Abstract: A system for active heave compensation of the running block in a drilling derrick on board a floating off shore platform comprises a double-acting hydraulic cylinder (1) which is connected to a hydraulic power unit (3) for the supply of hydraulic pressure fluid to the hydraulic cylinder (1), a control unit (6) which regulates the supply conditions of the pressure fluid to the at any time active side (A, B) of the hydraulic cylinder, the hydraulic fluid concurrently being permitted to leave the passive side (B, A) of the hydraulic cylinder. The hydraulic power unit (3) comprises a pump unit (4) which via respective conduits (9a, 9b) are directly connected to the two sides (A, B) of the hydraulic cylinder (1) in order to form a generally closed hydraulic system therewith. The hydraulic fluid delivered by the pump unit (4) to the conduits (9a, 9b) to the active cylinder side is drawn from the conduit (9b, 9a) to the passive cylinder side, while the control unit regulates the output of the pump unit.

Abstract: A system for active heave compensation of the running block in a drilling derrick on board a floating off shore platform comprises a double-acting hydraulic cylinder (1) which is connected to a hydraulic power unit (3) for the supply of hydraulic pressure fluid to the hydraulic cylinder (1), a control unit (6) which regulates the supply conditions of the pressure fluid to the at any time active side (A, B) of the hydraulic cylinder, the hydraulic fluid concurrently being permitted to leave the passive side (B, A) of the hydraulic cylinder. The hydraulic power unit (3) comprises a pump unit (4) which via respective conduits (9a, 9b) are directly connected to the two sides (A, B) of the hydraulic cylinder (1) in order to form a generally closed hydraulic system therewith. The hydraulic fluid delivered by the pump unit (4) to the conduits (9a, 9b) to the active cylinder side is drawn from the conduit (9b, 9a) to the passive cylinder side, while the control unit regulates the output of the pump unit.