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 blowout preventer, particularly for use in drilling bore hole sections near the sea bed, is adapted to prevent blowout of shallow gas in the bore hole. It comprises at least one annular, preferably flexibly expansible and contractible packing element (59, 59'), which by radially directed expansion is adapted to rest sealingly against the wall of the bore hole and close the passage through the annular space of the bore hole. The blowout preventer comprises an inner sleeve element (1) being limited telescopingly displaceable in relation to the outer housing (8) of the blowout preventer and being spring loaded (9) towards extended telescopic position when it is not subjected to extra weight loading, and means which in the relative contracted telescopic position of the sleeve element (1) and outer housing (8) is adapted to close the passage through the inner cavity (48) of the blowout preventer and establish liquid connection to the packing element or elements (59, 59') for inflation thereof.