Abstract: A system for connecting and disconnecting a lower end of a marine riser (25) to and from a blow out preventer stack on a subsea Wellhead comprises gripping members (26) for the marine riser and a lock element (27) for locking the gripping members (26). The system comprises first primary actuators (28), second primary actuators (29) and secondary actuators (30) for moving the lock element (27) to an unlock position, and hydraulic circuitry for actuating the actuators. The system further comprises a hydraulic backup unlock circuit (9, 11, 16) comprising a triple flow divider (8) for dividing fluid flow from a source (16) into one flow for actuating the first primary actuators (28), one flow for actuating the second primary actuators (29) and one flow for actuating the secondary actuators (30).

Abstract: A system for connecting and disconnecting a lower end of a marine riser (25) to and from a blow out preventer stack on a subsea wellhead comprises gripping members (26) for the marine riser and a lock element (27) for locking the gripping members (26). The system comprises first primary actuators (28), second primary actuators (29) and secondary actuators (30) for moving the lock element (27) to an unlock position, and hydraulic circuitry for actuating the actuators. The system further comprises a hydraulic backup unlock circuit (9, 11, 16) comprising a triple flow divider (8) for dividing fluid flow from a source (16) into one flow for actuating the first primary actuators (28), one flow for actuating the second primary actuators (29) and one flow for actuating the secondary actuators (30).

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. The triggering mechanism comprises a cam ring (5) secured to a displaceable part (4) of a flex joint for the riser (2), and an actuator ring (8) which by means of hydraulic cylinders are translatory movable towards a stationary part (3) of the flex joint. An angular displacement (&agr;) of the riser (2) causes an angular displacement (&agr;) of the cam ring (5), which contacts the actuator ring (8) and forces the actuator ring (8) towards the stationary part (3) of the flex joint, causing an activating of a trigger (13) for the triggering valve (1).