Enhancing the effectiveness of offshore cranes

28 November 2011

Construction costs are an important consideration in offshore wind farms and drilling platforms. However, traditional crane technology has proved to be a safety issue during the construction phase with standard floating cranes often encountering difficulties if the waves crest at 30cm or greater. Even minor swaying, of just 2 or 3°, can move the tip of the crane by up to 5m which can result in an unstable load which poses a safety issue.

In a bid to solve this problem, Barge Master worked with Bosch Rexroth to develop a comprehensive solution including all the necessary drive and control components. The resulting system is suitable for all kinds of standard marine vessels and cranes and is said to drastically reduce the manufacturing cost and operational expense of offshore projects.

"With Rexroth heave compensation we have expanded the application window for floating cranes handling waves of up to 150cm," said Jan-Paul van der Bos of Barge Master BV. This is achieved through a moving platform which neutralises roll, yaw and heave. Three hydraulic cylinders, affixed vertically, attach the crane to the hull of the ship through joints that incorporate ball bearings. Connection rods with limited mobility freeze the remaining three degrees of freedom so that the cylinder movements can compensate for wave action.

The controls are the heart of this solution. Special sensors deliver motion data that is used to calculate target values for the compensatory movements that keep the platform stable. Even with irregular swells and crests of over 1m, 95% of motion can be neutralised said a spokesperson for the company. This has allowed Barge Master to expand the use range for standard floating cranes.

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