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Industrial dust collection goes modular

Grid concept makes dust and fume collection flexible

With the grid concept, as more equipment is added, the dust collection grid can expand to accommodate.

In various processes, but in welding especially, fume collection has helped make many metal fabricators safer and a more enjoyable place to work. It’s not uncommon to hear stories of major customers who visit their fabrication suppliers, see the smoke and fume, and ask why managers haven’t invested in clearing the air.

Large-scale, local fume collection systems (that is, systems that collect fumes and dust at the source) can be somewhat inflexible. One centralized system can have dozens of welding cells connected with a web of ductwork, all designed with specific airflows. To maintain and balance the proper air speed, the ductwork needs to step up in diameter as it gets closer to the dust collector. In many ways, the fume collection operates as a singular organism; if you change any part, it isn’t as effective.

“For example, if you moved just six out of 30 fume collection stations, you may introduce airflow imbalance issues, if you install the wrong duct sizes,” said Jim Reid, managing director at RoboVent®. “You then continue to make changes [without taking the duct diameter into account], and the system ultimately doesn’t work anymore.”

For this reason, Reid said, much of the dust collection market has been moving away from large ducted systems. Even if a shop has 20 weld cells that could benefit from a centralized system, the company still may opt for many dust collection systems versus one giant one, just so it would have the flexibility to move those cells down the road. Moreover, the company rarely uses all 20 weld cells at once. If, say, only 11 are in use, the entire system draws the same amount of power as if it were collecting dust for all 20 weld cells—constantly. That’s a lot of wasted energy.

For many applications, though, a large dust collection system still makes the most sense. Could a large system be more flexible and less of an energy hog?

Reid and others turned to the wall plug—or, more specifically, the power grid. As energy distribution goes, the power grid is just about as flexible as you can get. Sure, as any user of power-hungry fabrication equipment knows, a building has only so much power flowing to it, and a facility does need certain electrical boxes to be placed in certain areas to ensure needed power levels are maintained. Beyond that, though, a machine installer can unplug a machine, move it to the other side of the shop, and plug it back in. As long as the basic electrical infrastructure can handle it, the machine should have enough electricity to operate.

This is the basic idea behind RoboVent’s Grid™ technology. Instead of wall plugs, the grid introduces fume collection ports with spark arresters—what the company calls Delta Gates™—across the factory ceiling. When a welding, cutting, or other fume-producing process starts, the gate opens; when the process stops, the gate closes.

Snap-together, interchangeable ducts, all of identical diameter, are installed along the column lines in the ceiling. “You can tap into the duct at any port,” Reid said, “and the closest dust collection system will be the one that draws air from that port.” As shown in the figures, the technology is modular. If a company adds more equipment, it can add on to the grid as well.

The system still needs to accommodate for changes in air speed when more or fewer systems are plugged into those fume collection ports. When a new weld cell, for instance, is plugged into the grid, not only does the closest dust collector (all of which are a standard size) automatically draw air from that application, but the system also balances itself to maintain consistent airflow in other areas of the grid.

It does this, Reid explained, with sensors that communicate with variable-frequency drives (VFDs) inside each dust collector. VFDs introduce an infinite number of available blower speeds, along with different levels of power consumption.

When a welding cell starts to weld, a gate in the fume collection port opens, allowing fume to be drawn into the system. Sensors in the grid sense the drop in pressure. This in turn tells the VFDs to ramp up to compensate. “This means the system is continually maintaining constant pressure and constant airflow in every area,” Reid said.

Tapping into an electricity grid, you’re charged only for the power you use. In the grid concept for dust collection, the dust collectors (with their VFDs) provide only the airflow needed, no more and no less, and this depends on how many of those Delta Gates, or ports, are open and drawing fume.

“If you have 12 stations and only six are welding, the other six [fume collection gates] will be closed,” Reid explained, “and the system will modulate in real time to half-speed, so will be using only half the energy.”

Equipment can also be right-sized for the application. For instance, no welding department has 100 percent arc-on time throughout an entire shift, and rarely is every machine being used at once. Knowing this, the fume collection equipment supplier can provide a system based on a department’s average arc-on time. “For most of the time, the system will average at a much lower CFM [cubic feet per minute],” Reid said. After all, why have a massive dust collector that can accommodate umpteen more welding stations, when there’s no way the room could fit more?

Reid added that this follows the theme behind this fume collection technology. “It’s really about using only what you need.”

About the Author
The Fabricator

Tim Heston

Senior Editor

2135 Point Blvd

Elgin, IL 60123

815-381-1314

Tim Heston, The Fabricator's senior editor, has covered the metal fabrication industry since 1998, starting his career at the American Welding Society's Welding Journal. Since then he has covered the full range of metal fabrication processes, from stamping, bending, and cutting to grinding and polishing. He joined The Fabricator's staff in October 2007.