When jetting with air we have to remember the distinctive differences in physical properties between water and air. Water does not compress while air does. When jetting with water, there will be a relatively consistent outflow of water into the workspace being jetted and water tends to rise to the surface in a relatively uniform manner. With air the outflow will vary based on the resistance of the sand or mud and the pressure can build up until it blasts material out in small "air explosions." When jetting directly into mud or sand, the air bubbles can build and then rise to the surface under pressure, and in doing so produce distracting splatter if this reaction is not anticipated. When the material being jetted is covered by a layer of water, the outward disbursal of material is more controlled.
Inventory and Storage
The air supply equipment is stored under the portable stock tank on the portable water supply trailer.
Main elements include the SCUBA cylinder, air hose and "Air Supply" box. The large hose shown is also fitted with an air chuck. It can be filled with air and used as a floating boom.
Air Supply Box Inventory
- Regulator and pigtail
- One-to-four manifold with air chuck adapter
- Double male air chuck adapter (for inflating the air boom)
- Tire filler
- Air nozzle (for filling flotation devices)
- Pressure gauge
- (2) lengths polypropylene rope (floating rope) with clips
- (2) rolls of webbing
When running combination water - air systems, all hoses used should be industrial grade and capable of handling 120 psi pressure. If lower pressure hoses are used on the "garden hose" side of the manifold, the air supply will have to be controlled at the manifold rather than at the jetting wands in order to prevent excessive air buildup in the hoses supplying the wands.
We have discovered a weakness in pipe thread to garden hose adapters that have swivel hose connections. We have received reports of the swivels failing. We use non-swivel type pipe to garden hose adapters and have experienced no problems. Brass quarter-turn shutoff valves with swivel connections have yet to give us any trouble.
Please note that none of the descriptions that appear on this site are intended to discourage anyone from acquiring pre-engineered purpose-built equipment. If you do build your own equipment, be sure to check the specifications and ratings of each component to verify that it is appropriate for the service intended. (We consulted with high pressure air experts before designing our systems.)