Product Information - Active Heave Compensation

Active Compensation

Fast reacting and stable, even when waves are considerably high; Active Heave Compensation Systems (AHC) significantly enlarge your window of operation and work safely under all conditions.

Active Heave Compensation systems utilise actively controlled devices, which can operate in various modes depending on the required characteristics. They maintain a constant vertical position (AHC-mode) of a free hanging load or a constant tension (CT-mode) to a supported or fixed load.

Types of active heave compensation

Active Heave Compensation systems can be based on hydraulic cylinders, on primary and secondary controlled rotary hydraulic motors or on electrical motors. We have already carried out all these designs, ranging from 5 metric tonnes to 40,000 metric tonnes. The reliability and versatile functionality of any AHC is a direct result of adjusting all drive and control components. Only Rexroth can supply all these adjusted components from a single source, and has the experience for quality turn-key solutions.

Primary controlled rotary AHC

The output data of the MRU ( Motion Reference Unit ) is relayed to the main controller that uses the information to control a hydraulic motor connected to a variable pump. These components power the winch so that the load hangs idle relative to the fixed world (i.e. the drilling rig or the seabed).

Secondary controlled rotary AHC

The rotating or secondary active heave compensation system is based on use of a secondary regulated motor connected directly to the winch. By varying the capacity of the motor, it is possible to vary the speed and direction of the winch.

Electric rotary AHC

Electric rotary Active Heave Compensation Systems (EAHC) work similarly to rotary Active Heave Compensation, in that they also recover, store and reuse energy. Their hardware controls are identical to the hydraulic variants, simplifying operation, diagnosis and spare parts management.

Linear AHC

The differences between the active heave compensation systems lie in their components and how they are controlled. With a linear system, the stroke of the cylinder determines the length of the winch cable and thus the position of the load.