I have found during my career, as both a lubricant sales person and a lubrication specialist, that many manufacturing plants and maintenance shops overlook air line maintenance. Compressors are often serviced by outside contractors, but rarely does the maintenance contract cover the entire air system within the facility. Wet dirty compressed air and improper lubrication can rob the air system of useful power, cause rust and air leaks, and reduce the power and efficiency of air tools. Air line filters and lubricators are used to help reduce and control these harmful contaminates and to administer lubricant to air powered equipment.
Avoid Contaminated Air Line Filters & Oilers
Often, air line filters and oilers can be found in poor health. Some can be seen filled or empty of lubricant, while others can contain rusty water, dirt, bacteria and fungi. Since pneumatic cylinders, air motors, air valves and air powered tools rely on air quality, contaminates like water, dirt and rust can reduce component life.
A simple visual check to inspect the water trap/filter and lubricator should be made weekly (or as required) to ensure air quality and sufficient lubrication. The visual inspection should include draining the water trap/filter of freestanding water. Most lubricators have a drop indicator sight glass and an adjusting screw that controls the volume of oil flowing into the air stream. Lubricant volume requirements can vary, but in general for pressures in the 90 – 100 psi range, one drop in 3 minutes is sufficient to lubricate most air powered components. Be careful to not over-lubricate. Too much oil can be as bad as too little.
Testing Air Line Lubrication
A simple test for lubrication is to hold a clean sheet of paper over the air discharge port on the component while in operation. The paper should have evidence of “slight discoloration” but should not be wet or show excess oil. In addition to weekly checks, the air line filters and lubricators should be cleaned out on a semi-annual or annual basis. For the air line lubricant, choose a light viscosity oil (SAE 5 or 10) additized with rust and oxidation inhibitors. Non-detergent circulating oils like Mobil DTE Light work well.
Spending a little extra time on your air lines can result in improved equipment reliability and reduced operating expenses.