FAQ

Technical

What is the difference between Pressure, Flow, and Thrust?

Pressure is the measure of potential energy stored within compressed air. Pressure is measured in pounds per square inch (psi). In general, most tow-behind compressors deliver pressures between 80 and 120 psi. The electrical equivalent of pressure is voltage.

Flow is the volume of compressed air traveling through an air line during a given period of time. Flow is measured in cubic feet per minute (cfm). In general, higher flow requires an increased capacity (larger horsepower) air compressor. In general, increasing the amount of flow may require a larger capacity (larger diameter) air line. The electrical equivalent of flow is amperage.

Thrust is the effective force produced by an air nozzle and is generated from the combination of air pressure and air flow. Thrust is measured in pounds (lbs) and the higher the thrust, the more excavation force available. The electrical equivalent of thrust is wattage.

How does AirSpade work?

The patented supersonic nozzle in the AirSpade turns compressed air into a high-speed, laser-like jet moving twice the speed of sound; Mach 2. All of the energy and momentum of this air moving at approximately 1,200 mph is focused onto the soil, dislodging it in a fraction of a second. Soil is an unconsolidated assemblage of solid particles that may or may not contain organic matter. The voids between the particles are occupied by air and/or water. The aggregate nature of soil aids the ability of the air to fracture it; while stronger materials and ones that are not porous like metal or plastic pipes, cables, or even tree roots are unaffected.

What size air compressor do I need to properly run my AirSpade?

Tow-behind air compressors typically have model numbers that nominally describe their air capacity measured in cubic feet per minute (cfm) at a pressure of 100 pounds per square inch (psi). For example, a "185 compressor" delivers 185 cfm at 100 psi. AirSpade nozzles are designed to optimally operate at 90 psi and are designated by the volume of air delivered at 90 psi. Six nozzle sizes are available to cover the size range of most tow-behind compressors. For more information on matching a compressor to your AirSpade, see Compressed Air Requirements.

Will adjusting my compressor to deliver a higher pressure make the AirSpade work better?

No! AirSpade nozzles are designed to operate optimally at 90 psi. Supplying higher pressure to a supersonic nozzle that has been optimized for 90 psi actually defocuses the air-jet, thus degrading performance while dramatically increasing air consumption.

What size air hose do I need for my AirSpade?

Compressed air flowing through a hose experiences a pressure loss from constrictions and friction proportional to the length of the hose. Air volume, operating pressure, hose ID and smoothness also determine the loss. For more information on air hose pressure loss see Compressed Air Requirements. Generally speaking, air hose of at least 1" ID is recommended for most AirSpade applications. To ensure satisfactory digging performance, air hose can always be sized larger than required, but not smaller.

What about connectors and fittings?

Be sure that fittings and/or connectors do not restrict the air flow in any manner. Use fittings that are rated the same size, or larger, for a given air line size. We recommend the use of Chicago "Air King" style fittings, used in conjunction with safety pins.

In what types of soils does AirSpade work?

Because of its unique, focused air-jet, the AirSpade is effective in virtually all soils and even hard clays. In general, the AirSpade will not cut through rock. However, shale may be broken apart by the AirSpade if the jet is directed between the laminations of the rock. Similarly, the AirSpade will not dislodge hard, frozen soil that tends to behave like pavement or concrete. More information on soil types is contained within Soil Characteristics.

Can I use the AirSpade for digging in clay?

Tests show the AirSpade to be effective in compacted soils with unconfined compressive strengths well above the values listed for hard clay.

What size AirSpade nozzle should I use?

This depends on soil classification and the desired rate of soil excavation. Typical soil excavation rates that can be expected for various AirSpade nozzle sizes are summarized in Digging with AirSpade.

What is the best way to dig with the AirSpade?

The AirSpade will effectively dig up to several inches deep in a medium to stiff soil. Unless the soil is highly compacted, dwelling on the same spot is unnecessary and tends to increase spray. Ideally, the AirSpade should be moved over the soil surface at a rate of about 1 to 2 feet per second. When several inches of soil have been loosened, the soil should be removed to expose a fresh working face for the air jet. Watering the work area ahead of time can sometimes be helpful. Water reduces soil strength thus making digging easier. Water also reduces airborne dust if the soil is extremely dry. Combining the use of the AirSpade with a low-pressure water source (garden hose) can aid the excavation of highly compacted or sun-baked soils.

What are the advantage of digging with AirSpade as opposed to high-pressure water?

• Dangerous, high-pressure water jet can easily cut through clothes or work boots.
• High-pressure water can inadvertently cut through a plastic electric or gas line and/or harm pipe coatings.
• Liquid introduced into the excavation site increases the volume and weight of soils slated for disposal.
• Resulting muddy conditions promote poor footing around job site.
• Mud and splashing water is messy to contain, and often results in wet worker clothing.
• Mud generated from water-excavated, contaminated soil can become a much larger disposal problem.
• Mud, when dumped onto a given area and dried, does not blend-in and thus secondary operations may be required.
• Water has a tendency to accidentally undermine areas adjacent to the excavation.
• Water is heavy, bulky and poses transportation and storage issues.