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Evaluation of mist exposure control following installation of air cleaners on machining centers.

Yacher-J; Heitbrink-W; Sullivan-M
American Industrial Hygiene Conference and Exposition, May 19-23, 1997, Dallas, Texas. Fairfax, VA: American Industrial Hygiene Association, 1997 May; :30
The concentration of mist generated by the use of synthetic metalworking fluid (MWF) consisting primarily of water and triethanolamine (TEA) in enclosed and partially enclosed machining centers was determined by direct-reading aerosol instruments, impingers, and filter cassettes. The results were then compared to measurements made before the installation of air cleaners on twenty- five of these machining centers. The mist was generated when MWF was flooded over the parts being milled, drilled, tapped, or turned to provide lubrication and cooling and promote chip removal. The air cleaners consist of three sections: a fal-out chamber, a filter section to capture metal chips and mist, and a blower section providing airflow of approximately 0.094 m3/s. The MWF and entrained metal chips are discharged to a "hydromation unit" for recirclation and filtration. The following instruments were used to measure aerosol concentration and size distribution and to locate emission sources: an eight-stage ambient cascade impactor (Andersen Samplers, Inc.), a quartz crystal microbalance cascade impactor (California Measurements), an eight-channel optical particle counter (Grimm Labortechnik GmbH), a hand-held aerosol monitor (HAM)/photometer (ppm, Inc.), and a real-time, respirable aerosol monitor (RAM}/photometer (MIE, Inc.). The ambient cascade impactor indicated a concentration of 0.111 mg/m3 over a 72-hour period at a sampling point between two of the machining centers; the quartz crystal impactor indicated MWF concentration of 0.025-0.31 mg/m3 in that same location. At a location near the "hydromation unit," the values were 0.138 mg/m3 and 0.028-00.046 mg/m3, respectively. These aerosol measurements were made only after installation of the air cleaners. Area samples for TEA were also taken using miniature impingers. The results for TEA improved from about 0.29 mg/m3 before installation of the air cleaners to 0.032 mg/ m3 after. Similar results were obtained for total particulate (37-mm filter cassettes at 4 lpm), which was reduced from approximately 0.3 mg/m3 to less than 0.05 mg/m3. These results show the effectiveness of enclosure, ventilation, and filtration to greatly reduce the exposure to MWF mist generated in modern machining centers.
Metalworking-fluids; Machine-shop-workers; Machinists; Aerosols; Impingers; Filters; Exposure-levels; Air-filters; Particulates; Emission-sources; Monitors; Ventilation
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American Industrial Hygiene Conference and Exposition, May 19-23, 1997, Dallas, Texas