Making the Most of Mist
Understanding dust suppression is key to increasing job site safety and complying with Occupational Safety and Health Administration regulations. Dust suppression cannons are one of the most common pieces of equipment used to address dust.
Contractors should examine several considerations before renting or purchasing a dust-suppression cannon. Ben Dowdy, fleet support product trainer for Carroll, Ohio-based Company Wrench, provides answers to frequently asked questions involving dust-suppression cannons.
Q: How do dust-suppression cannons operate, generally?
Ben Dowdy (BD): First, water is supplied to the dust-suppression cannon from a water source, normally a hydrant or water truck. The unit pressurizes the water and atomizes it. The atomized water is pushed into the air by a high-powered fan, which then covers large areas of contaminated air. The atomized water absorbs the dust particles and falls back to the earth.
Q: What are some factors to consider before renting or purchasing a dust-suppression machine?
BD: One of the most important factors to consider is water usage because demolition contractors have to pay for the water they use if they are pumping from a city’s mainline, and with something as inefficient as a fire hose or a garden hose, operators are going to use a lot of water. This ultimately raises operating costs. Whereas, when water is atomized, it provides more efficient dust control.
Operators also should consider how much [surface] area they need to cover. This comes down to water throw and square footage. The water throw measures how far the dust-suppression cannon sprays water in one direction, whereas the square footage outlines the total area in which the machine disperses water as it oscillates.
The final consideration that can sometimes be overlooked is access to a power source. The availability of a power source can be one of the deciding factors when operators are choosing between an electric or diesel unit.
Q: How do diesel and electric dust-suppression cannons differ from one another?
BD: Many of the differences between diesel and electric dust-suppression cannons are seen in their setup, efficiency, operational capabilities and maintenance requirements.
The electric unit is a … good option because it is very efficient, but it requires access to a 480-volt power source [to operate]. If the site does not have the proper electrical hookups, or if operators want a more mobile electric unit, they could purchase a unit with a generator.
Electric units also have lower operating costs because they require less maintenance and boast reduced energy costs compared with diesel units.
While electric dust-suppression units are more efficient, diesel units have more horsepower and only require water and fuel to operate. The increased horsepower means diesel units can produce more atomized water and throw it farther than their electric counterparts. The diesel units also can rotate 360 degrees, whereas the electric models [typically] only can rotate 330 degrees.
Q: How do you determine where to place your dust cannon?
BD: The first thing operators should understand is that the placement of their dust-suppression cannon will likely change multiple times throughout the day.
An operator may be demolishing a certain area of a building that requires dust suppression. As the demolition moves to other areas of the structure, so should the dust-suppression cannon. That is why many customers opt to have their dust-suppression cannons mounted to a trailer for fast, easy transportation.
Another important element to consider is wind direction at the job site. Operators should be aware of changes in wind direction at the site so they can adjust the direction of their dust-suppression cannons.
Most units come with a remote control that allows operators to modify the angle of the cannon without leaving the safety of their cab.
Q: Aside from directly applying atomized water as the demolition project occurs, how else can dust suppression cannons be used on a demolition project?
BD: Most of the time, dust-suppression cannons are seen as equipment that addresses dust after it already is airborne from one specific source. While cannons are incredibly productive at treating airborne dust particles, there are a few other ways they can suppress dust. For example, construction and demolition material could be presoaked before it’s processed to limit the amount of dust that becomes airborne in the first place.
There also is a more indirect means of trapping fugitive dust before it leaves the site. This method involves positioning one or more dust-suppression cannons at an upward angle on the perimeter of the site to create a curtain of atomized water that knocks down the dust before it leaves the area.
Q: Are there other applications where dust-suppression cannons can be used?
BD: Yes, dust-suppression cannons are very versatile pieces of equipment that can be used in various situations. Aside from suppressing dust, they can be used for odor suppression, draining water from leach beds and fire control.
Operators who want to control odor should place the dust suppression cannon on the outer perimeters of their waste facility and spray toward the pile. This will suppress the odor and push it away from the perimeter.
The dust suppression cannon also is capable of pumping water out of a leach bed, atomizing it and spraying a fine mist that quickly evaporates back onto the waste pile. This saves waste facilities tens of thousands of dollars because they no longer have to pay a company to dispose of leach bed water.
Operators who are using dust suppression cannons for fire control should consider the best position for the machine. If operators are not careful, they could inadvertently strengthen the fire with the cannon’s high-powered fan. Operators should soak a wide surface area around the fire. Ultimately, this will help slow the fire.
Q: What are some of the maintenance requirements for dust-suppression cannons?
BD: The maintenance requirements differ between diesel and electric dust suppression units. The electric models need less maintenance because they take motor grease on the two three-phase motors that power the machine, and there also are a couple of moving joints that need to be greased daily. Outside of greasing, that is really all the maintenance for the electric units unless it is powered by a generator, which requires its own maintenance.
The diesel models are on a 250-hour maintenance schedule, so every 250 hours there should be an engine oil change. These units also have daily greasing intervals because they have a lot of moving parts.
This story also appears in Construction Demolition Recycling Magazine.