Importance

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Abstract

A tool (10) for the installation and removal of back pressure valves or plugs in a wellhead under pressure conditions to permit repair and replacement of wellhead outlet valves. The tool (10) comprises an elongate cylindrical housing (31, 32, 33) in which a manipulator rod (30) is slidably mounted in axial alignment therewith. The tool (10) includes a piston (55) which is sleeved about the rod (30) and adapted to be selectively clamped thereto. The manipulator rod (30) is provided at one end with a back pressure valve of plug (84) attached thereto. The tool (10) includes a fluid controls system which is connectable to an external fluid pressure source (P) or the pressure of the well itself. The fluid controls system with associated valves effects pressure balancing of the rod by well pressure and permits actuation of the piston (55) to effect insertion of the manipulator rod (30) into the well against the wellhead pressure in a series of steps utilizing fluid pressure from the external source (P) or from the well itself to drive the piston (55). The manipulator rod (30) is inserted by clamping the piston (55) to the rod (30) during the down strokes until the back pressure valve or plug (84) engages a threaded portion of the bore of the wellhead. By axial rotation of the manipulator rod (30), the back pressure valve or plug (84) is threadedly connected into the wellhead bore to shut off the well and permit the removal and replacement of wellhead valves. The manipulator rod (30) may then be removed from the wellhead by manually gripping and lifting the rod after its detachment from the plug (84), the tool housing and piston (55) or by a series of steps utilizing the pressure source (P) to repeatedly actuate the piston with selective clamping of the piston to the rod (30) during the up strokes to push the rod (30) out of the wellhead.

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First Claim