User Manual

8 Utility AirSpade Technical Applications Bulletin
AirSpade Supersonic Nozzle: Soil fractures from stress (force per unit
area) applied to its surface. Focusing this force on a small unit area
results in faster, and more efficient soil excavation. As shown in the
diagrams below, air exiting from an open pipe, or from a conventional
nozzle, expands rapidly outward, across 3 to 4 times the unit area,
versus the focused output of the Supersonic Nozzle. In addition, open
pipes or conventional nozzles operate at speeds below Mach 2. Thus,
the Supersonic Nozzle outperforms these by a wide margin.
As dry excavation has grown for underground utility applications, the
need for a specialized tool to meet safety and other concerns has
become more acute. Given the potential hazards and costs associated
with excavation of underground lines, Guardair Corporation drew upon
expertise from utilities across the US to design the Utility AirSpade.
Their concerns included:
•
Maximizing digging efficiency of the tool
•
Eliminating potential for spark-induced accidents
•
Optimizing human factors and safety
•
Providing protection from high voltage, underground electric lines
MAXIMIZING DIGGING EFFICIENCY
The key to maximizing digging efficiency is the design of the output
nozzle. Proper nozzle design starts with an in-depth understanding of
the effects of directing compressed air into soils.
Soil is an unconsolidated assemblage of solid particles including clay,
sand, silt, rock, and sometimes organic matter. Voids between the
particles are occupied by air and/or water. When compressed air is
directed into soil at close range, it enters the voids, expands, and
fractures the soil in a fraction of a second. Non-porous materials such
as metal or plastic pipes, cables, or even tree roots are unaffected.
To optimize nozzle performance, Guardair engineers recognized the
importance of maximizing the exiting air speed (and subsequently
the force) and tightly focusing the exiting air jet. This led to the
development of the AirSpade Supersonic Nozzle, which converts
compressed air into a high-speed, highly focused air jet moving at
twice the speed of sound – Mach 2.
Equipped with the Supersonic Nozzle, AirSpade performs better in
compact soils, provides faster excavation rates, and operates more
efficiently by consuming less (expensive to produce) compressed air,
thus saving time on the job site compared to other air excavation
tools equipped with conventional nozzles. With a documented
excavation rate of 1.0 to 1.5 cubic feet per minute (depending upon
soil strength), the AirSpade is 2 to 3 times faster than hand digging
and is highly effective in time-sensitive projects, while still protecting
underground utility lines.
More efficient usage of compressed air also reduces air compressor
operating hours. This translates directly into lower fuel costs and less
wear and tear on the air compressor.
Conventional Nozzle Supersonic Nozzle
UTILITY AIRSPADE INNOVATIONS AND FEATURES