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Encyclopedia of Marine and Energy Technology

Cable laying and repair vessel ATLANTIC GUARDIAN


According to MER April 2002

The 3250dwt stern working cable vessel was built by Van der Giessen-de Noord BV, The Netherlands, in 2001. The ship has a number of features designed to ensure that both sea keeping and station keeping performances are high. The length of the vessel, 102.13m, was selected to suit good characteristics at zero speed (cable repair work) combined with a good performance at transit speed up to sea state six. An Alstom dynamic positioning (DP) system of the ADP 21 duplex type, with automatic backup facility, allows better control of the ship when station keeping. The DP control system is specifically programmed for cable working and gives the operator full control of the vessel, linked to satellite positioning and Differential Global Positioning System (DGPS).

All cable operations are carried out over the stern; a system first applied to CS ASEAN RESTORER built by Kvaerner Masa-Yards in 1994. This has proved very successful in operation, and has been adapted for the new vessel to provide more working space in the stern, and heavy working machines and equipment have been better placed in more sheltered locations. Working areas such as the jointing and testing rooms, and thewheelhouse are positioned amidships in order to reduce the effect of roll and pitch on the performance of the crew. To reduce downtime due to water on deck significantly, the ship benefits from a 5.7m (minimum) freeboard to the cable working deck.

The ship is equipped to repair damaged cable (10/70mm diam) in ocean depths down to 5000m; some laying and shallow water ploughing work can also be done. Two 12m-diameter main cable tanks and two 6m diameter spare tanks enable the ship to carry up to 1070m3 of cable.

Cable handling machinery supplied by Dowty is operated by built-in hydraulic power packs. The ship is equipped with two 4m-diameter cable drum engines, each with a 40t brake and 28t-line pull, two four-wheel-pair draw off/hold back engines and diverters. Twin two-wheel pair cable transporters are also installed. The cable machinery includes also two 3m-diameter cable lying/repair sheaves, a plough towing sheave supported by a 10t A-frame, two deck cranes of 5t and 1.5t SWL and two 2.3t SWL gantry cranes.

The vessel is fitted with a remotely-operated vehicle (ROV) capable of operating at water depth of 2000m. As safety is of chief importance during hazardous cable maintenance operations, the amidships wheelhouse/operations room offer a clear view of cable working areas and the ROV deck.

The ship is propelled by two Wärtsilä Lips L-type azimuthing propulsion thrusters(2x2200kW) operating in high efficiency nozzles. Contributing to the DP system are three bow thrusters (3x900kW). All are supplied from a high voltage diesel-electric propulsion installation using three ABB 2690kW alternators driven by Wärtsilä 9L26A diesel engines.