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Blast-One Weekly Tips
Tip #67
Choose the correct air compressor size and wind up the pressure

17-ways

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.

compressor

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

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

air-consumption-chart

*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.

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

Read the article 'Compressed air supply for abrasive blast cleaning' here.

 

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