Why Clean Air Need Not Come at the Expense of Hot and Cold AirFriday, May 22, 2009
What plant manager would consciously allow energy costs to go up in smoke? In a very literal sense, such a scenario plays out across a broad range of metal-product manufacturers who choose to vent smoke and other dirty air from welding and cutting operations to the outside. With heating and air conditioning systems working overtime to replace this lost air, gas and electric bills skyrocket on a seasonal basis.
Instead, a new approach is evolving that favors application-specific, turnkey systems that filter air at the source of generation, focusing the solution at a modular level instead of basing it on plant-wide needs. Because point-of-source systems return air to within the building they reduce expenses associated with “make-up” air, helping to slash gas and electric costs. At the same time, smaller, less-energy-consuming motors also contribute to overall savings, as compared to massive centralized fans that vent dirty air outside. As extensive ducting is unnecessary with modular systems, installations costs also drop.
Considering that plants located within air quality districts often require less permitting by not venting polluted air, and that modular systems involve almost zero “footprint,” the arguments for investigating this money-saving option prove quite convincing.
Why waste utility dollars?
The need for smoke removal from manual and robotic welding and cutting, laser and plasma cutting, machining, grinding, polishing and a myriad of other “metal bashing” processes is an ongoing issue among all primary metal suppliers and fabricators. Whether building motor vehicles, ATVs, construction or farm equipment, lawn tractors, fitness equipment or any other of a thousand different parts and assemblies made of metal, manufacturers are now waking up to the significant impact that air filtration has on bottom-line performance.
Traditionally, facilities that produce smoke or oil mists often collect and exhaust the dirty air to the outside with colossal roof-mounted blowers connected through a maze of ductwork from welding areas.
“Any dumping of heated or cooled air to the outside is done so at great expense,” cautions Fergie Haughton, systems sales manager at Clean Air America, Inc. (Rome, GA), a provider of turnkey, point-of-source filtration systems for robotic integrators and integrators of laser cutting and plasma cutting tables.
“Whether it’s zero or 97 degrees outside, bringing in ‘make-up’ air at any volume above 50% is very costly,” continues Haughton. “Some plants run 80-90% make-up air, and that not only throws money out the window but it forces the HVAC system to work extremely hard. We found one new plant with the A/C coils covered with oil and soot from the welding. They were changing filters to the tune of $20-25,000 each month.
Those that suddenly realize they are blowing “comfort” air outside the plant, along with heating and A/C dollars, sometimes cut back on the quantity of air they vent. The consequences become readily visible with increased smoke inside the plant, putting employees’ health at risk.
Another workaround involves running positive pressure within the building to cut down on what gets drawn in from outside. But what really takes place is air gets forced out through any openings in the building.
“In one case we measured the velocity of air rushing out of one plant door at 80-90 feet per minute,” recalls Haughton. “When you turned the handle on the door it actually popped open outward and you could feel the cool air rushing right passed you.”
Venting inside smoke into the atmosphere also sucks dollars from the profit and loss statement in that such practices often draw the attention of air-pollution regulatory districts.
“As soon as you start blowing polluted air outside, somebody in management must apply for a permit with the local air quality authorities and start quantifying what they are putting into the environment,” cautions Haughton. “This can involve lots of expense and headache.”
Zeroing in on the solution
Rather than taking an expensive shotgun approach by managing air filtration on a plant-wide basis, facility managers are starting to target air filtering efforts to only those areas that require them. Benefits to the bottom line accrue quickly given today’s energy costs.
“Heating and air conditioning costs are about $2.00 cfm and $4.00 cfm respectively at our plant,” says Glen Tuplin, Facilities Manager at F&P Georgia, a manufacturer of subframe and suspension components for Honda and Nissan. The firm runs extensive welding, stamping and painting operations within its 200,000 sq. ft. facilities in Rome, GA.
While the original F&P plant was built in 2001 with a traditional air ventilation system,
when the plant was expanded in 2003 Tuplin opted to retrofit a new air filtration system that consists of modular hoods for welding cells and dust collectors to filter and return the air instead of exhausting it to the outside.
“Our exhaust total air volume is 103,000, and because the Clean Air system filters and returns plant air, it was simple math to see that we could save $200,000 annually with their system,” says Tuplin. “This strategy has really paid off. I believe the payback on our system was about one year, something that our own engineers and management would hardly believe.”
Localized control reduces electricity costs
Smoke, grinding dust, oil mist and other production pollutants are efficiently collected and cleaned through modular air filtration systems that often comprise a completely self-contained work center for welding and cutting that includes an adjustable height worktable, shelving, and lighting. No ducting is necessary, and all of the filtering apparatus sits above the welding area so that zero footprint is taken away from the production floor.
“Robotic welders utilize spools the size of 55 gallon drums that weigh about 900 lbs., but since the collector and filter goes over those spools, the air filtration system effectively disappears within the plant,” says Haughton. “This conserves floor space for important things like inventory.”
The use of down-flow filtering technology accounts, in part, for some of the efficiency of these modular systems to do more with less. Incoming dirty air flows downward through filters positioned vertically—as opposed to an angle—to readily shed dust such as found within welding smoke. The filters trap most of the small particles while larger ones fall into a dust-settling hopper. A jet-pressure wave cleans the system's row of filters, further propelling trapped dust to move downward into the hopper.
Point-of-source filtering also allows the use of several small motors to power fans in each of several modules, versus having large, roof-mounted central units. Here, the benefits extend beyond the realm of fluid dynamics into that of accounting.
“Smaller motors consume considerably less energy by themselves, but ‘economizers’ expand upon that savings by switching the blower off when the welding stops,” explains Haughton. “This is done automatically, as the economizer constantly monitors the arc on the welder. If there is no arc flashing for a set amount of time, the power to the blower gets cut.”
Modularization also permits the use of variable-frequency drive technology to control blowers
“A VFD consumes less power because it only draws the current that’s necessary to maintain the airflow that you want,” says Tuplin. “As far as we are concerned, this technology is saving significant energy and also enabling us to avoid spikes during peak usage periods.”
Given the benefits of reduced comfort air costs, more efficient filtering, and lessened blower electricity usage, it comes as no surprise that point-of-source concepts continue to grow in popularity if only from a financial standpoint—with a one-year ROI often possible. Additional benefits of maintaining a clean and healthy plant environment ensure that such strategies are here to stay.View all Industry News