Bosch Rexroth has introduced an upgrade to the electrohydraulic controller used on the company’s A4VSO and A4VSG hydraulic axial piston components, which function as secondary control units in the Rexroth Active Heave Compensation (AHC) system for offshore winching applications.
Replacing the previous DS1 model, the new Rexroth DS2R electrohydraulic controller features proportional valve technology for more reliability, easier maintenance and lower cost.
The controller is fitted directly to the secondary control unit – axial piston equipment that can serve as both a pump or motor to effectively manage variations in torque on winch drives in rotary AHC systems.
As part of the overall AHC system, the secondary control unit utilizes either a Rexroth A4VSO (open loop control) or A4VSG (closed loop control) axial piston unit to provide the winch torque control when the AHC system is engaged.
Winch control is an essential function handled by the Rexroth AHC system. In offshore operations where loads are being lifted or lowered deep underwater, the winch wire carrying the load is routed from the workboat or rig’s towing winch through the AHC system, which actively compensates for the ship’s movements to keep the load steady in the pitch and swell of the open sea.
The DS2R controller comes with the Rexroth 4WRPH high-response proportional valve and offers several key engineering and operational advantages, including:
- High dynamic response, which is crucial in continuously varying wave motion conditions
- Precise, accurate motion so the loaded winch cable remains continuously “idle” – moving up and down only according to the winch, not the surface wave motion
- Energy efficiency – through better control of hydraulic components, including the ability to use hydraulic accumulators to recover and re-use up to 70 percent of the secondary control unit’s installed power
- More reliability and easier maintenance, with a simpler design that eliminates a sandwich filter and is less prone to contamination.
In addition, the proportional valve included with the DS2R is capable of handling a greater range of fluid viscosities and requires less pressure drop to maintain control.
Reliability is also improved with a AWXF axial piston unit swivel angle sensor rated for IP67 standards, making it better suited to harsh open-sea operating conditions.
Besides the DS2R, a DS2E version is available without the fitted Rexroth proportional valve. In addition, a DS2S controller is available with a servo valve instead of a proportional valve for test stand or other applications with very high dynamic requirements.