Safety, Health and Environment in Welding Workshop
What this domain tests
Hazard recognition, PPE selection by process and current, statutory limits on gas and electrical equipment, and emergency response. Questions are scenario-based rather than definitional.
Core rules
- Radiation. The arc emits UV and IR. UV causes photokeratitis (arc eye) and skin burn. Filter shade rises with current: about shade 10 for 60–100 A SMAW, 11 for 100–200 A, 12 for 200–300 A, 13 above 300 A. Wear clear goggles under the helmet for chipping slag.
- Fume. Rutile SMAW gives iron-oxide fume; MIG/MAG on aluminium and CO2-shielded arcs generate ozone and nitrogen oxides; galvanised steel gives zinc fume and metal-fume fever. Local exhaust ventilation at the arc is the primary control, respirator is secondary.
- Acetylene. Never draw more than 1.03 bar (15 psi) gauge from a cylinder; free acetylene above about 1 bar can decompose explosively. Cylinders hold acetylene dissolved in acetone in a porous mass at roughly 15 bar.
- Oxygen. No oil, grease or jointing compound on regulators, hoses or threads - oxygen plus hydrocarbon ignites on impact.
- Cylinder store. Upright and chained, valve caps fitted, oxygen and acetylene at least 6 m apart or divided by a fire-resisting wall, flashback arrestors at regulator and torch.
- Electric shock. Open-circuit voltage of manual arc sets is limited to 80 V AC; earth the job and the set, never change polarity with the set live.
Worked example
A 250 A SMAW set (OCV 80 V) runs at 210 A. Which filter shade, and is the OCV acceptable? Reading the shade table at 200–300 A gives shade 12; UV intensity scales with current, so a shade 10 borrowed from a 90 A job is an arc-eye risk. The 80 V OCV equals the permitted maximum for manual metal arc, so the set is acceptable - but only if the earth return is sound, because the 80 V is harmless only while the return path is intact.
Traps
Quoting 15 bar as the working acetylene pressure (that is cylinder storage pressure, not delivery); forgetting the flashback arrestor; assuming a welding helmet protects the eyes while chipping.