A salvage operation on a ship wreck 3,200m below the surface of the South Atlantic has been successfully carried out thanks to the use of lightweight ropes made with Dyneema® ultra-high molecular weight polyethylene fiber.
Dyneema fiber, the world’s strongest fiber™, is manufactured by DSM Dyneema. It is used by Hampidjan, one of the largest fishing gear and “super rope” manufacturers in the world, to make DynIce Warp, an advanced patent-pending winch line for deep sea lifting and lowering as well as for towing fishing trawls. The DynIce Warp rope was used over several months on the MV Seabed Worker in a salvage operation to rescue valuable cargo from a sunken ship.
The depth of the wreck meant that use of steel rope would have been virtually impossible, since it would have had a weight in the water of over 35t. By contrast, the DynIce Warp rope containing Dyneema fiber weighed a mere 740kg, thanks to its relative density of 1.1. (Out of the water, 4.2km of the DynIce Warp rope weighs 6.5t, against around 50t for the same length of steel rope with the same strength).
This reduced weight affects not only the lifting operation but also the stability of the vessel and its deck load capacity. In fact, the MV Seabed Worker holds a 6,000m-long DynIce Warp rope for future operations, without needing to switch to a larger winch which would require a larger and thus more expensive vessel.
The ship is operated by the Norwegian Seabed Group, a long-established company equipped with ultra-modern equipment for deep-sea operations including wreck salvage. Seabed says that over the several months it has been using the DynIce Warp rope for the current operation, on a standard drum winch with an electronically controlled spooling system, it has experienced no problems at all with the spooling, even though the rope has a high number of layers on the drum.
The version of DynIce Warp used in this operation is a 12-strand braided rope with a diameter of 46mm. It has the same strength as a steel rope with the same diameter. Even pulling up heavy loads from over 3km below, it shows very little elongation. The rope consists of six different layers that together provide very high cross-sectional stability and axial stiffness.
In addition to their extreme strength-to-weight ratio, ropes containing Dyneema fiber are also very durable, with excellent resistance to abrasion and also to weathering. They require very little maintenance, and so help reduce operating costs and increase safety.