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Air Quality Issues in Automotive Manufacturing

The processes performed to assemble vehicles, plus the fume ventilation systems that keep employees safe, are detailed By TREVOR KENDALL, the technical director of VentMapping and engineering services at RoboVent (robovent.com), Sterling Heights, Mich. The opinions expressed in this article are those of the author. Reprinted with permission: The AWS Welding Journal

robots welding in an automobile factory

Manufacturers in the automotive industry are often looking for ways to maximize efficiency and improve productivity. At the same time, they are tasked with building and maintaining a safer, skilled workforce. However, poor indoor air quality in a facility may negatively impact these goals and, simultaneously, increase health risks of existing staff. Metalworking processes used in automotive manufacturing may expose workers to a variety of airborne particulates. Common processes that create hazardous indoor air quality include welding, machining, cutting and grinding, rubber manufacturing, and plastic processing. Therefore, following established guidelines and using air filtration units are necessary. This article applies to automotive manufacturing, without sufficient mechanical ventilation, in enclosed spaces. Adhering to OSHA Regulations The automotive industry employs more than 425,000 workers in the United States alone, and a great number of those people work in manufacturing. The air in manufacturing facilities, if not properly filtered or cleaned, may be hazardous to worker health and productivity. That is why the Occupational Safety and Health Administration (OSHA) establishes exposure levels for various compounds of hygienic significance, such as beryllium, cadmium, hexavalent chromium, manganese, nickel, and zinc (see Table 1). In addition, the American Conference of Governmental Industrial Hygienists establishes threshold limit values. Overexposure to these elements may cause short-term and/or long-term health problems. Where Do Air Quality Concerns Come From? Many air quality problems in metalworking plants may be traced in part to weld smoke and fumes. Not only may weld fumes result in a visible haze throughout a facility, but the airborne particulates in weld fumes may settle on surfaces, including sensitive electronics and equipment, where the tiny particles may cause significant damage. More importantly, excessive weld fumes may pose serious threats to workers’ health. That’s why workplace policies and procedures that address regulatory indoor exposure limits need to be in place. For example, during manual welding, using fume extraction guns to remove smoke and fumes at the source can help — Fig. 1. Robotic Welding. Because robots operate with tremendous speed and efficiency, more and more processes are becoming automated in manufacturing environments (see lead photo). While there are potentially fewer workers in this vicinity who could breathe the weld fumes, the toxicity may be severe, and overexposure to robotic welding fumes may be dangerous. Proper containment and collection of these fumes are paramount. Laser Welding. Laser welding is a rapidly growing process in manufacturing because of its high level of precision and efficiency. While the initial investment for laser welding systems is higher than most other systems, the benefits are profound in terms of ability and speed. However, laser welding operations incur serious challenges when it comes to weld fumes. While laser welding machines operate in a closed cell, away from a human operator, lasers do produce small particulate that needs to be captured inside the cell. In addition to concerns regarding toxicity and safety, laser welding machines need a fume-free environment so the laser may perform at its optimal level. If fume builds up near the laser, the particles within the fume may refract the laser beam, making the process less efficient and precise. Resistance Welding. Resistance welding, including the common methods of spot and seam welding, relies on the heat generated at the faying surfaces of the metal components between two electrodes. This process generates smoke from surface contaminants, like oils, that burn off during welding. Machining. Machining often requires metalworking fluids or lubricants that may create fine oil mists in a manufacturing facility. Specific health impacts vary depending on the chemicals in the fluid and the size of the particles generated by the manufacturing process. When these mists are inhaled, they may irritate the skin, eyes, nose, throat, or lungs. Prolonged overexposure has been linked to asthma, chronic bronchitis, chronically impaired lung function, fibrosis of the lung, and cancer. Other factors of oil mist to consider are slip-and-fall hazards for personnel. Oil mist may require a collection system to create a safer work environment. Cutting and Grinding. Cutting and grinding metals and other materials used in automotive manufacturing may create large volumes of dust. Carbon fiber and composite dusts are associated with skin irritation, contact dermatitis, and chronic lung disease. When inhaled, some metal dusts, fiberglass, and epoxy resins may do damage to the respiratory system; some are even carcinogenic. This dust may require tools being connected to a vacuum or dust collection system. What’s the Bottom Line? Careful collection and filtration of weld fumes are important for both worker safety and regulatory compliance. With the shortage of skilled workers in manufacturing, a cleaner and healthier environment will attract new employees. Companies may also save money on recruiting, job training, and loss of production caused by high turnover and the effects of poor indoor air quality. In addition, when workers are ill, absenteeism increases; yet when employees come to work and they are not feeling well, the work quality suffers and they are not as productive. With continued overexposure, health complications will likely worsen and healthcare costs may increase. Without compliance to OSHA standards, businesses could face costly legal ramifications due to unsafe working conditions as well. How Do We Begin to Minimize Challenges? Because there are so many variables when it comes to indoor air quality, the first step is to get a clear picture of what your challenges are. By working with a qualified industrial safety professional or industrial hygienist, businesses may determine the concentration and composition of the particulate in a facility and then begin researching the best ways to overcome the challenges. An experienced and qualified industrial ventilation expert may also “map out” and accurately calculate airflow volumes required to optimize air filtration system efficiency and effectively predict resulting fume concentration levels in your facility. Before jumping into air filtration systems, there may be a few engineering controls that can be implemented to help manufacturers begin reducing fumes and minimizing overexposure in facilities. These points are listed below.
  • Confirm the use of the best welding parameters, processes, and consumables for the application.
  • Weld fumes may be reduced by using power supplies that deliver pulsed current rather than a steady current.
  • Adhere to the wire manufacturer’s recommendations regarding the voltage and amperage settings that minimize fume generation.
  • Make sure welds are sized properly. Overwelding will increase fumes present in the facility.
  • Take care to ensure welding surfaces are clean. Oftentimes dust, oil, paint, and other residues on surfaces not only weaken the weld, but also form other fumes that may be toxic.
  • Adjust the position of the manual welder, welding machine, or location of the robotic welding cell to minimize overexposure to weld fumes.
Fume Ventilation Choices The next step in improving indoor air quality is to extract fumes from the building. Source capture is the optimal solution because it removes fumes directly at the source. Outlined below are other options.
  1. Hoods, cells, and arms work well for robotic and manual welding stations.
  2. Fume extraction guns remove the fumes directly at the weld. Modern fume extraction guns can be ergonomic and capture fumes at the source without compromising the quality of the weld. This is a useful option for welders working with large weldments that cannot be hooded. Fume guns also work well for welders who need to be mobile or work in tight spaces.
  3. Fume arms are a versatile solution for capturing dust and fumes. They are designed with movable arms that may be put into various movable positions to best capture fumes as weldments and welding positions change. Fume arms are not particularly cumbersome, but they do need to be moved into position by the welder.
  4. Crossflow and downdraft tables or backdraft hoods are a good option for welders working with smaller parts in a fixed location. This source capture system pulls contaminated air away from the welder’s breathing zone and returns clean air into the workspace.
  5. Unfortunately, fumes cannot always be captured at the source. In these cases, ambient air filtration systems are necessary for regulatory compliance. In some cases, plants will need to use both source capture and ambient extraction systems for the greatest effectiveness.
In addition, per OSHA Publication 3151, personal protective equipment is used when engineering, work practice, and administrative controls are exhausted or not feasible. Considerations for Ambient Air Filtration Systems A variety of ductless or ducted ambient air filtration systems are now available and have become a popular way of cleaning the air in conjunction with source capture equipment. It’s important to understand that ambient systems alone don’t protect welders from direct fume exposure, but they can be effective at lowering overall fume concentration levels and improving plant air quality for nonwelders. How Much Airflow Do You Need? It’s important to correctly calculate the amount of air required for an ambient system. Air flow is quantified in ft3/min, but typically measured in ft/min. The amount of airflow required directly affects the cost of an ambient ventilation system and the amount of energy it will consume during operation. An experienced ventilation professional should perform an in-depth analysis of the welding area to design an effective ambient air filtration solution. As an example, facilities may not be able to use the same air filtration unit for a grinding station that is being used for a welding station. Typically, grinding stations produce larger, heavier particulates so the dust collector must maintain a higher air velocity to prevent the contaminants from falling out of the air stream. Similarly, it’s important to keep some contaminants from mixing in the same air flow stream. A qualified industrial safety professional or industrial hygienist would be able to give the best advice on the most effective and efficient air filtration systems to use to keep employees safe and costs down. Filter Media Selection There are several kinds of filters that may be used to clean the air in manufacturing facilities. To get the best results, it’s important to ensure the most appropriate filters are being used for specific processes as well as consider the composition and volume of particulates being collected. High-efficiency particulate air (HEPA) filters are becoming increasingly popular in facilities with welding. Standards for HEPA filters are set by the U.S. Department of Energy. HEPA filters provide 99.97% efficiency at 0.3 microns. Make sure filters themselves are of high quality. In welding, filters made of flame-retardant material may be helpful in reducing the risk of air filtration unit fires. In oil mist collection, a packed-bed or coalescing filter may be a good choice; this filter pulls oil out of the air and allows the oil to drain off. It works even when saturated, whereas other filter media become much less effective when saturated. Activated carbon air filters may be effective at filtering volatile organic compounds and overwhelming odors from the air. For best results, choose filters that will not only be effective at removing contaminants from the air, but also have a longer filter life, lowering long-term costs. Direct Fumes Away from Breathing Zones Plants using manual welding need to keep in mind the location and position of its welders. Improper placement of air filtration units could draw fume and smoke through the welder’s respiratory zone, reducing the overall effectiveness of the system and potentially doing more harm than good. Long-Term Maintenance Costs To avoid repetitive maintenance costs, make sure to invest in a well-made system upfront. Durable, heavy-duty systems will feature sealed cabinets made of resilient materials and protect internal components from any potential hazards. Some systems may be equipped with “smart” controls that help companies keep track of the levels of particulates being collected. They may also save on energy costs and predict maintenance for better planning. Conclusion Taking steps to improve air quality safeguards employee health, ensures regulatory compliance, and improves the bottom line. Acknowledgments Thanks to the American Welding Society’s Safety and Health Committee, SH1 Subcommittee on Fumes and Gases, and SH4 Subcommittee on Labeling and Safe Practices for reviewing this article.

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