MMA Welding

There are many different types of safety hazards produced by MMA welding. The main risks are from electric shock, welding fume and radiation. Hazards may be present before, during or after welding.

The MMA 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 MMA 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 at what stage they may occur.

All the potential hazards need to be identified, measured where appropriate, assessed, and remedial or preventative measures put in place wherever necessary. It should also be remembered that different hazards may have the same effect on the body and so interactions between hazards should also be considered.

Types of Hazards in MMA Welding

The hazards encountered in MMA welding may be sub-divided into groups as follows:

  • Electrical and Magnetic Fields
  • Radiation
  • Heat, flames, fire and explosion
  • Welding fumes

Electrical Safety & Magnetic Fields

Power sources for MMA welding and associated pieces of equipment, such as electrode holders, leads and connectors all require electricity to operate. Power sources may be AC or DC, operate from a three-phase supply, from industrial single-phase supply or even from a domestic power supply, and are often designed to operate with high open circuit voltages (OCV).

Primary and secondary connections should be completed by competent persons.

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 MMA welding is started to reduce the risk of an electrical accident:

- Only qualified personnel should be allowed to install MMA equipment. Whoever does install  the equipment must ensure that it complies with national standards, any local regulations, the manufacturer's instructions and workpiece 'earthing' requirements.

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 on what to do 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 practices will help prevent electrical accidents:

- When welding is temporarily interrupted electrode holders should be placed where they are safe and the electrode cannot accidentally arc. It is safer if the electrode is removed from the holder.

- If welding is to be stopped for any length of time the welding set should be switched off.

Radiation

Arc 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). MMA welding does not produce ionizing radiation.

Burns to the skin and eyes due to exposure to arc radiation may not become apparent until some time after welding has ceased.

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 MMA welding. The welder should 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.

Fume consists of particulate fume, the part you can see, and gaseous fume, the part you cannot see, but can sometimes smell.

Particulate Fume

Particulate fume is mostly formed from vapourisation of the welding consumable. Fume from MMA welding aluminium is mostly aluminium oxide, chlorides and fluorides.

Gaseous Fume

With MMA welding there is very little gaseous fume produced under normal circumstances.

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 MMA welding processes, like all others, generates noise. Some power sources emit more than others and some additionally may generate higher frequency noise that can affect hearing.

Manual Handling

Back injuries are one of the most common industrial injuries suffered by workers. Cartons, packets, or tins of electrodes stored high off the ground can create a 'falling' hazard.

Confined Spaces

Any of the hazards associated with MMA welding will be exacerbated when welding is carried out in a confined space.

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.