Patent ID: 6568476
Filing Date: 2003-05-27
Classification: E21B,Y10S

Abstract:
A triggering mechanism for a triggering valve (1) of a hydraulic emergency unlock circuit for unlocking hydraulically operated gripping members of a riser connector which connects a lower end of a riser (2) to a wellhead on a sea floor, angular displacement (&agr;) of the riser (2) is allowed by a flex joint comprising a stationary part (3) connected to the riser connector by the gripping members and an angularly displaceable part (4) secured to the lower end of the riser (2), the stationary part (3) of the flex joint and the displaceable part (4) of the flex joint being coaxial when the riser (2) is in a non-displaced position, wherein the triggering mechanism comprises:a cam ring (5) which is secured to and coaxial with the displaceable part (4) of the flex joint, hydraulic cylinders (6, 6â€²) which are secured to the stationary part (3) of the flex joint and are parallel with an axis of the stationary part (3) of the flex joint, and which are arranged in a circle which is coaxial with the stationary part (3) of the flex joint, through-going piston rods (7, 7â€²) of the hydraulic cylinders (6, 6â€²), an actuator ring (8) mechanically connected to ends of the piston rods (7, 7,â€²) pointing towards the cam ring (5), the actuator ring (8) then being coaxial with the stationary part (3) of the flex joint, the actuator ring (8) is arranged with a clearance to the cam ring (5), the cam ring (5) and the actuator ring (8) then being parallel when the stationary part (3) of the flex joint and the displaceable part (4) of the flex joint are coaxial, pistons (9, 9â€²) dividing the hydraulic cylinders (6, 6â€²) in upper chambers (10, 10â€²) and lower chambers (11, 11â€²), the upper chambers (10, 10â€²) being on the actuator ring (8) side of the pistons (9, 9â€²), the through-going piston rods (7, 7â€²) ensure equal cross-sectional area in the upper and lower chambers, cross-connecting conduits (12, 12â€²) connecting upper chambers (10, 10â€²) with lower chambers (11, 11â€²) in oppositely located hydraulic cylinders (6, 6â€²), a trigger (13) for the triggering valve (1) located on the stationary part (3) of the flex joint, between the stationary part (3) of the flex joint and the actuator ring (8), whereby an angular displacement (&agr;) of the riser (2) causes an angular displacement (&agr;) of the cam ring (5), when the angular displacement (&agr;) of the cam ring (5) exceeds a predetermined angle the cam ring (5) contacts the actuator ring (8) and forces the actuator ring (8) towards the stationary part (3) of the flex joint, causing movement of the piston rods (7, 7â€²) and the pistons (9, 9â€²), causing hydraulic flow in the cross-connecting conduits (12, 12â€²), which ensure equal movement of pistons (9, 9â€²) and piston rods (7, 7â€²) in oppositely located hydraulic cylinders (6, 6â€²), the actuator ring (8) thereby move translatory, causing an activating of the trigger (13) for the triggering valve (1), irrespectively of the direction of the angular displacement (&agr;) of the riser (2).