Rexroth has introduced its latest development in Active Heave Compensation (AHC), designed for the controlled landing of loads on the seabed. With the addition of the innovative Active Tension Control (ATC) function, Rexroth’s AHC systems now provide new capabilities for delicate operations, scientific research and survey operations, offering greater protection and control in the handling of subsea payloads. In addition, ATC meets the demands for increased working hours in offshore applications, ensuring safety and accuracy are maintained while executing operations in deep water under rough weather conditions.
The Active Tension Control function has been developed by Rexroth engineers to maintain a constant cable force during the landing of loads on the seabed with a far higher precision than is possible using current passive heave compensation systems. This constant cable force is achieved by the Rexroth AHC system, controlled by the Motion Reference Unit (MRU), and the newly developed closed loop force control function.
Rexroth tests indicate that this new ATC function maintains cable forces, ensuring loads are positioned on the seabed to within 5% of the desired setting. Another major feature is that the desired cable force can also be adjusted by the operator whilst ATC is in operation, giving further flexibility in its performance.
At the heart of ATC is Rexroth’s newly developed closed loop force control function with dedicated software that enables the operator to smoothly switch between modes of operation, ensuring full control during complex operations. By compensating for more than 95% of the movement of the vessel upon the water high load precision is obtained even in extremely deep water.
Rexroth AHC systems are comprised of proven drive technology and advanced control systems incorporating Rexroth’s field-proven pumps, motors, valves, cylinders, manifolds and hydraulic power units. The available modes of operation are: Active Heave Compensation mode; Active Tension Control mode; Passive Heave Compensation mode; Empty Hook mode; Shock absorber mode; Standby mode; Off Mode.
Underlining its global network capability Rexroth recently delivered a 700 tonne (double fall) AHC system for the Saipem 3000 crane vessel. A global leader in drives and control technologies, Rexroth delivered the linear AHC system complete with ATC functionality on schedule. In addition, Rexroth’s locally-based and experience engineers successfully tested and commissioned the system in the Congo.