Page 43: of Maritime Reporter Magazine (June 2004)

2004 World Yearbook of LNG bunkering points along the sea rim, coupled with a circumspect nation- al energy policy, is expected to stimulate the uptake of gas-fuelled power and propulsion plant in coastal and offshore vessels. A small Norwegian LNG tanker and a modern tjord ferry currently use

LNG as fuel in their high-speed engine plant, while two sophisticated offshore support vessels working Norwegian fields are distinguished by dual-fuel, medium-speed prime movers. The planned adoption of dual-fuel plant in

French LNG carrier newbuilds has pro- vided a fillip to the advocates of that technology. However, Rolls-Royce con- tends that its medium-speed, purely gas- ingesting machinery provides a simple, highly effective solution to low-emis- sion powering needs, lending itself both to direct mechanical coupling to pro- pellers and thrusters, and to shipboard electricity production. Moreover, test results have demonstrated that there are no operational limitations on sustained low load or transient operations.

Among the claimed advantages of employing lean-burn, gas-fuelled. Otto cycle engine technology are the low level of Nox (oxides of nitrogen) emis- sion and the negligible release of Sox (oxides of sulfur) and particulates. LNG as a fuel has the attraction that its carbon content is lower than other hydrocarbon fuels such as diesel oil. If it is efficient- ly burned, the C02 (carbon dioxide) emissions from the engine are corre- spondingly low, a very positive factor for countries that have signed up to the

Kyoto Agreement, and salient also to anticipated future international edicts governing C02 from ships' machinery.

An added economic benefit is that lube oil consumption is low, and oil change intervals are long.

The main frame and much of the run- ning gear of the K-gas engine is derived from the successful Bergen K-series diesel engines used in hundreds of ves- sels. A power output of 220-kW per cylinder is available, with running speeds between 600- and 1,000-rpm.

The K-G4 has been released in configu- rations of 6, 8 and 9 in-line cylinders, and in 12-. 16- and 18-cylinder vee- form, covering unit powers to approxi- mately 4,000-kW. If required at some later stage, K-gas engines can be con- verted for operation on marine diesel oil, and the company has also declared its readiness to convert K diesel engines to burn gas. A much larger, lean-burn, spark-ignition engine, founded on the

B32:40 diesel engine hardware and K- gas engine technology, has been launched for unit power needs up to 8,800-kW. Offering 440-kW per cylin- der, in vee-type models of 12, 16 and 20 cylinders, the B35:40V-G design is said to have a thermal efficiency of 47-per- cent. Although the B-gas engine has been primarily conceived for the expanding market for reciprocating engines for stationary, industrial uses, the 350 mm-bore design offers scope as a marine power unit. In its 20-cylinder layout, the new Norwegian-built offer- ing is claimed to be the world's most powerful spark-ignited, reciprocating gas engine.

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The Bubbler is an electro-pneumatic level trans- mitter that allows remote level measurement using a 4-20mA analog output. The lack of air pressure poses no operational problems, due to an auto- matic one-way valve which closes as soon as the pressure drops below 1 bar, this prevents back flow in the bubbling line towards the transmitter.

Over pressure is also protected against by an automatic one-way valve. • It's the size of a grapefruit • Explosion proof housing • Accuracy .3% full scale • Automatic over-pressure valve • Automatic stop valve for air failure • Automatic cleaning of bubbling line • Connection for pressurized tanks • 2 pair 24 VDC and 4-20mA cable • Top or side mount

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June 2004 43