For any manager of a manufacturing plant, tracking and containing utility costs is always a high priority. In a metal fabricating operation — like manual and robotic welding and cutting, laser and plasma cutting, machining, grinding, and polishing — the manager’s task is complicated by the need to balance comfort cooling and heating against the need to remove smoke and particulates the plant atmosphere.

Toyotetsu America’s Somerset, Ky., plant solved this dilemma by installing a point-of-source, closed air-filtration system for its 330 welding stations at the same time as a 2,500-ton heating and air conditioning system. By filtering welding-generated smoke in a closed system that returns treated air back to the plant, Toyotetsu America managers cut natural gas usage by up to 85%, for a savings of close to $60,000 in one month (December) alone. This savings stems from not having to re-heat or re-cool air that is routinely lost when plants exhaust smoke to the atmosphere. As such, filtration systems can work to improve the bottom line of any facility that manufactures metal products.

As a division of Toyota, Toyotetsu America Inc. manufactures automotive stampings and other motor vehicle parts, accessories and hardware. Currently, its estimated annual sales stand at $82.9 million.

Since the plant opened in 1995, the 830 employees worked through hot and humid summers without the benefit of air conditioning. On the floor, over 30 welding robots and 300 spot welders generated smoke that had been partially controlled with wall louvers, high-mounted bay fans, and local exhaust fans that ducted the warm, smoke-filled air to the outside. On the lines, small personal fans attempted to direct smoke away from the faces of the workers, since the exhaust fans could not capture all of the smoke generated from the welders.

To improve working conditions, the plant managers decided to implement a plant-wide air conditioning system. At the same time, a new filtration system was needed to offset the exorbitant expense of cooling new air to make-up for plant air that was currently being ducted to the outside. Coupled with Kentucky’s frequently sub-freezing winter temperatures, the need to keep heated air within the plant was equally imperative from an energy-saving standpoint.

“It is essential that if you opt for air conditioning, that you must also have closed-system air filtration,” cautions Jorgen Brahm, senior vice president at Clean Air America Inc. “Otherwise you are wasting tremendous amounts of money.”

Clean Air America, in Rome, GA, is turnkey supplier for point-of-source filtration systems for robotic integrators, and an integrator 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 while reducing the lifespan of the HVAC system through excessive use.”

Filtration technology
Toyotetsu put out separate RFQs for the A/C and filtration aspects of its plant upgrade. Clean Air America’s returned the lowest bid, likely because it does not use distributors; rather, it manufacturers and installs its own filtration systems. Additionally, in the package it proposed to Toyotetsu, Clean Air America offered reduced maintenance and operation.

For example, hoods at each welding station capture the smoke at its point-of-source, rather than unnecessarily venting the entire floor-space. Smoke then gets ducted to a plenum on the roof that feeds the collectors that use down-flow filtering technology to improve filter life by directing incoming dirty air downward through filters positioned vertically (rather than at an angle) to shed dust efficiently. An on-line automatic jet-pressure wave periodically pulse-cleans the filters.

Electrical demands are lessened thanks to a variable-frequency drive within each collector unit that automatically adjusts the air-flow based on filter loading.

Installation “according to plan”
The installation project started in the spring of 2008 and involved extensive use of a helicopter for the rooftop installation of both the A/C and filtration units. By May 17 air filtration units were placed into service, each possessing 48 cartridge filters within each collector, for a total filtering capacity of 340,000 cfm.

Installation of the air-filtration project was finished, within budget, by the fall of 2008. At the same time, installation was completed for 40, 50-ton A/C units and several smaller pieces. Both systems were tied together via a single building automation system from Trane^® that allowed plant managers to run everything from a centralized computer.

By not having to heat or cool “make up” air, the new filtration system made it possible for Toyotetsu to record immediate utility savings. In December 2007, the Toyotetsu plant consumed 3,921 cubic feet of natural gas, at a cost of $59,371.20, to heat the building. In December 2008, after installing the air-filtration system, only 556 cubic feet were required, dropping the monthly gas utility cost to $8,407.15. Taking into account electric utility savings when running the A/C system during the summer of 2009, annual utility-cost savings are projected to approach $700,000.

Aside from reduced energy costs, Toyotetsu also benefited from a cleaner plant environment.

“Toyotetsu’s staff did a test after installation of the new filtration system,” says Brahm. “They found they had quite a bit more static pressure and a lot more cfms moving through the weld cells, so the personal fans at each weld station were no longer necessary. Additionally, temperature and humidity is now where it needs to be for employee comfort, so productivity may increase, especially during the afternoon shift.”

Given the success at Somerset, Toyotetsu’s sister plant in Owensboro, Ky., later installed closed-system air filtration units, too.