Patent ID: 8322443
Filing Date: 2012-12-04
Classification: E21B

Abstract:
1. In a wellhead assembly having a cylindrical bore, a first plug located in and sealingly engaging the cylindrical bore, a second plug located in and sealingly engaging the cylindrical bore, the second plug being spaced axially apart from the first plug, wherein the cylindrical bore, the first plug, and the second plug define a cavity, the cavity being adapted to retain a trapped fluid between the first and second plugs, an apparatus for relieving pressure in the cavity, comprising: a vent passage in fluid communication with the cavity, wherein the vent passage has an outlet at an exterior of the wellhead assembly to flow at least a portion of the trapped fluid from the cavity; a conical seat formed in the vent passage at the outlet; an outlet flat shoulder located outward from the conical seat; a valve housing mounted to the exterior of the wellhead housing over the outlet; a valve member having a conical sealing surface that engages the seat and a valve member flat shoulder outward from the conical sealing surface, the valve member having a longitudinal axis having a handle being accessible from an exterior of the wellhead assembly, the valve member being secured by threads to the valve housing; and wherein the valve member is movable axially by rotating the handle to an open position, a restricted position wherein the valve member flat shoulder and the outlet flat shoulder are radially spaced apart from each other by a pre-determined distance, and a closed position, the open position permitting a fluid to flow through the vent passage at a first rate, the restricted position permitting fluid to flow through the vent passage at a second rate, the second rate being smaller than the first rate, and the closed position stopping fluid flow.