Q: How do I choose the right metal seal?
A: Selecting the most appropriate seal for your application can save a lot of money by eliminating the tremendous costs associated with machine downtime, unscheduled service, and spill remediation.
We offer a wide variety of metal seals designed to meet the challenges of high temperatures or cryogenics, high pressures, vacuum, corrosive chemicals and even intense levels of radiation. Unlike rubber, composite, asbestos, and other organic gaskets, metal seals do not deteriorate over time due to compacting, outgassing or blowouts. Seal performance is directly related to seal assembly load, which is dependent on the cross-section ("O", "C", "E", etc) and alloy selected.
In addition, because the seating loads for metal seals can be significantly less than those required for crush-type gaskets, the strength and mass of the flanges can be reduced. This is particularly important to designers concerned with reducing size and weight.
Review how the various metal seal types listed below meet different sealing needs.
Provides a good combination of leak tightness and springback. It is one of the most popular designs.
Offers the greatest amount of springback of all metal seals.
Used for over 60 years, the metal o-ring remains an economical choice for high-load, high pressure sealing.
Similar to the standard C-Ring, but it has an internal spring that produces much greater load for sealing against rough surfaces or when extreme leak tightness is required.
Low cost, high load, crush type seal used with smooth mating surfaces and minimum relative movement.
High load metal seals are designed for extreme leak tightness. High elasticity seals provide resiliency or springback needed to maintain effective sealing during mating surface separation, such as with thermal cycling.
Keep in mind that metal face seals, which are ideal for static applications, are compressed by approximately 10% to 20% of their original free height to produce preferred sealing loads for optimized performance. Axial seals can be used in either static or semi-dynamic applications to seal against shafts and bores.
Due to the relative rigidity of metal seals in comparison to elastomeric and polymeric seals, the axial seals must be produced to tighter tolerances than face seal grooves. Face seals are generally preferred instead of axial seals due to their relative ease of gland manufacture, installation and seal performance.
More FAQs
A: No metal seals are not considered to be reusable. Unlike many elastomeric seals, metal seals generally exhibit some amount of plastic deformation ("crush"), which makes their reuse impractical. This act of plastic deformation will weaken the base material, which will lower the seal's seating load and reduce the seal's springback capabilities. Also, plated metal seals will conform to the imperfections of the cavity's surface. If the seal is reinstalled, it is unlikely that the imperfections imprinted in the seal will line up with the cavity’s imperfections and this may introduce leak paths.
A: A finish of 16 to 32 Ra is suitable for most applications. Very demanding applications (sealing Helium for instance) may require a finish of 8 to 16 Ra. If in doubt, please submit an inquiry or contact the application engineering experts at Parker CSS Division's Advanced Products Business Unit.
A: Plating adds a soft surface to the seal. This surface deforms under pressure and helps to fill imperfections in the mating surfaces of the hardware. Note that typically only O-Rings and C-Seals are plated because they generate enough assembly load to deform the plating. E-Seals are usually not plated because they do not generate enough assembly load to deform the plating.
A: Yes, all metal seals have maximum allowable pressures. These pressure maximums are detailed in our Metal Seal Design Guide CSS 5129. Generally speaking C-Seals have cross sections with a maximum allowable of 99KSI, O-Seals have cross sections with a maximum allowable of 25KSI and E-Seals have some cross sections with a maximum allowable of 5KSI. As you can see, the maximum allowable pressure limit is dependent on the application conditions in conjunction with the seal type
A: Metal seals can be designed to achieve very low leak rates. Leak rates are dependent on application conditions as well as the fluid media. A metal seal may be a hermetic seal for thick oil, but may not be for helium. Please contact your local Parker Sales Representative and we will be happy to discuss with you metal seal options for your specific application.
A: Yes, Parker is fully prepared to provide all customers with seal and cavity recommendations for each application. So long as you have your application conditions prepared (fluid media, temperatures, pressures, expectations) Parker can provide you the best seal and cavity recommendation to achieve the lowest leak rate. In addition, all custom parts come with a fully detailed Parker drawing that is reviewed and approved prior to manufacturing of the seals.
A: Metal seals may be used in dynamic applications dependent upon the leak rate expectations. Generally speaking, metal seals should be primarily used in static applications. There are a few reciprocating applications which can utilize metal seals, but their use should be thoroughly evaluated on a case-by-case basis. Parker also offers a metal seal assembly solution called Chevron seals, that are used in high pressure dynamic sealing applications. Please contact us and we will be happy to discuss with you metal seal options for your specific application.
Our team of experienced application engineers is available to answer questions and help down select the appropriate solution for your application.