Download this presentation at http://www.Parker.com/Literature/Balston Filter/IND/IND Technical Articles/PDFs/DryingCompressedAirSlides.pdf Drying compressed air is important as liquid water is often trapped in compressed air distribution systems and can lead to critical problems such as rusted equipment or controls that stick. In this presentation, you will learn the basics on eliminating the water from compressed air, including where the water comes from in the first place, the drying methods available such as aftercoolers, and the best areas to locate filters. You will also learn about the different drying technologies available, including refrigerant dryers, chemical, desiccant, and membrane dryers. A guideline is provided to help you in specifying the right dryer. Parker's Allan Fish, Product Manager, Parker Hannifin.

1. August 26, 2013
Drying Compressed Air

2. Water in Air Distribution Systems
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Water in air distribution systems can
lead to critical problems:
• Rusted equipment
• Controls that stick.
For an economical solution, you
must:
• Clearly define the results
required.
• Specify the right equipment.

3. An Optimum Compressed Air System
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4. Cooling and Condensation
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• As air is compressed, its temperature rises.
• The air can thus hold more water vapor.
• The dewpoint also goes up.
• Any subsequent cooling could cause condensation.
Changes in 8 cubic feet of air as it is compressed, then cooled:
INTAKE OUTLET AFTERCOOLER
Volume 8 cu. ft. (227 liters) 1 cu. ft. (28 liters) 1 cu. ft. (28 liters)
Pressure (gauge) 0 psig (0BAR) 100 psig (6.9BAR) 100 psig (6.9BAR)
Temperature
(example)
68°F (20°C) 158°F (70°C) 68°F (20°C)
Water Content
(vapor)
2.1g 2.1g 0.6g
Relative Humidity 50% 30% 100%
Dew Point (at
pressure shown)
50°F (10°C) 97°F (36°C) 68°F (20°C)

5. What is “Drying” Compressed Air?
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• Compressed air contains
water the liquid and vapor
phases.
• “Drying” compressed air
entails removing water from
it.
• Methods range from:
o Trapping the
condensed water.
o Preventing additional
condensation.
o Removing almost all
the water present.

6. Drying Technologies
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• Aftercooler — Cools the compressed air and reduces its water
content.
• Water trap — Removes bulk water condensed by the
aftercooler.
• Drip leg — Controls slugs of water/oil.
• Coalescing filter — Removes liquids that bypass the water
traps.
• Pressure reduction — Drying through expansion.
• Refrigeration drying — To dewpoints of about 37°F (3°C).
• Chemical dryer — Reduces dewpoint by about 50°F (10°C).
• Desiccant dryer — Dewpoints of about -40°F to -100°F (-40°C
to -73°C).
• Membrane dryer — Variable capabilities to about -40°F (-
40°C) dewpoint.

7. Aftercoolers and Filters
• Air enters a 3500 scfh
compressor at 68ºF.
• And exits at 100 psig and
248ºF.
• The air releases about 13
gallons of water /day.
• Use an aftercooler
immediately after the
compressor.
• Also use an efficient
coalescing filtration system.
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8. Drip Leg Configuration Example
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9. Coalescing Filters
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• Coalescing filters remove water
droplets and also protect dryers.
• Locate them downstream after
the receiver.
• Minimally, use a moderately
efficient coalescing filter.
• i.e. A Balston Grade BX at end-
points eliminates all vapor.

10. Types of Dryers
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Dryers remove water vapor from a system.
• Refrigeration - dryers cool the air to low
temperatures.
• Chemical - dryers pass water vapor over beds of
chemicals.
• Desiccant – dryers passes compressed air over
one bed of desiccant material.
• Membrane - dryers use specially formulated
membrane microtubes.

11. Membrane Dryer Principles
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The tubes are
selectively
permeable to
water vapor.

12. Specifying the Right Dryer
• Beware of overspecifying:
o An entire system
doesn’t always need
low dewpoints
• Beware of underspecifying:
o Damage due to wet air
causes downtime.
• Be sure to use a dryer.
o This ensures removal of
all water vapor.
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13. Specifying the Right Dryer – Cont.
• Leverage the “drying” effect of pressure
reduction.
• Specify membrane dryers for:
o Systems with dewpoints of 35°F to 52°F
(2°C to 5°C) and flow rates up to 600
SCFM (17 NM3/min).
o Instrument-quality air.
o Air exposed to freezing temperatures.
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14. For More Information
Parker Hannifin Corporation
Filtration & Separation Division
242 Neck Road
Haverhill, MA 01835
1-800-343-4048 (U.S. and Canada)
978-858-0505 (local)
www.parker.com/balston
Read White Paper on the
Importance of Drying Compressed
Air
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