Investigation of welding fume plumes using laser diagnostics.

Abstract

In many occupations such as welding, workers are exposed to a combination of several hazards. One of these is the exposure to fumes, particularly those produced from welding processes involving electrical arcs. The inhalation of welding fume can cause both temporary side effects and longer term health complications. These health effects lower the productivity and quality of life of the welder which in turn costs the employer through reduced worker productivity and potential compensation. Current techniques of fume measurement determine bulk quantity of formation without regard to fume plume dissipation into the work place. While some research has been conducted into dissipation, measurements near the welding arc have proven difficult and either numerical or salt water modelling have been used. Such modelling aims to replicate the welding process but is ultimately detached from the actual welding variables involved and does not provide data on fume concentration. Since welder exposure is determined by both fume concentration and dissipation into the workplace measurement techniques which could provide both would be considered highly desirable. In the field of combustion research a number of different laser techniques are used to image soot particulates in flames. These techniques include laser scattering, laser extinction and laser induced incandescence. As yet none of these techniques have found application to the measurement or imaging of particulate matter in arc welding fume plumes. In the work presented here these techniques have been investigated for welding fume measurements of concentration and dissipation. Laser scattering was used successfully to image the fume plume close to the welding arc of actual gas metal and flux cored arc welding processes. The resulting images provided relative fume concentration maps that were quantified when combined with measurements from laser extinction. Laser induced incandescence, while successfully applied to the imaging of soot concentration in flames, was found to have limited capabilities when applied to welding fume particulates. Fume box measurements were undertaken for GMAW and FCAW to determine actual FFR in response to changes in welding variables. The results were in general agreement with those obtained from laser techniques and referenced in literature. The fume plume images collected from in-situ laser measurements were compared with those from previous modelling of plume shape, radial spread and virtual origin. Laser diagnostics demonstrated a number of capabilities not available with traditional fume measurements. The findings of this research provide unique insight into fume dissipation. Such findings can be applied to minimise the quantity of fume, the transmission to the breathing zone and ultimately worker exposure in the workplace.