Pressure balanced gate valve having selective actuator systems

摘要

A pressure balanced gate valve mechanism wherein a closed loop fluid interchange system interconnects the valve actuator stem area of the valve mechanism with the pressure balancing stem area and functions to accomodate volumetric changes to prevent the development of a hydraulic lock that might otherwise prevent or retard opening and closing movement of the valve mechanism. Internal back-face seating arrangements with combination metal-to-metal and elastomeric sealing elements establish seals between the valve stem and bonnet at one gate position and between the pressure balancing stem and valve body structure at the opposite gate position. An externally threaded portion of the valve bonnet is receivable within internally threaded receiver openings of a plurality of different actuator systems, including manual, mechanical, hydraulic and pneumatic actuator systems. The actuator systems are field interchangeable with the valve in service and under pressure. The valve mechanism is capable of being hydraulically energized by portable hydraulic equipment for moving the valve mechanism to a predetermined position in the event the primary drive system should become inoperative for any reason.