Active Heave Compensation
To control the relative position of a load to a fixed object, Active Heave Compensation (AHC) is used. The position is determined by the control system using the real-time signal of a Motion Reference Unit (MRU) as an input signal. In response to this signal the AHC system will pay in or pay out to keep the load at a constant elevation. Huisman can deliver Active Heave Compensation on hydraulic or electric winches and on hydraulic cylinders.
Active Heave Compensation on Hydraulic Winches
Huisman delivers a unique, in-house developed, secondary controlled hydraulic active heave compensation system. A secondary controlled hydraulic winch enables compensation of the heave motion of the vessel with an extremely fast response time at low power consumptions. In response to the signal of a motion reference unit the winch will pay in or pay out wire rope. Huisman has over 20 years of successful experience with this system.
With a secondary controlled hydraulic system, both active heave compensation and constant tensioning are available on the winch. Huisman is delivering hydraulic winches with a safe working load up to 250mt and up to 3,000m wire storage capacity.
Active Heave Compensation on Electric Winches
Huisman delivers electric driven winches with active heave compensation. High power, low inertia E-motors allow real-time compensation of the heave motion of the load. In response to the signal of a motion reference unit the winch will pay in or pay out wire rope. Huisman has over 10 years of successful experience with this system. Systems which are able to store electric energy in order to reduce power consumption fluctuations on the vessel’s power grid are currently under construction.
With an electric system both active heave compensation and constant tensioning are available on the winch. Huisman can currently deliver these electric winches with a maximum installed power of 2,300kW (3,000HP) per winch. Examples are the drawworks as installed on the Q4000 and the Bully drill ships.
Active Heave Compensation by Cylinders
Huisman also delivers active heave compensation systems which make use of a combination of active and passive cylinders. The heave compensator consists of a passive main cylinder, two additional active cylinders, and a sheave over which the main hoist wire runs. The main cylinder is connected via a medium separator to a pressure vessel unit. This passive system is balanced with the load in the wire that reduces the power requirement of the system considerably.
The active cylinders are connected to a hydraulic power unit. In response to the signal of a motion reference unit the active cylinders will extend or retract to keep the load at a constant elevation. Since the main load is compensated by the passive main heave cylinder, the active cylinders only have to compensate the unbalance in the actual load during active
This active heave compensation system is used on our deepwater cranes, A&R systems, MPT drilling systems and deepwater lowering systems.