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November 30, 2009

Boston Towing takes delivery of Neptune LNG tugs

Boston Towing and Transportation Company has recently taken delivery of two Robert Allan design tugs to serve the new Neptune LNG LLC, Deep Water Port, offshore Massachusetts Bay.

Built by Derecktor Shipyards in Bridgeport, Connecticut , the larger of the two, the 128 ft 4 inch LOA Independence, is an ASD 39/70 Class tug, configured for a wide range of duties including harbor towage and ship-handling, fire-fighting, coastal towing, salvage and rescue towing operations.

Its primary role will be standing-by for tankers using the Neptune LNG offshore mooring buoy, located in a fully exposed deep water location.

This ASD 39/70 design is very similar to comparable Robert Allan RAstar Class tugs from this office, but due to its many unique features it has been given a more general ASD type designation. The tug features a full raised forecastle running nearly half its length which provides a very high standard of accommodations, the ability to work in quite extreme sea-states and the best possible sea-keeping capability for operation in very exposed conditions.

The wheelhouse is designed for maximum visibility with a single control station providing maximum visibility to both fore and aft deck working areas.

The vessel is outfitted to the highest standards for a normal crew of up to eight people.

The forecastle level deckhouse incorporates a spacious suite for the Master. The main deck accommodations include two officers' single cabins and two crew double cabins. There is also a fully-equipped modern galley and a spacious lounge/mess room.

The noise level throughout the crew accommodations is predicted to be in the range of 65-70 dBA, based on utilizing advanced methods of vibration isolating main propulsion machinery, as well as high grade insulations.

Main propulsion for the ASD 39/70 comprises a pair of MTU 16V-4000 diesel engines, each rated 2,000 kW at 1,800 rpm and each driving a Rolls-Royce model US 255 CP azimuthing Z-drive propeller. The controllable pitch Z-drives provide enhanced fuel economy, operational flexibility, and enable efficient operation of the main engine-driven fire-fighting system.

This drive combination is guaranteed to deliver a minimum bollard pull of 67 tonnes, and provide a free running speed of not less than 13.5 knots.

Robert Allan says that by current standards the power is rather small for a tug of this size. However the vessel's size was dictated by the demands to provide a high standard of comfort and sea-worthiness for the crews who will be on station in fully exposed North Atlantic sea conditions for up to two weeks at a time. The sponsoned hull form, which this design has in common with the Allan RAstar Class tugs, provides roll amplitudes and roll accelerations less than half those of other recognized "standard" tug forms of equal size and displacement. These special design measures will provide the crew with a much safer work platform, and much better rest conditions.

Fire-fighting will be to a Fi-Fi 1 Class, with pumps driven by the main engines. The main hawser winch forward is a single drum, Markey EEPC-52 model, containing 750 ft of 10 inch circumference synthetic hawser, with a brake capacity of 264 short tons. The aft towing winch is a Jonrie model 512 with a 2,500 ft (760 m) 2.25 in SWR for towing.

JUSTICE

Built by J.M. Martinac of Tacoma, Wash., the smaller of the two Allan tugs delivered to Boston Towing for the Neptune LNG Operation is the 98 ft LOA (29.9 m) Justice. It is a modified Allan RAmparts 3000 Class tug. It will primarily be engaged in harbor duties, but will serve as the back-up for the larger tug (the ASD 39/70 Class Independence) during the latter's service periods. The RAmparts 3000 Class tug is designed for a wide range of duties including harbour towage and ship-handling, fire-fighting, coastal towing, however the key role will be standing-by for tankers using the offshore mooring buoy.

The propulsion plant comprises a pair of MTU 16V-4000 diesel engines, each rated 2,000 kW (2,681 hp) at 1,800 rpm, and each driving a Rolls-Royce model US 255 CP azimuthing Z-drive steering/propulsion unit. The controllable pitch Z-drives provide enhanced fuel economy, operational flexibility, and enable efficient operation of the main engine-driven fire-fighting system. They also significantly reduce prop wash when the tug is operating at low power in confined waters. This power plant delivers a bollard pull of 70 tonnes (154,350 lbs) and a free-running speed of 13 knots.

Fire-fighting is to Fi-Fi 1 Class, with two FFS pumps each rated 1360 cu.m/hour (6,000 US GPM) driven from front PTO's on the main engines.

The main hawser winch forward is a single drum, Markey DEPCF-50 model, containing 250 m (750 ft) of 254 mm (10 inch) circumference synthetic hawser, with a brake capacity of 180 tonnes (200 short tons). The aft towing winch is a Jonrie model 512 with a 2,100 ft (760 m) 2.25 inch SWR for ocean towing.

Ship-handling fenders comprise an 800 mm cylindrical fender above a row of 450 mm "W" block fenders. A 300 x 300 hollow "D" fender provides protection at the main and foc'sle deck sheer lines, in conjunction with aircraft tires. "Soft loop" style fendering protects the aft quarters, with an open transom for buoy-handling, etc.

Modern and comfortable accommodations are provided for a crew of six in two single and two double cabins.

JUSTICE

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