Understanding Your Alternatives in Today’s Market
Restoration of steel and concrete surfaces has relied heavily on sandblasting and other dry blasting techniques. For over a century, dry blasting has been an effective, but dusty approach in removing coatings, contaminants, corrosion, and residues, with emissions of silica and other abrasive or substrate particles linked to negative health and environmental impacts.
As an alternative to dry blasting, wet blasting was developed in the 1960s to minimize fugitive dust by mixing water with the abrasive spray. While effective in reducing dust, wet blasting was initially slow to catch on due to heavy water use and the problem of containing and disposing of contaminated water. Contractor familiarity with dry blasting and additional costs associated with the water and abrasives of wet blasting also limited acceptance of the newer technique. More recent developments have made wet blasting more attractive to contractors and owners facing tough restoration tasks.
BENEFITS OF FLUIDIZED ABRASIVE BLASTING VS. WET INJECTION SYSTEMS
A growing number of facility owners are exploring fluidized abrasive blasting, where water and abrasive are combined in a pot under water pressure, then injected into the airflow. Fluidized abrasive blasting, also known as Vapor Abrasive® blasting, provides finer control over the flow of water/abrasive mixture, allowing for blasting of a wider range of surfaces and reducing the amount of media and water expended. The finer control is achieved by metering pressurized water into the pressure pot instead of metering the water-abrasive mixture exiting the pot. Units such as the Graco EcoQuip 2 EQs Dual Line suppress dust up to 92 percent when compared to dry blasting and use less than one quart of water per minute (per nozzle).
Designed for industrial markets such as oil and gas, marine and infrastructure, the EQs Dual Line allows contractors to complete large blasting jobs faster, with two outlets and a 12-cubic-foot pressure pot capable of blasting up to four hours with two blasters at once.
Fluidized abrasive blasting addresses both the fugitive dust and the water discharge issues. The vapor abrasive approach wets individual grains of abrasive material in water, resulting in increased mass as the abrasive is propelled through the blast hose. Wetted abrasive achieves higher impact force because the wetted abrasive is traveling at the same velocity as it impacts the substrate. For this reason, it requires less abrasive compared to dry blasting to complete the same projects.
Fluidized abrasive blasting combines water and abrasive in a pot under water pressure, then injects the mix into the airflow. Graco has both a single-nozzle and a dual-nozzle version available.
Because dust is minimized, less containment is generally required, and media clean-up time can be reduced. With less water use than slurry or other water-based technologies, Graco’s Vapor Abrasive blasting does not leave pools of water behind, and the likelihood of toxic runoff is greatly reduced. It also reduces rebound of abrasive particles, which pose risk to workers and the environment. The fluidized systems provide adjustable, precise control over the air pressure and water/abrasive mixture and reduce the amount of media and water expended.
ATEX Certification
All of the Graco EcoQuip units are available in ATEX-certified models that can be used in explosive environments. The ATEX directive is a European law that covers equipment and protective systems intended for use in potentially explosive atmospheres. The EcoQuip ATEX-certified equipment has been approved for use in area classification Zone 1 and Zone 2. This means the system is approved to operate in an atmosphere consisting of a mixture of flammable substances that can form occasionally in normal operation.
EcoQuip ATEX-certified models use a pneumatic starting system to reduce the potential for explosions. Dry blasting can cast sparks charged with static electricity, which can lead to explosions in the presence of flammable gases. Wet blasting does not completely eliminate sparks, but when sparks occur they are cold sparks (without static electricity), minimizing the explosive potential.
Reduced Permissible Exposure Limit (PEL)
Graco retained a third party to perform an Industrial Hygiene Survey in order to evaluate potential exposures to respirable airborne dust and respirable silica during three separate blasting operations. Blasting parameters were kept constant for the three scenarios with the exception of the blasting equipment used and the usage of water. Blasting was performed on a 4 ft x 4 ft slab of concrete using medium crushed glass abrasive.
On the left are the results from blasting with a water injection system and on the right are results from an EcoQuip 2 Vapor Abrasive blaster. It takes 4.5 hours blasting with a wet/dry system using water injection before hitting OSHA’s Respirable Silica Limit versus 6.5 hours with EcoQuip 2.
Wet and fluidized abrasive blasting produced significantly lower levels of dust and silica than dry blasting with fluidized abrasive blasting as having the best results. To watch what happened during testing, visit the Graco Blasting channel on YouTube.
NAVSEA Adopts Wet Abrasive Blasting (WAB)
New in 2019 are the addition of SSPC-SP 10/M (WAB)/NACE WAB-2/M to the NAVSEA standards. With these new standards, NAVSEA moves toward a safer and more cost-efficient method of surface preparation, all while lowering ambient dust for worker safety, reducing consumption of abrasives and medias, and reducing disposal costs of spent materials.
SUMMARY
The environmental and efficiency gains of Graco’s Vapor Abrasive technology over dry blasting and traditional wet blasting make it attractive to owners facing tough cleanup tasks. Between slurry and fluidized blasting, the adjustable flow settings of fluidized blasting can improve efficiency and provide additional versatility in multiple situations. To learn more, visit graco.com/ecoquip.