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3. Description of Air Flow
With the vacuum pump operating, a vacuum is produced at the pump inlet. Air entering via the vacuum pump air
filter flows directly into the rotor housing where it is compressed. Compressed air passes through the complete
system and is discharged through the discharge port on the reservoir housing. The air/fluid reservoir is equipped with
a safety valve to protect the system in case of excessive restriction to the airflow in the separator element or the
discharge system.
4. Description of Fluid Flow and Vacuum Pump Cooling System
The fluid serves three functions: it lubricates the bearings and rotors; it removes heat from the air as the air is being
compressed thus lowering the compressed air discharge temperature; it also seals the rotor clearances.
Fluid Coolers
Removal of the heat from the fluid is achieved with either an air-cooled heat exchanger or a water-cooled heat
exchanger. The air-cooled fluid cooler is of the finned aluminum tube design. Ambient air is forced through the fins
by a motor driven fan, cooling the fluid in the tubes. To maintain proper vacuum pump operation, the temperature of
the ambient air should not exceed the temperatures listed in the QSVB specifications. 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 discharge temperature at the vacuum pump of
approximately 180°F. The water-cooled fluid cooler is of a shell and tube design. Minimum fluid injection
temperature is controlled by a water regulating valve which senses the fluid temperature entering the vacuum pump
and regulate the cooling water flowing through the fluid cooler. Fluid is circulated through the cooler, fluid filter,
and into the vacuum pump. In the vacuum pump, some fluid is diverted directly through internal passages to ensure
positive lubrication of the bearings, gears and shaft seal. The remainder of the fluid is injected into the early stage
of the compression cycle to seal clearances and cool and lubricate the rotors.
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