Measurement of Capture Efficiency of On-Gun Extraction for Welding (LVHV)

Measurement of Capture Efficiency of On-Gun Extraction for Welding (LVHV)

HSE sponsored Research Report RR1010 (2014) undertaken by HSL.

Key Messages from this Report:-

  • Two test methods for measuring the efficiency of integral on-gun welding fume extraction systems have been devised and assessed. As a result, Method 1 has been selected and is currently being developed by technical committee CEN/TC 121/SC 9/WG 4 (Testing and marking of equipment for air filtration for welding and allied processes) with a view to drafting an EU Standard.• On-gun extraction was found to be effective at removing welding fume when carrying out bead on plate welding. It was less effective during in the flat fillet welding.

    • Improvements to the welding torch positioning and clamping system are required in order to obtain better repeatability of fume emission rates, especially during fillet welding, so that more accurate measurements of capture efficiency can be made.

    • A reduction in on-gun air extraction flow rate resulted in a drop in fume capture efficiency and hence would likely increase worker exposure to welding fume. Therefore, the on-gun extract flow should be checked on a regular basis and if it drops significantly the reason(s) should be investigated,

    • During testing it was noted that the extraction line connecting the torch extract to the extraction unit was leaking, particularly where the water cooling line passed through the tube wall. This resulted in a reduced flow rate at the torch extraction point which would likely depend upon manufacturer and model. Therefore it is important that the true measure of extraction flow rate is measured at the gun and not close to the extraction unit.

    • Increasing the power of the fume extractor did not result in a large increase in extraction flow rate due to the high resistance to air flow inside the on-gun extraction hose. However, even a relatively small increase in extraction flow resulted in a noticeable increase in capture efficiency during in the flat fillet welding.

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