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Encyclopedia of Marine and Energy Technology

Pipelaying system of the MIDNIGHT EXPRESS


Deepwater installation vessel MIDNIGHT EXPRESS was converted from a former LASH barge by the Canadian shipyard Davie Maritime in Quebec. The vessel has a new, patented reellaying system, designed, manufactured and installed by Huisman-Itrec. After its conversion, the vessel is able to lay small- to mid-diameter rigid and flexible pipes in varying water depths, up to a maximum of 3000m. The J-lay system is configured to accommodate rigid pipes from 2.5-in. to 12.75-in. outside diameter, at tower angles ranging from 63° to 90°. The system is capable of pipe fabrication and spooling operations. It comprises the tower, an aligner wheel, one tensioner, a hang-off clamp, one adjuster, one abandonment and recovery (A&R) winch, two pipe storage reels, and associated workstation on the vessel deck.

The 12.3m long pipe segments are welded, inspected, and coated in the deck workstation. The pipe is spooled onto the reel via the deck tensioner. During unwinding of the first reel via the tower, the second reel is spooled with a new pipe. The total storage capacity per reel is 600t, with a spooling tension 200kn. The laying speed at maximum tension is 20 m/min.

During pipelay, the complete tower is automatically skidded sideway to keep it in line with the unwind position of the pipe on the corresponding reel. The shaft of the large aligner wheel can be adjusted lengthwise to ensure that the center of different pipe diameters remains at the same firing line.

The main 160t tensioner is equipped with four tracks. Depending on pipe diameter and wall thickness, two or four tracks are in operation. For the A&R function to handle the pipe’s loose end when laying is interrupted, a 250t traction winch is deployed in combination with a large storage winch suitable for 3,000m of wire. The traction winch is installed directly on the tower while the storage winch is kept below deck. During skidding of the tower, the storage winch is maintained in automatic active mode to compensate for length variation of the wire.

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