A GATE VALVE ASSEMBLY

摘要

A gate valve assembly has a body with a valve chamber that intersects a fluid conduit therethrough. A valve gate is disposed in the chamber for movement in a direction transverse to said conduit between open and closed positions. The gate is driven by a sliding stem that is actuated hydraulically by directing pressurised hydraulic fluid into a working chamber defined between part of the stem and a bore in the housing. The assembly also has a rotary override actuator that is actuated manually or by a ROV. The rotary actuator has an eccentrically mounted crank pin that is received in a slot of the stem. The pin and slot combination serve to convert rotational movement of the actuator into a translation movement of the gate member. The pin and slot connection permits operation of the valve through only one half turn. The sliding stem has a pressure balance passage defined therethrough to equalise pressure at both eiids of the stem, thereby eliminating stem ejection forces applied by the fluid passing through the fluid conduit.