Efficient Plant March 2022 - 7

The TRUTH About
COMPRESSED AIR!
Compare These Blowoffs
Th ere are a variety of ways to dry, clean or cool
products and surfaces, but which method is best?
To decide, we ran a comparison test on the same
application using four diff erent blowoff methods:
drilled pipe, fl at 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.
The following comparison proves that the
EXAIR Super Air Knife is the best choice for
your blowoff , cooling or drying application.
Th e 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).
Th e compressed air pressure required was
60 PSIG. Th e blower used had a ten horsepower
motor and was a centrifugal type
blower at 18,000 RPM. Th e table below
summarizes the overall performance.
If you think compressed air is too
expensive and noisy - read this.
The facts will surprise you!
Drilled Pipe Th is 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. Th e drilled pipe performed poorly. Th e initial cost of the drilled
pipe is overshadowed by its high energy use. Th e holes are easily blocked and
the noise level is excessive. Velocity across the entire length was very
inconsistent with spikes of air and numerous dead spots.
Flat Air Nozzles Th is inexpensive air nozzle was the worst performer. It is
available in plastic, aluminum and stainless steel from several manufacturers.
Th e fl at air nozzle provides some entrainment, but suff ers from many of the
same problems as the drilled pipe. Operating cost and noise level are high.
For some fl at air nozzles the holes can be blocked - an OSHA violation.
Velocity was inconsistent with spikes of air.
Blower Air Knife Th e 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 fl at air nozzle, but was comparable to EXAIR's
Super Air Knife. Th e large blower with its two 3 " (8cm) diameter hoses requires
signifi cant mounting space. Noise level was high at 90 dBA. Th ere was no
option for cycling it on and off to conserve energy. Costly bearing and fi lter
maintenance along with downtime were also negative factors.
EXAIR Super Air Knife Th e Super Air Knife did an exceptional job of
removing moisture on one pass due to the uniformity of the laminar airfl ow.
Th e sound level was very 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 with no moving parts to wear out.
The Super Air Knife is the low cost way to blowoff, dry, clean and cool.
Blowoff Comparison
Type of
blowoff
Flat
Air Nozzles
Blower
Air Knife
https://exair.co/48_akv_ad
SEE THE AIR KNIFE IN ACTION!
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 fi lters, belts and bearings.
Super
Air Knife
PSIG BAR
Drilled Pipes 60 4.1
60 4.1
3
Compressed Air Horsepower
Required
SCFM SLPM
174
257
4,924
7,273
0.2 N/A N/A
60 4.1
55 1,557
Here are some important facts:
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 $1000.
* Blower bearings wear out quickly due to the high speeds
(17-20,000 RPM) required to generate eff ective airfl ows.
* Poorly designed seals that allow dirt and moisture infi ltration and
environments above 125°F decrease the one year bearing life.
* Many bearings can not be replaced in the fi eld, resulting in
downtime to send the assembly back to the manufacturer.
Manufacturing Intelligent
Compressed Air® Products Since 1983
11510 Goldcoast Drive * Cincinnati, OH 45249-1621 * Phone (513) 671-3322
FAX (513) 671-3363 * E-mail: techelp@exair.com * www.exair.com
35
51
10
11
Sound
Level dBA
91
102
90
69
Purchase
Price
$50
$300
$7,000
$720
Annual
Approx. Annual
Electrical Cost* Maintenance Cost
$4,508
$920
$6,569
$1,288
$1,417
*Based on national average electricity cost of 8.3 cents per kWh. Annual cost refl ects 40 hours per week, 52 weeks per year.
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 diffi cult to
control since mechanical
adjustments are required.
https://exair.co/48_423
@EXAIR
$1,450
$1,500
$300
First Year
Cost
$5,478
$8,227
$8,288
$2,437

https://www.exair.co/48_akv_ad https://www.exair.co/48_423 https://www.exair.co/48_423 http://www.exair.com

Efficient Plant March 2022

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