Abstract: A backseat assembly for an expanding gate valve includes a sealing member slidingly disposed about the stem and a biasing member biasing the sealing member away from the gate. Upon the gate and segment traveling to the open position of the valve, the segment engages the valve housing and stops its further movement. The stem and gate continue their travel with the sealing member engaging an annular seat on the housing for sealing between the stem and housing. The sealing member includes an annular resilient sealing member which initially engages the annular seat of the housing. The biasing member places a preload on the sealing member such that upon engagement of the annular seat by the sealing member, there is initial sealing force placed on the sealing engagement. The fluid pressures within the valve chamber add an additional sealing force to the sealing member.

Abstract: A lockdown loading ring mechanism for a dual crossover seal in a pressurized wellhead which comprises a segmented loading ring assembly 60 of a plurality of arcuate segments 60a arranged in circular fashion within the wellhead annulus between the dual sealing devices of a dual crossover seal assembly 40. The ends of adjacent segments are spaced to allow for contraction and expansion of the assembly. Each segment is actuated by at least one holddown screw 66 of a plurality of holddown screws disposed in radial array about the wellhead axis in equiangular spacing and an equal number of holddown screws are employed to actuate each segment.

Abstract: A double acting manual override mechanism for the hydraulic actuator of a subsea gate valve, and a visual indicator device for indicating the gate position. The gate is normally held open by hydraulic pressure and is moved by a spring to a fail closed position in the event of a malfunction. The override includes a drive nut threaded onto the valve stem and a drive sleeve which is telescoped on the drive nut and connected therewith by a series of splines. Spaced apart abutment surfaces are provided on the sleeve to limit axial movement of the drive nut on the valve stem in both directions. Rotation of the sleeve by means of an adapter is translated into rotation of the drive nut which contacts one of the abutment surfaces and thereafter effects axial movement of the valve stem to open or close the gate. The indicator device includes a watertight, transparent housing within which an indicator disc moves in response to movement of the gate.

Abstract: A generally cylindrical seat for a gate valve is pressed in a recess in the valve body with a tight fit. A deformable seal fits within an opposed pair of grooves on the back face of the seat and the gate valve body and the seal is deformed when the seat is pressed in the recess. The seat has a relatively small annular channel spaced in outer concentric relation to the seal groove to provide a lubricant pocket to receive lubricant forced along the adjacent contacting surfaces defining the recess when the seat is pressed in and permit metal-to-metal abutting contact between the seat and valve body.