Platform mooring systems

Holstein Truss Spar (Top left - Image courtesy BP & Shell)
Moored in 1325m of water in BP's Holstein Gulf of Mexico oil and gas development, 150 miles south of New Orleans, the platform is the largest production, drilling and quarters (PDQ) truss spar in the world. The mooring system is the world's largest for a floating object, extending nearly a mile to the seabed.

A 16-leg taut chain-wire-chain mooring system was specified, calling for 16 individual chain jacks, stoppers and turn-down sheave assemblies, each chain link is over a meter in length and weighs 400kg. The 16 underwater rotary, pocketed whelp-type fairleads are designed for platform chain and a similarly sized messenger chain, and to allow the passage of a special installation connector with the same main dimensions as the common chain link.

Floating storage and offloading vessel Betina
Operated by Malaysia International Shipping Co, Betina is a converted tanker and is stationed on the South Angsi oil field off Malaysia. A 12 point spread mooring system was specified. Two main winches handle the moorings deployed at each end of the ship. Each winch can pull 75 tonnes with any number of layers of wire on the drum. Six fairleads rated at for a load of 800 tonnes at 105 degrees wrap are located on the aft deck, on the foredeck guides are built into the structure. There are altogether twelve fixed chain stoppers, six to hold down the forward moorings, six for aft.

Semi Submersible rig West E-drill of Eastern Drilling
At each corner of the rig a double windlass and fairlead system for eight point thruster assisted mooring is installed for pre-set mooring in deeper waters. The four double windlasses are designed for 76mm chain diameter R4 chain, eight fairleads take the same diameter chain together with four control cabins and a central release panel were all part of the Rolls-Royce supply.  Eight Rolls-Royce UUC355 azimuth thrusters each rated at 3,300kW provide the propulsive power.