and 2 degrees C 35 degrees F at 690 kPa (gage) 100
psig, and where this may be a problem the desiccant
air dryer should be used as a much lower dew point
can be attained.
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Provide for systems not exposed to freezing temperatures a self-contained
refrigerated type compressed air dryer capable of drying [_____] std. L/s
scfm of air to an atmospheric dew point of not less than minus 23 degrees C
10 degrees F with entering air at 38 degrees C 100 degrees F, saturated.
Dryer shall be complete with heat exchanger, a commercial quality
refrigeration system, a moisture separator and condensate trap. Maximum
operating pressure of the dryer shall be [_____] kPa (gage) psig. Install
dryer between the receiver and distribution line.
Provide internal tubing, wiring, and piping complete, such that only
connections to air inlet and outlet, to refrigerant compressor contractor,
and to condensate drain are necessary.
a.
Heat Exchanger: Heat exchanger shall consist of air and
refrigerant coils surrounded by aluminum granules of sufficient
mass to ensure adequate cooling capacity for varying air flow
loads without causing excessive refrigeration cycling. Moisture
separator shall be of centrifuge type and shall be located within
the heat exchanger to provide for moisture separation at point of
minimum air temperature. Suitably control heat exchanger
temperature and provide an automatic control system, whose sensing
element is located in the aluminium granules, to shut down the
refrigeration system on low or no load conditions. Provide means
to ascertain exchanger temperature.
b.
Refrigeration Unit: Hermetically sealed type and shall operate
intermittently at all but maximum load conditions. House entire
unit in a steel cabinet. Provide cabinet with access door and
panel for easy access to each part for maintenance and inspection.
c.
Instrumentation and Control:
Include control panel in dryer
cabinet containing:
(1) Indicators for the following services: Inlet air pressure
gage, discharge air pressure gage, inlet air temperature gage,
refrigeration compressor suction pressure gage, refrigeration
compressor discharge pressure gage, power interruption light, and
high temperature light.
(2) Electrical relays located in an enclosed portion of panel,
accessible for ease of servicing.
(3)
Green "POWER ON" indicating light.
(4) Controls and interlocks to maintain required compressed air
dew point and to cycle air-cooled condenser with refrigeration
compressor.
(5) Dryer capable of automatic zero to 100 percent capacity
control. Dryer shall use an automatic control expansion valve
with sensing bulb to control capacity; dryer to have automatic
shutdown switch sensor located at point of lowest temperature to
prevent freezing.
SECTION 15502N
Page 85
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