Abstract: An improved casing hanger and seal assembly includes a split seal ring disposed between annular plates on a support shoulder in a wellhead. A plurality of floating pedestals are received within the seal ring. A slip and bowl assembly is mounted over the seal ring in the head, and when loaded by the casing weight provides the force to energize the seal ring to seal the casing and head. The floating pedestals provide stops to limit seal energization to a predetermined amount, and are movable with the seal ring to assist in distributing stress equally across the cross-section of the seal ring.

Abstract: A fail-safe valve actuator includes a hydraulic piston (17) and cylinder (15) for driving the valve stem (9) and gate member (35) of a gate valve into a first flow control state responsive to sufficient pressure delivered by a fluid or gas supply line (92). Upon failure or other loss of sufficient control line pressure, a volute spring (7) drives the cylinder (15), and hence the stem (9) and gate member (35), axially outward resulting in the valve being moved into a second flow control state.