‘KL Sandefjord’ breaks bollard pull record
Although the massive and fast developing world of offshore operations is usually outside the scope of this regular feature, the recent delivery of the anchorhandling tug supply vessel KL Sandefjord is of special interest.
This new vessel for Norwegian owners K Line Offshore is claimed to be the most powerful anchor handler in the world, with a bollard pull of 390 tons.
KL Sandefjord, and yet to be completed sister ship KL Saltfjord, are described as multi-functional ultra-deepwater anchor handling tug, supply and service vessels. In addition to deepwater anchor handling and towing they are also equipped for seabed and ROV operations, ploughing, trenching, pre-lay work and supply duties.
The vessels were designed by STX and constructed by STX NOL (Langsten). Both measure 95m in length overall, with a breadth of 24m, a maximum draft of 7.82m, and weigh 7,800 gross tons. In addition to their impressive bollard pull, the tugs have a maximum free running speed of 18 knots.
One of the most interesting features of this design is the diesel mechanical/diesel electric hybrid propulsion system. Two Wartsila 16v32/8 main engines, each rated at 7,680 kW, are coupled to the propeller shafts and 4,900mm four blade controllable pitch propellers via reduction gearboxes. Each reduction gearbox incorporates a clutch on the main drive, a power takeoff coupling for a shaft generator and an input coupling for a frequency controlled electric drive motor.
Also installed are five diesel driven alternators powered by Caterpillar 3516C engines rated at 2 200 kW at 1,800 rpm. Electrical power from all five diesel generators, and the two shaft generators, is controlled by the main switchboard. The total power available in the propulsion system is approximately 35,350 bhp.
KL Sandefjord can be operated either in diesel-electrical, diesel-mechanical or hybrid modes, with either constant or variable pitch on the propellers and with constant or variable shaft revolutions. Diesel-mechanical mode means operating both propellers using the main engines via the driveline reduction gears only. In diesel-electric mode the propellers, and if necessary the thrusters, are powered by the electric motors, with current from the main switchboard. Hybrid mode is when a combination of both is employed, typically when operating under full Dynamic Positioning (DP) control and when the main propellers and thrusters are in use. When in transit either diesel-mechanical or hybrid modes can be used. When high bollard pulls are required the diesel-mechanical configuration is boosted by means of the electric motors.
Five thrusters are installed, all manufactured by Wartsila with fixed pitch propellers and electrically powered by frequency controlled motors. Two transverse thrusters of 1,200 kW and one 1,500 kW retractable unit are fitted in the bow and one transverse and one retractable at the stern.
With such a powerful and versatile propulsion system, the tugs have a spectacular outfit of towing and anchor handling gear to match, supplied mainly by Rolls-Royce Brattvaag. Five winches are installed, two single drum anchor handling, one ‘special handling’ and towing, and two secondary winches. A full description of each is not possible here but the specifications for the anchor handling drums alone illustrate the performance required from a modern deep sea anchor handler. Both drums have a brake holding capacity of 950 tons and a maximum line pull of 600 tons and are capable of taking wires of between 76mm and 103mm diameter steel wire rope (SWR). The ‘special handling winch’ drum can accommodate up to 14,800m of 76mm diameter or 8,940m of 96mm SWR used for towing or deepwater operations.
Other deck equipment includes a twin stern roller (with two separate elements on one shaft), four tugger winches and two sets of ‘Sharks Jaws’ and tow pins. An ODIM Anchor Recovery Frame (ARF) for handling large anchors of ‘Torpedo’ type is fitted on the aft deck and is flush with the main deck when in stowed position. A total of six rig chain lockers, located below main deck aft of the main winches, have a total capacity of about 1,000 cu/m. Two double jib Rolls-Royce Marine cranes with manipulators for safe deck operations travel the full length of the cargo rail cranes to serve the entire working area of the main deck. A 250 tons capacity ‘A’ frame is available for subsea construction work. .
KL Sandefjord is also fitted with an ROV hangar and an ODIM LARS (ROVLARS) system for handling inspection and work class ROVs used in underwater operations. As previously mentioned, the vessel is equipped with a dynamic positioning system, essential for subsea operations.
In addition to the equipment and facilities already mentioned, this powerful and sophisticated vessel also has a considerable cargo capacity. The after deck has an area of 750 sq/m and can accommodate 3,200 tons of cargo. Below decks, dedicated tanks are available to transport brine, mud and drill water.
Accommodation is provided for a maximum of 70 persons, with total of 20 single berth cabins for officers and crew. In addition there are 25 double berth cabins, a hospital, conference rooms, a ship’s office, lounges, a gymnasium and the all necessary galley , storage and sanitary facilities.
In March of 2009 it was reported in these pages that the record for the world’s highest bollard pull was claimed by the specialist offshore vessel Far Samson, with a maximum continuous bollard pull of 423 tons using all available power and more than 377 tons using just the main propulsion system. It was recognized at the time that Far Samson was designed principally for subsea ploughing and other specialized services and not intended for anchor handling and towing.
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