Lubes Keep Step With Diesel Development

Marine diesels are constantly evolving, with today's 12-cylinder monsters already weighing 2,000 tons and developing as much as 93,000 hp. Tomorrow's propulsion units are going to be even bigger and more powerful and will need highperformance lubricants to match.

Today's ocean-going vessels are driven by two main types of engine, both operating on heavy fuel oil: medium-speed (300-1,000 rpm) and low-speed (60-300 rpm) engines.

Medium-Speed Engines Medium-speed engines use a trunkpiston design where the connecting rod is linked directly to the piston, and they are connected to the propeller via reduction gearing. Their power rating can go as high as 2,010 kW per cylinder, with up to 18 cylinders in V-configuration. The largest bore used is 640 mm and the stroke/bore ratio can be as high as 1.4 maximum combustion pressure reaches 180 bar for a mep of 25 or 26 bar.

The leading designer-builders are MAN B&W, Wartsila Corp. and Caterpillar, with engines also built under license by other firms all over the world.

Low-Speed Engines The basic structure of low-speed engines is different to medium-speed units, with the cylinder section of the engine separate from the crankshaft section. Low-speed engines use direct drive to the propeller and can develop up to 5,710 kW per cylinder, with as many as 12 cylinders. The largest bore used is 980 mm, the stroke/bore ratio can be as high as 3.8 and rotation speed can go as low as 60 rpm. Maximum pressure reaches 150 bar for a mep of 19 bar. Three designers dominate the market, MAN B&W, Wartsila Corp. and Mitsubishi Heavy Industries, with the first two having 90 percent of the market in terms of installed power.

Circle 4 4 on Reader Service Card The preceding was excerpted from Lubmarine News, No.6.

Other stories from May 2002 issue


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First published in 1881 Maritime Reporter is the world's largest audited circulation publication serving the global maritime industry.