Patent ID: 9169713
Filing Date: 2015-10-27
Classification: E21B

Abstract:
1. A lock assembly for a blowout preventer of a wellsite having a tubular extending from a wellbore, the blowout preventer comprising a housing and a ram assembly, the housing having a bore and a channel therethrough, the tubular positionable through the bore and engageable therein, the ram assembly slidably positionable in the channel and engageable with the tubular, the ram assembly comprising a ram block, a ram cylinder, and a ram shaft operatively connecting the ram block to the ram cylinder, the lock assembly comprising: a lock cylinder operatively connectable to the ram cylinder, the ram shaft having an end slidably extendable into a lock cavity of the lock cylinder; a lock piston slidably positionable in the lock cylinder and separating the lock cavity into a variable volume lock chamber and a variable volume closing chamber, the lock piston movable between a locked and unlocked position, the lock piston having a ram surface engageable with the end of the ram shaft when the lock piston is in the locked position and having a ram hole therethrough to receive the end of the ram shaft when the lock piston is in the unlocked position whereby the ram block is selectively lockable about the tubular; and a ram valve triggered upon abutment with a ram shaft to selectively vent fluid from the variable volume lock chamber.