The major health hazards in welding and cutting are:

► fumes
► gases
► radiation
► noise
► various safety factors
► manual handling problems

The variables that influence exposure to these hazards include:
► variables in the welding process
► effect of the work area
► effect of the operator

Fumes are fine, solid particles, formed by the following general process:
1. Metal and flux undergo rapid melting accompanied by limited vapourisation
2. Vapours are oxidised
3. Reaction takes place with flux constituents and other materials present
4. Vapours condense and agglomerate to produce fine particles of fume of complex composition.

Gases may be produced in certain welding processes in the following ways:
1. Decomposition of flux or electrode coatings and base metal coatings such as paints and solvents.
2. Reaction products of the shielding gases.
3. Oxidation of elements present in the arc or flame.
4. Photochemical reaction of atmospheric gases due to ultraviolet radiation from the arc or flame.

The electrode coating is a complex mixture of various components such as:
1. Moulding Agents (aluminium and magnesium silicate)
2 Extruding Agents (alginates, starch, glucose and methyl cellulose)
3. Binders (potassium and sodium silicates)
4. Strengthening Agents (mostly mica which has replaced asbestos)
5. Slag Formers (carbonates, silicates, oxides-rutile (TiO₂) and fluorides)
6. Metal Powders (e.g., iron) to act as alloying additions, to increase deposition rate or act as deoxidants
7. Shielding Gas Formers (cellulose, calcium carbonate)
8. Fluxing Agents (fluorspar, calcium carbonate and sodium silicate)

Routes of entry into the body
► inhalation
► ingestion
► skin

Notes: Short term exposure limit (STEL) means a 15 minute time weighted exposure which should not be exceeded at any time during a working day even if the 8 hour average is within the exposure standard. Exposures at the STEL should not be longer than 15 minutes and should not be repeated more than 4 times per day. There should be at least 60 minutes between successive exposures at the STEL. A peak limitation should not be exceeded at any time. If required the STEL for carbon monoxide may be derived from the National Commission Documentation.

CONTROL OPTIONS
elimination, substitution and process modification
engineering controls administrative controls use of personal protective equipment

ARE YOU RISKING ELECTRIC SHOCK WHEN YOU WELD?

Although manual metal arc welding can be performed perfectly safely, there is a substantial risk of electric shock. It is obvious that poorly maintained or badly connected equipment may be extremely hazardous. What is not so well known is that an electric shock from the output terminals of the welding machine can cause death or serious injury.

Manual metal arc welding and arc-air gouging are particularly risky because the electrode is changed frequently while the electrode holder is electrically live. There is a high risk that the welder can receive a shock by simultaneously touching the electrode and work piece. Fuses or earth leakage contact breakers do not protect the welder from such a hazard. Many welders have suffered such shocks and have only experienced an unpleasant tingle, but muscle spasms from even a mild shock may lead to a fall from a height or injury by striking. Death by electrocution has occurred in such extreme circumstances.

Factors which affect the severity of the shock are: The no-load or open circuitry voltage (OCV) of the welding machine; Whether the machine supplies alternating or direct current (a.c. is 2 to 3 times more dangerous than d.c.) The pressure of moisture from rain, perspiration or other source; How well the victim is insulated from the electrode and the work piece; Which parts of the body are in contact with the work and the electrode. Current flow between the left hand and the torso is the most dangerous; the susceptibility of the victim to shock, which is dependent on health and other factors. Processes such as GMAW (MIG) do not require frequent electrode changes and are activated by a contact switch at the torch. They therefore carry less risk. To avoid electric shock: Avoid bare skin contact with the electrode; and either prevent contact with the work piece, or use a welding machine which is safe for electrically hazardous environments as defined by AS 3195, or which has a voltage limiting device fitted.

An environment is considered electrically hazardous whenever the welder has to work in physical contact with the work piece, particularly in a cramped (kneeling, sitting or lying) position. The environment is not electrically hazardous if the welder is electrically insulated from the work piece, but in many cases this may be impossible or uneconomical. Examples include shipbuilding work, inside vessels, pipes and structural components. The electrically hazardous environment does not need to be a confined space.

An electrically hazardous environment is compounded in wet, damp or hot locations where moisture or perspiration considerably reduces the electrical resistance of the human body and the insulating properties of accessories. The precautions described below can often be taken to the limit risk. If there is difficulty in keeping dry, a voltage limiting device should be used to limit the OCV to a maximum of 25 volts, or the power should be controlled by a contactor switch. Such damp environments include: underwater, in the splash zone, while standing in water, in rain, welding in a hot or humid area when it is impossible to avoid accumulation of perspiration or condensation, and in mines.

All persons who work near or assist in welding operations should be familiar with rescue procedures. The following precautions are required to protect from electric shock:

1. When a workplace hazard assessment is conducted, ensure the risk of such electric shock is considered and appropriate measures are taken to minimise the risk (see below).

2. The use of dry, hole free welding gloves on both hands while welding, particularly when changing electrodes should be compulsory and be a written safety policy.

3. Remove stub ends immediately after welding; do not leave an electrode holder with a stub end in it.

4. Turn off the power at end of each shift or when taking a break. Do not drag live leads to the work.

5. If possible make the environment electrically safe by using dry, fire resisting insulation. Wooden duckboards, leather covered cushions, leather aprons, leather jackets, heat resisting blankets should be used to cover those parts of the work piece which the welder may contact. It it is not possible to provide such insulation, or to keep it dry, the environment must be considered electrically hazardous, and equipment should be safe for such environments.

6. In hot conditions the risk of electrocution is increased because of clothing and equipment being soaked in perspiration. The risk is far worse in closed environments, such as tanks or vessels, particularly when these are exposed to the sun's heat. Take frequent rest periods, during which time dry off equipment and clothing. Frequently change or alternate gloves and protective clothing to avoid perspiration accumulating. Ventilate or if possible air-condition the work air. Ventilation will help dry perspiration and cool the body. Cool the face with an air mask. If clothing (including gloves) becomes soaked with perspiration, it must be changed.

7. If it is not possible to keep it dry, the environment must be considered extremely dangerous. Either a voltage limited welding power source should be used, or the power should be controlled by a contractor switch on the torch.

Welding Safety on the Site

•           Wear proper protective gear for welding.

•           Thoroughly clean any container that contained a combustible substance before welding or cutting it.

•           Maintain a fire extinguisher at the welding site.

•           Ventilate the welding area.

•           Keep tanks, valves and welding equipment in good condition.

•           Keep flames, heat and sparks away from combustible materials.

•           Avoid electric welders with defective jaws or poor insulation on the cables.

Personal Protective Equipment for Welding

The employer must provide the proper personal protective equipment needed for welding jobs on the farm. Fire-resistant gauntlet gloves, aprons, coveralls, leggings and boots are the basics needed. Welding helmets, respirators, ultraviolet radiation filter plates for arc welding, and goggles with filter lenses are a must.

Maintain, store, inspect, clean and evaluate respirators routinely. Make sure everyone using them has been fit-tested. Workers doing overhead welding should be provided with fire-resistant shoulder covers, head covers and ear covers. When welding highly toxic materials, provide work uniforms, coveralls or full body coverings. There should be lockers or separate areas to store or change into street clothing. Collect all welding clothing, and launder it properly.

All protective clothing should be routinely inspected and maintained. Keep clothes free of grease and oil. Retreat fire-resistant clothing after laundering. Prohibit upturned sleeves and collars, because sparks or other materials may get caught in them. Button sleeves and collars.

Before Welding

Properly train all people welding. Do not allow anyone to use the equipment until they know the exact instructions on how to operate it. Do routine maintenance to keep equipment in working order. Ventilate the work area well. There must be sufficient movement of air to prevent toxic fumes from building up or oxygen from becoming deficient.

Cutting Containers

Never weld or cut used drums, barrels, tanks or other containers unless they have been thoroughly cleaned of all substances that may produce flammable vapors or gases. Never use oxygen to ventilate a container, as it may start a fire or cause an explosion. As a final precaution after cleaning, a container should be vented and filled with water before welding or cutting begins. The container should be arranged so water can be kept filled to within a few inches of the point where the welding or cutting is to take place. Be sure there is a vent or opening to provide for release of air pressure or steam.

Safety in Cutting

Whenever cutting, always keep a fire extinguisher nearby. Never use a cutting torch where sparks will be a hazard, such as near rooms containing flammable materials (especially dipping or spraying rooms). Take extra precaution in greasy, dirty or gassy areas. If the cutting is to be over a wooden floor, sweep the floor clean and wet it down before starting the cutting. Provide a bucket containing water or sand to catch the dripping slag. Move combustible materials at least 40 feet away from any cutting or welding. If cutting is to be done near flammable materials and the flammable materials cannot be moved, use suitable fire-resistant guards, partitions or screens.

Safety in Gas Welding

Under no circumstances should acetylene gas come in contact with unalloyed copper, except in a torch. Any contact of acetylene with high-alloyed copper piping will generate copper acetylide, which is very reactive and may result in a violent explosion. After assembling, all piping must be blown out with air or nitrogen to remove foreign materials.

Safety in Arc Welding

Arc welding includes shielded metal-arc, gas shielded and resistance welding. Only general safety measures can be shown for these areas because arc welding equipment varies considerably in size and type. Specific manufacturers’ recommendations should be followed in each area.

Equip welding machines with power disconnect switches. Locate them at or near the machines so the power can be shut off quickly. Do not make repairs to welding equipment unless the power to the machine is disconnected. The high voltage used for arc welding machines can inflict severe and fatal injuries. Do not use welding machines without proper grounding. Stray current may develop, which can cause severe shock when ungrounded parts are touched. Do not ground to pipelines carrying gases or flammable liquids.

Whenever cutting, always keep a fire extinguisher nearby. Never use a cutting torch where sparks will be a hazard, such as near rooms containing flammable materials.

Do not use electrode holders with loose cable connections. Always keep connections tight. Avoid using electrode holders with defective jaws or poor insulation. Do not change the polarity switch when the machine is under a load. Wait until the machine idles and the circuit is open. Otherwise, the contact switch may be burned and the person throwing the switch may receive a severe burn from the arcing.

Do not operate the range switch under load. The range switch, which provides the current setting, should be operated only while the machine is idling and the current is open. Switching the current while the machine is under a load will cause the arc to form between the contact surfaces. Do not overload welding cables or operate a machine with poor connections. Operating with currents beyond the rated cable capacity causes overheating. Poor connections may cause the cable to arc when it touches metal grounded in the welding circuit.

Do not strike an arc if someone without proper eye protection is nearby. Arc rays are harmful to the eyes and skin. If other persons must work nearby, the welding area should be partitioned off with a fire-retardant canvas curtain to protect them from the arc welding flash. Never pick up pieces of recently welded or heated metal. Always wear protective eye goggles when chipping or grinding. A small particle of slag or metal may cause a severe eye injury.

Steps to Prevent Electrical Shock

Electrical shock can be deadly. There are steps that can be taken to prevent electrical shock. Use well insulated electrode holders and cables. Keep clothing and gloves dry. Never change electrodes with bare hands, wet gloves or when standing on wet floors. If the ground is wet, use a dry board or rubber mat to stand on. Ground frames of welding units. Keep welding cables dry and free of grease and oil. Protect welding cables and leads. Keep welding cables away from power cables. Never loop the welding cable around the body.

Air Contaminants

Welding generates fumes and gases. The amount and type of fumes and gases involved depends on the welding process, base material and filler material. The toxicity of the contaminates depends primarily upon concentrations. Provide adequate ventilation. Use exhaust hoods, air moving systems, and roof and wall exhaust fans. Also use natural ventilation.

Five Basic Rules for Safe Handling of Oxy-Acetylene Equipment

1.         Keep oxy-acetylene equipment clean, free of oil, and in good condition.

2.         Avoid oxygen and acetylene leaks.

3.         Open cylinder valves slowly.

4.         Purge oxygen and acetylene lines before lighting torch.

5.         Keep heat, flame and sparks away from combustibles.