January/February 2014
Mobile equipment designed for dust control can be more efficient and cost-effective on demolition sites than rudimentary measures such as hoses and sprinklers, manufacturers say.
By Diana Mota
Demolition work and dust go hand in hand, says Michael Taylor, executive director of the National Demolition Association (Doylestown, Pa.). Taking down a structure, whether with explosives or with heavy equipment, creates dust, as do the crushing, sorting, loading, and hauling of demolition debris, he explains. “The demolition industry works very hard to control dust on our job sites, both to protect our valuable work force and to be a good neighbor to the area around our sites.” Uncontrolled, the particles can remain airborne, affecting air quality for workers and those in surrounding areas, says Larry Matus of Gensco Equipment (Toronto).
Uncontrolled demolition dust can create environmental, health, and safety risks, says Edwin Peterson, CEO of Dust Control Technology (Peoria, Ill.). Safety risks include explosions and reduced visibility for workers (see “Keeping the Lid on Dust” in the January/February 2009 Scrap). As for health risks, airborne dust particulates can irritate airways or exacerbate existing health conditions such as asthma or emphysema, he says. Long-term exposure can cause lung cancer or silicosis, a result of prolonged inhalation of silica dusts, which are a basic component of sand and granite, he adds.
Dust control in demolition can be more challenging than dust control in a fixed location like a scrapyard. Demolition work moves from project to project and often must occur amid populated commercial or residential developments, says Patrick Duhaime, product manager of CW Environmental, a division of Company Wrench (Carroll, Ohio). When demolition dust settles on neighboring homes and businesses, it can create a nuisance, says Mike Dokell, division manager for commercial, residential, and interior demolition for Cherry (Houston). “We have to be respectful of our neighbors and local ordinances” or other regulations governing air quality. Further, whereas scrapyard dust generation typically occurs at predictable spots in the yard, such as where material is transferred or shredded, demolition sites change as work progresses, Peterson says, so flexibility is essential. Equipment must be mobile and easy to relocate, he adds.
Not every demolition company relies on specialized equipment for dust suppression. Some use a lawn sprinkler or assign a worker with a garden hose or fire hose and spray attachment to keep the dust down. The equipment manufacturers point out what they consider the shortfalls of these approaches:
They only control surface dust. Wetting a surface with a handheld hose or movable sprinkler can prevent dust on the ground or existing surfaces from becoming airborne, Peterson says, but once the equipment breaks a new surface during demolition, the material below the surface becomes exposed, creating additional airborne dust.
They can use too much water. “Site saturation is one of the things that must be managed,” Dokell says, “because too much water can create runoff, and we are concerned about what that runoff might contain.” The equipment manufacturers say their dust-control machines use less water than fire hoses and sprinklers and are designed to not oversaturate the site.
They’re not effective. Fire hoses in particular are inefficient because they use considerably more water than necessary, quickly turning a demolition site to mud, Gensco’s Matus says. Cherry’s demolition teams use charged fire hoses for small demolition jobs, Dokell says, but “if we anticipate a lot of dust, fire hoses are not an option because they’re not as effective. You don’t get the amount of coverage that you need.” Peterson agrees. “If you’re pulling apart a multistory building, you’re never going to capture airborne dust [from the higher stories] because a hose can’t reach that high.”
They’re not as safe or cost-effective. A fire hose could control the dust created while demolishing a one-story building, Peterson says, “as long as you keep workers out of harm’s way,” but having a worker hold a fire hose near the demolition work could put him or her at risk of being struck by falling debris, he says. He also suggests that companies compare the cost of paying an employee to hold a hose or move a sprinkler with that of purpose-built equipment that can do the same thing unattended.
Equipment Features
Manufacturers of dust-control equipment offer a variety of machine options for use at demolition sites. Prices vary based on model and features, from less than $10,000 for a model that does not oscillate to $100,000 or more. All the companies interviewed say their systems use small amounts of water, are easy to maintain, and are portable. Features to consider include the following:
Method of water dispersal. Each company takes a slightly different approach to sending small droplets of water across a broad area. “The act of colliding water droplets and dust particles serves to increase the specific gravity of the dust until it can no longer float in the air,” Peterson says. “That’s what drives it to the ground.” Dust Control Technology’s DustBoss machines use an atomized spray system that launches water droplets ranging in size from 50 to 200 microns. The ducted-fan system produces a laminar flow, meaning the water droplets move in parallel layers without disruption between the layers, Peterson explains. “This produces an entrainment effect,” he says, “drawing water droplets along with the air flow so they will collide with airborne [dust] particles and drive them to the ground.” Fans running at 7.5, 15, 25, or 60 hp—depending on the model—disperse as little as 1.4 gallons per minute or as much as 39 gpm (with a 10-hp booster pump) through brass nozzles, with nylon, stainless, midget, or ceramic nozzles optional. Standard units come with 30 nozzles, but the firm will configure the machines to suit specific dust-generating materials or conditions, Peterson says. “The nozzles themselves can also be changed to customize the droplet size, spray pattern, water flow, and other characteristics to tailor the machine’s output for maximum effectiveness at an individual customer operation,” he adds.
CW Machine Worx, a sister company to Company Wrench, produces a series of Dust Fighter models of dust suppression equipment as well as its top-of-the-line Dust Destroyer, “a high-pressure air-water cannon that creates a fine mist just short of being a vapor,” Duhaime says. The cannon has two nozzle rings that can operate independently or simultaneously. The inner (primary) water ring, with 30 brass nozzles, has a water flow of 12 to 23.3 gpm; the outer (secondary soaking) ring, with six brass nozzles, has a flow of 60 to 114 gpm. Combined, the nozzle rings disperse about 140 gpm at 150 psi per ring, Duhaime says. The nozzles don’t clog due to the use of high-velocity air and water, he adds.
The Monsoon line of dust control tools from Buffalo Turbine (Springville, N.Y.) uses a high-speed, turbine-style fan to spin a gyratory, atomizing nozzle 4,500 rpm, says Paul Syracuse, general manager. The nozzle sends water through a mesh screen that surrounds a rotating hub. As the turbine blows the water through the screen, it creates millions of droplets ranging in size from 80 to 200 microns. Water volume adjusts from zero to 20 gpm.
The Probe Rotary Atomizer from Probe America (Beckley, W.Va.) sends water through a wire mesh basket that rotates at 12,000 revolutions per minute around a fan, dividing the water into 900 billion droplets per gallon, each up to 20 microns in size. The machine creates a fine mist similar to mist machines used at amusement parks, says Tim Warden, president. “You feel it, but you don’t get wet.” Warden estimates the system uses about a quarter of a gallon to a gallon of water a minute.
Coverage area. These tools vary widely in how much area the spray will cover, either while stationary or while rotating or oscillating. Some companies also specify the vertical reach of the spray and how much users can adjust the coverage.
Power and water supply. All-in-one models come with their own water tank and power supply, typically from a gasoline- or diesel-powered generator; other designs require separate power and/or water sources. A water tank is essential if the site does not have a nearby available water supply, Probe America’s Warden points out, and it also allows the use of heavier concentrations of additives.
Mounting and mobility options. Machines might stand on their own, come with their own trailers, or mount on separate trailers, stands, lifts, or stationary objects such as towers or wind monitors. For those that are not trailer-mounted, consider how easy they are to transport. For example, Probe America’s two models can fit in a pickup truck or trailer and can be lifted with a small forklift, winch, or portable crane, Warden says.
Optional features. Some companies offer remote control or additives—such as odor controllers or surfactants—and ways to disperse them.
Control at the Source
Another type of demolition dust-control tool attaches to an excavator’s hydraulic boom, stick, and work tool—a pulverizer, hammer, concrete crusher, shear, or drill—to control dust at the point where it’s created, even if that’s 20 stories high. Gensco offers the Dynaset hydraulic high-pressure washer, for example, which consists of a hydraulic, high-pressure pump on the base of the excavator that sends water up a hose on the side of the boom to nozzles attached to the work tool, Matus says. The nozzles atomize the water and create a small envelope of mist at the point of contact between the work tool and the material being demolished. A second, optional set of nozzles that point toward the ground control dust from falling material. The firm can configure the two sets of nozzles to operate separately or simultaneously. The Dynaset can work with a water tank mounted on the excavator, Matus says, but most customers choose to get their water from a fire hydrant. Prices range from $7,000 to $14,000 depending on the pump size, whether the system uses one or two sets of nozzles, and whether the base machine needs additional hydraulic hosing, he says.
This equipment eliminates the need to raise other equipment to the height of the work tool and keeps workers at a safe distance from falling debris, Matus says, though it tends to cover a smaller area than a standalone machine.
Optimizing Performance
The manufacturers say these dust-control systems require minimum maintenance. “When you notice the throw distances shortened, we do recommend cleaning the back of the fan,” Warden says. Peterson recommends inspecting DustBoss nozzles once a year, greasing the fan motor and high-pressure pump every 10,000 hours, and greasing the oscillator bearing on a regular maintenance schedule or as needed.
One environmental condition that will decrease effectiveness, they say, is wind. “If you get a heavy crosswind or headwind, smaller machines don’t work as well,” Duhaime says. Even larger machines can suffer: Without wind, the Dust Destroyer cannon shoots air and water up to 300 feet, he says. “With a crosswind, you might only get 100 feet.” Peterson specifies that winds of more than 10 to 15 miles an hour can affect DustBoss performance. For best performance, try to position dust-control equipment upstream of predominant wind, Dokell says; remote controls allow users to respond quickly to wind conditions, Syracuse adds.
Freezing temperatures, on the other hand, are not necessarily a cause for concern. Even if the water freezes as its exits the machine and hits the cold air or ground, it will still pull dust down with it, Peterson says. Duhaime points out that the Dust Destroyer has operated in 10-degree F weather. “The water exiting the machine did freeze when it hit the ground,” he notes, but he adds that the equipment should not sit idle in cold weather. “You have to keep it running.” When the equipment is not being used, manufacturers recommend blowing the water out of it. Operators also can use additives such as antifreeze in the water to winterize the equipment, Warden says.
How can users get the most from their dust-control equipment? The number of machines and their placement are the key, these manufacturers say. When Duhaime hears customers complain that water suppression systems don’t work, “it usually means they either have located them incorrectly or they aren’t using enough of them,” he says. Implosions require multiple units and lots of water, for example. “You only have about 10 seconds to go after that dust.” Warden agrees that demolition companies tend to use too few machines. Begin by determining how much of an area you need to cover at a time and how much of an area one machine covers, then plan accordingly, he says. Peterson says planning ahead is essential to determine the optimum equipment, location, and aiming. “Identify the primary source of dust and then position the equipment in such a way to get the maximum amount of dust agglomeration.” Other considerations include where the predominant wind is coming from as well as traffic flow, he notes.
Many of the manufacturers offer assistance in designing a dust-control site plan. “It’s good to have an engineer go on site and figure out how many machines are needed,” Warden says—a service Probe America provides free to existing or prospective customers. Dust Control Technology provides phone or on-site support. CW Machine Worx will even serve as a dust-control subcontractor. “We provide the labor and set up the machines,” Duhaime says.
Because demolition jobs vary in size from site to site, many manufacturers both rent and sell their dust-control equipment. Demolition companies can supplement equipment they own with additional units to meet their needs on larger sites, Peterson says. Rental programs also give demolition companies an opportunity to test-drive equipment, Warden says. “If you’re not sure which machine would suit your needs, rent one.” Rent-to-own might be an option as well.
Cherry owns several systems that require the addition of a power source and supplements them as needed with rental equipment that incorporates the power source, Dokell says. He has been pleased with the latest models he’s rented, he says. Manufacturers have identified the needs and wants of the demolition industry and “have taken very positive steps to react to them,” he says. About five years ago, for example, “self-contained units didn’t generate the power we needed. The last few we rented did exactly what we wanted them to do.”
Dokell points out that “dust is dust, but every site is going to be a little bit different depending on what you are trying to accomplish. … It’s a matter of managing equipment that’s out there.”
Diana Mota is associate editor of Scrap.
Mobile equipment designed for dust control can be more efficient and cost-effective on demolition sites than rudimentary measures such as hoses and sprinklers, manufacturers say.