Successful repair of NELHA’s 40-inch deep-seawater pipe

Recently the repair works on NELHA’s 40-inch deep-seawater pipe were successfully completed. Operating at 150M depth and using remotely operated vehicles, it was quite an undertaking.

The high-density 1.2-mile-long polyethylene pipe, installed in 1987, extends to depths of 2,000 feet. The pipeline is the backbone of the Natural Energy Laboratory of Hawaii Authority’s coldwater aquaculture and research projects.

pipe1

Image shows a pipeline weight that has been rolling over onto its side and a partially broken chain bridle that holds the main transition anchor in place. Source: NELHA/Special To West Hawaii Today

Surveys of the pipeline in December 2007 showed the mooring bridles, which help hold the pipeline to the ocean floor, and transition anchors were beginning to deteriorate. (Source: NELHA’s deep sea pipeline coming loose – West Hawaii Today)

The recent repairs included replacing the bridles and anchor chains on the portion of the deepwater pipe where this pipeline transitions from being anchored to bottom to a floating reverse catenary. In addition, extra pipe buoyancy was added.

The repair work was conducted entirely by ROV’s underwater and a barge moored above the work area. “The barge was capable of lowering and raising a wide array gear and equipment to the bottom within a precision of 0.5-0.75 meters, such that all the ROV had to do was make the final connection with its mechanical arms”, said Jan War, operations manager of NELHA and in charge of the repair project. NELHA contracted Honolulu’s Healy Tibbitts Builders Inc. for the project.

“Makai Ocean engineering also did the enginering and construction oversight for this project. Furthermore the specifications, bid document drawings and extra staff were provided to oversee the work underway offshore for around 2.5 weeks. The shifts were split up into a night and a day shift thus that from a customer’s standpoint the project was supervised 24/7” Jan War continues.

NELHA’s Executive Director Gregory Barbour expects the repair work, a $4.7 million project, to extend the system’s life another 15 to 20 years.

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Images of the equipment used in the repairs of the deep-seawater pipeline. On the right, Jan War, operations manager with the NELHA and officer in charge of the repair project, is seen with one of the remotely operated vehicles on the barge off the North Kona coast. Source: NELHA/Special to West Hawaii Today

Sources:  

Remotely operated vehicles repairing NELHA’s 40-inch deep-seawater pipe – by Erin Miller, West Hawaii Today

http://westhawaiitoday.com/sections/news/local-news/remotely-operated-vehicles-repairing-nelha%E2%80%99s-40-inch-deep-seawater-pipe

Lawmakers working toward repair funds for NELHA pipeline – Jan 2008

http://friendsofnelha.wikispaces.com/file/view/PipeFund.pdf

NELHA’s deep sea pipeline coming loose – Dec 2007

http://friendsofnelha.wikispaces.com/file/view/LoosePip.pdf

Pumping pipes provide payday

http://friendsofnelha.wikispaces.com/file/view/Pumping.pdf

 

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