Add-on Wet Dust Suppression Systems for Rock Crushers

An add-on wet dust suppression system is a piece of equipment that connects to a rock crusher delivering water to the crushing surface.

Description:

Crushing rock and masonry material generates a large amount of dust that may contain crystalline silica and creates a hazard for everyone in the vicinity.
 
Using water to suppress the dust may be easier than using local exhaust ventilation in some circumstances, and is an important dust control option to consider. These controls use a pump to deliver water to the crushing surface where it combines with particles and reduces airborne dust levels. Adding moisture to the material will also reduce the amount of dust produced downstream from the crushing operation. Each of these systems must be configured for specific equipment, process and control requirements.
 
If properly designed, maintained and used, water spray systems may significantly reduce exposures near rock crushers, potentially to a level low enough that a respiratory protection program isn’t required.  Continuous use may exceed the OSHA Permissible Exposure Limit, even with the use of wet dust suppression, however.

 

National Environmental Service Company (NESCO) High Pressure Water Spray Systems

  • Wet dust suppression systems can cost from $15,000, for small portable rock crushers, to $75,000, for large stationary aggregate plants. The average installed cost of a system for a typical stationary aggregate plant processing 1,000 tons per hour is between $40,000 and $50,000. Costs will vary significantly with the addition of accessories, such as compressed air and antifreeze systems and heat tracing spray lines. 
NESCO DUST PRO Professional Series High Pressure Water Spray Systems
  • Used for dust control at crushing plants processing more than 500 tons per hour
  • Pump pressure: 200 pounds per square inch
  • Pump flow rate: 10, 20 or 40 gallons per minute
  • Standard Features:
    • Pressure gauge and relief valve
    • Remote control panel
    • Brass plumbing
  • Optional Features:
    • Air purge and glycol injection (for cold weather use)
    • Dual basket strainer
    • Trailer mounted
    • Automation
 

NESCO DUSTBOY High Pressure Water Spray Systems
  • Used for dust control at crushing plants processing less than 500 tons per hour
  • Pump pressure: 200 pounds per square inch
  • Pump flow rate: 10 or 20 gallons per minute
  • Standard Features:
    • Pressure gauge
    • 40 mesh basket strainer
    • Brass plumbing
 
 
Arch Environmental Equipment, Inc. Dust Fogger Systems
  • Modular water fog, or spray, system for controlling dust in and around rock crushers
  • Operating  pressure: 100-150 pounds per square inch
  • Available nozzle flow rates: 1.9, 2.9, 5.7, 11.5, 23.0 and 34.5 gallons per hour (gph)
  • Available pumps and flow rates (at 150 pounds per square inch):
    • ¾ horsepower – 270 gallons per hour
    • 1 horsepower – 480 gallons per hour
    • 2 horsepower – 900 gallons per hour
    • 3 horsepower – 1155 gallons per hour
Spray Heads
 
Pump

Risks Addressed:

Crushing rock and masonry material is a high dust activity that in the absence of controls would place workers at risk of lung disease, cancer, chronic obstructive pulmonary disease (COPD), lung scarring, silicosis, renal disease and autoimmune disorders, such as lupus and rheumatoid arthritis, with prolonged exposure.   Silicosis is an incurable, sometimes fatal, disease.  The NIOSH-recommended exposure limit is 0.05 mg/m3 as a time-weighted average concentration for up to a 10-hour workday during a 40-hour workweek. This is one-half of the OSHA standard when the dust is pure silica, but still twice the ACGIH-recommended threshold limit value of 0.025 mg/m3.  Silica has also been associated with lung cancer and chronic obstructive pulmonary disease (COPD).

 


How Risks are Reduced:

Water is delivered as a fog, mist or fine spray to the material before, during or after crushing, where it combines with airborne particles created by the crushing of stone, concrete and masonry materials, enlarging the particles and causing them to settle. Adding moisture to the material will also reduce the amount of airborne dust and silica generated during crushing, loading and transporting stone and masonry. Silica and dust from the concrete and masonry materials are only hazardous if inhaled; they pose no significant hazard from skin contact. As long as the dust does not become airborne, the hazard is reduced. The extent to which these systems are effective in meeting recommended exposure limits has not been evaluated by scientists or independent parties.

 

Using water will visibly suppress dust, but the extent that it reduces the small, respirable particles is unclear without additional testing. Although exposure is not reduced to zero, substantial reduction is expected. This is dependent on the amount of water used, the number, location and spray pattern of water nozzles, how effectively the system prevents suspension of particles in the air, the nature and amount of work and the extent to which workers are exposed to resuspended dust after it dries. While there is no published sampling data on these specific wet dust suppression systems, evidence indicates exposure to respirable silica can be significantly reduced through the use of wet methods.
 
In a study of granite processing facilities, Wickman and Middendorf (2002) stated that “the workplace controls, which are typically wet methods, implemented in the granite industry have been generally effective in reducing employees' exposures to below the OSHA PEL.” They recommended that “use of these controls should be implemented and enforced in other workplaces, such as rock drilling and abrasive cutting of concrete, where silica exposures remain problematic.”
 
On its website, NESCO states that “a high pressure water spray system suppresses visible dust and keeps the plant in compliance.”
 
In its dust suppression handbook, Arch Environmental Equipment states that “water spray systems remain the most efficient and cost effective means of dust control for both process and fugitive dust emissions.”

 


Effects on Productivity:

When used with rock crushers, wet dust suppression systems are expected to increase productivity. Wet dust suppression systems reduce the amount of dust produced and eliminate large amounts of airborne dust, providing a cleaner, more efficient means of crushing rocks and masonry.
 
Improved visibility can improve quality and productivity. Dust suppression may reduce site cleanup times. Dust suppression avoids exposing other workers, members of the public, adjacent property, cars and building occupants, which can be associated with increased liability and time consuming disputes. Improved worker comfort is a result of reduced airborne dust which may in turn result in less fatigue for the worker and greater productivity. In some cases, particularly where rock crushing is intermittent, using a water spray dust control may be adequate to reduce the need to wear a respirator, and the need for an employer respiratory protection program.

 


Additional Considerations:

Sources (Sivacoumar et al, 2006 and Archer, 2003) recommend a comprehensive approach to controlling dust from rock crushing processes. The crushers, conveyors and transfer points must be enclosed and well sealed for wet dust suppression to be effective and for dust to be controlled. In addition, walls should be used to reduce wind, roads should be wetted with water and paved where possible.
 
The use of water controls may result in wet and slippery ground and walking surfaces. During cold weather this may lead to the formation of ice and an increased risk of slips, trips and falls. Crushing debris that is not removed from the work area while wet may become airborne once dried, posing an inhalation hazard to anyone in the area. Maintaining a work area free of debris and excess water reduces the risk of these hazards.
 
The use of water as a dust control increases the risk of shock when electricity is used in the same area. Electrical cords and extensions must be rated for the tool's power requirements, be regularly inspected, replaced when damaged and used in combination with ground fault interrupt circuits.
 
The use of diesel and particularly gasoline-powered equipment poses the risk of carbon monoxide exposure, especially in areas where airflow is reduced. Steps to control exposure are important because the gas is invisible, odorless and tasteless. Poisoning by carbon monoxide can occur quickly indoors, but working outdoors does not ensure operators won’t be overcome. Small, inexpensive personal monitors should be worn by the operator to warn of unacceptable exposures. Equipment should not be left idling to cut down on carbon monoxide and to conserve fuel.
 
Rock crushers and related equipment frequently generate sound levels that are greater than 90 decibels, the OSHA Permissible Exposure Limit (PEL), and hazardous.  Appropriate hearing protection should be worn when working near a rock crusher, unless an industrial hygienist has conducted noise monitoring and verified that hearing protection is not required.
 
While more likely at higher pressures, wet dust suppression systems create a risk of injection and laceration from contact with high pressure water and a risk of injury from contact with a loose water line. 
 
As is the case with any construction equipment, users should follow manufacturer safety recommendations and comply with any applicable local, state or federal regulations.

 


Hazards Addressed:

Availability

National Environmental Service Company (NESCO) High Pressure Water Spray Systems
To obtain information, visit http://www.drdust.com or contact 1-973-543-4586 info@drdust.com

Arch Environmental Equipment, Inc. Dust Fogger Systems
To obtain information, visit http://www.archenvironmental.com or contact 1-800-553-4567 info@archenv.com

Return on Investment

To calculate the return on investment (ROI) for your specific application, please visit our Return on Investment Calculator. While a specific ROI example has not been developed for this particular solution, the ROI Calculator provides a useful tool and guidance on how to generate your own on investment analysis.