the safety catalogue - page 238

238
WELDING PROTECTION
Welding is the process of joining separate metal parts together through a cohesive bond involving the atoms of those parts
by melting the materials of the structural elements or adding a filler material similar to such elements. There are two ways to
create a cohesive bond: the materials are melted together with the filler material at the interface of the bond to form a common
weld pool (e.g. torch or arc welding) or other force is used to create molecular attraction (e.g. cold welding). The energy for
the concentrated heat required for welding may be thermal obtained by burning gas (gas welding), electrical (arc welding:
metal rod used as an electrode and arc ignited by touching the electrode to the work piece, thus melting it), radiation (laser
welding) or mechanical (friction welding). The coating on the rods (iron-manganese oxide, rutile, cellulose, etc.) stabilizes
the arc and prevents oxidization of the weld pool. Shielded metal arc welding uses a shielding gas (argon, helium, carbon
dioxide, etc.) to displace oxygen and nitrogen and ensure a narrow heat-affected zone.
Personal protective equipment for use in welding
Respirators (EN141, EN143, EN149, EN138)
-particle filter masks with activated carbon for use up to the occupational exposure limit (FFP2, FFP3) and half masks with
cartridge (P2, P3) to protect against welding fumes containing the evaporated metal oxides of the welded workpieces and
the filler material
-half masks equipped with filter cartridges suited for the hazardous material (A,B,E,K,P2,P3) or shields supplied with fresh
air to protect against irritant and toxic gases that may be generated (chlorine, sulfur dioxide, phosphorus, carbon dioxide)
Equipment for eye protection (EN175)
- filter glasses to protect against infrared and ultraviolet harmful radiation and related hazardous heats, the grade of such filter
glasses is determined by the materials used and the intensity of the energy source (e.g. the intensity of ultraviolet radiation
is proportional to the square of the welding current above 50 amps)
Gas welding
:
amount of acetylene in liter/hour
<70
70–200
200–800
800<
grade of filter glass
4
5
6
7
Gas cutting:
amount of oxygen in liter/hour
900–2,000 2,000–4,000 4,000–8,000 8000<
grade of filter glass
5
6
7
8
Arc welding:
Welding current (Amps)
5 10 15 20 30 40 60 80 100 125 150 175 200 225 250 275 300 350 400 450 500 (A)
Coated electrode
9
10
11
12
13
14
Consumable electrode CO
2
10 11
12
13
14
15
Consumable electrode gas mixture, heavy metal
10 11
12
13
14
Consumable electrode light metal
10 11
12
13
14
15
Tungsten electrode with argon
shielding gas
9
10
11
12
13
14
Arc gouging
10
11
12
13
14
15
Plasma cutting (metals and their alloys)
11
12
13
Protective clothing for use in welding (EN ISO 11611:2008)
- the base material and the seams should meet the following safety requirements (class 1):
- flame retardant: limited flame propagation tested with surface flame and edge flame (A1+A2 /10s)
- resistance against radiant heat with a heat intensity of 20 kW/m
2
(RHTI = 24°C temperature increase /7s)
- resistance against small splashes of molten metal (minimum 15 steel drops 0.5 g each/1 min.)
- adequate mechanical properties: material tensile strength (>400 N), seam tensile strength (>225 N), tear strength (>20 N)
- adequate electrostatic properties (electrical resistance <10
5
Ω)
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