A third vessel, the ‘Salvigilant’, is expected to join the Semco fleet on 12 July.

The tugs are designed for long distance towage and salvage but are also equipped to provide anchor-handling and mooring services. In keeping with other modern vessels in the Semco fleet, these latest additions are intended to undertake the towage of large, high value floating objects such as FPSOs and similar pieces of offshore plant. Salveritas and it sister ships are vessels of 2,658 gross tons classed by ABS; +A1(E) +AMS, ’Towing Vessel’.

All three vessels measure 68m in length overall, with a breadth moulded of 16.4m and a design draft of 5.2m. The hull configuration includes a very high forecastle and deep vertical fore-foot and a long clear after deck with an enclosed winch house and stern roller. The forecastle is a full two decks high, which with the compact superstructure and bridge design undoubtedly affords considerable protection in heavy weather.

A conventional twin screw propulsion system has been installed, utilising two Wartsila 9L32 main engines each rated 4,500kW at 750rpm, delivering a total of 12,000hp. Power is transmitted via a long shaft line and reduction gearboxes to LIPS controllable pitch propellers, rotating within fixed nozzles. The gearboxes are located unusually close to the stern and incorporate shaft generators. On trials this arrangement gave the first two tugs a bollard pull of 157 tons and free running speed of 15 knots.

Manoeuvrability is enhanced with the installation of two transverse thrusters, one of 800kW in the bow and one of 588kW at the stern.

Electrical power onboard is provided by two 1,200kW shaft generators, two main diesel generators of 330kW each and a 60kW emergency generator, all supplying 415v, 3 phase, 50 Hz.

The tugs are designed to operate over long distances, with the engines optimised to use heavy fuel oil. Internal tanks can accommodate 2,150m3 of heavy fuel, 200m3 of diesel oil, 1,000m3 of ballast water, 170m3 of fresh water, 13m3 of fire fighting foam and 13m3 of chemical dispersant. The after deck has a clear area of 350m2.

As with all tugs involved in deepsea towage and salvage, the towing winches are of prime importance. The winch fitted, in a fully enclosed ‘winch-house’, is a waterfall type double drum winch with a brake holding capacity of 400 tons. Two 1,500m towlines of 76mm diameter steel wire rope are fitted and two powered storage drums located at boat deck level have the same capacity. Other deck equipment includes two 20 ton tugger winches, a retractable hydraulic ‘sharks jaw’ (350 tons SWL), a set of retractable tow pins (200 tons SWL), two 10 ton capstans and a 350 ton stern roller. A single hydraulic deck crane with a telescopic jib has a lifting capacity of 2 tons at 14m.

All three tugs are equipped for fire fighting with two dual water-foam monitors, each with a capacity of 600m3/hour, equating to FiFi ½.

Fully air conditioned accommodation is provided for a maximum of 36 crew, in six single cabins, five double, and five with berths for five persons.

Early in May, Salveritas and Salviceroy started a major tow with the hull of the new Conoco-Phillips ‘China Bohai’ FPSO from Shanghai in China to Singapore. Semco is contracted by Conoco-Phillips China for the towage of this largest FPSO hull ever built in China and will also provide a riding crew and ballasting assistance onboard the vessel. The voyage from Shanghai to Singapore is expected to take about 14 days. On arrival in Singapore, the installation of the topsides will be carried out by SMOE at their yard in Sembawang. The completed FPSO will be towed to the Bohai Field on completion of the programme.