Asra Jawaid 2018-02-07 23:51:26
SIMPLY leaving the shop door open for ventilation isn’t always enough to prevent the inhalation of dangerous welding fumes. This is particularly true when hardfacing, welding stainless steel, or doing projects that require high arc-on time. Hardfacing also involves heavier flux-cored wire. “Hardfacing is an application that has higher fume-generation rates than just joining two pieces of metal together,” says Allan Hilbert, product manager for Filtair equipment at Miller Electric. “When you’re doing overlays and rebuilding surfaces on larger pieces of earth-moving equipment, there’s a lot of welding at any given time. And during that time a worker could be overexposed very easily.” A welder’s exposure can only be determined by taking a sample of the welder’s breathing air during the workday, which is essential when hardfacing, working with stainless steel, or joining other materials that require special ventilation products. The two most common exposure limits are permissible exposure limits (PEL), which were established by the Occupational Safety and Health Administration (OSHA) and Threshold Limit Values (TLV), which were established by American Conference of Governmental Industrial Hygienists (ACGIH). Hilbert believes the best way to prevent potential problems with welding fumes is to enact OSHA guidelines known as the Hierarchy of Controls (Fig. 1). The hierarchy includes elimination and substitution, engineering controls, administrative and work practice controls, and personal protective equipment (PPE). Elimination and substitution remedies are designed to prevent potentially harmful exposure. For example, you might consider switching to shielded metal arc welding (SMAW), to gas metal arc welding (GMAW) with a solid or metal coated wire, or opt to use low-manganese filler metal. “This could mean changing consumables away from heavier wire,” Hilbert says. “Take a close look at your process and what you’re using; there may be another way to accomplish your goal with less fume generation.” Engineering controls involve physical changes to the workplace. These can include isolation, such as enclosing the welding process, or ventilation, which includes capturing material at the source (local exhaust ventilation), and/or ambient collection. “Ventilation is the most common precaution,” Hilbert says. “There are a number of ways to achieve this.” Depending on the application and the workspace, natural ventilation, mechanical ventilation, or local capture devices can be used to keep fumes and gases out of a welder’s breathing zone. Administrative and work practice controls are those that require the welder or employer to do something. For example, welders should reposition their head and/or the work to keep their head away from the fumes. They should also reposition their body so that the air flows from back to front, away from the breathing zone. Employers can also introduce policies to ensure that welders are not overexposed to fumes and gases. “There are some companies that have gone to vision tests to make sure their welders could see well, because guys had their heads too close to the weld,” Hilbert says. To learn more, see the AWS Ventilation for Welding and Cutting Safety and Health Fact Sheet and clause 5 of Z49.1 Safety in Welding, Cutting, and Allied Processes. If OSHA mandated engineering and workplace controls cannot keep exposures below applicable limits, then welders must wear personal protection equipment (ppE) such as NIOSH-approved respirators. Each type of respirator is given an assigned protection factor (APF), which is the level of protection it will provide when used properly, together with a written respiratory protection program. To maximize the benefits of respiratory protection, it’s also important to ensure each employee has selected a respirator that provides a comfortable fit and doesn’t negatively impact productivity. Respirator inspection is an important precaution that can help ensure that the welding operator is fully protected. To learn more, see the AWS Respiratory Protection Basics for Welding Operations Safety and Health Fact Sheet and clause 4.5 of Z49.1 Safety in Welding, Cutting, and Allied Processes. What are welding Fumes and Gases? Welding fumes are made of very small, and thus easily inhaled, solid particles, that come from welding consumables, base metals, and base metal coatings (Fig. 2). In addition to the shielding gases used to protect and enhance the properties of the weld, gases are sometimes the byproduct of the welding process itself. The amount and composition of these fumes and gases depend on filler metal and base material composition, welding process, current level, arc length, and other factors. For example, the welding of mild steel produces fumes that commonly contain iron, manganese, and silicon, although the electrode or base metal may produce fumes with other compounds as well. Fumes generated from the use of stainless steel and hardfacing products are likely to contain chromium or nickel which have been reported to cause asthma as well as lung cancer in non-welding processes. Above recommended levels of manganese can affect the central nervous system, resulting in irreversible coordination problems, difficulty speaking, and tremors in the arms and legs. Welding galvanized steel can potentially expose welders to dangerous levels of zinc. This can lead to “fume fever” which causes symptoms like those associated with the common flu. The most common shielding gases used in arc welding include argon, helium, and carbon dioxide. While these gases usually do not pose a health risk, they can displace oxygen in the surrounding air. This, in turn, can causes dizziness, unconsciousness, and even death. Excessive levels of carbon monoxide can also be dangerous. If a welder feels overexposed to the fumes, he or she should stop welding and go outdoors for some fresh air immediately. If the unease persists, consult a doctor. The supervisor and any co-workers back at the shop should be aware of the situation and how best to avoid the hazard. It’s best to suspend welding until the situation is resolved. For more information, refer to OSHA’s Controlling Hazardous Welding Fume and Gas Fact Sheet. Asra Jawaid served as a contracted blog writer for the American Welding Society from 2016–2017. Article courtesy of American Welding Society, reprinted from their website, https://awo.aws.org/2017/05/welding-fumes-reclassified-asgroup-1-carcinogen/. Online Resources OSHA permissible Exposure limits—annotated tables https://www.osha.gov/dsg/annotated-pels/threshold limit values http://www.acgih.org/tlv-bei-guidelines/policies-procedures-presentations/overview AWS ventilation for welding and Cutting safety and Health Fact sheet https://www.aws.org/library/doclib/fs36-201404.pdf?_ga=2.166017150.1758031131.1516047652-1308510120.1515096341 ANSI Z49.1 safety in welding, Cutting, and allied processes https://app.aws.org/technical/AWS_Z49.pdf?_ga=2.196416492.1758031131.1516047652-1308510120.1515096341 AWS respiratory protection Basics for welding operations https://www.aws.org/library/doclib/fs38-201309.pdf?_ga=2.196571372.1758031131.1516047652-1308510120.1515096341 OSHA’S Controlling Hazardous welding Fume and Gas Fact sheet https://awo.aws.org/wp-content/uploads/2017/05/OSHA_FS-3647_Welding-Fumes-and-Gases.pdf
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