Shut=off for sea bed blowout-preventer shaft - can be quickly released and replaced without pilot pressure

摘要

Shut-off valve includes a housing through which there is a flow pasage with a shut-off valve body which is movable in the flow passage between an open and a closed position. It is designed to be lowered on the end of a train of pipes into a blow-out-preventer shaft at the upper end of a borehole below water. The valve body may be a ball which is displaced into the open position by an operating mechanism. This may be energised hydraulically via a pilot line so as to move the valve from the closed to the open position, whilst when pressure in the line is reduced a further mechanism acting on it, brings the valve back into the closed position. A support sleeve which can be lowered into the housing making a seal is fixed to the botton end of the train of pipes. The sleeve can be fixed detachably to the housing by means of locking details and the locking details can be bolted in place by a further hydraulic mechanism. This can be moved into the unbolted position by pressure in a second pilot line, whilst the opening pressure in the first-mentioned pilot lines moves the bolting mechanism into contact with the locking details. The train of pipes can quickly be released in an emergency and reconnected to the valve later. If pilot pressure fails and the latches and bolting mechanism cannot be disengaged hydraulically, the support sleeve can be unscrewed to release it. The couple between the housing and the support sleeve is transmitted by claws. Without load on the locking details so that when the couple is broken, the support sleeve can be unscrewed.