MetFab - Welding Fume Handbook - Flipbook - Page 31
9 Effect of shielding gas: ozone
FCAW
0.25
I
0.20
I
0.11
0.12
0.14
0.13
0.13
0.11
0.10
0.08
SPRAY
PULSED
SPRAY
PULSED
SPRAY
PULSED
PULSED
SPRAY
PULSED
SPRAY
PULSED
Innomaxx® Plus
Innomaxx® Plus
43% Ar/55% He/2% O
43% Ar/55% He/2% O
23.5% Ar/7.5% He/1.5% O
98% Ar/2% /CO/NO
98% Ar/2% /CO/NO
Innomaxx® 2
Innomaxx® 2
0.05
98% Ar/2% /O
0.00
I
0.05
0.09
I
0.10
0.15
98% Ar/2% /O
0.15
Ozone OES (15 minute reference period)
I
Exposure (15 minute reference period) ppm
Figure 11 shows the effect of shielding gas on fume emission rate for FCAW of mild steel.
shielding gas
Figure 22: The effect of shielding gas and mode of transfer on average exposure to
ozone during MAG welding of stainless steel (33% duty cycle)
TIG
Shielding gases commonly used for stainless steel TIG
welding are pure argon, pure helium, argon/helium mixtures,
and argon with small additions of hydrogen or nitric oxide.
Figure 23 shows the effect of different argon/helium
mixtures on ozone concentrations in the breathing zone of a
welder during autogenous TIG welding of stainless steel. The
argon/helium mixtures all generate less ozone than either
pure argon or pure helium, although for the test conditions
employed, exposure was less than the exposure limit (0.2
ppm) for all the gases examined.
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