Three Common Types of Flange Face Gaskets (Flat Faces, Raised Face Flanges, Ring-Type Joint Faces)30 June 2016
Gasket design can’t be limited by a generic shape, not when flange outlines muddy the waters by diverging in form. There are currently three common faces that require specialised flange face gaskets, of which we’ll begin with the basic flat faces family. After chronicling the planar profile, we’ll hop across to raised face flanges. Finally, we’ll conclude with ring-type joint faces.
Common Flat Faces Dominate Flange Design
In order to strengthen the seal between two fluid-conveying mechanical sections, shaped flanges must be partnered with matching flange face gaskets, the reinforced rings that support the uniquely contoured surfaces of the joint-strengthening mechanical asset. A flattened flange adopts a planar form so that the bolt ring and contact zone are on the same level. The gasket is seated flush against these interior plate sections, thus ensuring the flange mates evenly.
Raised Face Flanges Deliver Concentrated Contact Force
When the gasket area is machined so that it’s raised above the bolt circle, then compressible force is focused on that contact area. This feature enables a diverse range of gasket types to be employed within this reduced cross-sectional area. They include spiral wound and double jacketed gaskets, sealing types that function best when used in chemical processing plants and highly toxic production facilities. Mated raised face flanges are easy to identify because an initial glance fools an observer into believing a gap exists between the faces. A closer look reveals the ring of bolts surrounding the contact area while the external edges of the flanges are spatially free but subject to enhanced fastener compression.
Ring-Type Joint Faces
Called into service when specialised sealing applications arise, this flange type uses a proprietary oval and octagonal configuration, a groove surface contact area that requires the two facing surfaces to wedge together and create a tightly secured joint. Used in high-temperature and high-pressure industrial scenarios, the flanges are finely machined to guarantee initial line contact, so the accompanying gasket is also made from an alloy-reinforced material. In doing so, the mating surfaces wedge together in such a way as to generate a “microfine” joint. In effect, the soft metals weld together.
In flange engineering terms, flat faces are workhorse products, the full-contact champions that dominate most applications, but flange face gaskets don’t always favour a broad cross-sectional areal format, which is when ring-type joint faces and their ilk take over by focusing fastener pressure on a reduced contact zone, an area that requires metal gaskets and robust seals.
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