CURVED FLAPPER SEAL WITH STEPPED INTERMEDIATE SURFACE

摘要

A recess is provided at the periphery of the flapper so that a corner that defines this recess engages an o-ring seal in a seat for the flapper. A reduced contact area of the flapper on the o-ring seal results in increased pressure over the actual contact area. The pressure applied over the contact area also forces a distortion in the o-ring that has a part of the o-ring not restrained due to the presence of the recess moving out of the surrounding o- ring groove so that the corner on the flapper pinches the o-ring that now is partly in and partly extending from its surrounding groove. Sealing is obtained at lower differential pressures and the o-ring is better fixated as a result of the pinch effect of the corner on the flapper.