What 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 and a topography that looks similar to a mountain range or the surface of the moon. The roughness of a surface is generally linked to the … Continued
Elastomer rubbers look very similar – but are they all the same? With many different base groups and recipe formulations, there’s a huge range of elastomer materials suitable for applications with varying temperature ranges and chemical media compatibility. It’s critical to the seal performance to make the right choice. There are number of factors to consider, these include: … Continued
Tolerances are present in every man-made item. It is practically impossible to repeatedly manufacture something to an exact size or specification. In seal manufacturing, it’s important to understand which tolerances impact performance and by how much. This will ensure a system is optimized for overall performance, and whole-life product cost. Considerations for tolerances include the … Continued
How is it manufactured? A question we get asked in the seal design process, but perhaps not considered often enough. How a rubber seal is produced can affect a number of things; the cost, the material choice…even how a part should be designed. All of these can have a significant impact on the performance of … Continued
The 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 … Continued
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 … Continued
Cryogenic 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 … Continued
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 … Continued
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 … Continued
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 … Continued
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.
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.
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.
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.
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