How to achieve maximum garnet blasting performance with BARTON garnet abrasives
These abrasive blasting guidelines will assist in achieving maximum performance from BARTON’s blast-media garnet abrasives
Clean Blast Pot
Remove all foreign materials or other blasting abrasives. Contaminants make proper abrasive metering difficult and increase dust generation.
Clean Air Supply
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, 95 psi at the nozzle is recommended. Pressures above 100 psi at the nozzle help ensure optimum abrasive efficiency in the form of faster cutting, lower abrasive consumption and lower dust generation.
Very little garnet is required to produce a clean, uniform finish. In general, no more than half as much garnet will be needed as compared to coal slag, provided the correct grade of garnet is used. To set the metering valve, close the valve, then open slowly while blasting to introduce abrasive to the air stream. Find 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.
Determining the Correct Abrasive Grade
The garnet grade required is determined primarily by the profile specified and the coating/contaminant being removed. Testing should be conducted to determine the best grade, given application-specific performance. As a rule, use the finest grade that will create the needed profile and remove the coating quickly. BARTON offers four grades of blasting garnet including:
ADIRONDACK 36 CG
Profile: SSPC-AB 1, Grade 4. Used to remove thick coatings (20-50 mils) and rust. Typically produces a 3.5-4.5 mil profile on steel. Learn more about ADIRONDACK HPX garnet abrasive
ADIRONDACK 30/60 CG
Profile: SSPC-AB 1, Grade 3 and Grade 4, Class A. Used to remove heavier coatings (up to 40 mils) and rust while controlling profile. Typically produces a 2.5-4.0 mil profile on steel. Learn more about ADIRONDACK HPX garnet abrasive
ALLTEK 30/60 Plus
Profile: SSPC-AB 1, Grade 3 and Grade 4. Used for new steel and maintenance work on coatings up to 20 mils. Typically produces a 2.5-3.5 mil profile on steel. Learn more about ALLTEK HPA garnet.
ALLTEK 80 HPA
Profile: SSPC-AB 1, Grade 3. Used on aluminum and other sensitive substrates. Typically produces a 2.0-2.8 mil profile on steel. Learn more about ALLTEK HPA garnet.
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 are 1.5 sizes larger than the original orifice.
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.