BALL VALVE SEATS FOR LOW TORQUE OPERATION AND FULL PRESSURE RANGE SEALABILITY

摘要

Seats, seat seals, and seat pockets for a floating ball valve are disclosed, which permit full pressure range sealability and low operating torque over the entire range of working pressures. A cantilevered spring action biases seat seal lips into sealing engagement with the ball. Seat pockets in the body house the seat members and restrain them against bending or twisting. The seal lips extend radially inwardly and axially outwardly from the seat members, and are deformed into the seat pockets by the ball upon assembly, biasing them into sealing engagement with the ball on both sides of the valve with a self-centering effect. The main bodies of the seats each include a curved surface spaced apart from the seal lips, which make sealing contact with the sealing surface of the ball under predetermined conditions. An annular groove on the axially outer side of each of the seats, adjacent to the outer sides of the cantilevered seal lips, houses a resilient seal member which seals against the seat pocket and the lips under low operating pressures. The seal groove has an expanded portion at its radially outer end into which the resilient seal member may be moved by differential pressure under intermediate to high operating pressures, which causes the loss of the seal against the seat pocket. The seat pockets have lips which shield the seats from direct contact with the flow path through the valve, thereby protecting the seats from abrasive or otherwise harmful substances.