Wireline blowout preventer having mechanical and hydraulic sealing

Abstract

A single ram unidirectional wireline BOP system is provided having both mechanical and hydraulic sealing capability. A BOP body having a vertical flow passage and intersecting horizontal ram passages includes a single pair of opposed rams and appropriate actuators for moving the rams into sealing engagement with a wireline extending through the vertical flow passages. Each of the rams incorporates an elastomeric peripheral seal extending about a major portion of the periphery thereof and disposed for sealing engagement with internal wall surfaces of the body. The sealing system of the rams also incorporates a pair of vertically spaced inner elastomeric seals disposed for sealing engagement with one another and with the wireline. Between the upper and lower inner seals in the closed positions of the rams, is defined a small, centralized grease chamber through which the wireline extends. The body of the BOP incorporates a grease fitting for injection of grease into the grease chamber for hydraulic sealing about the wireline. Both the rams incorporate a relief valve controlled pressure relief system for relieving excess grease pressure to the upstream portion of the flow passage of the BOP. The BOP also incorporates a valve controlled pressure equalizing system to permit selective pressure equalization across the seals developed by the upper and lower inner sealing elements to thus reduce pressure energized frictional forces and permit the rams to be easily moved from the closed position towards the open positions thereof.