Hagglunds Goes ROVing with Subsea 7
For a number of years Hagglunds have provided the motor/brake assemblies used by subsea engineering and construction company Subsea 7 on ROV deployment winches together with the power units and controls designed specifically o the working environment and the duty required. This includes the auxiliary systems to operate the 'A' frames and other equipment.
Both vessels were built at the Merwede Shipyard near Rotterdam. Each is very well equipped, with a host of specialised equipment. Both have two permanently installed side launching workclass ROV systems rated to 3,000m.
The Lebus winches utilise 84 series direct drive Viking motors with band brake assemblies. The Viking motors have very high torque (mechanical) efficiency and so the tension control, which is important on the ROV umbilicals, is assured.
Lebus International has also been a longstanding user of Hagglunds motors, brakes, and valve blocks on their range of winches. Five other ROV systems, including the Viking 84 series motors and the PEC type power units, were supplied via Lebus and Soil Machine Dynamics Hydrovision for other Subsea 7 vessels.
The power units, starters and controls, all supplied by Hagglunds Drives UK, were housed in a soundproofed 20' purpose designed container. It included a stainless steel 1,200 litre reservoir with sea water cooling system and a full health monitoring system.
One container houses all the necessary systems to operate the two ROVs on each vessel. The containerised power unit can be set up and extensively factory tested before installation on the vessel.
Each power unit weighed some 15 tons and was supplied with a special four leg sling to take into account the uneven weight distribution inside the container, lifting the unit clean and within 5(DEGREES) of horizontal. To enable air paths for the electric motor cooling both in and out of the container and still maintain the strict noise levels, acoustic attenuators were designed and fitted on the roof of the container and anti-vibration type feet were used on the pump sets and to sit the container on the deck.
Each unit has two 290kW electric motors coupled to closed loop hydraulic transmission pumps for the winches using constant tension and wave riding with electronic proportional control for the pressure. This enables the winch to pull in and play out quickly at a et tension which is controlled to suit the ROV and the conditions. Constant power control is also included using current feedback from the electric motors to Hagglunds Spider control to gain maximum output from the winches for a given ROV load.
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