The new Serco Denholm tug fleet is rapidly taking shape

SD Jupiter

is part of a massive 29 vessel order placed with Damen Shipyards at Gorinchem in the Netherlands by Serco Denholm to service their contract to provide marine services in support of the Royal Navy.

The order comprises a wide variety of vessels of 15 different designs, including pilot boats, tugs, barges, multipurpose work vessels, a fast crew boat and a worldwide support ship (Maritime Journal – February 2008). Included in that order are 16 tugs of various types. Six tugs and six pilot/patrol vessels have now been delivered and the remaining craft will be coming into service in stages, with the entire order to be completed by the end of 2010.

The tugs now in the hands of Serco are the two Pushycats SD Emily and SD Catherine, the Stan Tug 1405 SD Tilly and the trio of Stan Tug 2608s, SD Hercules, SD Mars and SD Jupiter.

SD Jupiter, the third vessel of its type, was formally handed over at the end of June. At face value it is an established product from Damen’s standard range but a closer examination reveals some substantial changes made to satisfy the exacting criteria laid down in the Serco Denholm specification.

In commercial hands the Stan Tug 2608 has proved to be a popular and versatile conventional twin screw tug for coastal and port operations. For naval service the tug has a comprehensive outfit of equipment to fit it for a wide variety of tasks in addition to towage operations in port and at sea. Two towing winches are fitted, both from Kraaijveld. A combined anchor windlass and single drum winch is located on the foredeck and a double drum towing winch on the after deck. The latter has independent drums with a line pull of 10 tons at 30m/min and a brake holding load of 75 tons. A Heila HLM 20-45-S hydraulic deck crane is installed for transferring stores and equipment.

With a length of 26.61m, beam of 8.8m and draft of 3.40m, the tug has a particularly spacious after deck. The space is particularly suitable for the deployment of towed sonar arrays and, if necessary, an accommodation module can be carried to increase the number of personnel that can be carried from 12 to 30. SD Hercules, the first of the series, has passenger certification specifically for that purpose. Internal tanks have capacity for 65.5 cu/m of fuel, 12.0 cu/m of fresh water for onboard use and 20.2 cu/m of fresh water as cargo.

In the engine room a pair of keel cooled Caterpillar 3508B TA main engines produce a total of 2,200 bhp at 1,600 rpm to drive a pair of Promarin Kaplan II propellers, turning in fixed Van der Giessen Optima nozzles. This arrangement gives the tugs a bollard pull of 29.5 tons and a free running speed of 12 knots. A 90kW HRP hydraulically powered bow thruster is installed to enhance manoeuvrability at close quarters. Although the bollard pull is considerably less than many commercial variants, the propulsion system chosen provides an agile, fuel efficient and versatile performance.

Also housed in the engineroom are two Caterpillar C4.4TA powered auxiliary generators rated 125kVA each at 60Hz, 440V. A third, larger Caterpillar 3406C TA diesel powers a Sterling ZLNY 150-400 fire pump capable delivering 600 cu/m of water per hour to a manually operated monitor above the wheelhouse roof or deck level hydrants. This auxiliary diesel also powers the hydraulic pump for the bowthruster. Hydraulic power for the deck machinery is supplied by pumps driven by the main engines.

A versatile communications and navigational outfit has been chosen to enable the tugs to carry out harbour and coastal operations. Air conditioned and heated accommodation is provided for up to 6 persons in two single and two double berth cabins.

Among the other vessels due for delivery to Serco Denholm by the end of this year are two azimuthing stern drive (ASD) tugs built to the Damen ASD Tug 2509 design and the first of four purpose designed tractor tugs. The latter, designated the Damen ATD 2909, are required to handle the largest ships currently in service or planned for the future. The first example of this new design is being fitted out in the Netherlands and will be delivered in November.