Multi function heave compensator

A device for compensating for heave movements between a lifting device and a load lifted by the lifting device, the device comprising:

• an elongated length extension device comprising:
• a closed upper end;
• a lower end having an opening for a piston rod and a liquid outlet;
• an inner space divided by a slide-able first piston into an upper vacuum chamber and a first lower liquid filled chamber;
• a piston rod of length at least equal to the length of the length extension device, wherein a first end of the piston rod is attached to the first piston, and wherein the piston rod stretches through the first liquid filled chamber and further out through the opening in the lower end of the length extension device;
• means arranged at a second end of the piston rod for releasable attachment of the load;
• and
• means arranged at the upper end of the length extension device for releasable attachment of the lifting device;
• an elongated cylindrical gas accumulator comprising:
• an upper end having a first adjustable gas outlet, the first adjustable gas outlet having a first valve;
• a lower end having a liquid outlet;
• and
• an inner space divided by a slide-able second piston into an upper chamber and a second lower liquid filled chamber,
• an adjustable liquid transferring device fluidly connected to the liquid outlet of the lower end of the length extension device and the liquid outlet of the lower end of the cylindrical gas accumulator, the adjustable liquid transferring device having a second valve;
• an activator for selective opening or closing of one or both of the first valve and the second valve;
• a first and second pressure and temperature sensor for measuring a temperature and/or pressure of the liquid in at least one of the first lower liquid filled chamber and the second lower liquid filled chamber and the gas in the upper chamber of the cylindrical gas accumulator, respectively;
• a position sensor for measuring the position of the first piston;
• and
• a control unit comprising:
• a signal receiver unit and data storage memory for registering the measured temperatures and/or pressures of the liquid in one of or both of the first lower liquid filled chamber and the second lower liquid filled chamber, the gas in the upper gas filled chamber of the cylindrical gas accumulator, and the position of the first piston;
• a signal treatment unit for calculating a real equilibrium position of the first piston from the registered temperatures and/or pressures and the registered positions of the first piston;
• a data processing unit for calculating an amount of gas that needs to be ventilated out of the first adjustable gas outlet in order to obtain an intended equilibrium position of the first piston;
• and
• a signal transmission unit engaging the activator of the first valve and/or the second valve such that the intended amount of gas exits through the first adjustable gas outlet and such that the first piston obtains the intended equilibrium position.