SUBSEA HEAVE COMPENSATOR

摘要

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 slide-able 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.

主权项

1. A heave compensating device for compensating heave movements between a lifting device and a load lifted by the lifting device, the heave compensating device comprising:
an elongated length extension device comprising:
side walls;a closed upper end;a lower end having an opening for a piston rod and a liquid outlet;an inner space divided by a first slide-able piston into an upper vacuum chamber and a first lower liquid filled chamber;a piston rod of a length at least equal to a length of the length extension device, wherein one end of the piston rod is attached to the first piston, and wherein the piston rod stretches through the first lower liquid filled chamber and further out through the opening in the lower end of the length extension device;means arranged at the second end of the piston rod for releasable attachment of the load; andmeans arranged at the upper end of the length extension device for releasable attachment of a lifting device; an elongated 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; andan inner space divided by a second slide-able piston into an upper chamber and a second lower liquid filled chamber; a regulated liquid transferring device fluidly connected to the liquid outlet of the length extension device and the liquid outlet of the gas accumulator; activation means for selective opening or closing of the first valve; a first and second measuring means for measuring a temperature and/or a pressure of the liquid in at least one of the first and second liquid filled chambers and the gas of the upper chamber of the gas accumulator; a third measuring means for measuring the position of the first piston; a reserve gas tank comprising:
a pressure resistant container containing an adjustable heat source and a thermally degradable compound in liquid or solid state; andan adjustable gas transmission device fluidly connected to the upper chamber of the gas accumulator, the adjustable gas transmission device having a second valve; and a control unit comprising:
means for registering the measured temperatures and/or pressures of the liquid in one or both of the first and second lower liquid filled chambers and the gas in the upper gas filled chamber of the gas accumulator and for registering the position of the first piston;means 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;means for calculating the amount of gas that needs to be ventilated out of the first gas outlet in order to obtain an intended equilibrium position of the first piston; andengaging means for engaging the activating means of the first valve of the first gas outlet such that the intended amount of gas exits through the first gas outlet and the first piston obtains the intended equilibrium position.