Arc welding is a safe occupation when sufficient measures are taken to protect the welder from potential hazards. When these measures are overlooked or ignored, however, welders can encounter such dangers as electric shock, overexposure to radiation, fumes and gases, and fire and explosion - any of which may result in fatal injuries.
Like a football player's shoulder pads and helmet, arc welders require similar precautions. Generally, protective clothing must allow freedom of movement while providing adequate coverage against burns from sparks, weld spatter and arc radiation.
Many types of clothing can protect against exposure to ultraviolet (UV) radiation. Typically, excessive UV exposure appears as a skin burn (much like sunburn). Under the worst conditions, however, severe burns and skin cancer may result. If possible, keep clothes clean of grease and oil, as these substances may ignite and burn uncontrollably in the presence of oxygen.
Protective wear for heavy work or especially hazardous situations includes flame-resistant suits, aprons, leggings, leather sleeves and shoulder capes, and caps worn under helmets.
It is essential to protect eyes from radiation exposure. Infrared radiation can cause retinal burning and cataracts. Even a brief exposure to UV radiation can cause an eye burn know as "welder's flash."
While this condition is not always apparent until several hours after exposure, it causes extreme discomfort and can result in swelling, fluid excretion and temporary blindness. Normally, welder's flash is temporary, but repeated or prolonged exposure can lead to permanent eye injury.
Although nonwelders may avoid looking at an arc, the only preventative measure available to a welder is the use of proper eye shading. Refer to a lens shade selector chart for the recommended shade numbers of various arc-welding processes.
Helmet-type shields and hand-held face shields offer the most complete shading against arc radiation. The shade slips into a window at the front of the shield so it can be removed and replaced easily. The shields, made from hard plastic or fiberglass, protect the head, face, ears and neck from electric shock, heat, sparks and flames. Also use safety glasses with side shields or goggles to protect eyes from flying particles.
Visible light also can be harmful, but it is easy to tell if the light is dangerous: If it hurts to look at, it is too bright. The same is true for infrared radiation, which is usually felt as heat. There is no real way to sense exposure to UV radiation. Do not take chances: Always wear eye protection.
The hazard of electric shock is one of the most serious and immediate risks facing a welder.
Contact with metal parts, which are "electrically hot," can cause injury or death because of the effect of the shock upon the body or a fall as a result of reaction to the shock. The electric shock hazard associated with arc welding may be divided into two categories:
- Primary voltage shock (i.e., 230 or 460 volts), and
- Secondary voltage shock (i.e., 60 to 100 volts).
The primary voltage shock is very hazardous because it is much greater than the secondary voltage of the welding equipment. Welders can receive a shock from the primary (input) voltage by touching a lead inside the welding equipment with the power to the welder "on" while the body or hand touches the welding equipment case or other grounded metal.
Remember that turning the welding equipment power switch "off" does not turn the power off inside the unit. The input power cord must be unplugged or the power disconnect switch turned off.
Never remove fixed panels from welding equipment, which should be installed by a qualified electrician. Always have a qualified technician repair welding equipment.
A qualified electrician can correctly wire the primary voltage that supplies the power and connect the case to an earth ground. The ground allows a fuse to blow if a problem develops inside the welding equipment. A blown fuse is a warning that something is wrong and requires repair.
A secondary voltage shock occurs when touching a part of the electrode circuit - perhaps a bare spot on the electrode cable - and another part of the body touches both sides of the welding circuit (electrode and work, or welding, ground) at the same time. To prevent secondary voltage shock, develop and use these safe work habits:
- 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 the body, including arms and legs, and the metal being welded or ground (i.e. metal floor, wet ground).
- Keep welding cables and electrode holders in good condition.
Sometimes the work site conditions increase the likelihood of a severe shock, such as with wet conditions and when welding in or on the work piece, such as a metal framework or metal tank.
Because moisture increases the potential and degree of electric shock, keep dry. Use plywood, rubber mats or some other dry insulation to stand or lie upon. Do not rest the body, arms or legs on the work piece, especially if clothing is wet or bare skin is exposed (it should not be exposed with proper protective clothing). When working in wet conditions, or when perspiring heavily, be even more careful to insulate the body from electrically "live" parts.
The condition of electrode holders and electrode cables is also important. The plastic or fiber insulation on the electrode holder protects the welder from touching the "electrically hot" metal parts inside. Always inspect the electrode holder before turning on the welding equipment. Replace the holder if it is damaged. Do not try to repair it without correct replacement parts.
The electrode cable should be replaced or repaired using good electrical tape. Check that the tape is secure before turning on the welding equipment.
Fires and Explosions
Be aware of fire hazards because of extreme temperatures associated with any arc welding process.
The heat of the welding arc can reach temperatures of 10,000 F, but this heat in itself is not generally a fire hazard. The danger of fire results from the effects of this intense heat upon the work and in the form of sparks and molten metals. Because these can spray up to 35 feet from the work, welders should recognize and distance themselves from combustible materials.
Keep the work away from contact with any combustible that may ignite when heated. These materials fall into three categories: liquid (gasoline, oil paints and thinners); solid (wood, cardboard and paper); and gaseous (acetylene and hydrogen).
Watch where the sparks and metals are falling from the work: If there are flammable materials, including fuel or hydraulic lines, in the work area, move the work or the combustible substances, or put a fire-resistant shield in place. When welding above the ground or off a ladder, make sure there are no combustibles underneath. Do not forget co-workers, who will not appreciate being hit with slag or sparks from welding work.
Particular care must be taken when welding or cutting in dusty locations. The dust may be extremely volatile in the heat of the arc or in the presence of a hot spark. Fine dust particles may readily oxidize without warning, resulting in a flash fire or even an explosion.
Before starting to weld, inspect the work surface. Look for flammable coatings or any unknown substances that would ignite when heated. Because of the extreme fire and explosion hazards inherent to welding on or around containers and piping that may have combustible materials, assign only experienced welders for such work.
Know the location of fire alarms and fire extinguishers. Check the pressure gages for empty extinguishers. If there are no extinguishers in the area, have access to fire hoses, sand buckets, fire-resistant blankets or other fire-fighting equipment.
When welding within 35 feet of flammable materials, use a fire watcher. He can watch for landing sparks and, if needed, grab an extinguisher or sound an alarm. The welder and the fire watcher should wait for a half hour after all welding is finished to find and put out any smoldering fires.
As with other emergencies that may result from welding accidents, the first rule is to not panic. Depending on the size of the fire, shut off the welding equipment, sound the fire alarm to warn others and the fire department and move to a fire exit as quickly as possible.
Fumes and Gases
Because of the variables involved in fume and gas generation from arc welding and allied processes (such as the welding process and electrode, the base metal, coatings on the base metal and other possible contaminants in the air), treat the subject in a rather general way, lumping all but the more hazardous situations together. Although health considerations vary according to fume and gas composition and individual reactions, these precautions hold true for all fumes and gases.
The fume plume contains solid particles from the consumables, base metal and base metal coating. Depending on the length of exposure to these fumes, most acute effects are temporary and include symptoms of burning eyes and skin, dizziness, nausea and fever. For example, zinc fumes can cause metal fume fever, a temporary illness that is similar to the flu. Chronic, long-term exposure to welding fumes can lead to siderosis (iron deposits in the lungs) and may affect pulmonary function.
Cadmium, however, is a different story. This toxic metal can be found on steel as a coating or in silver solder. Cadmium fumes can be fatal even under brief exposure, with symptoms much like those of metal fume fever. These two should not be confused. Twenty minutes of welding in the presence of cadmium can be enough to cause fatalities, with symptoms appearing within an hour and death five days later.
The gases that result from an arc welding process also present a potential hazard. Most of the shielding gases (argon, helium and carbon dioxide) are nontoxic. When released, however, these gases displace oxygen in the breathing air, causing dizziness, unconsciousness and death the longer the brain is denied needed oxygen.
In contrast, heat and UV radiation can cause eyes to tear and irritate the lungs. Some degreasing compounds such as trichlorethylene and perchlorethylene can decompose from the heat and ultraviolet radiation. Also, when UV radiation hits the air, it forms ozone and nitrogen oxides. These gases cause headaches, chest pains, irritation of the eyes and itchiness in the nose and throat.
There is an easy way to reduce the risk of hazardous fumes and gases: Keep the head out of the fume plume. As obvious as this sounds, it is a common cause of fume and gas overexposure because the concentration of fumes and gases is greatest in the plume.
In addition, use mechanical ventilation or local exhaust at the arc to direct the fume plume away from the face. If this is not sufficient, use fixed or moveable exhaust hoods to draw the fume from the general area. Finally, it may be necessary to wear an approved respiratory device if sufficient ventilation cannot be provided.
As a rule of thumb, if the air is visibly clear and the welder is comfortable, the ventilation is probably adequate.
To identify hazardous substances, first read the material safety data sheet for the electrode posted in the work place to see what fumes can be reasonably expected from use of the product.
Second, know the base metal and determine if a paint or coating would cause toxic fumes or gases. If a welder starts to feel dizzy or nauseous, there is a possibility of overexposure to fumes and gases, or suffering from oxygen deficiency. In either case, try to improve the ventilation. If that does not work, turn off the welding equipment, get fresh air immediately, and notify the supervisor and co-workers.
When arc welding in a confined area, such as a boiler, a tank or the hold of a ship, all hazards associated with normal arc welding are amplified, so precautions are even more important. For example, there is a greater danger that enough flammable gases may be present in the confined space to cause an explosion.
Ensure that the welder's body is insulated from the work piece and ground by dry insulation. Wear dry gloves and only use a well-insulated electrode holder. The metal of the enclosure can become part of the welding circuit, so any touched metal (walls, floor, ceiling, etc.) is electronically "hot."
Welding fumes can accumulate more rapidly, with a higher concentration, and gases can force out the breathable air, leading to suffocation. So make sure there is adequate ventilation (be it forced or through an air-supplied respirator) and that there are no flammable coatings, liquids or gases nearby.
Lastly, have someone outside the enclosure trained to handle emergencies, with resource procedures and a means to disconnect power to equipment and pull out the welder if danger arises.
No matter how experienced welders are, do not attempt work of this nature without constant communication with the person outside the confined area. Supervisors must be careful when assigning welders to work a confined area. Any problem that arises can immediately become life-threatening.
About the author: Ken Brown is a project research manager at The Lincoln Electric Co. in Euclid, Ohio. Lincoln Electric is a world leader in the design, development and manufacture of arc welding products, robotic welding systems, and plasma and oxyfuel cutting equipment.
Sidebar: Inspection and Maintenance of Equipment and Work
A general safety checklist before starting a welding job includes:
For the welder:
- Are all the connections tight, including the earth ground?
- Are the electrode holder and welding cable in good condition?
- Are the settings correct for the job?
For engine-driven welding equipment:
- Are all hoses on tight?
- Is the fuel cap on tight?
- Is the engine leaking gasoline or oil?
- Is the original enclosure and fan guarding in place? Check with the welding equipment manufacturer if unsure.
For work in general:
- Are the work area conditions such that normal safety precautions can be observed, or must special equipment (i.e., welding equipment protective equipment, safety equipment) or procedures be used?
- Are the cables the right size for the job?
- Are the cables spread out and run neatly to prevent overheating?
- Is the gas cylinder connected properly and secure?
- Is the work stable and easy to reach from the work position?
- Is the work lead connected securely?
- Is there enough insulation between the welder's body and the work piece?
- Is there adequate ventilation in the work area?