An upstanding surf rider

 Heave compensation uses a moving platform to neutralize the roll, yaw and heave caused by the waves.
Marginal Column

July 2011

 

Barge Master BV, a Dutch company, has installed Rexroth heave compensation to enhance the usefulness and deployability of offshore cranes.

 
 

Wind farms at sea, drilling platforms far from the coast. Offshore installations are experiencing a real boom, all around the orld. Construction costs play a major role here. One reason is that there was really no convincing crane technology available in the past. “Right now, standard floating cranes encounter difficulty with waves cresting at thirty centimeters. Safe crane operation can no longer be guaranteed,” is how Jan-Paul van den Bos explained the challenge. Even at minor swaying of just two to three degrees, the tip of the crane, carrying the load, moves by four to five meters and endangers the crew,” Martijn Koppert adds.

These are the two men who founded the Dutch firm, Barge Master BV. The company’s mission was to solve this problem. Working together with Rexroth, Barge Master developed a comprehensive solution including all the necessary drive and control components. The system is suitable for all kinds of standard marine vessels and cranes, and drastically reduces the manufacturing costs and operating expenses for offshore projects.

Mastering five times the swells

This development also does the exceptional in terms of technology. “With Rexroth heave compensation we have expanded the application window for the floating cranes – handling waves of up to 150 centimeters,” van den Bos points out proudly. The heave compensation system engineered by Rexroth uses a moving platform to neutralize roll, yaw and heave. Here three hydraulic cylinders, affixed vertically, attach the crane to the hull of the ship by way of joints incorporating ball bearings. Connection rods with limited mobility freeze the remaining three degrees of freedom so that the cylinders’ movements can compensate for wave action.

The controls are the heart of the solution. Special sensors deliver motion data, which are used to calculate target values for the compensatory movements that keep the platform stable. Barge Master thus considerably expands the use range for standard floating cranes. “Even at irregular swells, with crests of 1.5 meters and frequencies of six to twelve seconds, we can neutralize 95 percent of the motion,” Koppert calculates. At mid-2012 the C400 Barge Master will be ready for use with cranes weighing about 400 tons and payloads of up to 160 tons. Jan-Paul van den Bos is confident that with this step the company will be significantly expanding the utility of standard cranes.