The Super Air Knife is the low cost way to blowoff,
dry, clean and cool.
Type of blowof PSIG BAR
Comp. Air Horsepower
Cost SCFM SLPM
Drilled Pipes 60 4. 1 174 4,924 35 91 $50 $4,508 $920 $5,478
If you think compressed air is too expensive and noisy - read this. The facts will surprise you!
Compare these Blowoffs
Tere are a variety of ways to blow the water from the bottles shown in the photo below, but which method
is best? To decide, we ran a comparison test on the same application using four different blowoff methods:
drilled pipe, flat air nozzles, Super Air Knife (each using compressed air as a power source), and a blower
supplied air knife (using an electric motor as a power source). Each system consisted of two twelve inch
long air knives. Te following comparison proves that the EXAIR Super Air Knife is the best choice for
your blowoff, cooling or drying application.
Te goal for each of the blowoff choices was to use the least amount of air possible to get the job done
(lowest energy and noise level). Te compressed air pressure required was 60 PSIG which provided
adequate velocity to blow the water off. Te blower used had a ten horsepower motor and was a centrifugal
type blower at 18,000 RPM. Te table at the bottom of the page summarizes the overall performance. Since
your actual part may have an odd configuration, holes or sharp edges, we took sound level measurements in
free air (no impinging surface).
Tis common blowoff is very inexpensive
and easy to make. For this test, we
used ( 2) drilled pipes, each with ( 25)
1/16" diameter holes on 1/2" centers.
As shown in the test results below, the
drilled pipe performed poorly. Te initial
cost of the drilled pipe is overshadowed
by its high energy use. Te holes are
easily blocked and the noise level is
excessive - both of which violate OSHA
requirements. Velocity across the entire
length was very inconsistent with spikes
of air and numerous dead spots.
Flat Air Nozzles
As shown below, this inexpensive
air nozzle was the worst performer.
It is available in plastic, aluminum
and stainless steel from several
manufacturers. Te flat air nozzle
provides some entrainment, but suffers
from many of the same problems
as the drilled pipe. Operating cost
and noise level are both high. Some
manufacturers offer flat air nozzles
where the holes can be blocked -
an OSHA violation. Velocity was
inconsistent with spikes of air.
EXAIR Super Air Knife
Te Super Air Knife did an exceptional
job of removing the moisture on one
pass due to the uniformity of the
laminar airflow. Te sound level was
extremely low. For this application,
energy use was slightly higher than the
blower but can be less than the blower
if cycling on and off is possible. Safe
operation is not an issue since the Super
Air Knife can not be dead-ended.
Maintenance costs are low since there
are no moving parts to wear out.
Blower Air Knife
Te blower proved to be an expensive,
noisy option. As noted below, the
purchase price is high. Operating
cost was considerably lower than the
drilled pipe and flat air nozzle, but
was comparable to EXAIR’s Super
Air Knife. Te large blower with its
two 3" (8cm) diameter hoses requires
significant mounting space compared
to the others. Noise level was high
at 90 dBA. Tere was no option for
cycling it on and off to conserve energy
like the other blowoffs. Costly bearing
and filter maintenance along with
downtime were also negative factors.
Facts about Blowers
Energy conscious plants might think a blower to
be a better choice due to its slightly lower electrical
consumption compared to a compressor. In reality,
a blower is an expensive capital expenditure that
requires frequent downtime and costly maintenance
of filters, belts and bearings. Here are some
Filters must be replaced every one to three months.
Belts must be replaced every three to six months.
Typical bearing replacement is at least once a year
at a cost near $1,000.
• Blower bearings wear out quickly due to the
high speeds ( 17-20,000 RPM) required to
generate effective airflows.
• Poorly designed seals that allow dirt and
moisture infiltration and environments above
125°F decrease the one year bearing life.
• Many bearings can not be replaced in the
field, resulting in downtime to send the
assembly back to the manufacturer.
Blowers take up a lot of space and often produce
sound levels that exceed OSHA noise level
exposure requirements. Air volume and velocity
are often difficult to control since mechanical
adjustments are required.
To discuss an application, contact:
11510 Goldcoast Drive
Cincinnati, Ohio 45249-1621
Fax: (513) 671-3363
See the Super Air Knife in action.
Circle 501 on card or visit www.exair.co./61_akva_ad