A passive heave compensator comprising: a main hydraulic cylinder, including a moveable piston having a piston rod extendible through the main hydraulic cylinder and a piston head, a gas phase above the piston head, and at least one oil phase below the piston head separated by a boundary; an upper connection point associated with the main hydraulic cylinder and a lower connection point associated with the piston rod; and at least one accumulator, the or each accumulator having a moveable separator to divide the accumulator between a gas phase above the separator, and an oil phase below the separator, and the or each oil phase being in communication with an oil phase in the main hydraulic cylinder; characterized in that the main hydraulic cylinder further comprises a cylinder sleeve co-axial with the piston head to provide, in co-ordination with the piston head, the boundary between the gas phase and the at least one oil phase in the main hydraulic cylinder. In this way, the variation in the coordination between the shape, longitudinal position, or both of the piston head, which naturally must be smaller in cross-section than the cross-section of the main hydraulic cylinder, and the transverse extent of the cylinder sleeve, provides variation in the cross-sectional area of oil volume in the main hydraulic cylinder, and thus different damping effects along the length of the main hydraulic cylinder, which are available to the user.

A passive heave compensator comprising: a main hydraulic cylinder, including a moveable piston having a piston rod extendible through the main hydraulic cylinder and a piston head, a gas phase above the piston head, and at least one oil phase below the piston head separated by a boundary; an upper connection point associated with the main hydraulic cylinder and a lower connection point associated with the piston rod; and at least one accumulator, the or each accumulator having a moveable separator to divide the accumulator between a gas phase above the separator, and an oil phase below the separator, and the or each oil phase being in communication with an oil phase in the main hydraulic cylinder; characterized in that the main hydraulic cylinder further comprises a cylinder sleeve co-axial with the piston head to provide, in co-ordination with the piston head, the boundary between the gas phase and the at least one oil phase in the main hydraulic cylinder. In this way, the variation in the coordination between the shape, longitudinal position, or both of the piston head, which naturally must be smaller in cross-section than the cross-section of the main hydraulic cylinder, and the transverse extent of the cylinder sleeve, provides variation in the cross-sectional area of oil volume in the main hydraulic cylinder, and thus different damping effects along the length of the main hydraulic cylinder, which are available to the user.

A heave compensator with adjustable dampening properties includes a length extension device having an inner space divided by a slide-able piston into a vacuum chamber and a liquid filled chamber, a gas accumulator divided by a slide-able piston into a gas filled chamber and a liquid filled chamber, and a gas tank having an expansion chamber. The liquid and gas chamber are fluidly connected to each other with valve controlled conduits. Further, the device includes pressure and temperature sensors that register pressure and temperature in the gas and liquid phases. The device further includes a control unit having a signal receiving unit, a writeable computer memory, a data processing unit, and a signal transmitting unit. The data processing unit contains computer software that calculates suited amounts of gas and gas pressure in the gas accumulator and/or gas tank based on the information of which lifting operation is going to be performed. The data processing unit further engages activation means such that the suited amount of gas and gas pressure are achieved and maintained during the different phases of the lifting operation.

A heave compensator with adjustable dampening properties includes a length extension device having an inner space divided by a slide-able piston into a vacuum chamber and a liquid filled chamber, a gas accumulator divided by a slide-able piston into a gas filled chamber and a liquid filled chamber, and a gas tank having an expansion chamber. The liquid and gas chamber are fluidly connected to each other with valve controlled conduits. Further, the device includes pressure and temperature sensors that register pressure and temperature in the gas and liquid phases. The device further includes a control unit having a signal receiving unit, a writeable computer memory, a data processing unit, and a signal transmitting unit. The data processing unit contains computer software that calculates suited amounts of gas and gas pressure in the gas accumulator and/or gas tank based on the information of which lifting operation is going to be performed. The data processing unit further engages activation means such that the suited amount of gas and gas pressure are achieved and maintained during the different phases of the lifting operation.

A winch system for driving an output includes a gear connected to the output, an electric motor connected to the gear, and a hydraulic motor connected to the gear. The electric motor and the hydraulic motor are distribute energy via the gear to the output.

The present invention relates to a motion compensation system for an element hanging from a mobile unit, the system comprising two blocks, at least two articulated arms, a compensation cylinder and a cable. According to the invention, at least one characteristic length of the articulated system (for example: the length of a link or the distance between two sheaves of two articulated arms) is adjusted according to the motion to be compensated for.

The invention is a system for controlling the relative movement of a load P, comprising at least one main damper having a longitudinal action of stroke C and two ends with one end being connected to a frame and the other being connected to the load. A compensation device is included having at least one secondary damper of longitudinal action with two ends with one end being secured to the frame and the other end is connected to the end of the main damper connected to the load The secondary damper is arranged so that, at one point of stroke C, the secondary damper has an action orthogonal in direction to the direction of the movement.

The invention is a system for controlling the relative movement of a load P, comprising at least one main damper having a longitudinal action of stroke C and two ends with one end being connected to a frame and the other being connected to the load. A compensation device is included having at least one secondary damper of longitudinal action with two ends with one end being secured to the frame and the other end is connected to the end of the main damper connected to the load The secondary damper is arranged so that, at one point of stroke C, the secondary damper has an action orthogonal in direction to the direction of the movement.

A hoisting system is for hoisting a vertically-suspended object. The hoisting system has a winch having a winch drum with a hoisting rope. A first part of the hoisting rope has a first diameter and a second part has a second diameter being larger than the first diameter. The first part is connected with a first end of the second part. The first part is an inner part on the winch drum when the winch drum is completely wound. The second part has a further end that is connectable to the object for hoisting the object. A ratio between the first diameter and the second diameter is such that the minimum breakable load of the first part differs less than a factor of four from the minimum breakable load of the second part, and preferably less than a factor of three. A corresponding method is disclosed.

A method of upgrading a knuckle-boom crane to a heave-compensating crane includes: removing a knuckle-boom from a main boom; mounting a main boom extension to the main boom for increasing the length of the main boom; and mounting a heave-compensating boom at a far end of the main boom extension such that the heave-compensating boom extends in a downward vertical direction (Z) in operational use of the heave-compensating crane. The heave-compensating boom is configured to be pivotable with respect to the main boom extension in both horizontal directions (X, Y). A heave-compensation system is provided to the knuckle-boom crane, wherein the heave-compensation system compensates for horizontal variations by controlling the orientation of the heave-compensating boom relative to the main boom extension, and compensates for vertical variations by means of a further vertical heave-compensation system, such as a winch-based heave-compensation system.