Drivable Masonry Saws with Wet Dust Suppression

Drivable masonry saws use a pump or line pressure to deliver water to the saw blade where it combines with particles and reduces airborne dust levels.

Description:

Cutting concrete and other masonry materials generates a large amount of dust that may contain high levels of crystalline silica and create a hazard for everyone in the vicinity. Wet suppression is a control option for dust generated while cutting masonry materials with drivable masonry saws. These controls use a pump or line pressure to deliver water to the saw blade where it combines with particles and reduces airborne dust levels.

If properly designed and used, exposures can be significantly reduced. If use of drivable masonry saws is brief and intermittent, wet dust suppression may reduce exposures 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.

Husqvarna RS 8500 D rideable flat saw

  • Used for joint repair, cleaning and widening, highway patch and repair and cutting green concrete
  • Cost: $40,259 (with blade clutch and 26 inch blade and guard)
  • Fuel: diesel
  • Horsepower: 85
  • Blade diameter: 14 to 26 inches
  • Maximum cutting depth: 10 inches
  • Blade speed:  2,940 rpm for 14 inch blades / 2,100 rpm for 26 inch blades 
  • Weight: 2,050 pounds
  • Water supply: ¾-inch hose connection
  • Sound pressure level: likely to exceed 90 dBA (OSHA’s Permissible Exposure Limit for an 8-hour time-weighted average)  

 


(Photo courtesy of Husqvarana AB Construction Division)

Risks Addressed:

Silica dust exposure may cause silicosis or lung scarring 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. Silica has also been associated with lung cancer and chronic obstructive pulmonary disease (COPD).

How Risks are Reduced:

The saw blades are partially enclosed in shrouds with water spray nozzles which are generally located near the top of the blade. When water is pumped through the nozzle, it combines with particles near the point of dust generation and, due to increased weight, the now larger particles settle to the ground. Silica and dust are only hazardous if inhaled and are not hazardous for skin contact. As long as the dust does not become airborne, the hazard is reduced.

In a review of NIOSH sampling data, Linch concluded “systems using water on the saw blade greatly reduce the amount of respirable dust generated.”

In a study of stationary masonry saws, Yereb et al. concluded “wet cutting substantially reduces worker exposures to silica dust, but does not entirely eliminate them.” Beamer et al. and Meeker et al. came to similar conclusions in their separate but similar work with stationary masonry saws.

Effects on Productivity:

Wet dust suppression systems can have either positive or negative effects on productivity, but definitely improve the quality of the work by suppressing large amounts of airborne dust, which allows a cleaner, more efficient means of masonry cutting.

Dust suppression also reduces site cleanup times. Dust suppression avoids exposing other workers, members of the public, adjacent property, cars and building occupants, which can increase 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 saw use is intermittent, wet dust suppression may be adequate to reduce the need to wear a respirator, and the need for an employer respiratory protection program.
 
Some additional issues should be considered. Time may be required to allow masonry materials to dry after cutting and before use, which will depend on the material, the amount of water used and the application. The saw needs to be equipped with a water tank or located near a source of water.

Additional Considerations:

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. Cutting 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.
 
Concrete and masonry saws frequently generate sound levels that are greater than 90 decibels, the OSHA Permissible Exposure Limit (PEL), and hazardous. Hearing protection should be worn when using masonry saws unless an industrial hygienist has conducted noise monitoring and indicated that hearing protection is not required.
 
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: