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Drying Compressed Air | Filtration Technology - Parker Hannifin


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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.

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Drying Compressed Air | Filtration Technology - Parker Hannifin

  1. 1. August 26, 2013 Drying Compressed Air
  2. 2. Water in Air Distribution Systems 2 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. 3. An Optimum Compressed Air System 3
  4. 4. Cooling and Condensation 4 • 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. 5. What is “Drying” Compressed Air? 5 • 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. 6. Drying Technologies 6 • 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. 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. 7
  8. 8. Drip Leg Configuration Example 8
  9. 9. Coalescing Filters 9 • 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. 10. Types of Dryers 10 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. 11. Membrane Dryer Principles 11 The tubes are selectively permeable to water vapor.
  12. 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. 12
  13. 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. 13
  14. 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) Read White Paper on the Importance of Drying Compressed Air 14