Brochure

UNFOCUSED AIR FLOW FROM
IMPROPER LY DESIGNED NOZZLE
FOCUSED AIR FLOW FROM
AIR-SPADE SUPERSONIC NOZZLE
HOW DOES AIRSPADE WORK?
The patented, supersonic nozzle in the AirSpade turns
compressed air into a high-speed, laser-like jet moving
at twice the speed of sound, Mach 2. All of the energy
and momentum of this air moving at approximately 1200
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 wooden
tree roots are unaffected.
WILL HIGHER PRESSURE MAKE
THE AIRSPADE WORK BETTER?
All AirSpade nozzles are developed to operate optimally
at 90 psig. Supplying higher pressure to a supersonic
nozzle that has been optimized for 90 psig actually
defocuses the air jet, thus degrading performance while
consuming more air. For example, doubling the air pres-
sure to 180 psig increases the air jet force by only 10%
and the exit momentum ux (stress seen by the soil) by only
45%.
IN WHAT TYPES OF SOIL WILL
AN AIRSPADE WORK?
Because of its unique, focused air-jet, the AirSpade works
in most soils, even hard clays. Cohesive soils can be clas-
sied and described by unconned compressive strength
as shown in the chart to the right. Tests have shown the
AirSpade to be effective in compacted soils with uncon-
ned compressive strengths, well above the values listed
for hard clay.
Watering the work area ahead of time can
sometimes be helpful. Water reduces most airborne dust if
the soil is extremely dry. It also reduces the soil’s strength
making it easier to dig. Combining the use of the AirSpade
with a low pressure water jet is effective even with
extreme cases of highly compacted or sun-baked soils.
The AirSpade in general will not cut through rock. Shales,
however, 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 which may
behave like pavement or concrete.
HOW DOES AIRSPADE OUTPERFORM
OTHER AIR TOOLS?
In head to head tests, the AirSpade dislodged
harder clay soil and dug faster than other air
digging tools. Soil fractures from compressive stress,
tons per square foot (tsf), exerted on its surface.
As shown above, for the same pressure and ow,
compressed air exiting from an improperly designed
nozzle expands outward rapidly to 3 to 4 times the
area versus the jet from the patented supersonic
nozzle in the AirSpade.
HOW SHOULD I DIG WITH THE AIRSPADE?
The AirSpade will dislodge 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. The AirSpade can 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. Vacuum suction, as provided by our AirVac
unit, is an excellent companion to the
AirSpade since it is likewise non-damaging.
Strength of Clays
Consistency Unconned Compressive Strength
(tsf)
Very Soft 0 to 0.25
Soft 0.25 to 0.5
Medium 0.5 to 1
Stiff 1 to 2
Very Stiff 2 to 4
Hard > 4
OSHA Cohesive Soil Classications
OSHA
Type
Unconned
Compressive
Strength
Description of
Cohesive soils
A
≥ 1.5 tsf
Clay, silty clay, sandy
clay, clay loam, caliche.
hardpan, and sometimes
silty clay loam and sandy
clay loam.
B
<1.5 and >0.5 tsf
Granular cohesive soils
like angular gravel, silt,
silt loam, sandy loam, and
sometimes silty clay loam
and sandy clay loam.
C
≤ 0.5 tsf
Granular soils such as
gravel, sand, loamy sand,
submerged soil, or soil
from which water is freely
seeping.