IX Международная студенческая научная конференция Студенческий научный форум - 2017

Incredibly high temperatures and a bright arc flash aren’t the only two dangerous elements of welding. Harmful ultrafine particulate matter generated during welding operations can pose major health risks to welders. Modern extraction and filtration systems are designed to provide effective industrial safety. In many cases, fabricators find that the added filtration equipment contributes to increased productivity as well.

Welding emission reduction is something that interests all metal fabricators, and today’s welding technology does a good job of removing welding smoke that can contribute to health risks. This can be misleading, however.

At the nanolevel, invisible to the human eye, the concentration of particulate matter can pose a great risk to welders. Studies show that welding fume particles are mostly smaller than 0.1 micrometer, which makes nearly all welding fume particles respirable. They can penetrate deep into the alveolate region of the lungs during inhalation and remain firmly fixed there.

Dust particles can be divided into three groups according to their size:

1. dust particles up to 100 micrometers (µm), which were formerly classified as «total dust»;

2. particles less than 10 µm, which includes particulate matter that penetrates the pulmonary vesicles (alveoli) and can accumulate there;

3. particles smaller than 0.1 µm, which also are called ultrafine particles. Of all welding fume particles, 98.9 percent are less than 0.4 µm in size.

Welders exposed to welding fumes on an ongoing basis run a significant risk of health-related problems. The most common symptoms include fatigue, breathing difficulties, shortness of breath, bronchial diseases, manganese poisonings, lead and cadmium oxides, episodes of metalworkers’ fever when welding galvanized materials, and even damage to the central nervous system. The harmful particulate matter generated during welding of nickel, chromium, and cadmium compounds can be considered carcinogenic.

Additional health risks are associated with filler materials. Ninety-five percent of harmful substances that make up welding particulate originate from the filler metal, and only the remaining 5 percent comes from the parent metal.

What safety measures should be employed to protect metal processing workers from such risks?

Conducting a risk assessment

The first question in a risk assessment focuses on what materials and welding procedures are used. Gas metal arc welding (GMAW) and arc welding with coated rod electrodes demonstrate the highest risk potential for producing dangerous particulate matter. The most hazardous particulates are generated in welding processes involving chrome-nickel steel.

Proper ventilation measures should be used for processes with at least a medium hazard class rating as well. This includes gas tungsten arc welding (GTAW) of toxic and irritant materials, such as manganese and copper oxides.

Using a different filler material when welding can help to mitigate the risk, but metal fabricators should use extraction and filtration systems to eliminate as much harmful particulate matter from the ambient air as possible.

At-the-source welding fume extraction

With the potential hazards identified from the assessment, the fabricator can turn to controlling emissions. The most important factor when using clean air technologies is this: Welding fumes should be contained at the point of origin.

When properly used, indirect capture methods can help to prevent the spread of harmful substances in the ambient air. Low-powered vacuum source extraction systems are used most frequently in manufacturing settings.. They capture harmful substances with the use of extraction hoods and flexible extraction arms at a distance of about 1 foot from the point of origin.

Extraction systems integrated into welding torches, connected directly to the welding gun, and funnel- or slit-shaped, high-powered vacuum source extraction systems that are held in place by magnets offer an alternative to low-powered vacuum source extraction systems.

In automated welding, extraction hoods with large lateral coverage provide protection against crossflows. The size depends on the operating area of the robotic welding cell.

Welding fume extraction for larger areas

Source extraction systems are frequently pushed to the limit when used in conjunction with the welding of large workpieces at multiple sites. Welders might not put the ventilation device in the right position, or they simply can’t reach a particular area of work.

Worker safety can be maintained in these cases with room ventilation systems in addition to source extraction systems. They also help to protect nonwelders in the production facility from exposure to harmful substances and improve the quality of air in the working area.

Welders who have their heads buried in welding fumes should consider additional respiratory protection equipment. For instance, a welding helmet with an autodarkening filter can be provided with an attached ventilation unit.

To ensure further industrial safety, a metal fabrication facility should consider high-quality filtration for recirculated air from room ventilation equipment. This type of filtration ensures that the air supplied from the filtration system can be recirculated into the working area without the presence of dust.

For example, metal fabricators should use only filters that offer the highest efficiency when welding chrome-nickel steel. The filters should be certified.

This recirculation of air also can contribute to energy savings in the winter because the shop is not required to heat the air from the ventilation equipment; it has been heated already upon discharge from the equipment.

Focus on efficiency

The discussion of industrial safety should not be limited to costs because a safer work environment can be linked to increased worker productivity as well.

Workers that are effectively protected against inhaling hazardous particles do not display as much fatigue or shortness of breath as workers exposed to welding fumes on a continuing basis. In the long run, those working in industrial environments with clear air also are less likely to suffer from bronchial diseases, manganese poisoning, and other illnesses that might affect them in dirtier work environments.

Healthy workers have fewer job interruptions and health-related absences. They also are likely to have higher rates of job satisfaction.

Summary

Choose a hood design in the following descending order of effectiveness:

Enclosing hoods are by far the most effective in controlling welding contaminants; however, they restrict access and force reconsideration of material and product handling.

Capturing hoods are less effective than enclosures but can be adequate if properly used.

General ventilation filters the air in the entire room to reduce the airborne fume concentration. Consider this method only if source capture is not possible and/or practical. Because general ventilation does not remove fume at the source, it does not limit exposure at the worker’s breathing zone.

Adequate ventilation removes the fumes and gases from the welder’s breathing zone and general area. It prevents overexposure to contaminants. Approved respirators may be required when ventilation is not adequate. To minimize worker overexposure to fumes and gases:

• keep your head out of the fumes, and do not breathe the fumes;

• reposition the work and your head to avoid the fumes;

• choose the correct ventilation method(s) for the specific operation;

• use enough ventilation, exhaust at the arc, or both, to keep fumes and gases from your breathing zone and the general area;

• understand what is in the fumes;

• have a technically qualified person sample your breathing air and make recommendations;

• keep hazardous air contaminants below allowable limits;

• wear the proper respirator when necessary.

References:

1. HSE - Health and Safety Executive, Controlling airborne contaminants at work: A guide to local exhaust ventilation (LEV). 2nd ed. HSE Books, 2011.

2. Industrial Ventilation. A Manual of Recommended Practice. American Conference of Governmental Industrial Hygienists, Cincinnati, Ohio.

3. Karpinski, E.: Worker Exposure to Welding Fumes and Gases in Federally Regulated Workplaces. Human Resources Development Canada - Labour Program.

4. EU-OSHA - European Agency for Safety and Health at Work EU-OSHA, Workplace exposure to nanoparticles, European Risk Observatory Literature review, no date.

5. HSE - Health and Safety Executive, EH40/2005 Workplace exposure limits, 2011.

6. ACGIH, Industrial Ventilation: A Manual of Recommended Practice for Design, 27th ed, 2013.

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