Busting Dust

One of the chief operational challenges facing concrete crushers is suppressing dust that can cause safety and health concerns.

At fixed plant sites, most operators quickly assess what will need to be done to keep dust down, and a system can be put in place.

Dust suppression can be trickier at temporary job sites, where local requirements and ordinances can differ. Fortunately, equipment does exist to help contractors stay in compliance with the various standards that exist.

Romero Construction, Long Beach, Calif., faced a dust suppression challenge when it undertook a task to crush concrete on site in Long Beach, where air quality standards for industry are as tough as in any other part of the country.

The company was awarded a contract to crush and remove concrete and asphalt at the 10-acre site of a former shopping center. Before setting up shop, the firm needed to secure a permit from the South Coast Air Quality Management District (SCAQMD).

The agency’s first set of requirements spelled out for Romero to set up three baghouses to collect dust and to limit its production to just 400 tons per hour of crushed material—less than half of the plant’s full production capacity.

Romero sought alternatives both to the use of expensive baghouses and to the production limit. The contractor worked with Cooley Equipment, a dealer of dust suppression systems made by NESCO, Mendham, N.J.

Cooley was able to design and install a NESCO water spraying mist system to control dust not only at the crushing stage, but also at key points along the screens, hoppers and conveyors, as well as the stockpile.

Prior to the Long Beach project, the SCAQMD had never permitted a spray mist system to control crusher dust, according to a NESCO news release. However, George Koch, a consultant retained by Romero Construction, was able to prepare a permit application that included negotiated language that allowed for the use of the NESCO spray system, subject to testing and inspection.

The system eliminated visible dust emanating from the crusher at its Long Beach site, and the SCAQMD allowed Romero to more than double its original production limitation to 1,000 tons per hour.

During a presentation at the 2002 ConExpo/ConAgg show, NESCO’s Mark Kestner noted that an increasing number of companies are beginning to realize the importance of dust control. "Some see it right away—they get it," Kestner remarked, citing Vulcan Materials Co., Birmingham, Ala., as one such company. "There’s another set of contractors that won’t budge and think dust is a necessary byproduct, and the final third is sort of in the middle," he commented.

Kestner admitted that, unlike high-volume crushers or impressive heavy iron earth-moving machines, "This is not equipment that contractors get excited about."

But Kestner says that dust suppression should be viewed as important not only because permits sometimes require it, but also because of its overall safety, health and productivity benefits. "Good dust control equals good process control," he remarked.

NESCO spray systems, known as Dust Pro and Dust Boy, are advertised as eliminating visible dust while using less than half a gallon of water per ton of material processed. The systems feature high-pressure spray nozzles, remote electronic control and heavy-duty fabrication. They do not use chemicals or compressed air.

The company also makes wheel washing systems to prevent trucks from tracking mud and dirt off site—thus creating a different type of potential dust hazard.

The DirtSquirt system uses about 20 gallons of water per truck, according to NESCO. The product is advertised as one that can stave off "complaining phone calls" and "hassles with City Hall."

Like many of the other NESCO systems, the wheel washing system is portable and can be installed without a great deal of site preparation.

The author is editor of C&D Recycler and can be contacted via e-mail at btaylor@gie.net.