Quincy Compressor QSI Series Instruction Manual page 9

Air Flow
With the compressor operating, a partial vacuum is
produced at the compressor inlet. Air entering via the
compressor air filter flows through the air inlet valve into
the rotor housing where it is compressed, then discharged
into the air/fluid reservoir. Compressed air passes
through the complete system then through a minimum
pressure check valve to the service connection.
Cooling System
Fluid Coolers
Fluid coolers may use either air or water as a cooling
medium. The following descriptions point out the major
differences between the two types of coolers.
Air-cooled Fluid Coolers
The air-cooled fluid cooler and aftercooler are of the
finned aluminum tube, one piece design. Ambient air is
forced through the fins by a motor driven fan, cooling the
fluid and air in the tubes. To maintain proper compressor
operation, the ambient air temperature should not exceed
the temperatures listed in Appendix B - Technical Data.
The cooler fins must be kept clean at all times. Fluid
leaving the receiver passes through a thermal mixing
valve before traveling on to the cooler. The purpose of
the thermal valve is to maintain a minimum fluid dis-
charge temperature at the compressor of approximately
180°F.
Water-cooled Fluid Coolers
Water-cooled fluid coolers are of the shell and tube de-
sign. Fluid passes through the shell transferring its heat
to the water flowing through the tubes. Fluid leaving the
cooler does not pass through a thermal mixing valve as
in an air-cooled unit, but goes directly to the fluid filter
and the compressor. Fluid discharge temperature at the
compressor is maintained by a water temperature regulat-
ing valve located in the discharge water line. The water
temperature regulating valve uses a probe to sense fluid
temperature and opens and closes, governing water flow
through the cooler.
Aftercoolers
Aftercoolers reduce the amount of water in the dis-
charge air. They are used to lower the temperature of the
discharge air thereby condensing water vapor from the
compressed air. This allows most of the contained water
to be trapped and expelled from the unit, reducing water
related problems downstream.
Air-cooled aftercoolers are part of the air-cooled fluid
cooler. Cooling air from the fan is blown through the
aftercooler and the fluid cooler.
Water-cooled aftercoolers are placed in series with the
fluid cooler. Incoming water is first directed through the
aftercooler and then on to the fluid cooler.
A combination moisture separator and water trap is pro-
vided for collecting and expelling water to the customer's
drain.
Quincy Compressor-QSI
®
Section II - Description
7