Cover Plate Seals
Cover plate seals are especially for high-pressure, high temperature apparatuses designed to withstand high working conditions. Self-sealing closures offer a large variety of advantages in comparison to commercial flange connections. On the basis of the function principle much of flange and cover material can be saved, provided the design is optimised.
For high-pressure apparatuses and fittings, closures with soft material cover plate seals have been proven more successful than commercial flanged connections, especially for the larger sizes.
Metal cover plate seals are classified as main load gaskets. As long as the inner pressure is lower than the bolt seating pressure, the total seating stress flows across the sealing areas.
As soon as inner pressure exceeds the seating pressure, the bolts will be strained strain and the distance between the sealing areas increases. The internal pressure will expand the gasket to maintain the seal. In other words the gasket acts as self-sealing element. It is important that radial expansion and compression through initial bolt seating stress can be compensated by the elastic behaviour of the gasket material.
The typical initial seating stress for self-sealing gaskets is lower than the necessary values for gaskets in the main load. However, the bolts must to be designed to withstand the internal pressure.