Welding

This archived article is from May 2006. Although every effort has been made to make sure the information presented is accurate, please note that it may contain information that is out-of-date.

Technological advances have led to better welding techniques and more materials that can be welded. But these advances have also increased the possible hazards to which a welder can be exposed. Whatever process is used, welding requires a lot of energy to melt or fuse the metals. This release of heat and energy can cause chemical and physical reactions that don't normally happen at room temperature. Whatever process is used, welding requires a lot of energy to melt or fuse the metals. This release of heat and energy can cause chemical and physical reactions that don't normally happen at room temperature.

Handling and storing fuel cylinders

Most welding operations use fuel gases, which can be a serious hazard in case of fire or explosion.

1.     Always double-check the availability of an MSDS before using any cylinder gas. Don't assume that it must be oxygen because that's where the oxygen is supposed to be!

2.     Release the pressure from regulators and hose lines before the cylinders are moved or placed in storage. When the work is done, close the cylinder valves and put the valve protection caps on.

3.     When you move cylinders, keep them upright with their caps securely on. Always use cylinder carts, and proper lifting procedures and equipment.

4.     Use cylinders in the order received from the supplier. When a cylinder runs out, close the valve, detach the regulator, put the valve protection cap back on and mark the cylinder to show it's empty.

5.     Store full and empty cylinders of each type of gas separately. Never store cylinders of oxygen close to acetylene cylinders.

6.     Store cylinders securely where they will not be knocked over or damaged. Never store them near radiators or any other heat source, or allow them to touch electric wires.

Explosion and burns

Good housekeeping can help prevent fires and explosions. Keep your work area clean and free of flammable and explosive materials. Use fire barriers like metal sheets or flame retardant blankets when they're needed. Also watch for cracks and crevices in the floor: they should be filled to prevent sparks or slag from falling into them.

Most minor burns are the result of not wearing protective equipment or not wearing it properly. To prevent burns on your forearms, wear appropriate welding gloves and don't roll up your sleeves. Mark newly welded items "hot" to warn other employees who handle them.

Arc welding: Electric shock

Electric shock is a hazard with electric resistance and electric arc welding. A shock can happen because the equipment isn't properly grounded, or from contact with the current by moist gloves or clothing, damp floors or humid air. Even if the shock itself isn't too serious, the jolt could throw a welder out of position causing major injuries. A fairly minor slag burn could also startle a worker just long enough to lose balance and fall. Safety belts or lifelines should always be used when welding in high places and wherever a slip or fall could be dangerous.

To reduce the risk of shock, use an insulating mat when welding on steel work or plate. Wear rubber gloves under welding gloves when working in wet or damp locations or when the heat makes your hands sweat.

If anyone in the shop suffers an electric shock, shut off the power source immediately. If the casualty isn't breathing, start artificial respiration first. Then check for a pulse: if you can't find one, a qualified person should start CPR (cardio-pulmonary resuscitation). Send for medical help as quickly as possible.

Voltage reducing devices (VRDs) protect workers against electric shock when changing an electrode or if an electrode accidentally touches the worker. VRDs lower the electrode voltage when the stick machine is not welding.

Eye protection

You have to be concerned about all kinds of light in welding: the kind you can see and the kinds you can't.

Special safety precautions are required when using laser beam welding equipment. A laser beam is intensely focussed, high power light, which can cause severe damage or blindness if the eyes are caught in the direct path of the beam.

Visible light rays reflecting off walls or other surfaces can cause eye problems for anyone nearby who is not wearing good eye protection with the right lenses. Intense visible light can cause eye strain and even temporary blindness.

The kinds of light that you can't see include infrared (IR) and ultraviolet (UV).

Infrared is the kind of light that feels warm. If you are exposed to it you may feel a temperature increase on bare skin. Exposing your eyes to infrared radiation without proper protection can cause cumulative effects leading to cataracts (the development of an opaque white film over the eyes, which can lead to blindness).

Ultraviolet or UV rays cause "arc eye" or "flash." If you notice yourself developing a sensitivity to light or watery eyes, or feeling like you've got sand in your eyes, you may have arc eye. Let your eyes rest. If there is any pain, cover the eyes with a thick, moist dressing or a clean, moist towel. See the doctor for an examination.

X-rays are another kind of invisible light. They're produced by electron beam welding and are sometimes used to check the integrity of welds. The shielding of the welding chamber must be complete to insure there is no radiation hazard to the operator.

To protect your eyes from harmful rays a welding hood or helmet is critical. A flip front lets you do a close inspection of your work, but never leave it open while you're welding. When welding in an area that is not enclosed or isolated, make sure everyone within 25 metros (75 feet) of an arc is wearing anti-flash goggles before you start.

Fumes, dust and toxic gases

Fumes, dusts and toxic gases can come from the base and filler metals being used, any coatings on the base metal, electrode coatings or shielding gas, or from a reaction caused by the welding process.

Metal fume fever is caused by breathing in metal oxide particles produced by welding galvanized metal. The particles react with the lining of the lungs, making the worker start to feel sick a few hours after exposure.

Exposure to toxic gases produced by welding can cause serious problems including inflammation of the lungs, fluid in the lungs, emphysema, chronic bronchitis and suffocation.

Toxic hazards can be controlled through ventilation and safe work practices. Always use the ventilating equipment designated for each job, whether this means just checking to make sure the local exhaust vent is turned on or using a supplied air hood.

The hazards of working with solvents must be controlled. All traces of solvents must be removed before welding starts because heating them produces poisonous fumes. You must also take care that vapors from chlorinated solvents are not exposed to UV radiation because this causes a reaction releasing poisonous gas. Store and use solvents in a separate room and never use them on pieces that are going to be welded.

If any worker in the shop starts to show symptoms like nausea, vomiting, headache, fatigue, confusion or chest pain, it might mean that there are toxins in the air. Everyone should get out into the fresh air. Anyone showing signs of distress should receive first aid, and medical help should be called. Only someone wearing respiratory protective equipment should go back inside to attempt a rescue or check for the source of the hazard.

In summary, to prevent injuries in the welding shop the key precautions are: good housekeeping practices, proper protection and careful handling of fuels.

This feature is intended as useful general information to supplement existing occupational health and safety programs. It is not suitable as a replacement for a proper full program.

We thank Canadian Liquid Air Ltd. for their assistance with this article.

Safety Canada (January 1998)

Updated May 2006