This class of tug is built to operate in heavy ice and complies with the stringent requirements of Ice Class 1A FS. The design is a variant of Irving’s well known 5,000 horsepower ASD class that is in use in large numbers in Canada and elsewhere. For this owner the specification is comprehensive and the vessels comply with the requirements of Lloyds; +100A1 TUG,+UMC, UMS, FiFi 1 w/waterpspray, Ice 1A FS.

Stevns Icequeen and its sisters are vessels of 30.8m in length with a beam of 11.14m and maximum draft of 5.5m. Each has a large ‘escort skeg’ forward to enhance performance while operating in the indirect towing mode and improve course stability while going astern. To prevent damage when working in ice two ‘ice-diverters’ are fitted beneath the stern to stop large pieces of ice reaching the ASD units. A small ‘ice stop’ is also welded to the forward lower edge of the skeg to prevent the hull riding up onto the ice. Although this breed of tug has considerable inherent agility, a Kamewa 45TV bow thruster of 150 kW is installed to enhance manoeuvrability further and help overcome any resistance to turning caused by the forward portion of the skeg.

The hull has a distinctive sheer and a semi-raised foredeck.  A normal heavy fender is fitted in the bow for shiphandling and rubber belting is provided all round the vessel. ‘Cutaway’ bulwarks at the stern are carefully faired adjacent to a stern roller. A neat feature found in this design and very few others, is the pair of ‘headlights’ set in the bow, on the side of the central Panama lead.

The tug is powered by two Caterpillar 3516B HD main engines, each generating 2,500 bhp at 1600 rpm, coupled to a pair of Rolls-Royce Aquamaster US255 CP propulsion units. Each unit incorporates a controllable pitch propeller of 2.4m diameter, obviating the need for slipping clutches. On trials the tug achieved a bollard pull of 60 tons towing ahead, 54.9 tons astern and a speed of 14 knots.

Electrical power onboard the vessel is generated is by two Caterpillar C9 diesel driven alternators rated at 165kW. A power takeoff on the free end of the port main engine drives a single dedicated fire pump rated at 2,700 m3/h to supply the FiFi 1 system. The pump feeds two remotely controlled FFS monitors, capable of discharging 1,200 m3/h, mounted on a platform aft of the wheelhouse roof. The obligatory protective water curtain is also supplied by the same pump at 300 m3/h. 

A comprehensive outfit of towing gear includes two electrically powered Ridderinkhof towing winches. For shiphandling, a single drum towing winch is located on the raised foredeck. The winch has a 150 ton brake load and is equipped with heavy duty spooling gear and carries 122m of 89mm Spectra manmade fibre towline. A large tubular ‘staple’ type fairlead is positioned well forward, on the spacious fore deck.

A similar frequency controlled Rinderinkhof winch is fitted aft for towing and anchor handling over the stern. The single drum is fitted with 762m of 51mm diameter steel wire towline. Also provided on the after deck is a set of 200mm hydraulically operated tow pins from Western Machine Works complete with a ‘hold down hook’. The stern roller, from the same manufacturer, is 1.53m wide and 533mm in diameter. A Ridderinkhof combined capstan and tugger winch is also fitted along with a 75 ton Washington Chain quick release tow hook.

To assist with stores and towing gear a Palfinger knuckle boom crane is mounted on the starboard side adjacent to the aft winch. The crane has a lifting capacity of 590kg at 12.4m reach and 2,160kg at 4.4m.  

Stevns Icequeen, in keeping with it sister ships, is fully equipped with European compliant equipment and materials. To ensure the lowest possible noise levels and to comply with the stringent Danish Maritime Authority regulations, floating floors are fitted throughout, together with double thickness joiner panels and extensive insulation in the engineroom.

Comfortable accommodation is provided for six persons in four single and one double cabin. The Captain and Chief Engineer’s cabins are located on the main deck with the galley and mess room, with the remainder below decks.

The well established wheelhouse design used by Irving has changed little externally for a decade. It is well located and has few blinds spots. The exhaust uptakes are simple pipes, emerging from very short funnels and impinge very little in the line of sight. And the view forward gives the tugmaster sight of the winch and fairlead. Virtually all of the controls and instruments are arranged on a ‘U’ shaped console with the usual Captain’s chair placed centrally and in easy reach of all of the major items.

A Rolls-Royce Aquamaster controller, combining azimuthing unit rotation and engine speed/propeller pitch, is located on each side in the usual manner. Immediately in front of the tug master is a neat display panel, with a graphic display showing the status of all the main systems and alarms. Adjoining the display are the winch and bow thruster controls. A nice touch is the positioning of the azimuthing unit position indicators, one on each side of this central display along with small revolution indicators, all just below the line of sight. Two radar sets are fitted with displays on either side and the usual outfit of navigational and communications equipment.

Stevens Icequeen will join sister tugs Stevns Iceflower and Stevns Icecap and the larger Ice class ASD tugs Stevns Ocean and Stevns Arctic, also built in Canada in recent years for Nordane Shipping. To date all of latter have both been marketed successfully on the ‘spot market’ and appear in various ports around Europe and Scandinavia on short term shiphandling contracts or short sea and offshore towage projects.

By  JACK GASTON