A method for mitigating the effects of cable wear in an active heave compensated hoisting system of an offshore vessel in a locked to bottom mode of operation is disclosed. The method comprises supporting an upper end of a string which is connected to a subsea well from a travelling block of the hoisting system, wherein the travelling block is suspended from a crown block via a cable. The method further comprises operating an active heave compensation system to control a drawworks of the hoisting system to pay in and out the cable to compensate for motion of the offshore vessel and maintain a target overpull in the string. The method further comprises adjusting a ballast system of the offshore vessel to vary the draft of the vessel, and controlling the drawworks in accordance with the variation in the draft of the vessel to cause a length of cable to slip through the hoisting system and maintain the target overpull in the string.

A method for mitigating the effects of cable wear in an active heave compensated hoisting system of an offshore vessel in a locked to bottom mode of operation is disclosed. The method comprises supporting an upper end of a string which is connected to a subsea well from a travelling block of the hoisting system, wherein the travelling block is suspended from a crown block via a cable. The method further comprises operating an active heave compensation system to control a drawworks of the hoisting system to pay in and out the cable to compensate for motion of the offshore vessel and maintain a target overpull in the string. The method further comprises adjusting a ballast system of the offshore vessel to vary the draft of the vessel, and controlling the drawworks in accordance with the variation in the draft of the vessel to cause a length of cable to slip through the hoisting system and maintain the target overpull in the string.

A heave compensator includes a main hydraulic cylinder including a first connection device located at an upper end of the main hydraulic cylinder and a first piston having a piston rod. The interior of the main hydraulic cylinder is divided by the first piston into an upper first chamber and a lower second chamber filled with hydraulic liquid. The piston rod has a second connection device located at a lower end of the piston rod. The heave compensator includes a lifting accumulator comprising a second piston dividing the interior of the lifting accumulator into a third chamber filled with gas and a fourth chamber filled with hydraulic liquid. The fourth chamber is fluidly connected to the second chamber by a first liquid conduit having a first actuator controlled valve regulating the flow of hydraulic liquid in the first liquid conduit. The heave compensator includes a lowering accumulator comprising a third piston dividing the interior of the lowering accumulator into a fifth chamber filled with gas and a sixth chamber filled with hydraulic liquid. The sixth chamber is fluidly connected to the second chamber by a second liquid conduit having a second actuator controlled valve regulating the flow of hydraulic liquid in the second conduit. The sixth chamber is fluidly connected to the fourth chamber by a third hydraulic liquid conduit comprising an actuator controlled pump unidirectionally regulating the flow of hydraulic liquid from the sixth chamber to the fourth chamber. The heave compensator further includes a sensor kit including a motion sensing unit registering the vertical movements of the main hydraulic cylinder, a logical controller unit including a processor loaded with a Valve Regulation Module containing logic commands which when executed controls and regulates the actuator of the first actuator controlled valve, the actuator of the second actuator controlled valve, and the actuator of the actuator controlled pump, and signal transferring lines electronically connecting the logic controller unit to the motion sensing unit of the sensor kit, the actuators of the first and the second actuator controlled valves, and the actuator of the actuator controlled pump.

A heave compensator includes a main hydraulic cylinder including a first connection device located at an upper end of the main hydraulic cylinder and a first piston having a piston rod. The interior of the main hydraulic cylinder is divided by the first piston into an upper first chamber and a lower second chamber filled with hydraulic liquid. The piston rod has a second connection device located at a lower end of the piston rod. The heave compensator includes a lifting accumulator comprising a second piston dividing the interior of the lifting accumulator into a third chamber filled with gas and a fourth chamber filled with hydraulic liquid. The fourth chamber is fluidly connected to the second chamber by a first liquid conduit having a first actuator controlled valve regulating the flow of hydraulic liquid in the first liquid conduit. The heave compensator includes a lowering accumulator comprising a third piston dividing the interior of the lowering accumulator into a fifth chamber filled with gas and a sixth chamber filled with hydraulic liquid. The sixth chamber is fluidly connected to the second chamber by a second liquid conduit having a second actuator controlled valve regulating the flow of hydraulic liquid in the second conduit. The sixth chamber is fluidly connected to the fourth chamber by a third hydraulic liquid conduit comprising an actuator controlled pump unidirectionally regulating the flow of hydraulic liquid from the sixth chamber to the fourth chamber. The heave compensator further includes a sensor kit including a motion sensing unit registering the vertical movements of the main hydraulic cylinder, a logical controller unit including a processor loaded with a Valve Regulation Module containing logic commands which when executed controls and regulates the actuator of the first actuator controlled valve, the actuator of the second actuator controlled valve, and the actuator of the actuator controlled pump, and signal transferring lines electronically connecting the logic controller unit to the motion sensing unit of the sensor kit, the actuators of the first and the second actuator controlled valves, and the actuator of the actuator controlled pump.

A lifting element, such as for a vessel or vehicle, comprising a lifting element, such as an oblong element, rotated by a number of electrical motors via a rotatable, such as an eccentric, element. The eccentric element ensures that the lifting element can only be tilted within a predetermined angle area increasing the safety thereof. Multiple electric motors are used where one motor counteracts the other within an angle interval to ensure that the tilting element does not tilt undesirably.

Disclosed is a system for the recovery of a surface marine craft by a carrier ship. The system included a lifting device with which the carrier ship is intended to be equipped and which included a lifting unit of the davit type, equipped with a lifting cable including, at one end, a connection interface, a pole bearing a guide cable, an anchor connected to one end of the guide cable, the connection interface for the lifting cable being coupled removably to the anchor, and a hauling cable. The system also included a receiving device with which the marine craft is intended to be equipped, the receiving device including a forward module.

A wave-induced motion compensating crane includes a hoist assembly. At least two departure sheaves are mounted at opposite lateral sides of the jib. The object suspension device is supported both by two hoist cables extending laterally from the jib and a third hoist cable that runs via another departure sheave. The hoist assembly is adapted to hoist and/or lower the object suspension device with an object connected thereto, between a lower position and a position at a height up to the departure sheaves while the hoist cables together define a reverse pyramid, diverging upwards in between the object suspension device and the departure sheaves.

In embodiments, motion may be arrested and/or dampened using a motion arresting and dampening device comprising a lifting spreader bar, one or more bar mounted winches, deployment wire, a restorative inflation device, restraining wires and winches, hoses and controller, mechanical connection release system circuitry. Multiple restraints from winches mounted strategically on a vessel crane's boom may be applied to the spreader bar to restrain the bar during the lifting operation. The forces induced into the lifted object by the movement of the crane as it deploys the object into installation position are attenuated by the physical restrain of the adjustable wires. These adjustable wires may also be used to provide rotation of the object during final alignment of the object during installation.

A method for handling of an offshore wind turbine component includes using a vessel having a hull on which a motion compensating crane is mounted. The crane includes a main boom; a main boom luffing assembly; a mobile hoist cable suspension member; and a hoist winch and a hoist cable driven by the hoist winch. An object suspension device is suspended from the hoist cable. The mobile hoist cable suspension member is supported by a motion compensating support device that is fitted to the tip end of the main boom, the motion compensating support device including one or more motor powered motion displacement actuator assemblies and a motion compensating support device controller. The method includes connecting the offshore wind turbine component to the object suspension device; and operating the motion compensating support device to provide motion compensation in at least one direction of the object suspension device and the connected offshore wind turbine component. The crane is provided with one or more nacelle position detectors that are configured and operated to sense at least one of actual position and actual motion of the nacelle or of one or more components in or on the nacelle, and the one or more nacelle position detectors are linked to the motion compensating support device controller.

A method for handling of an offshore wind turbine component includes using a vessel having a hull on which a motion compensating crane is mounted. The crane includes a main boom; a main boom luffing assembly; a mobile hoist cable suspension member; and a hoist winch and a hoist cable driven by the hoist winch. An object suspension device is suspended from the hoist cable. The mobile hoist cable suspension member is supported by a motion compensating support device that is fitted to the tip end of the main boom, the motion compensating support device including one or more motor powered motion displacement actuator assemblies and a motion compensating support device controller. The method includes connecting the offshore wind turbine component to the object suspension device; and operating the motion compensating support device to provide motion compensation in at least one direction of the object suspension device and the connected offshore wind turbine component. The crane is provided with one or more nacelle position detectors that are configured and operated to sense at least one of actual position and actual motion of the nacelle or of one or more components in or on the nacelle, and the one or more nacelle position detectors are linked to the motion compensating support device controller.