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June 9, 2010

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The main hazards faced by welders at work

Alan McArthur provides an overview of the main hazards faced by welders in their work and suggests the best measures to deal with them.

Welders face many hazards during their work – optical hazards in the form of ultraviolet (UV), infrared (IR) and visible light; injury to the skin from metal spatter, heat and UV light; hearing damage from noisy welding processes and associated activities, such as grinding; respiratory harm, from airborne contaminants; and musculoskeletal problems, as a result of carrying out what is often precision work in a fixed or awkward posture, sometimes in confined environments.

All of these must be adequately assessed and addressed to ensure that operators are working safely and legally. Providing personal protective equipment (PPE) is one way of reducing the risk of hazards causing harm, but employers should not immediately turn in this direction. Following a full risk assessment, they should first consider other engineering and administrative controls, depending on the specific situation and whether other work methods are applicable.

The light-not-so-fantastic

Perhaps the most obvious hazard encountered by welders is light radiation – ultraviolet, infrared and visible light – which is an inevitable by-product of arc-welding processes. The most likely eye injuries from UV/IR radiation are retinal burns and flash burns to the cornea, while ‘arc eye’ – inflammation of the cornea and conjunctiva – is also common. Chronic complaints related to permanent damage to the retina and cataracts can occur over many years of exposure. However, all of these high-intensity light injuries are completely preventable when the proper protection is worn and used appropriately.

New regulations giving workers more protection from the dangers of artificial light came into force at the end of April. The Control of Artificial Optical Radiation at Work Regulations meet a European Union directive to protect workers from harm arising from exposure to hazardous sources of artificial light.1

Even though the arc shield has been around for a hundred years, eye injuries continue to be one of the most common acute conditions suffered by welders. The problem is that while they offer perfectly adequate protection against light radiation, arc shields do not provide clear vision for the user between processes – for example, when inspecting their work – with the result that wearers have to remove them frequently. If they then forget to replace their shield before starting work again, the shield obviously offers no protection.

The invention of the auto-darkening welding filter in the early 1980s went a long way towards addressing these problems. With the shield in the safe ‘down’ position, the welder has a clear view through the welding filter. Within a fraction of a second of the arc strike, the filter has switched to the dark state, automatically returning to the light state after welding is complete. This allows for immediate and safe inspection of the weld, as well as the preparation for the next weld, so there is no need to remove the shield between tasks.

Eye and face protection equipment is covered by these European standards:

  • EN166 (visors); EN169 (shade/ transmittance of filter in scale numbers);
  • EN175 (welding shields); and
  • EN379 (auto-darkening welding filters).

There are four levels of mechanical strength for products – S, F, B (from strongest to weakest), and T, which indicates that the test for energy impact is conducted at extremes of temperature (-5°C to +55°C). EN166 and EN379 feature optical tests to measure the light transmission across the welding filter and light scattering from the filter layers. The optical quality of the product is classified from 1 to 3, with 1 being the best. For auto-darkening filters there are four classifications: optical class, diffusion of light, transmittance and an optional test for angle dependency.

Burning issue

Welders are also at risk from metal spatter – molten metal that can fly up during the process and burn unprotected skin. The hands, arms, legs and feet are particularly vulnerable so should be protected by gloves or gauntlets, spats and jackets (often made from leather). Leather safety footwear should also be worn by welders.
Prolonged exposure to the heat from welding may lead to reddening of the skin of the face, although modern welding shields offer protection against this.

Noise nuisance

Hearing protection should be worn if the welding technique employed is particularly noisy, or if the operative is working in an area where other noisy processes, such as grinding, are taking place.

The Control of Noise at Work Regulations 2005 detail two noise action values and one exposure limit value for employee exposure to occupational noise. If the lower action value of 80dB(A) or 135dB(C) is exceeded, employers are required to make hearing protection available upon request. Where exposure exceeds the upper action levels of 85dB(A) or 137dB(C), employers must provide personal hearing protectors where noise cannot be reduced by other means.

Anything above 85dB(A) is deemed as excessive noise likely to cause hearing damage. However, wearing hearing protection equipment that reduces noise levels to below 70dB(A) can cause other problems, as the employee may experience difficulties communicating or hearing warning signals and, as a result, become isolated from their environment.

Welding shields are available with integral hearing protection, while welders can also select separate ear muffs or plugs to be worn under their shield.

Respiratory issues

Welding generates harmful airborne particles and gases – as a result of the high temperatures involved, the action of ultraviolet light on the air, and the presence of coatings and contamination on the metal being welded. Particle hazards from grinding, paint and other coatings can also be a problem. The welding process itself uses oxygen during combustion, while other gases present may displace or dilute air.

The primary particulate hazard generated during welding is metal fume – particles formed as a result of the intense heat applied to metals. As metals are heated beyond their boiling point, vapour is given off. This vapour oxidises in the air, cools, and then condenses into very fine metal-oxide particles.

The metal fume originates mainly from the consumables used, such as electrodes and filler wire, as well as the base metal. Its composition and toxicity are therefore determined by the type of metal being welded and the electrode used. For example, metal fume from welding stainless steel may contain chromium and nickel – both of which have the potential to cause cancer. However, these materials are unlikely to be present in the fume produced when welding mild steel.

Inhaling metal fume can lead to metal-fume fever. This illness typically manifests itself through symptoms similar to flu, such as chills, nausea, thirst, cough and aching limbs. Recovery is swift, generally within 24 hours. However, frequent exposure to zinc fume (usually produced when welding galvanised steel) produces a temporary immunity that is quickly lost, meaning the symptoms are often noticed more on a Monday, or after a holiday.

Exposure to metal fume also causes irritation to the nose, throat and lungs, but more concerning are the long-term respiratory problems created, which are associated with a build-up of scar tissue in the lungs.

Harmful and irritating gases, such as nitrogen dioxide and ozone, are also formed as nitrogen and oxygen in the air react with the ultraviolet light generated during arc welding. The amount of gas generated varies depending on the welding method and the metal.

As coatings burn, carbon monoxide and carbon dioxide are given off. Applying high levels of heat to contaminants like oils and degreasing agents also generates potentially harmful gases. Degreasing agents can generate phosgene, which was used as a chemical weapon in the First World War.

The workplace exposure limits for some common types of airborne hazard are given in the panel below.

Controlling exposure

Airborne hazards generated during welding fall under the requirements of the Control of Substances Hazardous to Health Regulations 2002 (COSHH). In the case of welding, the control typically applied is local exhaust ventilation (LEV), in the form of an extraction system to draw contaminants away from the welder. These systems must be designed properly, and inspected and maintained to ensure they function correctly. Some systems have fixed inlets but welders often use systems with inlets that they position to suit their work. The position of the inlet significantly influences the protection offered, so welders must be trained in the correct use of the system.2

PPE, in the form of respiratory protective equipment (RPE), is often used as a secondary control measure with an extraction system. In certain situations – for example, one-off on-site jobs – RPE may be the primary control measure.

RPE must be adequate and suitable for the work being undertaken. Different types of RPE offer different levels of protection, and the level of protection selected must be adequate to reduce exposure to a safe level. The RPE must also suit the wearer and the situation; it must fit correctly, be comfortable to wear, robust enough for the environment in which it will be used, and compatible with any other PPE being worn.3

RPE broadly breaks down into two types: those that filter contaminants from the air and those that supply clean air from an outside source (supplied-air systems). The choice between the two will depend on the level and type of contaminants in the air, and the preference of the user. Various items of RPE are available, which are fully compatible with welding shields and offer protection against most common types of fume.

Specifiers and users can typically choose between disposable and reusable RPE. Consideration must be given to the storage and maintenance of reusable types to ensure both welders and the investment in RPE are protected. Maintenance of RPE will involve ensuring spare parts are available, and an administration system to keep records.
Welding is a vital process in many industries and while it does present a range of health and safety issues, the availability of clear guidance and state-of-the-art equipment backed by extensive ongoing research and development means there is no reason why it cannot be safely undertaken.

2    For a previous SHP article on local exhaust ventilation, see ‘Another LEVel’ by John McAlinden, SHP January 2009, Vol.27 No.1, pp51-52.
3    For a previous SHP article on selecting and fitting RPE, see ‘Fit for life’ by Matthew Judson, SHP January 2010, Vol.28 No.1, pp54-56.

Alan McArthur is part of 3M’s technical service team for PPE.

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