Step 4: Finishing up
The white system is the original sandblasting setup, the red system is the new Harbor Freight system that has been modified for the foot switch. To use the system it is important to turn the valves on and off in order... if you were to turn off the supply first for example... air could be sucked in from the pressure pot... along with the grit... and pas backward through the pressure regulator. This would damage or destroy the regulator.
Normal activation of the new red system would be like this...
1) Turn on main air supply. This feeds clean 90 PSI into the system to the regulators through the water trap.
2) Set the regulators (top) for 40 PSI, and (bottom) for 65 PSI. This sets the system to the correct pressures.
3) Open the RED pedal valve. This causes the pinch valve to close preventing the system from spraying grit all over.
4) Open the RED pot valve. This causes the grit pot to pressurize.
Of course... be sure the lid is screwed down well... you don't want it to do a grit volcano in the workshop! And before you pressurize the system... ALWAYS WEAR A MASK!!! You really don't want to breathe this stuff... so again... ALWAYS WEAR A MASK!!!
Shutdown is pretty simple...
1) Turn off the pot valve.
2) Turn off the pedal valve.
3) Turn off the main air valve.
4) Step on the pedal to allow the system to bleed down. Some grit will escape.
If you don't want any grit to get out... you could close your grit mix valve at the bottom... but usually it's more trouble than it's worth.
The last image shows the Harbor Freight pressure pot valves. It also has a secondary water trap that automatically vents when the pressure drops below about 15 PSI. It is actually better equipped than the $900 pressure pot that she got with the system. The image also shows the two valves that are no longer being used... they could be used on your system as the pot and pedal valves. You would just replace them with a standard pipe fitting.
I hope this helps you to set up your own system, we completed the entire project for about $600 including the cabinet, pressure pot, and all the plumbing for the air supplies. It cost us less than what the pressure pot alone would have cost.