Plasma Cutting
A plasma cutter sends an electric arc through a jet of compressed air or gas to melt and blow through metal. It’s fast and doesn’t need fuel gas, but it combines the hazards of arc welding (shock, bright light, fumes) with sparks, molten metal and a lot of noise.
- Construction
- General Industry
- Fabrication
Electric shock
Plasma cutters use high open-circuit voltage, often well over 200 volts DC, more than a typical stick welder.
- Inspect the torch, lead and work clamp before use. Replace damaged insulation.
- Attach the work clamp to clean metal close to the cut.
- Wear dry gloves and clothing, and don’t stand in water or on wet metal.
- Turn the machine off and unplug it (or lock it out) before changing nozzles, electrodes or shields.
Arc light
The arc gives off intense ultraviolet and infrared light that can cause “arc eye” and skin burns like a sunburn. Use a filter lens shade matched to your cutting current, as listed in the cutter’s manual or the ANSI Z49.1 shade table. Higher amperage needs a darker shade. Wear a welding helmet or face shield with the right lens, plus safety glasses, and cover exposed skin. Use screens to protect people nearby. See Welding Helmets.
Fumes and gases
- Cutting makes metal fumes, plus ozone and nitrogen oxides from the arc.
- Coated, painted or galvanized metal adds more hazards. See Galvanized Metal & Metal Fume Fever.
- Stainless steel fumes contain hexavalent chromium. See Hexavalent Chromium.
- Use local exhaust or a downdraft table, keep your head out of the plume, and wear a respirator if the exposure assessment calls for one. See Welding Fume.
Noise
Plasma cutting, especially at high amperage, can be louder than 100 decibels. Wear earplugs or earmuffs. Earplugs also keep sparks out of your ears. See Noise.
Sparks, slag and fire
- Molten metal sprays out of the cut, often farther than with a torch. Clear combustibles from at least 35 feet or cover them. See Sparks & Fire Risk.
- Follow the hot work permit and fire watch rules. See Hot Work Permits.
- Never cut containers that held fuel or chemicals unless they’ve been properly cleaned and tested. See Drums & Tanks.
- Wear flame-resistant clothing without cuffs or open pockets, and leather gloves and boots.
Water tables and aluminum
Cutting aluminum over a water table can produce hydrogen gas that collects under the plate and can explode. Keep water circulating or aerated, cut aluminum above the water where the manufacturer recommends it, and clean out aluminum dross regularly. Follow your table maker’s instructions.
CNC plasma tables
Automated tables move fast and can start without warning. Keep guards and light curtains working, and lock out the table before reaching into the cutting area. See Machine Guarding.
Before cutting
- Torch, lead and work clamp inspected
- Correct lens shade, safety glasses and hearing protection
- Ventilation or fume extraction running
- Combustibles cleared or covered; extinguisher nearby
- Air supply dry and at the right pressure
Standards & references
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