Pressure compensation/control for fail-safe gate valve

摘要

A fail-safe gate valve for sub-sea use features a floating, pressure biased compensating piston whose movement prevents internal pressure buildup from opening movement of the gate. A pre-charged fluid chamber provides the bias on the balancing piston. Using unequal piston diameters reduces the charge pressure. The balancing piston is not connected to the gate so that internal pressures can be employed to act on a net area, which biases the gate toward its fail-safe position.