【作者】

Oyvind Toft，Henrik Rolsted，Per Samuelsson

【摘要】

论文已在中国上海举行的2013年CIMAC大会上发表。论文的版权归CIMAC所有。 The typical time between overhaul of 2-stroke main engine cylinder units has been in the range of 10,000 to 15,000 hours. This has been regarded as best practice in the shipping industry for the last 3 decades a practice that has ascertained safe and reliable operation. The development of design and material technology in this period has lead to significantly higher outputs, improved reliability, lower emissions and higher cost efficiency. Examples are improved designs of the turbocharger, combustion chamber, bearings, fuel system, lubrication system and piston rings. There may still be challenges in certain areas, but all in all the gains have been considerable.At the same time ship operators have increasingly been challenged by their business partners as well as the public at large to operate within ever larger safety margins. Amongst others, this has implied that even planned overhauls requiring disabling of the main engine when the ship is in service, becomes increasingly difficult especially for any kind of tanker vessels. For a long time, there have been restrictions in place hindering overhauls when alongside at terminals. This restraint has recently also been imposed by authorities of some of the most strategic anchorages. Disabling main engines commonly requires stand-by tugs in these areas theeby increasing costs for overhauls to a large degree, and many operators see this as shrinking opportunities to carry out planned maintenance in a cost effective way. To mitigate this situation attempts have been made to operate main engines from ’dock-to-dock’, i.e. at 5-year intervals which requires about 30.000 hours between overhauls. This would entail several advantages. Clearly, planning,lead time for acquiring spare parts, availability of assistance etc. would improve the quality of work and perhaps also reduce spare part costs to some degree. Further, the time loss would become reduced. The results from the aforementioned tests have been encouraging to the degree that one could think of main overhaul intervals of even up to 10 years which would require safe operation for up to 60.00 hours. Largely prolonged service periods as well as the trend towards higher engine outputs would call for changes to the specifications for some highly loaded key components whose service life is not always predictable. A section of this paper explains the specific challenges for piston rings. Various types of coating on the running face and on the side face are now state of the art for the high efficient two stroke engines. The design of the ring groove plays also an important role if one wants to chieve running hours of approximately 60,000 hours. The hard chromium plating used today might not always be the right choice. New coatings in the piston grooves besides on the piston rings may be a necessity. Further, as the engine designers have come up with more and more powerful engine versions, it has increased the demand on the piston rings. Besides that a more prolonged TBO together with the new SECA regulation will have an important influence on the ring design for the future. The exhaust valve spindle is another example where heavy duty material may be required to withstand the stress and fatigue imposed by such long service time. Since costs for overhauls when the ship is docked tend to increase somewhat due to yard assistance and increased costs for heavy duty components, the proposition to carry out overhauls at alternate dockings becomes much more interesting as cost efficiency would increase sharply and more than outweigh operating costs associated with current practices. The paper reports on results obtained with two MAN B&W 6 S 60 MCC engines and discuss requirements to components and operational procedures. Further and outline of a maintenance programme based on condition monitoring to achieve 10 year intervals between main overhaul .

【会议名称】

第27届CIMAC会议

【会议地点】

上海

【下载次数】

1

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