Troubleshooting & Maintenance Tip #25: Grit in the controls
When direct-pressure blast machines act erratically and the blast is slow to turn on or shut off, here’s a helpful tip that doesn’t appear in the instructions.
Under certain circumstances abrasive can find its way into the control lines. That can cause blockages and lock up moving parts inside the valves. This holds true for portable blasters and industrial blasters alike, regardless of the brand.
So what happened? And what can be done to stop grit from getting into the pneumatic controls?
Here’s the inside story: When the vessel holding the abrasive is pressurized – and then the air compressor is turned off, the pressurized air will run back to the compressor, seeking an easy exit to atmosphere. And along with the streaming air, dust and grit can be siphoned and deposited into places they don’t belong.
The key is never to remove the air source when blasting. And by that we mean don’t use the compressor to “signal” the operator that it is lunch break. Also avoid power outages if possible, such as running out of fuel for the compressor. In other words, be sure the air compressor is on any time the blaster is pressurized, and don’t shut the compressor off until the gauge is at zero on the blaster.
When you need to stop blasting, make a habit of fully depressurizing the blaster first. Then shut down the air compressor. Reversing this sequence is a big mistake.
Thoroughly cleaning out the valves and interconnecting control lines is challenging – but if not completely cleaned those problems can come back again and again. Sometimes it’s more expedient to simply replace the hoses and valves. Inline filters can be added to the control lines (our part # 2301-902-90). But the most important thing is to follow recommended procedure in the first place.
Always consult the operating manual and follow safety procedures. Since one solution doesn’t fit all situations, our customers are always welcome to contact our expert technical service personnel for troubleshooting.
The photo shows a disassembled regulator on a soda blast pot that was a victim of improper procedure. The unit was brought back to life by Dawson-Macdonald service personnel.
