This page was exported from veltak [ http://veltak.is ] Export date:Thu Nov 21 10:06:49 2024 / +0000 GMT ___________________________________________________ Title: Oil Mist and Machinery Space Fires --------------------------------------------------- Engineroom 2015 Engineroom 2015 Engineroom 2015 OIL MIST AND MACHINERY SPACE FIRES by Dr MH Holness PhD, C Chem, FRSC, M Inst Pet. (Petrohaz) for Quality Monitoring Instruments Ltd Ref. PO 065721 7 June 1995 Summary A review is presented of the role of oil mist as a principal agent in machinery space fires. The ways in which oil mist can be produced are described and the distinction between mist and spray. The contrast between the oil mist conditions inside crankcases and that in the general atmosphere in machinery spaces is discussed. Methods of measuring oil mist and spray are described and equipment suitable for monitoring conditions inside machinery and in machinery spaces is discussed. Recommendations are made to improve safety on board ship and in industrial plant. Contents Introduction Burning of Liquid Fuels Properties of Oil Droplets Crankcase and Gearcase Explosions Fires in Machinery Compartments Oil Drops in the Atmosphere Detection of Oil Mist 5 Conclusions Recommendation References 2 2 3 4 4 4 7 7 8 Oil Mist and Machinery Space Fires by Dr MH Holness (Petrohaz) Introduction A large proportion of machinery space fires have been caused by fuel or lubricant leaks. However, leaks of this kind, while providing fuel, do not inevitably lead to a fire. In most cases a hot surface of some kind has produced the conditions necessary to produce flammability and has also acted as the ignition source. A typical set of circumstances is a leak of fuel from an injector pipe, the fuel falls onto (say) the turbocharger casing, vaporises and is ignited. This sounds like simple cause and effect, however there are a series of intermediate stages which ought to be considered. Burning of Liquid Fuels Liquid fuels do not burn as liquid, they burn only as vapour. Inevitably, the conversion from liquid to vapour must require the input of some energy. This can be provided by compression in an engine or with a hot surface, a spark or a flame. Outside of an engine or boiler, oil products not usually regarded as "fuel", may also burn under uncontrolled conditions producing a fire or explosion. Fuel from an injector, under pressure, may escape as a jet or spray so that it can reach a hot surface. At this point it will vaporise and form a cloud of vapour expanding away from the heat. As the vapour moves away from the surface, it cools and re-condenses, forming a cloud of fine mist droplets. During this time, the droplets of fuel near to the hot surface may reach a sufficiently high temperature for spontaneous ignition to occur and, after a delay period, the whole mist cloud becomes ignited. Similarly, hydraulic oil from a high pressure line will follow the same mechanism if it contacts a hot surface. The same process can take place inside machinery, if a mechanical failure occurs creating a high temperature. This mechanism is well understood and has been described in relation to crankcase explosions in the 1950's (1), and to marine gearbox explosions in the 1970's and 80's (2). Read full text of Article OIL MIST AND MACHINERY SPACE FIRES, Dr MH Holness PhD, C Chem, FRSC, M Inst Pet. --------------------------------------------------- Images: http://veltak.is/wp-content/uploads/2015/10/DSCF1045-300x224.jpg http://veltak.is/wp-content/uploads/2015/10/DSCF10401-300x224.jpg http://veltak.is/wp-content/uploads/2015/10/DSCF1042-300x224.jpg --------------------------------------------------- --------------------------------------------------- Post date: 2015-10-07 17:12:22 Post date GMT: 2015-04-09 16:45:56 Post modified date: 2016-02-09 13:48:24 Post modified date GMT: 2016-02-09 13:48:24 ____________________________________________________________________________________________ Export of Post and Page as text file has been powered by [ Universal Post Manager ] plugin from www.gconverters.com