Arc Welding & Electrical Hazards

The arc welding process requires a live electrical circuit. This means that all arc welders using hand held equipment will be at risk of electric shock and electrical burns. The risk for MIG/ MAG and TIG welding is much less as the welding current is normally switched on and off using the trigger or foot switch. The hazard of electric shock is one of the most serious and immediate risks you face as a welder. Contact with metal parts which are “electrically hot” can cause injury or death because of the effect of the shock upon your body or a fall which may result from your reaction to the shock. On most manual arc welding operations, the electric current ranges from 10 amps to 600 amps. Remember that it only takes 70 to 100 milliamps to kill most people and 70 milliamps is only a fraction of one single amp. Your best protection is to keep from becoming grounded.

The electric shock hazard associated with arc welding may be divided into two categories which are quite different:

- Primary Voltage Shock (i.e., 230, 460 volts)
- Secondary Voltage Shock (i.e., 20-100 volts)

Primary Voltage Shock

The primary voltage shock is very hazardous because it is much greater voltage than the secondary voltage. You can receive a shock from the primary (input) voltage if you touch a lead inside the welder with the power to the welder “on” while you have your body or hand on the welder case or other grounded metal.

  • Remember that turning the welder power switch “off” does not turn the power off inside the welder. The input power cord must be unplugged, or the power disconnect switch turned off.
  • Never remove fixed panels from welding equipment, this should always be installed by a qualified electrician.
  • When electrical supply lines are connected to a welder, check the welder capacity nameplate and connection instructions to be sure the input is the correct phase (single phase or three phase) and voltage.
  • Many welders may be set up for single phase or three phase and for multiple input voltages. Be certain the welder is set up for the electrical supply to which it is connected.
  • Only a qualified electrician should connect input power.
  • The case must be grounded so that if a problem develops inside the welder a fuse will blow, disconnecting the power and letting you know that repair is required.

Never ignore a blown fuse because it is a warning that something is wrong.

Secondary Voltage Shock

A secondary voltage shock occurs when you touch a part of the electrode circuit – perhaps a bare spot on the electrode cable – at the same time another part of your body is touching the metal upon which you’re welding (work). To receive a shock your body must touch both sides of the welding circuit – electrode and work (or welding ground) – at the same time. To prevent secondary voltage shock, you must develop and use safe work habits:

  • Remember the voltage at the electrode is highest when you are not welding (open circuit voltage).
  • Wear dry gloves in good condition when welding.
  • Do not touch the electrode or metal parts of the electrode holder with skin or wet clothing.
  • Keep dry insulation between your body (including arms and legs) and the metal being welded or ground (i.e., metal floor, wet ground).
  • Keep your welding cable and electrode holder in good condition. Repair or replace any damaged insulation

Remember, a stick electrode is always “electrically hot” when the welder is on – treat it with respect. If you do experience a shock, think of it as a warning – check your equipment, work habits and work area to see what is wrong before continuing to weld.

SUMMARY

HAZARD

FACTORS TO CONSIDER

PRECAUTION SUMMARY

Electric shock can kill

  • Wetness
  • Welder in or on workpiece
  • Confined space
  • Electrode holder and cable insulation
  • Insulate welder from workpiece and ground using dry insulation. Rubber mat or dry wood.
  • Wear dry, hole-free gloves. (Change as necessary to keep dry.)
  • Do not touch electrically “hot” parts or electrode with bare skin or wet clothing.
  • If wet area and welder cannot be insulated from workpiece with dry insulation, use a semiautomatic, constant voltage welder or stick welder with voltage reducing device.
  • Keep electrode holder and cable insulation in good condition. Do not use if insulation is damaged or missing.