Doctor of Philosophy
School of Mechanical, Material and Mechatronic Engineering - Faculty of Engineering
Slater, Geoffrey R, Welding fume plume dispersion, PhD thesis, School of Mechanical, Material and Mechatronic Engineering, University of Wollongong, 2004. http://ro.uow.edu.au/theses/384
The main concern with welding processes has in the past, generally, concentrated on productivity and quality. However, the occupational health of the welder has become a major focal area in the last decade, and the working environment of the welder is becoming a more important area of investigation. One particular area of interest is the amount of fume present in the operator’s breathing zone. With the potentially hazardous material present in the breathing environment of the welder, an effective method of controlling this airborne contaminant must be adopted to limit exposure levels to within occupational health and safety limits and to ensure the well being of the worker. This investigation examines the distribution of fume and breathing zone concentration within a controlled space using the gas metal arc welding (GMAW) process. The controlled working environment provided the basis for quantifying breathing zone exposure concentrations, and the ability to predict operator exposure. The initial evaluation focused on determining the breathing zone concentration and the welding fume plume dispersal within a confined enclosure. Within a sealed environment GMA welding was performed for approximate 100% duty cycle with two types (copper and non-copper coated) of ER-70S filler wire. The breathing zone and background enclosure concentrations were measured. The purpose of this initial investigation was to evaluate the breathing zone concentration within a confined environment, and to determine a fundamental concentration for direct evaluation of control procedures. The inclusion of the non-copper (low-fuming) coated electrode was to validate the measurements obtained during the study. The low-fuming electrode provided the expected reduction in exposure concentrations in comparison with the copper coated wire, however the concentrations measured over a 15 minute welding cycle were substantial higher than Occupational Health and Safety (OHS) exposure limits. To aid the evaluation of fume control effectiveness, various ventilation strategies were incorporated into the controlled environment. Utilising various modes of general and local extraction enabled an evaluation of the measured breathing zone concentration to be compared with the non-ventilated situation, as well as indicating their relationship with the occupational exposure limits for welding fume. This enabled the breathing zone exposure concentration to be effectively reduced to meet the OHS exposure limits. Although all techniques significantly reduced the exposure concentration, in direct comparison with the confined ‘fundamental’ concentrations, only an appropriately installed local extraction technique provided the required reduction. As well as the breathing zone evaluation, a model to predict the initial dispersion of GMAW fume was developed, aiding in better determining welding fume plume flow behaviour characteristics. This analysis, in addition with classical plume theories, enabled a model of the fume plume characteristics to be developed.