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 method and heave compensator for eliminating snap-load and heave effects at offshore deposition of a load into or onto the sea or seabed involves a heave compensator suspended between the load and the lifting device having a relatively stiff stroke response at small to moderate stroke lengths and then a softer stroke response at larger stroke lengths to avoid exceeding the dynamical amplification factor (DAF)-limitations of the crane/lifting device or on the load.
E21B 19/00 - Handling rods, casings, tubes or the like outside the borehole, e.g. in the derrickApparatus for feeding the rods or cables
E21B 19/09 - Apparatus for feeding the rods or cablesApparatus for increasing or decreasing the pressure on the drilling toolApparatus for counterbalancing the weight of the rods specially adapted for drilling underwater formations from a floating support using heave compensators supporting the drill string
B66C 13/04 - Auxiliary devices for controlling movements of suspended loads, or for preventing cable slack
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.
B66C 23/53 - Floating cranes including counterweight or means to compensate for list, trim, or skew of the vessel or platform
B66D 1/52 - Control devices automatic for varying rope or cable tension, e.g. when recovering craft from water
F16F 9/06 - Springs, vibration-dampers, shock-absorbers, or similarly-constructed movement-dampers using a fluid or the equivalent as damping medium using both gas and liquid
B63B 27/30 - Arrangement of ship-based loading or unloading equipment for cargo or passengers for transfer at sea between ships or between ships and off-shore structures
A heave compensator for heavy lifts with adjustable dampening characteristics is able to operate above and below the water line in environmental pressures ranging from the atmospheric up to several hundred atmospheres pressure. A method for automatic regulation of the available stroke length of the heave compensator during the lifting operation, based on the realization that heave compensating devices utilising a slideable piston as a volume expanding mechanism to reduce the tension forces upon relative movements between crane and load, may obtain a simple compact construction able to execute a range of different compensation functionalities by registering the pressure and temperature in the gas filled chambers of the device, and employing this information to regulate the amount of gas in the single gas filled chambers.
B66C 23/53 - Floating cranes including counterweight or means to compensate for list, trim, or skew of the vessel or platform
B66D 1/52 - Control devices automatic for varying rope or cable tension, e.g. when recovering craft from water
E21B 19/00 - Handling rods, casings, tubes or the like outside the borehole, e.g. in the derrickApparatus for feeding the rods or cables
F16F 9/06 - Springs, vibration-dampers, shock-absorbers, or similarly-constructed movement-dampers using a fluid or the equivalent as damping medium using both gas and liquid
B63B 27/30 - Arrangement of ship-based loading or unloading equipment for cargo or passengers for transfer at sea between ships or between ships and off-shore structures
