Confined Spaces

A confined space is usually small and difficult to get into and out of. As such, the normal hazards of welding are intensified when carried out in confined spaces. Asphyxiation is the main danger and the most common cause of death in confined spaces. A formal 'safe system of work' should be followed at all times.

Many of the everyday hazards encountered in welding can be exacerbated if the work is being carried out in a confined space. A significant number of deaths involving people working in confined spaces occur each year, with asphyxiation being a major cause of those deaths, so extra vigilance is needed.

One dictionary definition of 'confined' is 'imprisoned', and a confined space is one where the means of entry and exit are restricted. The space itself does not have to be small and cramped, but if it is then there is likely to be restricted ventilation, which can allow the build up of a hazardous atmosphere. Then it may be described as 'confined'. An example of confined spaces would be a storage tank, it may also contain, or have contained, toxic, flammable or hazardous substance, vapour or gas.

So it is clear that working in such spaces requires a greater awareness of potential hazards and safe working practices than normal.

Welders working in enclosed spaces must be properly trained, equipped and supervised. Additional protective and monitoring equipment over and above that normally necessary may be required when welding in a confined space. It is also recommended that a formal 'safe system of work' should be followed at all times.

Major Hazards

When welding in confined spaces some hazards become more intense and require more attention. These are ventilation and the maintenance of a safe working atmosphere, the risk of falls or entrapment, the risk of electric shock, the risk of fire or explosion, and radiation or heat problems.

Ventilation/Fume

Maintaining an atmosphere that is fit to breathe inside a confined space can be difficult as fumes and gases may build up and displace the oxygen present. This presents one of the most insidious hazards, since lack of oxygen, or the presence of a toxic, explosive, flammable or inert gas cannot be seen and more often than not cannot be smelled either. The danger is that an operator could unwittingly enter what seems to be a perfectly normal area and quickly find out that it is not, and by then it may be too late!

Falls and Entrapment

Due to the difficult and restricted entry and exit it is easy for someone to trip, stumble or fall whilst getting into or out of the space. Merely slipping on a wet or greasy floor inside a confined space can be serious, the casualty could become trapped in a position where his breathing may be restricted and he may suffocate.

Electrical

Particular attention should be paid to electrical safety when welding in a vessel or tank. The metal of the enclosure will become part of the welding circuit and you may be standing on part of the vessel that is electrically 'hot' and any metal you touch may also be part of the welding circuit.

Radiation and Heat

When welding inside vessels made of reflective metal or alloy, for example, aluminium or stainless steel, the problems presented by glare and UV radiation can intensify. The risk of getting arc burns to the skin or 'arc eye' or arc flash due to reflected radiation increases.

Fire and Explosion

There is a great danger that flammable gas and vapour may collect in a confined space, and these may ignite when welding or cutting takes place leading to an explosion.
Fuel gas processes also increase the risk of fire and explosion particularly if leaking equipment is left in the confined space, allowing a build-up of fuel gases or oxygen. Any heat from welding or cutting, or just an electric spark, can then result in a fire or explosion.

Precautions

Ventilation/Fume

It is essential that the atmosphere in any confined space is tested and passed fit before entry. An atmosphere fit for working in is one that is breathable (i.e. has about 21% oxygen) and there are no toxic, flammable, or explosive gases or vapours present. It is also important that there is no enrichment of the atmosphere with inert gases or oxygen.

Evaluation of confined space atmospheres must include measurements for oxygen plus any other relevant gas.

Falls and Entrapment

Precautions to avoid trips and falls are basically common sense, vigilance and good housekeeping. Keep floors inside the space as dry, grease-free and free from obstructions as far as possible.

Electrical

To reduce the risk of electric shock, it is recommended to locate electric welding power sources outside and ensure all cables entering the area are properly insulated.

Welders and others should make sure that they are insulated from the workpiece and grounded by dry insulation.

Radiation and Heat

Wherever possible use radiation and heat shields to prevent burns.

Take plenty of replacement fluid when working for lengthy periods in hot conditions to avoid dehydration and possible heat exhaustion.

Fire and Explosion

When using fuel gas processes extra care should be taken to ensure that the equipment is not leaking, as this can result in build-up of gas and possible explosion.

Oxygen should never be used to enrich the atmosphere in a confined space. It is a severe fire and explosion hazard.

Safe Working Systems

All those engaged in working in confined spaces should work to a formal, written, 'safe system of work' that defines precisely what happens before, during and after each job, and assigns responsibilities for all actions.

A safe system of work should require assessment, measurement and control of risk at all stages. A preliminary assessment of the risks involved in carrying out the work would include such things as:

- What was the area or vessel used for?

- Could there be any chemical or physical hazards present that may require cleaning or purging?

- What ventilation might be required?

All personnel should be trained for the conditions they will be required to work under and this training must include an appreciation of all the hazards of working in confined spaces.

No welder should be expected to work alone.

Regulations

There may be regulations regarding work in confined spaces embodied in law in the country in which you are working. If not, the health and safety authorities will have available written approved codes of practice or recommendations for safe working in these conditions. Such documentation should be sought and adhered to whenever possible to ensure you are complying with the law or working in an approved and safe manner.

Special regulations may apply to purging of tanks, which have previously contained flammable or explosive materials.