Dry abrasive blasting equipment and safety procedures
The popularity of abrasive blasting has surged since the 1990s, in part due to stricter environmental rules that meant a cleaner way to remove coatings and prepare surfaces was needed.
Dry abrasive blasting, also known as air abrasive blasting, is one of the main blasting techniques that has emerged. But specialized equipment and safety concerns make dry abrasive blasting systems and safety worth understanding in greater detail.
Components of dry abrasive blasting equipment
Many components combine to form a dry abrasive blasting system, like the compressor that supplies air, the blast machine that supplies and regulates abrasives, the hoses and nozzle that transport and deliver the air and abrasives to the surface and the respirator and protective suit that ensures operator safety.
Air compressors gather and compress air from the environment and send it to the blast machine. It’s important to ensure the right air compressor is used on a project. Featured in Painting Manual Vol.1: Good Painting Practice is a table showing minimum air supply requirements based on other equipment variables. Also note that air compressors should be placed upwind of blasting operations and that their inlets face away from any sources of contaminants that could jeopardize proper system function.
Filters and moisture separators act as another line of defense against contaminants. Oil and airborne moisture each can cause serious problems for dry abrasive blasting operations. Equipment manufacturers can help uses determine what kind of filter or separator needed based on the work environment.
Blasting machines receive compressed air and supply abrasive material, but this is done in two different ways. In suction blast systems, abrasives are moved via a secondary hose and join forced air as it issues from the nozzle. These systems are best for light-duty work. In dry pressure blast systems, metered valves govern the incorporation of abrasives into the pressurized air stream. Then, both air and abrasives are sent through the hose connecting the machine and the operator. Pressure blast systems are better suited for large-scale, heavy-duty jobs.
Air supply lines deliver compressed air to the blast machine and then move the air plus abrasives to the blast nozzle. Note that air moves best through straight lines and that blast systems lose 2 – 3 psi of pressure for every 50 feet of additional line. If it makes sense to the site, portable blast systems and short, straight hose lengths are best. However, some large-scale jobs require long distances between central blast equipment and operators. In these cases, hard lines may be installed to minimize power loss.
Blast hoses and couplings are subject to severe stress in abrasive blast operations. While a wide variety of hoses and couplings are available, choose the sizes that best fit the job. High-quality hoses and couplings should be purchased. While more expensive up front, they last longer and keep repeat equipment purchase costs under control.
Nozzles focus air and abrasives by narrowing their paths of travel. Differing sizes and shapes of nozzles are available to suit specific project conditions, so consult a supplier or manufacturer to learn what’s best for your work. Nozzles also are subject to significant wear. Their openings will slowly degrade over time, altering the shape of the opening and the volume and pressure of the air and materials they deliver.
Ensuring safety in abrasive blasting
Extreme care must be taken to protect operators from hazards associated with abrasive blasting. Abrasive blasting often leads to the creation of toxic dust, so the Occupational Safety and Health Administration (OSHA) mandates the following safety measures:
- Operators must wear air respirators that meet applicable National Institute of Occupational Safety and Health (NIOSH) standards for abrasive blasting.
- Respiration equipment must include breathing air filters that meet Grade-D breathing air specifications.
- Carbon monoxide (CO) alarms must be included on any oil-lubricated air compressors.
- Operators must be properly trained. C7 certification for abrasive blast operators is internationally recognized for ensuring operator safety on abrasive blast jobs.
Also, local regulations that apply to abrasive blasting should be checked. For additional guidance on applicable standards, use OSHA’s abrasive blasting fact sheet.