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Fab shops can be filled with fumes and dust created by welding, laser cutting and other processes. Unless those contaminants are removed, an unhealthy working environment can result. The traditional way of clearing the air is the use of exhaust fans, but that also removes the heated or cooled air intended for worker comfort.
In determining how to upgrade the airflow system in an existing plant or in installing a system for a new plant or plant addition, the first consideration is the work itself.
DETERMINING A PLANT'S NEEDS
Considering this, Mike Ellis, president of Omaha-based consulting firm Environmental Air Technology, starts by looking at what materials are being welded, cut or ground and what problems the plant anticipates or is experiencing.
"Every application is different," Ellis points out. "We help the client by physically surveying the facility. We're very hands on and take everything from an engineering standpoint, how many exhaust fans they use and the physical layout of the facility. There's much more to it than just poking a hole in the wall and blowing everything outside."
While there are some common elements to all airflow systems, he says 75 percent of the final plan is application-dependent based on what is done in the facility and the plant's layout.
"Typically in the Midwest, the vast majority of our previous clients have been exhausting air contaminants," Ellis notes. "With high energy prices, it's extremely costly to exhaust the air contaminants because when you do that, you're also blowing out your heat. When we go in to design a system, we design a system that will clean the air and that will keep them in compliance with OSHA regulations. We will recycle the conditioned plant air, and doing that is typically about one-third of the bottom-line cost compared to exhausting all the air. We can clean the air. It's less expensive to do that than to exhaust it and create new heat."
Geography does make a difference. "In the southern states where it's warm, exhausting won't properly address the air contaminant problem, but the energy costs are not as big a concern as in the Northern states where heat is an issue," Ellis comments. "In any case, most industrial manufacturers don't air condition their facilities. The only time a manufacturer should air condition is for tolerance where the machine or product must be kept cool to keep the metal from expanding.
"In an industrial environment, there are only two reasons you should exhaust: either extreme temperatures or hazardous fumes like paint fumes or vehicle exhaust fumes," Ellis says. "Welding smoke, grinding dust and general industrial contaminants generally don't fall into those categories."
HOW THE SYSTEMS WORK
These air recycling systems work by removing the contaminated air, running it through a filter that traps the contaminants and then returning the cleaned air to the plant. The exact components used in the airflow system depend on the nature of the work. If the work involves welding something small on tables, Ellis recommends using source capture air cleaners in which contaminants are captured only where they are created.
For welding large items, source capture will inhibit production because the worker will have to keep moving things so the air cleaner reaches all the contaminants. For these applications, it is often more appropriate to use an ambient system in which a series of air-purification systems create a circular air pattern to capture smoke, dust and air contaminants from a whole area after they have been generated.
"The major advantage to the company operator and plant owner of an ambient system is that it requires no effort from the employees like movement of hoods," Ellis says. "The drawback to an ambient system is the capture efficiency is a little lower than with a source-capture system." Ambient systems typically capture only 75 percent of contaminants compared to 90 percent for source-capture systems.
While most contaminants are in particulate form, making them easy to capture with mechanical filtration, some processes create gas fumes. "If you weld stainless steel, you produce phosgene gas, so we put in gas phase filtration," Ellis notes. "It's the same thing with another kind of filter."
EQUIPMENT PLACEMENT
"You never want to have your air cleaning equipment hung more than 12 feet off the ground," Ellis emphasizes. "The air contaminants we're trying to capture become non-buoyant between 8 and 12 feet off the floor. If the air-cleaning equipment is installed in that 8- to 12-foot range, you'll properly capture the contaminants and you won't see a fog hanging throughout the facility. You're going to have to have someone service this equipment once in a while, and the 8- to 12-foot range makes servicing it much easier and much safer."
This routine servicing involves swapping out filters when they become clogged with contaminants. Ellis says filters in self-cleaning cartridge systems can last up to two years.
COST SAVINGS AND WORKER COMFORT
When designing systems, Ellis runs a five-year cost analysis. He compares the cost of exhausting air outside versus recycling it using an air-control system. The typical payback is up to 60 percent savings with the recycling system even though this equipment is more expensive than buying an exhaust fan. The break even point comes after about two years.
Ellis says the return on investment for these systems is huge. In one he designed recently, the company had been spending $15 per hour to exhaust the contaminants and reheat the air. With its new system, the factory now spends only $6 per hour to remove contaminants, including electrical consumption, filtration and the new equipment.
Worker reaction to the installation of these airflow systems is positive. "You get higher production," says Ellis. "Happy welders are productive welders. There will be fewer sick days, better product quality and over-and-above OSHA compliance. There are also potential health insurance savings because workers are not sick as much."
ONE SUCCESSFUL INSTALLATION
American Athletic in Jefferson, Iowa, cuts, welds and drills metal to make high-quality basketball, gymnastics and volleyball equipment for high schools, colleges, professional sports teams and recreation centers. Prior to upgrading its airflow system in 2005, welding smoke created a haze in the building during the winter.
"You could see, but it was dirty and not good for people's health," recalls Production Supervisor Bill Cloninger. "Our main deal was health. We were worried about that because it was affecting the assembly people as well as the welders."
Ellis designed a system for the plant that used five Micro Air ambient hanging filtration units and one dust collector. "Mike measured the facility, the ceiling height, looked at where the welders were and then drew it up on AutoCAD and decided where to put the filtration units," Cloninger explains. American Athletic employees spent a day installing the equipment by hanging the units and running air and power to them.
While Cloninger does not have figures on energy savings, he says the building is now much warmer and easier to heat. Most importantly, he says, "the haze is gone."
When the filtration units were shut down for five days while awaiting new filters, Cloninger heard a lot of grumbling. "When we had them shut down, the workers were grumpy," he says. "They wanted them running again. You could tell they weren't on.
Cleaner air has had several positive outcomes here. "People are happier," Cloninger adds. "The air is clean. The equipment is cleaner. We had all that crud floating around, and it was getting on our finished goods parts, making them look like they had sat around forever when they hadn't. We have computers around the building, and they would get full of that crud; we'd have trouble with them. We don't have as much computer trouble now. They were sucking in all that goop, and now they aren't.
"Inside our building, we have a central air unit that runs all year long in the offices upstairs because of the heat of the paint unit," notes Cloninger. "Before we got the air system, it was always plugging up because it was sucking up all that smoke. We haven't had as much trouble with it since. The smoke was filtering clear up into our front offices where the management is. You couldn't see it in the room, but you could see brown stains on the wall from the soot.
"We also have a dust collector for the chrome polishing operation," Cloninger points out. "All that dust used to go up in the air when they were polishing. The gentleman who does all our polishing doesn't cough like he used to. It's made a big difference in his health. Before it seemed like he had the flu all the time. The area is a lot cleaner now because all that dust has been contained."
Editor's Note: Jean Feingold is a Gainesville, Fla.-based freelance writer. Photos courtesy of Environmental Air Technology, a division of Filter Specialists, Inc., www.environmentalairtech.com.
author: By Jean Feingold