MacGREGOR's Plimsoll Winch for FPSO is Biggest Yet

Single Buoy Moorings' Frade FPSO will be moored by an internal turret accommodating 33 risers, and the moorings and risers will be handled by a Plimsoll winch supplied as part of an equipment package by MacGREGOR's Offshore division.

A 485-tonne Plimsoll chain-tensioning/riser pull-in winch for Single Buoy Moorings' Frade floating production, storage and offloading (FPSO) vessel off Brazil is the largest yet from MacGREGOR's Offshore division. The package of Plimsoll equipment supplied by MacGREGOR also includes a 45-tonne auxiliary winch, electro-hydraulic power pack, local control station, and rotary platform.

The Frade Field is Chevron's first oilfield development project in Brazil. The field is located in the Campos Basin in a water depth of 1,000m, about 75 miles off of Rio de Janeiro, and is expected to begin production in late 2008 or early 2009.

Single Buoy Moorings Inc was awarded an engineering, procurement, construction and installation (EPCI) contract covering the provision of the FPSO, based on the conversion of its 277,000 dwt VLCC Lu San. In addition to the EPCI contract SBM is to operate the FPSO.

Moored by an internal turret accommodating 33 risers, the FPSO is fitted with topsides for the production of 100,000 barrels of oil, treatment and compression of 106 million standard cubic feet of gas and treatment and injection of 150,000 barrels of water per day.

The Plimsoll main winch is used for tensioning mooring chains and pulling in the pipeline risers that transfer well fluids from the seabed to the surface. It features a single main plain-cored drum with two storage compartments. Each of four variable-speed low-torque hydraulic piston motors drives through an epicyclic reduction gearbox and on to a final drive guarded spur reduction gearset. Totally enclosed plate type brakes mounted between the hydraulic motors and reduction gearboxes are hydraulically released and spring applied, so fail-safe to 'on'. Counterbalance valves are fitted into the hydraulic circuit to assist with controlled lowering on the winch.

For chain tensioning, the winch has a maximum (or 'stall') rating of 485 tonnes pull, a duty pull of 440 tonnes, and a brake holding load of 580 tonnes (see table). The riser pull-in drum has a stall pull at top layer of 330 tonnes, a duty pull of 300 tonnes, and a brake holding load of 450 tonnes at top layer.