Effect of oil contamination on metalworking fluid mist

A laboratory bench scale test was developed for evaluation of the misting properties of metalworking fluids. This device has been able to reproduce mist level measurements made during actual machining processes. Mist levels were found to depend upon the type of fluid and the composition. In general, synthetics generated less mist than semisynthetics and soluble oils. However; the presence of oily contaminants ("tramp oil") had a major effect upon the mist level. Up to a three times increase in misting was observed with the addition of three percent oil. Each fluid seemed to be affected differently by the presence of tramp oil. This study underscores the importance of good house keeping (including a good maintenance program to reduce oil leakage, and tramp oil removal equipment) when trying to improve in-plant air quality.