RAHC – Active Heave Compensation with Secondary-Controlled Winch Drive

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Positioning loads accurately on the seabed represents a challenge for any crane driver when a ship is heaving in rough seas. With the active heave compensation from Rexroth the ship’s movements are recorded and integrated into the closed-loop control process, with the result that over 95 % of the motions are compensated with the aid of secondary-controlled drives.

Secondary controlled drives can work motor-driven as well as regenerative under constant pressure. If the ship follows a wave through the winch cable needs to be winded up in order to keep the load in position. The secondary units operate as motors and use energy. When the ship moves upwards again, the drives unwind the cable, operating as a pump in generator mode. The energy recovered is stored by the hydraulic system for the next downward motion. The system can recover up to 70 % of the energy by this method, meaning that the installed power required for the power unit can be considerably reduced!

The ease of operation, the precision with which the winch and crane drives are put into motion, combined with swift and accurate compensation of heavy seas – this is what distinguishes the Rexroth RAHC.

 
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