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How to Build an Air Pressure Blasting Tank

Media blasting has become more accessible as low-cost sand blasters or media blasters are readily available at economy tool stores. There are a couple designs for media blasting using pressurized blasting tanks. Some require the blasting media to be placed inside the tank. The simplest kind, however, uses vacuum pressure to suck media into a pressurized air flow in the same way a carburetor sucks fuel into its air stream. While this is a simple design, it requires a very high-capacity compressor -- often more than small contractors' compressors can handle. A great way around this problem is to use a large overflow tank connected to a small contractors' compressor. The compressor will fill the tank, then you can blast from the pressure in the overflow tank for longer periods before the pressure drops enough to activate the compressor.

Things You'll Need

50 gallon or larger propane tank
Pressure gauge
Pneumatic couplings
Pneumatic hose

Instructions

- 1
  Flush your used propane tank. Open the release valve. Temporarily thread a pneumatic hose coupling into the main valve, using a crescent wrench. Note there are more than one standard profiles for hose couplers and hose ends, so you need to use couplings that match your hose, or vice versa. Blow any residual propane out of the tank. The propane tank will serve as your high-capacity overflow pressure tank.
- 2
  Remove the pneumatic hose coupling. Thread a T-type pressure gauge into the main valve. A T-type gauge will have male threads that thread into the main valve, a T where the pressure is gauged, and another set of female threads, identical to those of the main valve.
- 3
  Thread a two-way on/off valve into the main valve threads. This valve will have a central on/off valve that will open or close the main valve, allowing air to pass into the cylinder or flow out of the cylinder. The valve will also have a Y-intersection, each of which will have its own lever valve.
- 4
  Thread a blow-back or one-way valve (sometimes called a ball valve) into one of the valves feeding into the tank. It should be threaded into the valve you intend to use to fill the tank, not the valve that will lead to the sand-blasting nozzle. It will keep pressurized air from inadvertently flowing back from the tank toward the compressor, because back pressure will close it even if the lever is open.
- 5
  Attach a pneumatic hose from a traditional contractors compressor to the "in" valve on the overflow tank. Make sure the coupler fully engages the hose.
- 6
  Attach a second pneumatic hose from the "out" valve to a vacuum-fed media blasting nozzle.
- 7
  Fill a 5-gallon bucket with whatever kind of media you want to use -- from sand to crushed walnut shells -- and install a nozzle appropriate for the size of the media. Then, drop the tube that extends from the bottom of the media blasting nozzle into the bucket of granular media. If the end of the vacuum tube doesn't have a section of rigid pipe, slide the vinyl hose over an 18-inch long section of PVC or metal pipe that will fit snugly in the hose.
- 8
  Close the out valve. Open the main valve. Open the in valve. Set the pressure gauge so it will "bleed off" pressure in excess of the tank's specifications. If you don't know the specifications, set it to the same pressure as your contractors' compressor. Fill the tank. Open the out valve before media blasting.

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