World’s First LNG Fuelled Tug

By Keith Henderson at January 17, 2012 06:11
Filed Under: Company News, Industry Events

Rolls-Royce Marine is to deliver gas engines and propulsion systems for the world’s first Liquid Natural Gas (LNG) fuelled tugs. The two vessels, with the dimensions of  LOA of 115 ft (35 m), beam of 50 ft (15.4 m) and draft of 24.6 m (7.5 m), have been ordered by Buksér og Berging AS, Norway and are scheduled to enter service in late 2013 for offshore oil & gas industry duties along the Norwegian coast.


Caption: Drawing of the world’s first LNG tug showing single LNG fuel tank and propulsion details.
Image Credit: Rolls-Royce Marine

Each tug will be powered by two in-line six-cylinder Bergen C25:33L6P series spark ignition, lean burn gas engines based on the C diesel series. The output power of this Tier III compliant model is in the approximately range of 1,880 hp to 2,346 hp (1,400 to 1,600 kW) at 900 or 1,000 rpm respectively. A feature of the C series is simplified maintenance achieved by using a two piece connecting rod, allowing the cylinder liner, piston (including upper con-rod) and cylinder head to be removed / exchanged as a single unit, thereby  reducing overhaul time and cost considerably.

Unlike some other LNG engines, the Bergen gas engines have spark plugs allowing it to operate purely on gas and not requiring pilot diesel fuel injection to initiate combustion. It therefore  eliminates the requirement of a secondary (diesel) fuel system and supply.

Opposite to the situation with diesel engines, LNG engines produce lower NOx emissions at lower engine loads. This is advantageous for tugs which have a duty cycle of majority use at low power outputs. NOx emissions for these new tugs is very low with an estimated reduction of about 92 per cent: the reduction in Green House Gas (GHG) emissions is up to 17 per cent. Further emission reductions are 98 - 100 per cent for SOx and 98 per cent  particulates.

Caption: An in-line Bergen C25:33L9P series spark ignition, lean burn LNG engine, is based on the C diesel series.
Image Credit: Rolls-Royce Marine

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