Abrasive blasting is a complex process with numerous variables that impact performance. Every blasting application is unique. Proper planning, close monitoring, occasional adjustments, and recycling as appropriate are necessary to create a safe, efficient, and environmentally sound blasting operation.
These abrasive blasting guidelines will help operators achieve maximum performance from BARTON’s blast-media garnet abrasives.
Clean Blast Pot
Remove all foreign materials or other blasting abrasives from inside the pot and make sure the filter is clean. Contaminants that remain from previous use make proper abrasive metering difficult and increase dust generation.
Use clean, dry air (use aftercooler/dryer as needed) with an air pressure range of 90-110 psi at the nozzle. Higher air pressure yields greater productivity, all things being equal, but it also increases particle breakdown. When recycling, BARTON recommends 95 psi at the nozzle. Pressures above 100 psi at the nozzle help ensure optimum abrasive efficiency in the form of faster cutting and lower abrasive consumption. When recycling, operator will need to determine optimal settings to balance cutting speed with recycled yield.
Very little garnet is required to produce a clean, uniform finish compared to other blast media. In general, you will use only about half as much garnet as compared to coal slag, provided you are using the correct grade of garnet (See grade selection guidelines below). To set the proper abrasive metering, close the metering valve, then open it slowly while blasting to introduce abrasive to the air stream until you reach the point where the optimal cut is achieved.
For new steel applications and to remove coatings under 5 mils, one indication of a proper abrasive metering is a “blue flame” at the nozzle. A coating that is thicker and more difficult to remove requires more abrasive to be metered into the air stream to maintain fast cutting.
Note: Running the abrasive too lean will reduce cutting speed. Running the abrasive too rich will waste abrasive, increase dust generation, etc.
Nozzles, Couplings and Whips
A venturi-type nozzle will yield maximum performance. A long-bore #7 or #8 is suitable for most applications. Use the largest nozzle possible given application and sufficient air pressure/volume. Replace nozzles once they become 1.5 sizes larger than the original orifice.