AIGI 30 A solid metal gasket that is softer than the mating flange material that is virtually 'crushed' into the flange face, creating a seal by filling imperfections and leak paths with gasket material. Under high sealing stress the gasket deforms but not the flange. They are used predominantly in the petrochemical industry (offshore oil platforms, refineries) due to the high service pressures required in their processes. Ring joint gaskets are machined to exact specifications and tight tolerances and come in a number of styles. Hardness of Materials On compression of the flange assembly, it is imperative that the ring joint gasket be significantly softer than the flange groove so that the gasket plastically deforms and not the groove. The use of harder ring joint gaskets can result in flange groove damage. For this reason, ring joint gaskets are supplied with the following maximum hardness values: Certified at API 6A-1069
