Video: Wet Abrasive Blasting, An Overview of Surface Cleaning Alternatives
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, however, 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, also known as vapor abrasive* blasting, which provides finer control over the flow of water-abrasive mixtures. This is achieved by metering pressurized water into the pressure pot instead of metering the water-abrasive mixture exiting the pot. Fluidized blasting can prepare a wider range of surfaces than wet injection systems while reducing the amount of media and water expended. The EcoQuip 2 EQs Dual Line Vapor Abrasive Blaster by Graco, for example, suppresses dust up to 92 percent, compared to dry blasting, and uses 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 fugitive dust and 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 it is traveling at the same velocity as it impacts the substrate. For this reason, it requires less abrasive than dry blasting to complete the same projects.
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, 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.
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.
Fluidized abrasive blasting has proven effective in restoring a variety of surfaces. In Colorado Springs, Col., it was used to clean the exterior of the stainless steel Julio Penrose Fountain, located inside America the Beautiful State Park in Colorado Springs. City restrictions precluded sandblasting, so Graco's vapor abrasive approach was used to successfully restore the sculpture to a new-looking appearance.
The restored lower portion of a sculpture in Colorado Springs provided a distinct contrast with the yet-to-be-restored upper portion.
Vapor abrasive blasting can address a variety of other removal and restoration situations, such as paint and coating removal on bridges and roadways, graffiti removal from walls and storage tank cleaning. A wide range of pressures and abrasive media can be used, providing flexibility for various applications.
In recent testing conducted by Graco, 4-foot-by-4-foot concrete slabs were treated with dry blasting, nozzle-based wet blasting, and fluidized abrasive blasting to compare respirable levels of dust and silica. Wet and fluidized abrasive blasting produced significantly lower levels of dust and silica than dry blasting, and fluidized blasting showed the best results.
Learn more about vapor abrasive blasting in this informative video:
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.
For more information, visit graco.com/ecoquip.
*Vapor Abrasive is a registered trademark of Graco, Inc. Claims or positions expressed by sponsoring authors do not necessarily reflect the views of TPC, PaintSquare or its editors.