Lined gate valve having improved seat

摘要

A lined gate valve having a seat proportioned such that the ratio of the unit bearing stress to the unit shear stress is substantially 0.68. In one form of the valve, the seat comprises a plastic ring having an embedded metal band. The seat is removable and is held in place by the end pressure of a pipe flange. The seat can be removed by tapping against the seat in an axially outward direction. In another form of the valve, the seat is integral but has the same proportions as above recited.