MetFab - Welding Fume Handbook - Flipbook - Page 29
9 Effect of shielding gas: ozone
Figure 20 shows a similar effect for a range of shielding
gases (Ferromaxx® 15, Ferromaxx® Plus and an argon/carbon
dioxide/nitric oxide mixture) for mild steel welding. This
demonstrates that the voltage is at least as important as the
shielding gas in determining ozone exposure levels.
The Ferromaxx® gases generated less ozone, over almost the
entire voltage range, than the mixture containing NO.
Average exposure to ozone ppm
0.35
0.30
92%Ar/ 8% CO/ NO
0.25
Ferromaxx® 7
0.20
Ferromaxx® 15
0.15
Linear (Ferromaxx® Plus)
0.10
Linear 92%Ar/ 8% CO/ NO)
0.05
Linear (Ferromaxx® 15)
I
27
I
28
I
29
I
30
I
31
I
32
I
33
I
34
Voltage
Figure 20: The effect of voltage on exposure to ozone during
MAG welding of mild steel (33% duty cycle) with spray transfer
and different shielding gases
FCAW
Figure 21 shows the effect of shielding gas formulation on
ozone emissions during FCAW of mild steel. The ozonereducing effect of carbon dioxide is apparent, while the extra
productivity offered by the helium containing gas is not
offset by any further increase in exposure to ozone.
However, comparison with the ozone exposure limit shows
that none of these gases would cause problems with ozone.
The low ozone levels may be related to the large amounts of
fume generated by FCAW.
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