Metal seals: when polymers just cannot cope
04 July 2007
Metal sealing products, now available from Moontown, can solve problems for the most demanding applications where conventional elastomeric and PTFE products are excluded due to extremes of temperature, pressure, radiation, permeability, fatigue, corrosion and so on. The company offers three metal sealing product series, designated ‘O’, ‘C’ and ‘E’. Generally designed for use in static applications, the special ‘U’ style design is manufactured to order for applications involving a limited degree of linear movement, as in expansion joints. Typical applications include automotive, aerospace and gas turbine engines, together with compressors, accelerators, heat exchangers and reactors. Other areas include pumps, valves and other equipment associated with a wide range of industry such as chemical, oil and gas and plastic moulding.
Metal ‘O’ ring seals are generally fabricated from tubing, including stainless steel, and high temperature alloys such as Inconel. These resilient materials enable the seal to ‘spring-back’, and are not subject to out-gassing, age deterioration or environmental incompatibility. They can be used for either liquid or gas seals, at temperatures from -253oC to 1,100oC, under vacuum conditions as well as at pressures up to 3,450bar. They can be supplied in free-height diameters from 0.89 to 12.7mm in O/D sizes (for internal pressure applications) and I/D sizes (for external pressures) of 9.52 to 3,048mm. Plain, non self-energised seals can be used for pressures from ultra-vacuum to 70bar positive pressure, while vented energised seals are recommended for operation at pressures above 70bar.
Metal ‘C’ ring seals are particularly suitable for applications involving pressure fluctuations and excessive heat. These highly resilient seals can be used for internal, external and axial pressures under extreme conditions that preclude the use of gaskets containing organic materials. Key to their performance is in the C-shaped construction providing relatively high spring-back levels compatible with lower flange load requirements. To combine strength with temperature resistance, the seals are manufactured primarily from X750 or 718 nickel alloys, but almost any alloy that can be formed can also be used. They can be supplied in free heights from 0.79 to 12.7mm and ID/OD sizes from 4.75 to 3,048mm. Spring energised versions of the ‘C’ ring seals can also be supplied for more critical and demanding applications including limited reciprocating and rotating motion.
Metal ‘E’ ring seals are designed for lighter loadings but provide superior flexibility and spring-back, resulting in very good fatigue resistance. These can be supplied for internal and external pressure applications in nominal free height sizes from 1.91 to 7.49mm and ID/OD diameters from 38 to 1524mm.
Most products are supplied in circular form but square, rectangular, oval and racetrack configuration, as well as special shapes, can also be accommodated. These seals can also be plated or coated, providing a soft, malleable seal surface that can bed into mating hardware, minimising surface imperfections and enhancing seal performance.
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