With improvements in oil formulations, oil mist lubrication systems are becoming increasingly popular in a variety of applications where only limited oil feed supply is required. Examples include bearings of electric motors, pumps and compressors in many oil refineries and petrochemical plants1; gears, cams, chains and sliding surfaces of machines in steel and paper mills; construction equipment and an increasing range of other industrial applications.2 Compact mist supply units are also available for use with electric motors, machine tool spindles and similar local applications.
Oil mist systems present an attractive alternative both to grease at low-to-moderate speeds and to circulating oil systems for high speeds and high temperatures. Properly installed oil mist systems offer the following advantages:
No oil changes and reduced maintenance requirements
Reduced lubricant consumption (up to 70 percent compared to sump lubrication)
Lower friction and reduced bearing temperatures
Mist delivery pressure blocks entrance of contaminants
Less wear and increased life of machine elements
Lower capital costs
Newer air/oil systems are used in steel mills as alternatives to oil mist.3 To minimize loss of stray mist to the surrounding environment, liquid oil is injected from a positive displacement pump directly into the air stream. The oil, injected at time intervals, is then propelled by the air stream along the feed line as droplets in a spiral motion to enter a bearing as an oil spray.