2.4
LOW PRESSURE COMPRESSED AIR DRYERS
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NOTE: Normally used for under 944 scms 2000 SCFM
capacity systems.
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Provide low pressure compressed air dryers of the mechanical refrigeration
type, equipped with an automatic temperature shutdown switch to prevent
freezing, a regenerative air to air exchanger (in capacity sizes above 4.72
or 28.31 scms 10 or 60 scfm as standard with the manufacturer), and a main
compressed air cooling exchanger. Refrigeration system shall cool
compressed air to dry the air. Dryer shall have no internal traps or
filters and shall have pressure drop not greater than [20.68] [_____] kPa
[3] [_____] psi [indicated]. Air shall leave the dryer at a temperature of
[_____] degrees C F and dew point of [_____] degrees C F, based on an inlet
temperature of [38] [____] [100] [_____] degrees C F. Provide internal
tubing, wiring, and piping complete, such that only connections to air
inlet and outlet, to refrigerant compressor contactor, and to condensate
drain are necessary.
2.4.1
Air Circuit
a.
Regenerative Heat Exchanger: Inlet compressed air to outlet
compressed air heat exchanger (in capacity sizes above 4.70 or
28.30 scms 10 or 60 scfm as standard with the manufacturer)
designed to reduce cooling load at design conditions minus 7
degrees C 20 degrees F by inlet air precooling.
b.
Main Heat Exchanger: Single-pass, with air in the tubes, heat
sink, direct expansion, or flooded cooler type.
c.
Separator: Fabricated in accordance with ASME B31.1; code stamp
not required; moisture separator low velocity type incorporating
change of air flow direction to prevent moisture carryover.
d.
Dryer Operating Pressure:
862 kPa (gage) 125 psig working
pressure.
e.
Drain Line: Provide with exterior mounted condensate trap to
facilitate servicing.
2.4.2
Refrigeration System
a.
Refrigeration Compressor: ARI 520. Hermetic, semi-hermetic, or
open reciprocating type equipped with automatic start-stop or
unloading capacity control; standard components include inherent
motor protection, crankcase oil strainer, and suction screen.
Refrigerant shall be R-22.
b.
Dryer Controls: Capable of automatic 0 to 100 percent capacity
control. Refrigeration controls shall maintain pressure dew point
within the specified range without freezing of condensate.
Controls shall include such devices as capillary tube, expansion
valve, suction pressure regulator, thermostat, or other approved
devices as standard with the manufacturer. Dryer shall have
automatic shutdown switch sensor located at point of lowest
temperature to prevent freezing.
SECTION 15211N
Page 17
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