Damen introduce a new tractor design

Market research and demands from customers revealed a gap in the product range and work was started about three of years ago on a ‘Compact’ tractor design employing fully steerable azimuthing propulsion units.

The first example of this new tractor design, the ‘PB Darling’, was completed in Damen’s Song Cam Shipyard, Haiphong, Vietnam and subjected to extensive trials before being delivered to its owners PB Towage Pty Ltd of Melbourne, Australia. A second vessel, the ‘PB Murray’, was completed just a few weeks later for the same client.

Designated a Damen ATD Tug 2412, the new tractor tug is just 24.63m in length overall with a massive 12.63m beam, giving the vessel an almost elliptical planform and a draft aft of 5.71m . The hullform incorporates a large skeg aft, forward mounted propulsion units and a small ‘docking skeg’ on the centreline beneath the bow.

A conventional bow configuration has been adopted and a heavily fendered stern. ‘Two stage’ fendering aft comprises a series of moulded rubber blocks, surmounted by a heavy cylindrical moulding at bulwark level, giving adequate protection to the stern and aft quarters. In use the tug tows over the stern, shiphandling in the push-pull mode from a winch on the after deck. Contained within the hull are tanks for 77 cu/m of fuel, 11.8 cu/m of fresh water, 5.3 cu/m of foam, 6.8 cu/m of lubricating oil and 5.7 cu/m of bilge water. The bulwarks are ‘built in’, increasing strength and reducing the need for maintenance.

Two Caterpillar 3516B TA HD/D main engines generate a total of 5,605 bhp, running at 1,600 rpm. Power is transmitted to a pair of Rolls Royce US 255 propulsion units with 2,600mm diameter propellers. The units are of the compact, built-in type welded into the hull structure. A remarkably spacious engine room for such a small vessel also houses two Caterpillar powered 64kVA auxiliary generators and a Caterpillar 3406E auxiliary driving a 1,200 cu/m/hour fire pump. To satisfy the needs of both main engines and auxiliaries, the forced ventilation system is rated at 60,000 cu/m/hour.

Reports on the performance of this new tractor design are promising. The tugs are said to be extremely agile and on trials achieved a bollard pull of 63.5 tons, and an almost identical free running speed ahead and astern of about 11.5 knots.

Deck equipment aboard PB Darling has been kept simple and the working areas have been kept as clear of obstructions as possible. A hydraulically powered Kraaijeveld towing winch with a single split drum is installed. The winch has a maximum brake load of 150 tons and a line pull of 30 tons at 11m/min. Two 360kg high holding power anchors are located in ‘pockets’ in the bow and handled by a small Kraaijeveld windlass.

The wheelhouse and accommodation follows standard Damen practice, the only departure being the positioning of the twin exhaust uptakes aft of the wheelhouse structure giving equally good visibility ahead and astern. A standard Damen control console had been adopted, with separate propulsion unit controls for each unit. A navigational and communications equipment package has been selected which is compatible with port operations.

Air conditioned accommodation is provided for up to four persons in three cabins and including a pantry, mess/day room, switchboard room and sanitary facilities.