Occupational Health Assessment of the High Velocity Oxy-Fuel Thermal Metal Spray Process

摘要

Abstract Exposure assessment of metallic aerosols, gaseous emissions, and noise from a robotic-assisted metal spray [high velocity oxy-fuel (HVOF)] process was conducted such that safety can be designed into the manufacturing system prior to production. Combustion gases such as carbon monoxide, carbon dioxide, and hydrocarbons were monitored by direct readout instruments or gas chromatography. The overspray metallic aerosols were characterized by an eight-stage microorifice uniform deposit impactor in the 0.072 to 10-μm size range. A complete frequency spectrum for HVOF noise in the 2 to 25,000-Hz range was also determined with a high resolution data acquisition system developed for impulse noise. During the actual metal-spraying operation, concentrations of carbon dioxide and the hydrocarbon gases were at or below ambient levels except for carbon monoxide, which averaged 15 ppm. The metallic aerosols in the spray booth were mostly ultrafine particles in the 0.05 to 0.2-μm range, and the average mass concentration was 0.01 to 0.05 mg/m3. Thus, personal exposures at the current premanufacturing research and development stage do not present a serious health risk. However, due caution should be exercised as the process is scaled up, or if other alloys containing the more toxic species such as nickel or chromium are used. The HVOF noise is 125 dBA at 2 m from the spray gun and the broad band high frequency spectrum extends to 25 kHz, with a peak at 5 kHz. Workers involved in troubleshooting or start-up work inside the spray booth are required to wear both earplugs and earmuffs. As the HVOF process moves toward production, the operation of the system will be done in a control room where noise levels are below 70 dBA.