Displaying Hyflo’s Capabilities As An Industry Leader
Hyflo Southern Africa, a BMG Group company, was contracted by Denith Engineering to design and build the Electro-Hydraulic portion of the AHC (Active Heave Compensated) winch, to provide high speed, control of the 40ton payload. This included the design and fabrication of thirteen hydraulic cylinders built in accordance with Lloyds rules to complete the system.

The LARS (Launch and Recovery System) is designed to deploy and recover a crawler, which is responsible for subsea trenching in order to lay power cables. The power cables are predominately used for off-shore wind farms and are laid up to 600m below sea level.

The winch is driven by 10 Poclain 5000cc motors, and is powered by a 1.5MW power pack. The control is taken care of by two of MOOG’s latest NG32 Digital Axis Control Valves. These valves are synced together using a CAN network to control the 3000L/min of flow required. The valves are mounted on two 1.1 ton locally manufactured manifold blocks, designed and machined in-house by Hyflo.

This AHC winch is designed to keep the payload at a constant height relative to the seabed in a swell of up to 2.5m. This is accomplished by the Moog valves, which receive three important reference signals. The first signal is from a MRU (Motion Reference Unit). The second and third signals are the position and tension, which are received from an encoder and load cell respectively. The key to the system is the high speed de-centralized control that is directly programmed onto the valves. This achieves a loop time of less than 1ms. The Moog valves are connected to a Profibus network which allows all the parameters and modes to be monitored and updated accordingly.

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