling during assembly. Consequently, 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. This is 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, the risk that any contaminant could keep the gasket off the surface that it’s supposed to be sealing against. As a result, the integrity of the seal can be severely compromised.Neither of these approaches can be recommended. 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 is used. This ensures that they provide sufficient squeeze to prevent the gasket being easily dislodged, whilst not 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.By positioning retention bumps at either end of the bend, the thermal contraction will be controlled to minimize leakage risk. 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 is 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 will be either with the human eye or an automated vision system. However, this does not ensure correct seating all around the gasket length. Additionally, it 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.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
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
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
Moulded gaskets for an automotive applicationMoulded gaskets for an automotive application An 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. Here we explore more about our solution for a moulded gasket for this automotive application. The application This gasket is used within a valve housing in an automotive application. The original competitor gasket was experiencing failure at the "T-junction" areas of the seal. Therefore, our customer had experienced chronic failures of their existing design at high temperatures and high pressures.A pulsating pressure of up to 50 Bar and temperatures up to 150°C provide an extreme environment for the seal. Consequently, 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 We manufactured prototype parts using a single-cavity soft tool and sent them to the customer for in-house testing and validation. The prototype gaskets nearly passed testing but fell just short of the 50 Bar pressure requirement at 150°C, achieving 42 Bar instead. Even so, they significantly improved on the performance of the customer’s original gasket.Upon analysis of customer test data and furthermore by reviewing images of the tested parts, improvements were needed. We determined there were areas where the gasket was sliding in the groove and then shearing as the pressure pulsed. To resolve this issue, our engineers added beads to the rear of the T-intersections of the gasket. This provided additional support, further stabilising the gasket at the high-pressure stress points in the groove. This reduced the amount of movement within the housing.Furthermore, 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 With the new design approved, the customer moved to production tooling stage and sample parts were produced to PPAP Level 3. These parts have since been approved and full production quantities have been ordered manufacturing builds in 2022.For more about our mouldings & gaskets, see our dedicated page HERE.
Special O-rings for an automotive applicationSpecial O-rings for an automotive application Our customer manufactures high performance oil and vacuum pump solutions, and approached our engineers with a new O-ring for their automotive application. The application Our customer required an FKM (Viton™) 60 shore O-ring to meet Porsche material specification PN707 Class 2 (Oil), Class 5 (Fuel/FAME mix) and Class 12 (Blowby gas).This was a very cost sensitive project and the lead time required was very tight; especially as we did not have an existing grade in our materials portfolio to meet this specification. The challenges Our engineers reviewed the application, and we provided two material options. The first was a lower cost grade of FKM (Viton™) A grade. This possibly meets the Porsche specification required. The second material to be offered was a medium to higher cost FKM (Viton™) B grade. This solution determined the best fit for the specification.We supplied a quotation for both material options. These included production tooling, PPAP Level 3 submission (with samples), testing programme for both material variants and a pre-production batch of O-rings. This was an urgent project. Consequently, we could accommodate PPAP Level 3 grade O-rings for both materials to be manufactured from the same tool. Additionally, to save time we would conduct material testing in tandem with the manufacture and preparation of the production tool. The choice of compound 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. As a result, 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 vehiclesHigh speed Rotary seals for electric vehicles The 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 over 30 years’ experience of providing pioneering technologies globally to the mobility industry. This established company is a supplier of powertrain solutions for electric and hybrid vehicles, additionally traditional internal combustion power engines.Their team of powertrain development experts approached our engineers for a rotary shaft sealing solution for the gearbox within an electric vehicle. The position of the seal was required 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 and pressed radially by a tension spring onto the shaft. Additionally, it required a dust lip to provide protection against environmental dirt and debris on the dry motor side.The shaft and housing dimensions were all fixed by the customer. However, they provided a full dimensional, surface finish, pressure, temperature and media specification. This enabled 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 was 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 was designed to act as a dirt and dust excluder, with slight clearance from the shaft to avoid friction. This prevents damage to the seal and unnecessary wear to the rotary system as a whole.In the wet transmission side, it was imperative that the oil was kept away from the e-motor with the same minimal friction requirements. As a result, our engineers have designed the seal with an inlaid PTFE lip with 15% graphite fill. It was energised with spring to ensure force which achieves ultimate shaft sealing performance.Read more about our rotary seals HERE
Why use PTFE seals?Why use PTFE seals? Polytetrafluoroethylene (PTFE) is a thermoplastic polymer. PTFE seals can be used in a variety of sealing applications. It’s suitable when application conditions exceed parameters of elastomeric seal use but not to the extent of a metal seal. What is PTFE? It has a high melting point (342 °C) and morphological characteristics. These allow seal components made from virgin PTFE to be used continuously at service temperatures of up to 260 °C. 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 multiple:Functionality at high and low temperaturesDynamic sealing with high wear capabilitiesHigh pressure sealing (using combinations of PEEK back-up rings)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. However, 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). 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?Why use metal seals? Using metal seals as an engineered sealing solution is appropriate when it’s not possible to use elastomeric or polymer seals. This will be because of 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 and 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 seals 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. They can be used in internal, external and axial pressure conditions. There are different base material characteristics and heat treatments, along with material thickness and cross section of the seal. These all determine the compressive load and 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 have been selected (depending on the application), a variety of platings and coatings are available. This is to 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. However, 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, therefore preventing 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.With ever changing industry demands and fast paced technology developments – particularly from our customers in the Oil & Gas, Aerospace & Defence and Automotive markets – we are challenged daily with applications where the boundaries are being pushed to the absolute limit. We’ve 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 are 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?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. This will have the same profile as the centre line of the groove, and simply drops into place, 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 will 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. Other variables such as life requirement, equipment serviceability and seal compression set will all be considered. Arguably though, compared to other sealing applications there are considerations when designing face, cover or flange sealing solutions. It is imperative to consider the packaging requirements and assembly issues of gasket sealing options. For example, if there is a need to avoid or seal around bolt holes (or other retaining/clamping devices). Additionally, consideration around optimizing hardware wall sections or depths can play an 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. 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. This will be often where the two housing parts are being brought together. A common solution is designing a custom moulding with the same profile as the centre line of the racetrack groove. This will simply drop 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. This can occur when the component needs to be inverted or has the potential for rough handling during assembly. Consequently, 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. This is 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, the risk that any contaminant could keep the gasket off the surface that it’s supposed to be sealing against. As a result, the integrity of the seal can be severely compromised.Neither of these approaches can be recommended. 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 is used. This ensures that they provide sufficient squeeze to prevent the gasket being easily dislodged, whilst not 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.By positioning retention bumps at either end of the bend, the thermal contraction will be controlled to minimize leakage risk. 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 is 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 will be either with the human eye or an automated vision system. However, this does not ensure correct seating all around the gasket length. Additionally, it 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.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
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
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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.
