Quincy Compressor 50093-103 - Manual (Page 37)

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Air Flow
During pump operation, a vacuum is produced at the
pump inlet. Air entering flows through the air inlet valve
into the rotor housing where it is compressed, then
discharged within the air/fluid reservoir. The air
discharged from the pump contains fluid which is
separated from the air as it passes through a fluid
separator located within the air/fluid reservoir. The gas,
now at near atmospheric pressure, is exhausted through
the discharge port on the reservoir housing. The air/fluid
reservoir is equipped with a safety valve to protect the
system in the event of excessive restriction to the air flow
in the separator element or the discharge system.
Fluid Flow & Cooling System
The fluid in the system serves three functions: it lubricates
the bearings and the rotors, it seals rotor clearances to
improve efficiency, and it removes heat from the gas as the
gas is being compressed, thus lowering the discharge
temperature.
Fluid is pumped out of the air/fluid reservoir through a
fluid filter and then into the airend. In the airend, some of
the fluid is diverted directly to the bearings through
internal passages to insure positive lubrication to the
bearings, the remainder of the fluid is injected into the
early stage of the evacuation cycle to seal clearances and
lubricate the rotors.
Fluid Coolers
Removal of the heat from the fluid is achieved with either
an air-cooled or a water-cooled heat exchanger. The air-
cooled fluid cooler is a finned tube unit. A continuous
supply of cool air is forced across the fins and tubes by a
fan mounted on a separate drive motor. Minimum fluid
injection temperature is controlled by a thermal mixing
valve which permits a controlled amount of hot fluid to mix
with the cooled fluid before entering the vacuum pump.
The water-cooled fluid cooler is of shell and tube
construction. Minimum fluid injection temperature is
controlled by a water regulating valve which senses the
fluid temperature entering the vacuum pump and regulates
the cooling water flowing through the fluid cooler.
Air/Fluid Reservoir & Air/Fluid Separator Element
The air/fluid reservoir serves as a fluid reservoir and
contains the air/fluid separator element. The discharge
pipe from the vacuum pump enters the reservoir at a point
below the normal fluid level and then turns upward inside
the reservoir. The air/fluid mixture is discharged into the
reservoir above the fluid level and impinges on the
underside of the separator element. The air/fluid reservoir
is provided with a fluid filler opening and fluid level gauge.
As the air/fluid mixture impinges on the bottom of the fluid
separator element, most of the fluid separates from the air
and drops to the bottom of the reservoir. The remaining
fluid, suspended in the air stream, passes through the
media of the separator element and is removed from the
discharge air stream. The fluid is then returned to the
vacuum pump by means of a scavenging line connected
from the bottom of the air/fluid separator element to the
inlet housing.
It should be noted that the separator element is sized
larger for a vacuum pump than it would be for the
equivalent displacement compressor, and only Quincy
approved separator elements should be used.
Vacuum Control System
Assume the control system is set to operate between 20”
to 23” HgVand is in the power-off state. When the start
button on the vacuum pump is activated, two operations
occur. First, electric power is routed through normally
closed contacts on the vacuum switch to the normally
open solenoid valve causing it to shift closed. Second, the
inlet valve permits air to flow from the vacuum system to
the vacuum pump inlet where it is compressed to
atmospheric pressure and discharged through the air/fluid
reservoir.