WORLDSCALE 19 1/2; 235,000 DWT; BASIS SLOW STEAMING (TECHNICAL PROBLEMS INVOLVED IN SLOW-STEAMING RATES IN MOTOR TANKERS

Most VLCC tanker tonnage operating recently from the Arabian Gulf has been at slow steaming rates, not enough to reduce fuel consumption, but enough to effectively reduce total crude-oil transportation capacity. If the steam-turbine plant involved incorporates a twin-boiler installation there are few problems as only one boiler need be fired; however, with single-boiler installations the overall plant efficiency may be considerably reduced. Motor tankers are a little better off, but turbocharger performance drops off rapidly, leading to a loss of efficiency. Sulzer has introduced modified fuel valves with smaller holes to improve the part-load characteristics of the Sulzer engines. GMT has also been carrying out extensive tests, both at the Trieste works and at sea on a series of four 254,000-dwt tankers powered by GMT 10-cylinder slow-speed engines. With these ships, slow steaming at 50% of the m.c.r. will produce a fuel consumption of 40% below average, while some 20% less crude oil will be carried over the course of a year. At 32% of the m.c.r., consumption drops to 55% with 30% less crude oil carrierd annually. Recordings carried out on a VLCC after approximately 6,000 hours operation at 55% m.c.r. indicated that an increase in specific wear of some cylinder liners had reached 100%. To maintain the neutralising effect and hinder the possible trend to higher wear, it was decided to increase the specific rate of liner lubricating oil. The results obtained with all four vessels are discussed. Order from BSRA as No. 49,319.

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  • Corporate Authors:

    Fairplay Publications, Limited

    1 Pudding Lane
    London EC3R 8AA,   England 
  • Publication Date: 1978-3-16

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Filing Info

  • Accession Number: 00185299
  • Record Type: Publication
  • Source Agency: British Ship Research Association
  • Files: TRIS
  • Created Date: Jan 13 1979 12:00AM