In-cylinder VRVTs improve undersea operations

VRVT transducers from Penny and Giles Controls have been incorporated in special aluminium subsea cylinders that are used to disconnect offshore oil pipeline bundles from towing vessel wires.

VRVT transducers manufactured by Penny & Giles Controls Ltd, have been incorporated in special aluminium subsea cylinders that are used to disconnect offshore oil pipeline bundles from towing vessel wires.

Forty of the cylinders, which weigh a fraction of their steel counterparts, were manufactured from 7075 aircraft grade aluminium by Whittaker Engineering of Stonehaven near Aberdeen, who specialise in the design of lightweight ancillaries for remotely operated vehicles (ROVs).

The cylinders, which are installed in the 'bundle' interface steelwork, were ordered by Rockwater Ltd, part of the Halliburton Subsea Group, a major underwater contractor.

The rigid pipeline bundles, which can be several kilometers long, are fabricated on land and towed to site for installation.

Wires connecting the 'bundles' to the towing vessels are released remotely by the cylinders, which operate 200 tonne shackle pins and a variety of hydraulic control valves.

The interface steelworks, including the cylinders are recovered for use in future operations.

Recovery is independent of water depth.

Positioning signals from the in-cylinder VRVTs are monitored in the control cabin from which the operator also controls the hydraulic systems.

A spokesman for Whittaker Engineering explains that the VRVTs have now replaced limit switches, which were fitted outside the cylinders and could provide only a simple in/out position signal.

"Besides being more reliable because they are protected inside the cylinder, the VRVTs provide a variable signal via their remote electronics and can therefore give the exact position of the cylinder at all times." He says.

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