The MIG welding process is the most common welding process now used in manufacturing. It is capable of being used on a wide range of material types from common steels, to titanium.
The MIG process produces a variety of hazards, not only to those carrying out the operation but also in many instances to others in the vicinity such as inspectors, labourers and even other welders. Some of the hazards encountered are specific to MIG welding while others are of a more general nature.
Different hazards occur before welding commences, during welding and sometimes after welding has finished. When we look at the major hazards we will also consider when they may occur.
Types of Hazards in MIG Welding
The hazards encountered in MIG welding may be sub-divided into groups as follows:
- Electrical safety and Magnetic Fields
- Compressed gases, including inert gases
- Radiation
Electrical Safety & Magnetic Fields
Power sources for MIG welding and associated pieces of equipment, such as wire feed systems, welding guns, leads and connectors all require an electricity supply to operate. Power sources may operate from a three-phase supply, from industrial single-phase supply or even from a 13amp domestic power supply.
It should always be remembered that electric shock can kill.
Due to the potential severity of the hazard, the following is a guide on what to do before any MIG welding is started to reduce the risk of an electrical accident:
- Only qualified personnel should be allowed to install MIG equipment.
- The equipment must be tested to ensure it is operating correctly and safely before being put into service.
During welding the possibility of electric shock is one of the most serious risks encountered by a welder.
Most electrical accidents occur as a result of carelessness, poor workmanship or due to faulty equipment.
The following points provide a guide to what to reduce the risks:
- Welders should not remove panels from a welding power source if it stops working correctly. Touching a lead inside the welding set with the power still on can result in a serious primary voltage shock.
- Never ignore a blown fuse, it is a warning that something is wrong.
The following practice will help prevent electrical accidents:
- When welding is temporarily interrupted welding guns should be placed where they are safe and the gun switch cannot be activated accidentally.
Compressed Gases
Shielding gases used for MIG welding may be 100% inert, 100% active, or a mixture of inert and active gases. Whatever their composition, the main risk to welders and others from the shielding gas is that of asphyxiation.
Inert gases are not toxic, but will not support life.
The following should be considered to ensure safety while this is being carried out:
- Always use the correct regulator for the gas and ensure that it suitable for the pressure contained in the cylinder.
- Never modify a regulator for use with another product.
Radiation
MIG welding produces electromagnetic radiation over a wide range of wavelengths. These wavelengths cover three distinct types of 'non-ionizing' radiation, namely, Ultraviolet (UV), Visible Light and Infrared (IR). MIG welding however, does not produce ionizing radiation.
Some points to bear in mind are:
- Radiation is only generated while the arc is generated and the amount emitted generally increases as the welding current increases.
- Burns can be avoided by wearing proper protective clothing and ensuring no areas of skin are left exposed.
Heat
Sources of heat include welded components, the electrode holder and hot or discarded electrodes, and any of these can cause burns to the skin.
A hot environment can cause the body to overheat, and this is known as Heat Stress.
However those working in welding shops can reduce the risk by adhering to the following recommendation:
Always assume all metal objects in a welding shop are hot.
Welding Fume and Gases
Welding fume is an unavoidable by-product of MIG welding, although fume generation from the process is generally low. However, the welder should still be aware of what fume is likely to be generated while welding is taking place and the potential hazards of exposure to the welding fume.
Particulate Fume
Particulate fume is mostly formed from vapourisation of the welding consumable.
The following general statements are a rough indication of what the constituents of the particulate fume are likely to be:
- Fume from MIG welding aluminium is mostly aluminium oxide.
- Fume from MIG welding steel is mainly iron oxide plus a small amount of manganese oxide and other alloying elements.
Gaseous Fume
Welding processes with open arcs, such as MIG, are likely to promote the formation of gaseous fume as a result of the action of ultraviolet light and heat on atmospheric oxygen and nitrogen.
The main factor controlling its production are:
- Argon-rich shielding gases are more likely to promote ozone production than are helium-rich shielding gases or 100% carbon dioxide.
Exposure to Fume
Whilst all components of welding fume may present a risk to health, given a high enough concentration, some present a greater hazard than do others. The potential effect of exposure to welding fume depends upon:
- The composition of the fume.
- The volume of fume produced.
Noise
The MIG welding processes, like all others, generates noise. Some power sources, notably some pulsed MIG and synergic MIG sets, are noisier than others and some adivitionally generate high frequency noise that can affect hearing.
Manual Handling
Back injuries are one of the most common industrial injuries suffered by workers. Welding consumables may be heavy or awkward to lift.
Confined Spaces
Any of the hazards associated with MIG welding will be exacerbated when welding is carried out in a confined space.
Solvents
Flammable solvents may have been used to clean components prior to welding and may still be present around the welding area, presenting a fire or explosion hazard.
The welder should allow all traces of any solvents to disappear from component surfaces and ensure no containers of solvent are in close proximity before welding starts.
Workshop Safety
General workshop safety is really a matter of common sense and good housekeeping and the following actions may be used to avoid accidents:
- Maintain a tidy work area, especially free from trip hazards.- Keep walkways clear and free from welding cables, spare material, consumables, etc.
Practical Considerations
The advice given above is general in nature but forms a good overview of the potential hazards associated with the process. There are, however, things that can be done to help reduce the possibility of problems occurring in the workplace:
Training
There is a considerable amount of misinformation in the fabrication industry about the health hazards associated with welding. There is also a lack of understanding among welders as the how they can influence the type and severity of hazard. The main cause for this is often poor training and some welders appear to be unwilling to operate at welding conditions that will keep fume production to a minimum.
Routine Maintenance, Safety Audit and Equipment Inspections
Simple routine maintenance and a formalised system of safety audits on welding equipment has been shown to help reduce the number of safety related incidents within the industry.
Personal Protective Equipment
Welders should ensure that they wear appropriate clothing for the operation they are carrying out. Flame-retardant boiler suits, gloves or gauntlets, safety shoes, leather aprons, etc, should be in good condition and as free from oil, grease and moisture as is physically possible as these can reduce the effectiveness of the safety equipment.