Soft rope traction winch for spar platform

Soft rope traction winch for spar platform

When this client was designing the platform’s subsea asset deployment and retrieval system, it faced a problem: at water depths over 8,000 feet, a traditional wire rope drum winch system would be too heavy for the platform on which it was to rest. A revolutionary new winch/rope system was needed.

This platform is part of the world’s deepest oil production facility. It is the most remote producing platform in the Gulf of Mexico, located almost 220 miles off the coast of Texas. This platform is the only development in the region to use subsea separation and boosting equipment. The development features 22 wells and 13 more well tie-backs, which must be changed out and serviced at regular intervals. Rather than deploying offshore service vessels to the remote development at great expense, its design includes a winch system allowing the platform to service the subsea equipment itself.

However, operating in nearly 9,000 feet of water while handling payloads of up to 90,000 pounds can be a challenge. Compounding the problem, the design places the winch on a cantilevered deck (a smaller deck extending out from the main platform) imposing significant weight restrictions. A traditional steel wire rope of this length would be prohibitively heavy. Weighing 81,750 pounds, it would double the necessary lifting capacity of the winch. This would in turn increase the size of the winch and cause significant structural modifications.

We delivered

The client turned to Doedijns for a simple, yet unique traction-style winch design and to Samson for its expertise in high-strength, lightweight synthetics. This combination met the weight and footprint restrictions of the cantilevered deck and was more than capable of performing the subsea operations. Samson provided 9,200 feet of 2-1/2″ diameter Quantum-12 rope.Weighing 85% less than a wire rope of similar size and length, this greatly reduced deck weight. The biggest advantage, however, is that Quantum-12 is neutrally buoyant and adds no weight to the payload. This allows the winch to work at full capacity regardless of depth.