Systematic measurement of UV radiation emissions during oxyfuel gas welding and pulsed welding methods

Status:

completed 02/2015

Aims:

A number of different welding methods are available; selection must be made according to the application. The methods range from oxyfuel gas welding, through stick electrode welding, to modern pulsed welding methods. Considerable UV radiation, to which the workers are exposed, is generated during welding. It is already known that the occupational exposure limits for artificial optical radiation set out in Directive 2006/25/EC and in the relevant German OSH ordinance may be exceeded after only a few seconds by certain stick electrode welding methods. The situation is much less clear for the oxyfuel gas and pulsed welding methods. For these methods, data are still unavailable on emissions from the radiation sources and on the exposure of workers. The objective of the project was to determine the radiation emission during oxyfuel gas welding and pulsed stick electrode welding. One intention was to determine whether new evaluation criteria are required for pulsed radiation.

Activities/Methods:

Measurements of the irradiance were conducted at the SLV welding testing and training institute in Duisburg and at companies selected by the German Social Accident Insurance Institution for the woodworking and metalworking industries (BGHM). Besides oxyfuel gas welding methods, modern pulsed welding methods such as the CMT method (cold metal transfer, a new droplet detachment method) were studied. Radiation emissions were also studied on a range of arc-welding methods, including as a function of the welding current. The measurements at the SLV in Duisburg were conducted under expert supervision for the purpose of systematic study of CMT welding processes. Measurements during oxyfuel gas welding were also performed under realistic conditions at a member company of the BGHM.

Results:

The results of the measurements conducted with the new CMT method revealed no systematic increase or decrease in the irradiation values attributable to the use of this method. Differences were observed according to the welding methods used (e.g. MAG vs. WIG). Study of the oxyfuel gas welding methods showed that UV radiation exposure was attributable to the combustion of the gas, and that it was reduced by virtue of the process being obscured by the workpiece. This relationship cannot be specified numerically, however, owing to the influence of the type of workpiece. Whereas the UV radiation emission level was not affected by increasing duration of work on the workpiece, it rose substantially in both the visible and infrared ranges owing to the rise in workpiece temperature. To summarize, it was ascertained that the observations regarding the emission behaviour of gas torches that were made in the course of IFA Project 4144, Emissions of optical radiation during the treatment of glass workpieces by means of gas torches, could also be transferred to oxyfuel gas welding methods. The project served as a useful preparatory project with regard to the CMT method, and as an extension to the results of earlier projects with regard to the oxyfuel gas welding method. It had the function of collating experience for a follow-on project, revealing difficulties to be anticipated and identifying foci for the most common welding methods and jobs.

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