Mud saver valve

Abstract

A drilling mud saver valve connected to the lower end of a kelly allows down flow of mud or other drilling fluid when pumps are actuated to circulate drilling fluid, but closes when the pumps are off, thereby retaining drilling fluid thereabove in the kelly to prevent loss of fluid when the kelly and valve are disconnected from the drill pipe. The valve includes a tubular body and a top sub screwed therein. A replaceable seat is carried by the lower end of the top sub. A poppet type valve closure is urged upwardly against the seat by a helical spring strong enough to close the valve against the weight of drilling mud in the kelly. The poppet valve closure has a central flow passage therethrough, communicating with the stem and controlled by an upwardly opening check valve, to communicate drill pipe pressure to the kelly when the pumps are off. The check valve closure is frangible for easy break out if wire line tools need to be run through the valve. The check valve closure includes a frangible metal disc threaded to a tubular metal guide stem and a polyurethane cover bonded to the disc. The cover has a snap-on lip extending down around the periphery of the disc, the lip being captured between the disc and guide stem, the lip also providing a seal ring the check valve closure to its seat. The poppet valve closure has a tubular stem extending down through the spring. The stem has ports to allow fluid passing below the closure to enter the stem and flow down therethrough, bypassing an annular chamber between the stem and body in which the spring is disposed. The chamber is sealed by upper and lower semi-floating annular seal means between the stem and body and is kept at substantially atmospheric pressure. Pressure differential due to the sealed chamber holds the valve open without throttling when the valve opens. A soda straw type check valve controls a port in the sealed chamber and weeps if the seal means leaks. The stem includes upper and lower sections having respectively downwardly and upwardly facing shoudlers. The sections are screwed together and provide screw jack means for initial compression of the spring to facilitate assembly; the spring being captured between the upper and lower seal means whose axial separation is limited by the shoulders. The upper seal means includes upper and lower seal rings sealing between the stem and valve body. The inner lip on each of these seal rings is protected against assembly hang up by back up means including a back up ring for the upper seal ring. The back up ring is sealed to the stem by a stationary seal. The lower seal ring is backed up by the upper end of a spacer sleeve. The sleeve extends down below the threaded connection between the stem sections, sealing with the stem therebelow and thereabove and providing a bearing for the upper end of the spring. The back up ring and spacer ring are made of metal softer than steel.