Using Vehicle-Mounted Rock Drilling Rigs

Rock drilling during construction can expose workers to high levels of silica dust. Employers should take the following steps to reduce the risks:

• Develop a site-specific safety and health plan. This plan should help workers recognize when silica dust may be generated, and explain strategies for controlling or eliminating dust, including engineering controls, personal protective equipment, and work practices.
• During rock drilling operations, wet or dry control systems should be used to control dust. Wet systems are efficient, but in cold temperatures they may freeze up. Of course, caution is needed when using wet systems around electricity. Consider dust control features when purchasing equipment. Always use the installed dust control system, and keep it well maintained. Do not use equipment if the dust control system is not working properly.
• Develop a documented maintenance program for all dust control systems. Drill deck shrouds need to be carefully maintained in dry systems. When changing filters, workers may be required to use respirators.
• Create a safety margin. Minimize the presence of workers near rock drilling. Use warning signs and barriers to separate workers, pedestrians, and vehicles from rock drilling equipment.
• Train all rock drillers and assistants in the use of protective controls and work procedures.
• During rock drilling activities, perform air monitoring of respirable crystalline silica exposures to make certain that all engineering controls are working.
• Make sure that all wet drilling systems are working properly. Wet drilling systems pump water through the drill stem to prevent dust from becoming airborne. Drill operators control the flow using a control valve. Often, drills are equipped with a flow meter. Raising the water flow improves dust capture, but too much water causes operational problems.
• Make sure that dry collection systems are working correctly. Dry collection systems use an enclosure around the area where the drill stem enters the ground. The enclosure is created by simply hanging a rubber or cloth shroud from the underside of the drill deck. The enclosure has ducts connected to a dust collector that has a fan outside of the filter opposite the drill hole. The fan creates negative pressure inside the enclosure. The system captures dust as it leaves the hole during drilling. The dust is removed into the collector.
• Whenever possible, use rock drilling equipment with enclosed positive-pressure cabs with air conditioning and a filtered air supply to isolate the operator from being exposed to the dust. Older cabs can be retrofitted with systems that will filter, heat, and cool the air.

To learn more about Construction Silica visit our Construction Silica Safety Online Training web page.