Blasting Guidelines

Blasting Guidelines   

These 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.

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 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.

Abrasive metering

Very little garnet is required to produce a clean, uniform finish. Generally speaking, no more than half as much garnet as compared to coal slag/silica sand will be needed, provided the correct grade of garnet is used. To set metering valve, close 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 that more abrasive 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 general rule of thumb, use the finest grade that will create the needed profile and remove the coating quickly. BARTON offers several blasting grades of garnet including:

  • BARTON 36 CG – Profile: SSPC-AB 1, Grade 4. Used to remove thick coatings (20 – 50 mils) and rust.
  • BARTON 30X40Profile: SSPC-AB 1, Grade 3 and Grade 4. Used to remove heavier coatings (up to 40 mils) and rust while controlling profile.
  • BARTON 30X60 Plus™ Profile: SSPC-AB 1, Grade 3 and Grade 4. Used for new steel and maintenance work on coatings up to 20 mils.
  • BARTON 80 HPA® Profile: SSPC-AB 1, Grade 3. Used on aluminum and other sensitive substrates.
  • BARTON 100 HPA® Profile: SSPC-AB 1, Grade 2 and Grade 3. Used for new steel, aluminum, or fiberglass surfaces. It effectively replaces staurolite offering significant reductions in material consumption, improvements in productivity, and reductions in nuisance dust.

Nozzles, couplings & 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 original orifice.

Summary

Abrasive blasting is a complex process with numerous variables that impact performance. Every blasting application is unique. Proper planning, close monitoring and occasional adjustments are necessary to create a safe and efficient blasting operation.