Back pressure valve with contingency release

Abstract

A back pressure valve ('BPV') for use in a wellhead assembly has a contingency release means. The BPV is coupled to the wellhead assembly with a threaded connection, that is formed by engaging threads on the BPV with threads in a tubing hanger inside the wellhead assembly. The contingency release means is activated by applying an overpull to the BPV, which retracts the BPV threads radially inward and away from engagement with tubing hanger threads. Disengaging the threads uncouples the BPV from the tubing hanger allowing BPV removal from the wellhead assembly. The BPV threads are on blocks that are disposed around the BPV circumference. The blocks are biased radially inward with springs. Concentric sleeves inside the blocks resist block inward movement. The overpull telescopes the concentric sleeves allowing the springs to urge blocks radially inward, which moves the BPV threads away from the tubing hanger threads.