Faced with the challenge of installing one of southeast Asia’s largest offshore platforms – without damaging a complex network of existing pipelines and sensitive subsea structures – Dockwise knew that anchor lines made with Dyneema® were the only solution. After all, ropes containing Dyneema® are strong enough and light enough to get the job done, no matter how tough.
A demanding job – in demanding conditions
Dockwise, the world’s biggest heavy transport shipping company, operates a fleet of 23 ships and semi-submersible vessels. The team decided the Black Marlin, an open-stern heavy transport vessel, was the right ship to take on the challenge in Malaysia.
But there were some key requirements to fulfil. First, Dockwise would have to safely load and transport the topside platform from Pasir Gudang to the field off the coast of Terengganu. Weighing 18,900 MT and standing at 124 meters in height, the topside was one of southeast Asia’s largest offshore platforms. Second, the float-over installation needed to be carried out without damaging the existing, and extensive, underwater infrastructure in a field dating back to 1978.
Quicker installation with Dyneema®
With all this in mind, Dockwise replaced the Black Marlin’s normal complement of steel wire anchor lines with synthetic lines made with ultra-high-molecular-weight polyethylene (UHMWPE). “We were working close topipelines and other subsea assets,” explains Aart van den Hoonaard, Senior Project Manager at Dockwise. “In such a demanding and precise operation, it might have been possible to use steel wire rope with mid-line buoys, but it would have required much more installation time.”
When one of the first UHMWPE lines it tried failed, Dockwise turned to another anchor rope manufacturer – and settled on the Oliveira X-Trema Line 12-strand rope, made with Dyneema® SK78 fiber. Mooring lines made with Dyneema® are as strong as steel wire rope of the same diameter, but at less than one-seventh of the weight. Plus, a rope made with Dyneema® is about 60% of the diameter and 30% of the weight of an equally strong polyester or nylon rope.
A flawless float-over
As the loading window approached, the Black Marlin was outfitted and prepared for the skid-out operation that would slide the topside onto the vessel. Two days’ sailing later, and the team executed a perfect float-over installation!
The operation involved three tugs and a four-point anchor mooring arrangement, with the four Dyneema®-based mooring lines holding the Black Marlin in position – while preventing any damage to the existing field layout.
Meet the Black Marlin
Maximum draft: 10.08 meters
Water depth above main deck FPP/APP: 10.00 meters
Deadweight: 57,021 t
Speed: 14.5 knots
Length o.a.: 217.50 meters
Breadth molded/max.: 42.00 meters
Deck area: 165.60 x 42.00 meters
Depth: 13.30 meters
Draft submerged at FPP/APP: 23.34 meters
Length b.p.: 206.57 meters
Dyneema® takes the strain
The lines: 12-strand braided Dyneema® SK78 fiber (MBL 3,210 kN; 800 meters long; 64 mm diameter)
Mooring configuration: rope with Dyneema® > shackle > SWR > steel chain > anchor
Total length of mooring system: approx. 1,450 meters
Anchors: 15 t, positioned using an anchor handling vessel
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