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AGA CW Handbook A4_32130-UK
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9 the work environment contents 3.1 background 3.2 air impurities typical 3.3 dust and
fumes
3.4 fume composition 3.5 gases generated during
welding
3.5.1 ozone 3.5.2 nitrogen monoxide to
welding
environments 3.5.3 nitrogen dioxide 3.5.4 ozone and nitrogen dioxide 3.5.5 carbon monoxide 3.1 background all
welding
methods include risk factors endangering the health and safety of the welder. the risk factors include
fumes
, gases, radiation, heat, noise and heavy lifting. in recent years, more and more attention has been paid to the creation of healthy and safe working conditions. interest has been increased by the general growth in environmen- tal awareness, new regulations and the realisation that a good work environment also improves the productivity of work and therefore the profitability of the entire company. see below for some reasons on which the increase in productivity through improved work environment is based: → poor working conditions will likely lead to several absences due to illness or injury → the replacement needs training, and the amount of correction work required on the
welding
is often increased → poor working conditions also often cause the work performance level to fluctuate during the day, in particular with regard to produc- tivity and quality → motivation and work satisfaction are increased when the employees notice that the employer actively invests in their well-being with regard to the work environment, this handbook focuses on air impurities generated during
welding
, the amount and quality of which we can significantly affect merely by selecting the right shielding gas. 3.2 air impurities typical to
welding
environments air impurities related to
welding
comprise dust,
fumes
and gases gener- ated during
welding
. the existence of dust and
fumes
is usually easy to notice by eye. however, the generated hazardous gases are often invisible to the naked eye. the welders must be protected from the generated impuri- ties, for example by arranging sufficient general ventilation and using local extraction or fresh air helmets. it is important to avoid the plume of combustion gas rising from the weld and use
welding
parameters giving a stable
arc
. the choice of shielding gas also affects the work environment. for example, by selecting a mison ® shielding gas, you can reduce the probability of exposure to harmful ozone levels during
welding
. 3.3 dust and
fumes
in a
welding
context, particles which are larger than 1 μm (0,001 mm) are defined as dust. they fall near the
arc
and mainly comprise
welding
spatter.
welding
fumes
are formed of particles smaller than 1 microme- tre.
fumes
generally remain floating in the air and can be carried far from the
welding
location.
fumes
mainly consist of metal oxides. they are generated when the molten metal is first vaporised in the
arc
and is then condensed and oxidised due to the surrounding air. in mig/mag
welding
,
fumes
are almost entirely generated from the filler material and the substances it contains. the base metal contributes only a minor amount of the total
fumes
. in cored wire
welding
, the powder contained in the wire affects the generation and composition of
fumes
. spatter plays an integral role in the generation of
fumes
– the more spatter, the more
fumes
. the amount of spatter is affected by the weld- ing parameters and the composition of the shielding gas. when moving from the globular
arc
region to a spray
arc
, fume genera- tion is clearly reduced and is at its lowest when a stable spray
arc
has been reached. if the current and voltage are further increased, the fume generation rate will also increase.if the carbon dioxide content of the shielding gas exceeds 25–30 per cent, a stable spray
arc
is no longer pos- sible and there is heavy fume generation. the work environment. in the short and spray
arc
regions the
arc
is stable, resulting in lower fume generati- on than in the globular
arc
region. the higher fume generation in the spray
arc
region compared to short
arc
is explained by the increased metal vaporisation. mag
welding
, unalloyed steel, wire diameter 1.0 mm short
arc
globular
arc
spray
arc
0 100 150 200 250 300 600 400 200 0 generation of
fumes
(mg/min) current (a)
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