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.

PLIMSOLL MAIN WINCH FOR FRADE FPSO
Model PC-HCTRW/SD-485/580T

Chain-tensioning drum
Stall pull 485 tonnes
Duty pull 440 tonnes at 0-1.5m/min
Light line speed 0-6.2m/min
Drum capacity 52m of 128mm-diameter wire rope in one layer
Brake holding load 580 tonnes
Drum core diameter 2,175mm (17:1 ratio)
Drum flange diameter 2,690mm (one free layer)
Drum flange distance 1,065mm

Riser pull-in drum
Stall pull at top layer 330 tonnes
Duty pull at top layer 300 tonnes at 0-3m/min
Light line speed
at top layer 0-10m/min
Drum capacity 323m of 103mm-diameter steel wire rope in four working layers
Brake holding load 450 tonnes at top layer
Drum core diameter 2,175mm (21:1 ratio)
Drum flange diameter 3,210mm (one free layer)
Drum flange distance 1,075 mm

The Plimsoll auxiliary winch has a stall pull at top layer of 45 tonnes, a duty pull at top layer of 40 tonnes, and a brake holding load of 55 tonnes at top layer

The power pack is designed to operate both winches simultaneously for wire tensioning, and has an estimated maximum noise level of 90dB.

The stainless steel local control station is mounted on the rotary platform in a position chosen to suit the operator. Monitoring equipment includes line tension indicator with overload alarm, wire length measuring system, and automatic stop when the winch reaches the last four turns on the drum.

The rotary platorm is designed to carry the main riser winch, hydraulic power unit and control stand. The platform is mounted on wheels that run on deck-mounted rails.

MacGREGOR