Some potential hazards of welding and cutting

By
Saturday, 19 June, 2004

Welding and cutting operations present a variety of hazards, not only to those carrying out the operation but in many instances also to others in the vicinity.

In the workshop there are a number of hazards specific to welding or cutting and others, of a more general nature, which may also be present in the fabrication environment. Potential hazards need to be identified, measured where appropriate, and assessed, and remedial measures put in place wherever necessary.

Although Personal Protective Equipment, PPE, should not be issued as the primary method of reducing a hazard, it should be issued to all personnel if beneficial.

Employers and employees should be made fully aware of the dangers that can arise and take all reasonable care to ensure the health and safety of all.

The hazards encountered in welding and cutting may be sub-divided into a number of groups:

  • Electrical
  • Magnetic fields
  • Compressed gases
  • Fuel gases
  • Inert gases
  • Cryogenic gases
  • Radiation
  • Heat, flames, fire and explosion
  • Welding fumes and gases
  • Chromium formation
  • Noise
  • Material and manual handling
  • Confined spaces
  • Thoriated electrodes
  • Solvents

Electrical
The possibility of electric shock is one of the most serious risks encountered by a welder. Touching 'live' electrical components, including the electrode and the workpiece can result in serious burn injury or, more seriously, electric shock. Electric shock can kill, either by direct action on the body, or by a resultant fall, if working at height.

An electrical accident may occur as a result of carelessness, poor workmanship or due to faulty equipment.

Welding equipment should be installed in accordance with national standards and the manufacturer's instructions, by qualified personnel, and tested to ensure it is correctly wired in and properly 'earthed'.

The workpiece 'earthing' requirements should be in accordance with the welding power source being used.

Magnetic fields
Magnetic fields arise from the motion of electric charges and, consequently, when an electric current is flowing through power sources, equipment and welding leads there are associated magnetic fields being produced.

The effects of these magnetic fields have been studied and have been shown that in some cases they may affect the functioning of some heart pacemakers.

There is no evidence of any other adverse health effect, although there is an indication that these may also reduce sperm counts.

Compressed gases
A wide range of gases is used in welding and cutting and all gas producers will have material safety data sheets outlining the particular hazards associated with each product. However, there are other hazards of a more general nature which should also be considered.

Gas regulators should only be fitted to cylinders using the correct tools.

Use the correct regulator for the gas and the required working pressure and never modify a regulator for use with another product.

Fuel gases
Gases included in this category are Hydrogen, Acetylene, Propane, Propylene and MAPP (Methylacetylene-Propadiene Stabilised). Oxygen is included too, since, although it is not flammable, it will support combustion, and is commonly used in conjunction with fuel and flammable gases.

All fuels gases form an explosive mixture with air or oxygen and the ratios differ for each gas.

Propane, Propylene and MAPP have a higher density than air and will tend to accumulate in low-lying areas, which can create a significant safety risk.

Inert gases and mixtures
A wide range of the gases used in arc welding and cutting contain high percentages of inert gases, the most common of which are argon and helium. All gas producers will have material safety data sheets outlining the particular hazards associated with each product.

Inert gases are non-toxic, non-flammable and will not support combustion.

Inert gases will not support life so they are particularly hazardous in confined spaces where they could cause asphyxiation in certain cases.

Safe use of cryogenic gases
Cryogenics is a branch of science concerned with phenomena occurring at very low temperatures, below -100°Celsius. Many of the applications involve use of gases, such as Argon, Nitrogen, Helium and Oxygen, in their liquid state.

When working with cryogenic gases it should be noted that these liquid gases could cause severe tissue damage to the body.

Radiation
All welding and cutting arcs produce electromagnetic radiation and the wavelength emitted tends to be within the range of 100 to 1400 nm. This band covers three distinct types of 'non-ionising' radiation, namely, ultraviolet (UV), visible light and infrared (IR).

Arc welding and cutting processes arcs and high energy processes such as laser emit UV, visible and IR radiation.

Fuel gas processes emit only visible and IR radiation.

Heat, flames, fire and explosion
The welding and cutting environment is one that produces a lot of heat from a number of different sources. If hot objects or flames make contact with unprotected areas of skin or eyes, they can cause burns, which can be serious.

To minimise the risk of burns, it must always be assumed that all metal objects in a welding shop are hot and nothing should be picked up without ensuring it is cool enough to handle.

Welding fumes and gases
Welding fumes are an unavoidable by-product of the welding and cutting process. All these processes generate fumes, only the type and amount varies from process to process. It consists of particulate fume, the part you can see, and gaseous fume, the part you cannot see, but can sometimes smell.

Exposure of welders to welding fumes depends on many factors; the most important of which is what actual type of welding is being done.

For example, FCAW, MMA, MIG, thermic lancing and plasma cutting tend to produce the highest amounts of most particulate fumes, while TIG, plasma welding, oxy-fuel welding, laser welding, laser cutting and submerged arc normally give very little.

TIG, plasma welding, MIG, laser cutting and welding tend to produce the most gaseous fumes while MMA, plasma cutting and FCAW normally produce very little.

The potential effect of exposure to welding or cutting fumes depends on the composition of the fumes.

The health effects of exposure to fumes include irritation of the upper respiratory tract (nose and throat), tightness in the chest, wheezing, metal fume fever, lung damage, bronchitis or pneumonia, possibly even cancer or emphysema.

Possible control measures include doing things such as changing or modifying the process, or the way the job is done.

Chromium formation in welding
When arc welding takes place on materials containing chromium, or by using consumables containing chromium, some of the chromium will be volatilised and escape from the protective gases in and around the arc. This metal vapour will be oxidised by the atmosphere to give particulate fumes.

Depending on the specific welding process being used, chromium can be present in the fume in several different valency states, including trivalent, Cr3+ and hexavalent, Cr6.

The major toxic effects of chromium in industry are concentrated on the nose, the skin and the lungs.

The nose or, more specifically, the mucous membranes of the nasal septum, together with the skin of the hands and forearm, are the areas targeted by chromic acid and its salts.

When welding stainless steels using the MMA process there is a higher level of particulate fume generated than with MIG welding. However, an analysis of the fume generated would show that the MIG fume has a higher percentage of chromium present, typically 10 to 14 per cent; this can be compared to about 6 to 8 per cent for MMA.

Noise
All welding and cutting processes generate noise, with some processes generating more noise than others. For each process there will be variations in the level of noise produced as some power sources are noisier than others and some additionally generate high frequency noise.

In welding and allied industries it is often difficult to engineer a reduction in noise.

However, it is essential, and in many countries, mandatory to protect workers from exposure to such high levels of noise or industrial deafness could be the result.

The processes that generate very high levels of noise are air-arc gouging and plasma cutting, often well in excess of 100 dB(A).

Material and manual handling
Back injuries are one of the most common industrial injuries suffered by Australian workers. While not specific to the fabrication environment, these often occur through bad practice and poor instruction as to the correct procedures to carry out.

Material and manual handling hazards can be reduced by implementing such procedures as maintaining a tidy work area, especially free from trip hazards, moving and positioning welding equipment so that it is not in the way. Caution must be observed, as these units are often heavy; even the so-called portable units.

Confined spaces
Many of the hazards can be exacerbated if work is being carried out in a confined space. Each year, a significant number of deaths occur of people working in confined spaces.

Arc welding processes use shielding gases that can cause asphyxiation so therefore it is advisable to be using an oxygen monitor.

Additional protection from heat, glare and UV radiation is usually necessary and particular attention must be paid to electrical safety and ventilation.

Thoriated tungsten
Some tungsten electrodes used in TIG welding are alloyed with 2 or 4 per cent thorium oxide to improve arc striking and stability. Thorium is a naturally occurring radioactive alpha emitter as it decays.

It must be pointed out that Thorium Oxide is radioactive.

Solvents
Flammable solvents may be present in many degreasing agents, paints and other materials that are sometimes used in and around the welding area.

Workers in the welding and cutting fields must treat all flammable materials with extreme caution when being used in or around the welding environment in order to prevent fires or explosions.

For further information contact BOC Gases Australia Ltd
PO Box 288, Chatswood 2057

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