During the past decade, engine loadings have continuously been escalated to brake mean effective pressures of over 20 kg/cm2 (284 psi) for 4-cycle and 11.5 kg/cm2 (162 psi) for 2-cycle engines. This has placed an ever heavier burden on the sealing requirements of the engine. In addition, many engines over 250 mm bore (9.842'') and most engines over 300 mm (11.811'') in Europe are required to operate satisfactorily on residual fuel with viscosities running up to 3500 seconds Redwood, sulphur content up to 4.0 % and ash content reaching to 0.05 %. The combination of the very high specific engine loading with the very poor residual fuel characteristics has lowered ring life in diesel engines to such a degree, that the cost for early engine teardowns because of ring changes, (8000 h to 10000 h in 4-cycle medium speed engines and only 3000 h to 8000 h in 2-cycle crosshead engines) has made the economic viability of diesel power for large tankers and container ship propulsion questionable. In these two services with the short turn about time of 6 to 10 hours, ring replacements result in costly lay-ups of the entire ship. This paper will describe the latest concepts in piston ring designs and materials to eliminate scuffing, reduce oil consumption and ring wear by the use of fewer, narrower rings, and balanced pressure and directional crowned face designs. For engines burning residual fuel with its high sulphur (corrosive) and ash (abrasive) constituents, the improvements in ring wear and life made possible with the very hard anti-scuff plasma face coatings will be described. The combination of the new ring designs with plasma coated compression rings for the top or top two grooves is expected to achieve ring life between overhauls of 20000 hours in residual fuel operation, which will enable ships to delay engine teardown to 2.5 to 3 years, or until drydocking for hull cleaning becomes necessary. A breakthrough in ring operating life in the large cathedral-type 2-cycle crosshead engines is expected with the same plasma coatings applied on ductile iron, in order to obtain both long wear as well as eliminate the ring breakage problems.


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    Titel :

    Modern ring design for high output engines


    Weitere Titelangaben:

    Modernes Kolbenring-Design für Hochleistungsmotoren


    Beteiligte:
    Braendel, H.G. (Autor:in)


    Erscheinungsdatum :

    1973


    Format / Umfang :

    23 Seiten, 17 Bilder


    Anmerkungen:

    (+ S. 117-120 Discussion)


    Medientyp :

    Aufsatz (Konferenz)


    Format :

    Datenträger


    Sprache :

    Englisch




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