Solid Metal Gaskets
Lens Type Gasket
A Lens Type Gasket is a line contact seal for use in high pressure piping systems and in pressure vessel heads. The lens cross section is a spherical gasket surface and requires special machining on the flanges. In ordering lens gaskets, complete drawing and material specifications must be supplied.
A delta gasket is a pressure actuated gasket used primarily on pressure vessels and valve bonnets at very high pressures in excess of 5000 PSI. As with the lens gasket, complete drawings and material specifications must be supplied. Internal pressure forces the gasket material to expand when the pressure forces tend to separate the flanges. Extremely smooth surface finishes of 63 microinches or smoother are required when using this type of gasket.
The bridge-man gasket is a pressure activated gasket for use on pressure vessel heads and valve bonnets for pressures of 1500 PSI and above. The cross section of the gasket is such that internal pressure acting against the ring forces it against the containing surface making a self-energized seal. Bridge-man gaskets are frequently silver plated or lead plated to provide a softer surface and minimize the force required to flow the gasket metal into the flange surface.
Another gasket concept with origins from the German industrial market are weld gaskets. As standard, two variants exist; Weld Membrane Gaskets in accordance with DIN 2695 and Weld Ring gaskets.
- Weld Membrane Gaskets
The Weld Membrane Gasket consists of two similar rings each of 0.157" (4mm) thickness. For chemical compatibility and in order to ensure controlled thermal conductivity and weld compatibility, the gasket material must always be the same as the flange material. Each ring is individually welded to its mating flange. Upon flange assembly, a second welding operation joins the two rings at their outer diameter which provides for a fully welded joint.
- Weld Ring Gaskets
As with Weld Membrane Gaskets, Weld Ring Gaskets are used in pairs. As standard, each ring is manufactured to similar materials to that of the flange, thus ensuring full compatibility. All welding is conducted on the outside of the gasket and flange, thus ensuring ease of location, especially in restricted applications where space is limited. Two styles exist, Style SR and Style SRL. Style SRL is recommended when there is flange differential radial expansion.