A self-contained air cleaning system designed for weld operations promotes safety and efficiency.
A source capture system with filtration can be locally installed, like this unit from United Air Systems (www.uasinc.com)
Lincoln Electric's portable Mobilflex fume extractor
The recent courtroom drama surrounding a lawsuit over welding fumes raises the question: Just how clean is your shop's ambient air? Industries overall have instituted significant advances in air quality for workers, but there's still room for improvement in many companies.
Four basic methods of air filtration in use today are general ventilation (ambient air treatment or exhaust), ambient filtration, source capture exhaust, and source capture filtration. Each method has particular uses, benefits and drawbacks.
General ventilation (exhaust) systems, using large fans to draw contaminated air from the plant and exhaust it directly outside into the environment, typically through the roof or walls. Such a system generally is used in geographical areas where climate is temperate, heating and cooling costs are a minimal concern, and contaminants in the plant's air do not violate EPA air quality standards and can safely be emitted into the environment. However, this method sucks climatecontrolled air out of the plant, which in colder climates amounts to greatly increased energy costs to keep the plant comfortable for employees. Additionally, without area-specific ductwork, eddy currents of slow-moving air form in corners of the plant, due to structural obstacles restricting airflow and weak air currents generated by poorly placed or undersized fans. In such areas, the chance of employee exposure to weld fumes or other inplant formed atmospheres increases.
The ambient air filtration method is very similar to the general ventilation system with one notable difference. Contaminated air from the plant is collected in the same manner but is forced through a filtration media and returned to the plant. This eliminates much of the increased energy costs for climate control because climate-controlled air is kept inside the building; however, maintenance and cleaning costs increase as the filter media needs to be frequently replaced and the area around the intake must be cleaned often of dust deposits that build up rapidly. Moreover, the method still does not address the possibility of workspace-localized weld fume exposure.
An improvement that better addresses weld fumes is the source capture system, which uses either specially-designed intake hoods, or a containment structure such as a hood or walled area in the welding area. Hoods used in such a system range from large hoods that are mounted above and cover the entire welding area, to small hoods that are installed inches from the welding activity. The captured contaminated air is drawn through a duct system and exhausted outside the plant into the environment. As with a general ventilation system, the plant's climate-controlled air is exhausted out, also, affecting energy costs in colder regions. Additionally, this method is subject to EPA regulations regarding the contaminants exhausted into the environment. Moreover, the ductwork involved in such a system generally is permanent, making production line changes in the plant difficult and more costly. Finally, hoods and ductwork close to the welding activity must be resistant to risk of fire posed by sparks sucked into the system.
The most effective method is source capture with filtration, with filtration equipment incorporated into the process to clean the captured air, which then is returned to the plant. With this system, there is little or no impact on energy costs as climatecontrolled air stays inside of the plant. The filtration units can be mounted near or above the welding activity, eliminating the need for extensive ductwork. Initial investment for this equipment is higher than other systems, but operational costs are low. Most importantly, industrial HVAC specialists and purveyors of fume filtration systems say that cleaning a shop's breathing air can lead to a reduction in health risks to employees, which in turn translates to less absenteeism and improved individual performance.
A proper fume ventilation program does not need to wait for a company to move to new quarters, or even cause lengthy shutdowns of a production line. Moreover, new technologies in blower motor design, such as variable-frequency drive control, incur lower energy costs than units of a decade ago.
Modular fume treatment systems are available to fit nearly anywhere in a plant. For confined spaces, several manufacturers, including Great Lakes Air Systems (www.robovent.com), Lincoln Electric (www.lincolnelectric.com) and Torit (www.donaldson.com/en/industrialair), offer cabinet-sized units that can be rolled next to a work area and operate off of a standard 120V power outlet. A flexible duct extends from the body of the unit, allowing exact placement of the fume intake close to a weld operation.
Fire suppression is a key factor when choosing any fume venting equipment that is to be used around a welding process. Users have to ensure that the extraction opening is not close to the actual welding point so that sparks have a chance of extinguishing before entry, and that intake hoods and ducting can withstand a barrage of hot metal sparks. Additionally, collection units currently on the market include internal systems that incorporate spark arrestors, baffles, changes in air velocity, or other mechanical means to extinguish sparks and prevent accumulated dusts from igniting.
Filtration varies from manufacturer to manufacturer, both in filter media and the method incoming air is passed through the filter. Selection will depend on the amount of use the system is expected to receive, ease of maintenance of the filter and, if there are space constraints, how the filter affects the size of the collection unit. Many units offer automatic filter cleaning systems that extend the life of the filter while reducing the frequency of unit maintenance.
Fume removal systems are available designed specifically for robotic welding stations. Such equipment may include a surrounding curtain to enhance the efficiency of the fume collection within the weld cell, while control of the exhaust motor can be delegated to the robot's computer so that activation and shut-off are tied to the weld cycle. Alternatively, several robot cells can be ducted to a single collector appropriately designed for the intended volume of air.
To illustrate the effect a source capture system with filtration has on a manufacturing facility, consider Lear Corporation's Roscommon Plant, located outside Detroit, Mich. Temperatures during Michigan winters can easily drop into negative numbers outside the walls of the 300 employee, Tier-Two automotive industry supplier. As the plant grew to include 39 robotic welding cells, management recognized the need to improve air filtration systems.
The decision was made to install RoboVent self-contained air filtration systems, manufactured by Great Lakes Air Systems of Clawson, Mich. The units mount above each robotic cell and use no ductwork. According to Bob Fryzel, welding project engineer at the Roscommon plant, "The RoboVent fit seamlessly with our existing welding cells and required no downtime to install. It also saved floor space, and should be easy to move when plant reconfigurations are needed."
Air testing has been done in the plant multiple times since installation of the units, with results always well within the allowable limits set by OSHA.
Fryzel notes that employees have noticed the difference, which he believes positively affects productivity.
"The employees who work in the robotic welding area of the plant appreciate the clean air generated by the air filtration units," he says. Additionally, Fryzel says that the utility costs in the traditionally costly winter months began to plummet as heated air was cleaned and recirculated rather than expelled out of the plant.
"Looking back, I'd say the ability to clean and re-circulate the air and save on utility costs was the biggest — and somewhat unexpected — benefit of the new air filtration system," Fryzel concludes.
Concord Tool & Manufacturing of Mt. Clemens, Mich., is another, smaller automotive supplier. Founded in 1966 as a tool manufacturing company, the company has received more work within the last 12 years involving spot welding, MIG welding and fabricating which, in turn, has brought an increased need for air filtration in the plant, according to Terry Peltier, Concord's plant manager. The company initially used a self-contained smoke eater, and then tried another air filtration system, neither of which was very effective.
Concord's spot welding and high volume MIG welding puts out 20,000 units a week and 1 million inches of MIG welding a month. Two automated robotic welding cells are dedicated to making parts for the GM Astro van. Four additional cells produce GM Trailblazer parts, many of which are made from galvanized stock that incurs more weld smoke and added health issues.
The company also selected RoboVent units from Great Lakes Air Systems. "We didn't have to modify our existing cells," Peltier says. "They (Great Lakes) just came in and measured it up and built to that."
"We also liked the flexibility," adds Neil Dichtel, Concord's vice president of manufacturing. "With the type of ductwork that Great Lakes uses, a company can move a machine with very little downtime. In our company, if we get another big package we may have to move machines. With fixed type ductwork, you pretty much have to rebuild."
While a facility in the American southeast has less concern for cold winters, air quality was still a concern for F&P Georgia, a manufacturer of components for Honda and Nissan. The original plant was built in 2001 with plant air exhausted to the outdoors. When undergoing an expansion to 200,000+ sq. ft. two years later, facilities manager Glen Tuplin recommended switching to a modular system from Clean Air America Inc. (www.clean-air.com) that returned air into the plant.
"Heating and air conditioning costs are about $2.00 cfm and $4.00 cfm respectively," Tuplin explains. "Our exhaust total air volume was 103,000. Because the Clean Air America system filtered and returned plant air (rather than exhausting it to the outside), it was simple math to see that we could save $200,000 annually with their system."
Many different plant operations at F&P Georgia produce dust, aromatics, oil mists and other flammable substances. "We use a stamping oil during our stamping operation," Tuplin explains. "When the metal is welded, the aerosols mix with the oxides and are drawn up into the smoke handling units. There is the possibility that this 'dust' can be ignited by an uncontrolled welding spark." For that reason, Tuplin had Clean Air America include a fire suppression system with F&P Georgia's air filtration system.
Work with an HVAC specialist
When considering fume control for a shop, a plant air specialist will help determine air volumes, unique work area requirements, and any other factors that will affect system selection. "It can be a serious mistake to treat plant air filtration systems as an afterthought," according to Bertil Brahm, president of Clean Air America. "When you take that approach you leave gaps. Or, maybe you use multiple contractors, and everything doesn't come together as you had planned, so they end up blaming one another about whose fault it is while you tear your hair out. The real shame is that a specialist can put it all together for you in a turnkey package."
It should also be noted that, with all three case histories mentioned in this article, the plant managers each noted that employee morale improved after the company's installation of an improved fume control system. Accordingly, production quality and output improved, a benefit achieved without blowing any smoke.