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Blast-One Weekly Tips
Tip #106
Differential pressure and how it affects your daily life

Differential pressure is all around us every day. It's what causes the weather to change, it's what makes our ears pop when we drive up hill, and it is also what causes 90% of the problems with our blasting equipment.

A common cause of differential pressure is because the pot is choked. This means that the ball valve on the pusher line is partly closed to assist the abrasive flow. This has been done by the blaster or the pot tender to overcome a negative pressure issue (a leak in the pot seals) or a moisture issue, causing the abrasive to stop flowing out of the blast pot. It is a quick fix which many blasters do every day. Abrasive not flowing – choke the pot for a minute, forces more air into the pot and clears the blockage

Pressure Gauges

If you have a moisture problem, you will find that the blaster will:

  1. Leave the pot partially choked while blasting.
  2. Open the abrasive metering valve more than needed.

Why is this an issue?

  1. You are wasting abrasive. The pot is forcing more abrasive into the air stream then needed. You buy more, blast more and clean up more.
  2. You are flooding your blasting stream. The abrasive is wearing out on itself and your equipment and not doing its effective job.
  3. You are destroying your metering valves. Forcing abrasive through your valves is wearing them out very quickly.
  4. Every PSI that you lose because of differential pressure, will lower your productivity by 1.5%. This means that a 10 PSI pressure loss will make your job last 15% longer!

Fixes?

  1. Use a correctly sized and constructed air dryer to rid yourself of moisture problems – the largest contractors swear they would never go to a job site with out one. No matter where they are in the country.
  2. Do a pressure loss audit all the way from your compressor to your nozzle. Find out where the pressure is being lost and fix it.
  3. Follow a strict maintenance schedule. Ensure that all your valves, pop up seals and gaskets are sealing properly.
  4. Check the ball valve on your blast pot every day – is it choked - even a little? You could learn something is wrong.

 

Differential Pressure

 

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