BlastOne

Choosing the Correct Compressor Size is Very Important

A good air compressor is an essential part of your blasting system.

It is important to size your compressor correctly to the number and the size of the nozzles you are running.

If you are running multiple nozzles on a project you need to allow 500 cfm per nozzle. That means, if you are running two x #7 (or 7/16; 10mm blast nozzles) you need 1,000 cfm of compressed air available for the blast pot. Only if you have the correct pressure available will you get the maximum performance from both nozzles. It is important to set up the compressor correctly and wind up your pressure as far as you need to. Most high production blast equipment is rated to 150 psi working pressure, and you need to adjust your compressor to maintain that much pressure. By winding up the pressure the engine will have to work harder and of course, it will use more fuel. But, the extra diesel consumed will be well worth it.

Air Compressor on-site
Typical Blasting Compressor

How much air do you need to run a blast machine?

Air consumption (CFM) per blast nozzle using garnet abrasive.

Nozzle Size Nozzle Pressure
50 psi 60 psi 70 psi 80 psi 90 psi 100 psi 120 psi* 140 psi
No. 2 1/8" 14 17 19 21 24 26 30 34
No. 3 3/16" 32 37 42 47 52 57 67 77
No. 4 1/4" 57 66 75 84 93 103 119 136
No. 5 5/16" 89 103 117 131 145 158 186 214
No. 6 3/8" 129 149 169 189 209 229 269 309
No. 7 7/16" 176 203 230 258 285 312 367 422
No. 8 1/2" 229 265 300 336 371 407 478 549
No. 10 5/8" 356 412 468 524 580 632 744 856
No. 12 3/4" 516 596 676 756 836 916 1076 1236
Efficiency 47% 55% 64% 74% 86% 100% 130% 165%

*Ensure equipment is rated for these pressures.

The table above shows the amount of air each nozzle size needs when the nozzle is new. But what happens when the nozzle starts to wear a bit? (i.e. after 2-3 weeks). Many blasters have said, “I could blast a lot faster when my nozzle was new – but now I’ve lost pressure.” You are going to need more and more air to maintain the same pressure at the nozzle.

In summary, when you are considering an air compressor for your blast system, you should allow sufficient volume for each nozzle (from the table above) plus 20 cfm for your airfed helmet PLUS a 50% reserve to allow for the nozzle wear factor.

For Example: A new No.7 nozzle needs 312cfm PLUS 20cfm for helmet PLUS 50% reserve of 155cfm: Minimum compressor size required = 490cfm.