Sophisticated heave compensation

The Zirfaea is a survey vessel from Rijkswaterstaat. Scanning the seabed of the North sea and monitoring water quality are some of the daily tasks of the vessel and crew. The crane highlighted in the picture below, is used to lower a watersampler in conjunction with a Seabird CTD into the sea. Various sensors  measuring the changes in the water colomn this informs to the operators that the tubes have reached a layer of algae. The purpose of the tubes is to take water samples including the algae. The layer of algae however is thin. The tubes have to be closed to bring the sample up. Timing is crucial for the ship is dancing on the waves. EMCE was invited to find a solution for a winch with motion control, to drive and keep the tubes into the layer, compensating the ships motion.

A  gyroscope MRU (Motion Reference Unit) related solutions have proven to be rather expensive and complex. The requirement for motion control and wave compensation in offshore lifting is huge and EMCE regognizes the demand for a compatible answer. The answer was born using a Nintendo controller that moved a pointer on a screen by hand motion. Sensortechnology is so advanced that it can easily be used for stand alone motion control or wave compensation. 

Extensive testing and simulations based on the actual MRU data have been performed at EMCE in co operation with sister company ELSTO Controls. Finally we managed to develop a system that, with a safe margin, can be sold as a reliable motion control reducing the movement of the load compared to the crane tip to < 15%. The winch is electric driven with 500 kg capacity and ultimate speeds upto 120 m/min.

Operator Peter de Boer, Rijkswaterstaat team Zee en Delta, mobile measurement;

The controls are easy and the system is ultimately silent compared to the hydraulic driven unit.We consider the replacement  success and are satisfied with the interaction with EMCE. Meanwhile the next EMCE electric 5 Tons general purpose winch is deployed.”