Evaluation of leakage from a metal machining center using tracer gas methods - a case study.
Earnest-GS; Heitbrink-WA; Mickelsen-RL; Mead-KR; D'Arcy-JB
Metalworking Fluids Symposium II, The Industrial Metalworking Environment: Assessment and Control of Metal Removal Fluids. September 15-17, 1997, Detroit, Michigan. DA Felinski, JB D'ARcy, eds., Washington, DC: American Automobile Manufacturers Association, 1998 Nov; :163-167
Engineering controls for reducing worker exposure to metalworking fluids were evaluated for a machining center during face milling operation. An enclosure was built around a vertical metal machining center (LANCER model 1000, Cincinnati Milacron) with an attached ventilation system consisting of a 25-cm diameter duct, a fan, and an air-cleaning filter. The evaluation method included sulfur hexaflouride (SF6) tracer gas to determine the ventilation system's flow rate and capture efficiency, a respirable aerosol monitor (RAM) to identify aerosol leak locations around the enclosure, and smoke tubes and a velometer to evaluate air movement around the outside of the enclosure. Results of the tracer gas evaluation indicated that the control system was approximately 98% efficient at capturing tracer gas released near the spindle of the machining center. This result was not significantly different from 100% efficiency (p=0.2). The measured SF6 concentration, when released directly into the duct, had a relative standard deviation of 2.2%. When SF6 was released at the spindle, the concentration had a significantly higher relative standard deviation of 7.8% (p=0.016). This increased variability may be due to cyclic leakage through a small gap between the upper and lower portion of the enclosure. Leakage was observed, using smoke tubes, a velometer, and an aerosol photometer. The tool and fluid motion conbined to induce a periodic airflow in and out of the enclosure. These results suggest that tracer gas methods could be used to evaluate enclosure efficiency. However, aerosol instrumentation, such as optical particle counter or aerosol photometers, should also be used to locate leakage from enclosures.
Case-studies; Engineering-controls; Workers; Occupational-exposure; Metalworking; Metalworking-fluids; Aerosols; Air-filters; Air-flow; Ventilation-systems; Oil-mists; Metalworking-industry
U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, 4676 Columbia Parkway, R5, Cincinnati, OH 45226
Metalworking Fluids Symposium II, The Industrial Metalworking Environment: Assessment and Control of Metal Removal Fluids. September 15-17, 1997, Detroit, Michigan