Undersea advances, from ropes to deep-water repair robots

21st February 2013

Allseas Group, a Swiss offshore pipelaying company, has collaborated with DSM Dyneema to improve the safety and speed of underwater pipe-laying using next-generation rope technology.
The two companies have worked to replace traditional steel wire rope used to adjust pipelay stingers with a new product from BEXCOropes that is made with ultra-strong, lightweight polyethylene Dyneema fibre. The new rope, which has been installed on Allseas’ pipe-laying vessel Audacia, enables faster, easier and safer operations (Fig. 1).
“Adjusting the stinger is a critical part of the pipe-laying process because it determines the precise curvature of the pipe as it enters the water,” explained André Steenhuis, Allseas Innovation Manager. “The heavy, rough steel wire rope hampered our crews, slowing down our operations. With the rope’s high strength and low weight provided by Dyneema fibre, we can achieve the precision we need more quickly and easily. Our partnership with DSM Dyneema has led to a major advance in pipe-laying efficiency and safety.”
Because of the heavy weight of the 150-metre steel wire rope, Allseas’ crews experienced difficult handling, and higher risk of damage and injury. Also, corrosion shortened the rope’s useful life. In contrast, the new stinger adjustment rope is easy to lift and manoeuvre, is exceptionally durable, and can help avoid injuries. The high
strength-to-weight ratio of the polyethylene fibre enables use of thinner ropes that are easier to deploy, recover and store. For example, the rope made with Dyneema fibre only weighs 9.8 kg/metre; steel wire rope of equivalent strength weighs about 65 kg/metre.
BEXCOropes created the load-bearing portion of the adjustment rope from 100percent Dyneema fibre. The core of the 136mm diameter rope is protected against abrasion by a Deltaflex cover, which is BEXCOropes’ proprietary technology. Adjustment ropes, which are kept on a winch, can be subjected to as much as 250 tonnes of force.
Rigo Bosman, Market Segment Manager Offshore at DSM Dyneema said: “We have closely collaborated with Allseas Group and BEXCOropes to perfect new rope technology based on Dyneema fibre, which will help pipelaying companies improve the efficiency and safety of day-to-day operations. Although this is the first use of Dyneema fibre in this industry, its strength, light weight and durability have proven their value in many other marine applications, and we see great potential for it in new offshore applications such as abandonment and recovery ropes.”

Robot for pipeline repairs

Meanwhile Statoil is building on its leading role in underwater technology development with a new pipeline repair robot capable of working at depths down to 1000 metres.
The new remotely operated welding machine will undergo testing and final adjustments before being deployed in an emergency response role during the year.
“We’re getting a lot of enquiries from international oil and gas companies,” says Kjell Edvard Apeland, who is heading the development job. “They’re interested in using our robot for pipeline repair and field operations in such areas as the Gulf of Mexico.”
Work on the new device is taking place in Haugesund north of Stavanger, where Statoil’s pipeline repair system (PRS) pool is located.
The robot will join a number of other remotely operated tools used in deepwater operations, including tie-in of new pipelines in water depths beyond the reach of divers.
Measuring about four metres long by two metres high, the new welding machine has been developed by Statoil and built in cooperation with external suppliers.
The robot cuts out the damaged pipe section before welding in a new piece inside an enclosed habitat. Systems are provided for preheating and controlling the habitat atmosphere.
A submarine pipeline can be damaged by a shipwreck, for instance, or by having a trawl or anchor dragged over it.
“Many technological experts say that developing such technology and carrying out operations of this kind are more difficult than a moon landing,” says Asbjørn Erdal.
He is manager of the pipeline operation sector, which maintains 8000 km of pipeline and will probably be the biggest customer for the new robot.
The Norwegian government requires that oil and gas distributors have such equipment available. Regulations restrict diving to a maximum water depth of 180 metres.
Statoil currently has a deepwater emergency response system based on remotely operated vehicles that can seal leaks. With the new robot, the group will also be able to weld pipes. ❏

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