HMC Installs 1st Truss Spar to Use Polyester Mooring System

Heerema Marine Contractors successfully installed the first truss spar ever to use a polyester mooring system. The Mad Dog spar which is located in Green Canyon Block 782 in a water depth of approximately 1,348 meters is the first permanent polyester mooring system to be installed in the Gulf of Mexico. It has the largest diameter polyester rope ever made, with a jacketed diameter of 270mm and required the largest quantity of polyester mooring tethers ever produced for a single offshore mooring project.

Using its Deepwater Construction Vessel (DCV) Balder, HMC has installed several chain/spiral strand wire mooring systems. However this was the first installation of a polyester mooring system. The Balder's unique large mooring line deployment winch was used to handle the extensive quantity of polyester rope required for this project.

In preparing the installation, the HMC project team took both the similarities and differences of installing a polyester system to a sheathed spiral strand system into consideration. Since polyester ropes may not come in contact with the seafloor, HMC developed procedures to keep the polyester off the seafloor during all phases of the installation. Another area where differences applied in the approach is the vulnerability of polyester rope for contact with sharp edges, steel wires and heat. Snagging or tearing of any of the fibers could reduce the efficiency of the ropes strength in the future.

HMC project manager Michel Hendriks said: "From the award of this contract and throughout the entire project, forward planning by the HMC installation team in close liaison with industry experts and our Client BP, and the understanding of the particularities / features involved with polyester were key factors which ensured the total success of this first permanent polyester mooring system installation in the Gulf of Mexico."