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The M/V Nanuq and the M/V Tan’erliq, measuring 47 meters in length, are tractor tugs operated by Crowley Maritime Corporation’s subsidiary Vessel Management Services. The tugs, possessing unique maneuvering capabilities, provide an escort to every laden tanker transiting Prince William Sound in Alaska and are considered the world’s most powerful tugs of its kind.

They are ABS classified and outfitted for:

  • Tanker escort
  • Ocean towing
  • Emergency spill response
  • Firefighting
  • Harbor Service

Unlike most tugs, they have very high forecastle decks with protective bulwarks that are canted inboard. These tractor tugs can displace 1,447 tons of seawater at design draft with gross interior tonnage of just under 500 tons. Other key measurements include maximum beam of 48 feet and maximum draft of 24 feet, the deepest part of which is either the bottom of a massive hydrodynamically shaped skeg under the stern or the underside of a 30-foot-wide protection plate beneath the rotating cycloidal drives. 
These tugs get their power, more than 10,000 Hp each, from two Caterpillar engines each rated 5096 BHP at 900 RPM weighing more than 27 tons each, driving two Voith-Schneider propulsion units. They are propelled through the water by two sets of rotating and adjustable vertical blades projecting down from the hull about a third of the way aft of the bow.

They are capable of applying up to 210,000 pounds of static bollard pull in most directions and of achieving light cruising speeds of 15-16 knots. In the indirect mode, the vessels are capable of exerting up to 340,000 pounds of bollard pull at a speed of 10 knots.

The Nanuq requires only ten minutes to get positive control of a medium-sized tanker that loses steering or power at a speed of 10 knots. She can also use her power to assist with tight steering situations and to provide drag on a ship that desires to maneuver at low speed while still keeping up its propeller revolutions for better rudder effect.


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