Assessment of electromagnetic fields in a metal tubing manufacturing facility.
American Industrial Hygiene Conference and Exposition, May 19-23, 1997, Dallas, Texas. Fairfax, VA: American Industrial Hygiene Association, 1997 May; :4
The manufacturing of specialized metal tubing for use in the automobile and refrigeration industries requires the use of welding and annealing equipment that generates various types of electromagnetic fields (EMFs). The National Institute for Occupational Safety and Health (NIOSH) conducted a health hazard evaluation at a facility which used butt welders and annealing sources. The butt welder joins rolls of strip metal using high resistance heating produced by power line frequencies, mainly 60 hertz (Hz). The strip metal is then slowly bent by special machinery to form metal tubing that will be welded using either a direct current (DC), alternating current (AC), or a high frequency (450 kilohertz (kHz)) welding source. After welding, the tube is annealed using a resistance annealer or a 10 kHz annealer. Workers at this facility asked NIOSH to evaluate occupational exposure to the EMFs generated in the facility. Due to the wide range of frequencies generated by the various sources at the facility, it was necessary to use a large assortment of EMF equipment and meters. It soon became clear that it was not possible to obtain simultaneous measurements from any of the sources due to the need to use different meters, often at different locations, over wide frequency ranges. The results obtained from this evaluation suggest that workers in the facility who operate butt welder units, 400-Hz AC welders, or the 10-kHz annealer units may be exposed to magnetic fields in excess of occupational guidelines. Electromagnetic field exposure from other sources, as measured on the days of evaluation, appears to be below these guidelines. Excessive exposures are influenced by location of the worker relative to the EMF source, and exposure of extremities (often 10 times higher than the body exposure). Significant exposure reduction can be accomplished by locating workers further from EMF sources, and by determining whether tasks that require insertion of hands in close proximity to various sources are appropriate or necessary.
Automotive-industry; Refrigeration-equipment; Welding; Electromagnetic-fields; Measurement-equipment; Exposure-levels; Exposure-limits; Metalworking-industry; Metalworking
American Industrial Hygiene Conference and Exposition, May 19-23, 1997, Dallas, Texas