An oil mist lubrication system is the widely used bearing lubrication. A centralized lubrication system generates and automatically delivers the lubricant to machinery bearings to keep it lubricated for making moving parts reliable. The fine mixture of oil and air that is generated is called oil-mist. Oil -mist lubrication ensures a high standard of lubrication as and when required and prevents the ingress of contaminants to the bearing housing.\n\n\n\nVarious Type of Lubrication\n\n\n\nSplash LubricationGrease LubricationForced LubricationSolid LubricationMist Lubrication\n\n\n\nOil Mist System is a means of generating and transporting a finely dispersed oil mist from a central location to individual bearing housings.\n\n\n\nThe oil mist system uses compressed air to atomize oil into micron-size particles which can be effectively moved to lubrication points up to 600 feet (180 meters) through Pipes & TubesOne Oil Mist system can provide lubrication to 60 pumps and their drivers with approximate oil consumption of one gallon (3.8L) of oil per 24 hours.\n\n\n\nTypical Oil Mist System \n\n\n\nRefer to Fig. 1 which shows a typical oil mist lubrication system used for industrial application.\n\n\n\nFig. 1: Typical Oil Mist System\n\n\n\nTypes of Oil Mist Lubrication System\n\n\n\nThe oil mist lubrication system can be categorized into the following types.\n\n\n\nOpen Loop System (Fig. 2)Closed-Loop System (Fig. 2)Dry Sump (Pure Mist-Fig. 3)Wet Sump (Purge Mist-Fig. 3)\n\n\n\nFig. 2: Open and Closed Loop Mist Lubrication System\n\n\n\nPure & Purge Mist Lubrication\n\n\n\nPure Mist Lubrication System-\n\n\n\nThe bearing is lubricated by oil mist, not oil.Bearings can run 10-15 degC cooler with pure mist as compared to sump lubrication.The bearing housing is pressurized by continuous oil mist flow, then external contaminants (dust, moisture\u2026) are excluded.Centrally controlled hence attention for oil level is not required individually.\n\n\n\nPurge Mist Lubrication System-\n\n\n\nThe bearing is lubricated by oil, not oil mist.The bearing housing is pressurized by continuous oil mist flow, then external contaminants (dusts, moisture\u2026) are excluded.Here mist purges the bearing housing and provide partial fresh Makeup oil.Oil level must be checked and maintained for each equipment.\n\n\n\nFig. 3 below shows typical pure and purge mist lubrication systems.\n\n\n\nFig. 3: Pure and Purge Mist Lubrication\n\n\n\nComponents of Oil-Mist Lubrication Systems\n\n\n\nThe major components of an oil-mist lubrication systems are listed below:\n\n\n\nOil mist generator- the heart of the oil mist lubrication system, compressed air is passed through venturi or vortex to produce the oil-mist mixture.Oil mist cabinet-Stainless steel cabinet.Reclassifiers- Controls the mist flow to applicable points. Bearing type, shaft speed, and diameter dictate the sizing of reclassifiers.Air- Clean and Dry air free from toxic, corrosive, and flammable elements.Air Filter at the air inlet.Air regulator to control supply air pressureAir Pre-Heater-For cold climates to maintain the air temperature\n\n\n\nWhile selecting the oil for oil-mist lubrication system, the following factors need to be considered:\n\n\n\nOil Viscosity at the operating temperaturePour pointSurface tensionSolidification tendency of the oil at low ambient temperatures\n\n\n\nHow does oil mist Lubrication lubricates the bearing?\n\n\n\nThe following figure (Fig. 4) shows the working of the oil-mist lubrication system to enhance bearing life.\n\n\n\nFig. 4: Working of Oil-Mist Lubrication System\n\n\n\nMist Lubrication Suitability\n\n\n\nRolling element and sliding contact bearings can be lubricated with Oil Mist either Pure or Purge type.Oil mist is used to lubricate rolling element bearings of all types. Ball & Roller bearings are generally applied with Pure Mist Lubrication.When sliding contact bearings are used, oil mist alone does no provide complete lubrication & hence, an oil level is maintained in the bearing housing and is called Purge Mist Lubrication.\n\n\n\nAdvantages of Oil Mist Lubrication System\n\n\n\nOil mist lubrication system offers various advantages over the other lubrication systems as listed below\n\n\n\nPrevent the dust\/moisture ingress into bearing housing, due to pressurized systemIncreased Bearing LifeLower friction and thus reduced bearing temperaturesReduced maintenance, reduced handling, and spillage.As the bearings operate in a thin film of oil, so less power is required.Reduced Oil consumption (40% less & 50% of it can be recovered)More environmentally friendly than the conventional lubrication system.As the oil on the bearings is always new, it provides better lubricant properties.In technical papers released by end-users and bearing manufacturers, as well as in university research, bearings lubricated with oil mist have a longer life than bearings lubricated with oil sump or grease. Users report from a 50% to 90% reduction in lubrication-related bearing failures.Finally, it is economic to use.\n\n\n\nDisadvantages of Oil Mist Lubrication System\n\n\n\nEven though mist lubrication systems have various advantages and reduce reduce maintenance and operating problems, still there are few disadvantages of this system such as\n\n\n\nRelay on Instrument Air SystemLSC is the single vendor of the Oil Mist System for Hydrocarbon Processing IndustriesAn oil mist system is almost trouble-free but it cannot be installed and forgotten. Systems should be checked daily for correct air and oil temperature, oil level, and mist header pressure along with other weekly and monthly maintenance programs.The oil-mist lubrication system involves environmental hazards. OSHA requirement states that a person shall not be exposed to more than five milligrams of oil per cubic meter of air in an eight-hour period.The performance of the oil mist lubrication system is sensitive to temperature.