Vessel to Crane vessel relative wave motion data

DMM-Relative Motion provides the crane operator with accurate vessel to vessel relative wave motion data.

By providing heave motion from the selected load supporting deck area at the supply vessel and adding the heave motions from the cranes boom tip, the system calculates the relative motion in meter per second as well as relative “Effective Significant Wave Height” between the two floating units.

A crane’s rated capacity is limited by the impact of the sea state. Accurate information from the DMM-Relative Motion may allow lifting whereas the traditional sea state method would normally overestimate the motions and not allow lifting operation. Thus, the DMM-Relative Motion safely provides better use of the crane capacity.

When the supply vessel is within 1500m the crane operator can connect to the supply vessel’s DMM via IWLAN and monitor the motions and live video feed. As such the crane operator, can be well prepared for the lifting operation and, together with the vessels captain, decide whether to perform the lifting operation or to wait on weather.

Ease of Use

DMM-Relative Motion works independently of the weather conditions, the loads position and the cranes position, ensuring that constant and reliable 20 minutes wave (SWH) information is buffered up in all possible lifting positions. It is also possible to enter the cranes line velocity and use this as part of the red/green light equation.

DMM-Relative Motion continue measuring 20 minute values in all possible crane positions even at times when the crane is turned inboard. This makes it possible for the crane operator to know if the wave motions for the next planned lift are within the cranes load limitations.

The supply vessel captain and Crane operator can also use the DMM information to position the vessel ideally for the next lift.