Profiling mild steel welding processes to reduce fume emissions and costs in the workplace.
Keane MJ; Siert A; Chen BT; Stone SG
Ann Occup Hyg 2014 May; 58(4):403-412
To provide quantitative information to choose the best welding processes for minimizing workplace emissions, nine gas metal arc welding (GMAW) processes for mild steel were assessed for fume generation rates, normalized fume generation rates (milligram fume per gram of electrode consumed), and normalized generation rates for elemental manganese, nickel, and iron. Shielded metal arc welding (SMAW) and flux-cored arc-welding (FCAW) processes were also profiled. The fumes were collected quantitatively in an American Welding Society-type fume chamber and weighed, recovered, homogenized, and analyzed by inductively coupled atomic emission spectroscopy for total metals. The processes included GMAW with short circuit, globular transfer, axial spray, pulsed spray, Surface Tension Transfer, Regulated Metal Deposition, and Cold Metal Transfer (CMT) modes. Flux-cored welding was gas shielded, and SMAW was a single rod type. Results indicate a wide range of fume emission factors for the process variations studied. Fume emission rates per gram of electrode consumed were highest for SMAW (approximately 13mg fume g-1 electrode) and lowest for GMAW processes such as pulsed spray (approximately 1.5mg g-1) and CMT (approximately 1mg g-1). Manganese emission rates per gram of electrode consumed ranged from 0.45mg g-1 (SMAW) to 0.08mg g-1 (CMT). Nickel emission rates were generally low and ranged from approximately 0.09 (GMAW short circuit) to 0.004mg g-1 (CMT). Iron emission rates ranged from 3.7 (spray-mode GMAW) to 0.49mg g-1 (CMT). The processes studied have significantly different costs, and cost factors are presented based on a case study to allow comparisons between processes in specific cost categories. Costs per linear meter of weld were $31.07 (SMAW), $12.37 (GMAW short circuit), and $10.89 (FCAW). Although no single process is the best for minimizing fume emissions and costs while satisfying the weld requirements, there are several processes that can minimize emissions. This study provides information to aid in those choices. Suggestions for overcoming barriers to utilizing new and less hazardous welding processes are also discussed.
Workplace-studies; Welding; Welding-industry; Steelworkers; Metal-fumes; Emission-sources; Fumes; Arc-welding; Quantitative-analysis; Gas-welders; Manganese-compounds; Nickel-compounds; Iron-compounds; Industrial-processes; Sociological-factors;
Author Keywords: flux-cored arc welding; fume emissions reduction; fume generation rates; gas metal
arc welding; manganese generation; nickel generation; welding costs; welding fumes
Michael J. Keane, Health Effects Laboratory Division, National Institute for Occupational Safety and Health, 1095 Willowdale Road, Morgantown, WV 26505, USA
7439-96-5; 7440-02-0; 7439-89-6
Annals of Occupational Hygiene