A close-up view of the barge-handling lines.
harness and the system moved down the Port Arthur Ship Channel on its way to the Gulf and the 140-mile transit to the project site. Once on site, the VB 10,000 established position under its own propulsion, the tieback lines were released, and the rigging was made ready for use. Using its eight 1,000 HP Trustmaster thrusters,
the VB 10,000 maneuvered via its DP-3 Dynamic Positioning System over each platform in succession. Once in position, Versabar personnel began the delicately balanced proceedure of positioning the rigging to make the lift. Tis process involved the simultaneous paying out of the 3 ½” wire rope on the main hoist winches, and the pulling in of the 2” wire rope on the four 100-ton Claw winches in order to open the claw arms wide and enable them to span the topside and reach the legs beneath the structure. Once Te Claw arms were in the proper position, their Claw winches paid out rope until the lifting hooks were secured inside the preset lifting pins on the legs of the topside. At this point, the main hoist winches were engaged and the lift was made. With the eight-pile topside now suspended some 25
feet above the surface, the system slowly maneuvered away from the jacket. Now it was time for another rope-oriented procedure requiring a high degree of skill and timing. Operating from a raised control stand midships and inboard of each barge, the operators stood above their winches in view of the four Smithberger single sheave, balanced head fairleads. Samson-Turbo-75
synthetic rope was routed around the fairleads and tied off to bits on the transport barge. Te winch operators on each side of the system stayed in constant communication with each other to manipulate the transport barge into position. In the interest of safety, it is important to position the barge under the load swiftly and smoothly. Once the load was fully settled on the barge, welders went to work on the sea fastenings, (a process that may take anywhere from 2 to six hours) after which the barge was removed by tugs and towed to a Gulf Coast salvage yard. With each repetition, the VB 10,000 lift team became more skilled in the unorthodox process of lifting and setting of these large decks (averaging 1,500 tons apiece). Te last three of the four topsides, with an aggregate weight of 4,534 tons, were all lifted, placed on barges, and towed away in 30 hours, a remarkably short time for an operation of such scope and complexity. An even more complex operation, however, lay just ahead - the removal of the jackets. On other occasions the procedure for jacket removal had been the same as that of the topsides, lifting the structures and placing them directly on barges for transport to salvage yards. In this instance, however, the operation was complicated by the fact that the height of the jackets did not allow, even with the VB-10,000’s ample 175’ hook height, for adequate clearance to position a barge under the load. Te result was that after lifting the jackets – a fairly straightforward procedure which involved slipping doubled wire rope slings under hooks welded to the
20
NOVEMBER–DECEMBER 2016
WIRE ROPE EXCHANGE
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