Aftercoolers; Air/Fluid Reservoir And Air/Fluid Separator Element; Capacity Control System; Auto/Dual Optional - Quincy Compressor QMA Series Instruction Manual

Aftercoolers
Aftercoolers reduce the amount of water condensation
in the discharge air caused by the normal air
compression process. They are used to lower the
dewpoint of the discharge air of the compressor to allow
most of the contained water to be trapped and expelled
from the unit, reducing water related problems
downstream.
The air-cooled combination aftercooler, fluid cooler is
mounted at the top of the cabinet above the drive motor.
Cooling air from the fan is forced through the
aftercooler and fluid cooler.
A moisture separator and water trap is provided for
collecting and expelling water to the customer's drain.
This component is shipped "loose" for mounting at the
job site. Do not directly attach to the aftercooler–the
weight could cause cooler failure. Do not stress the
piping in any way.
Air/Fluid Reservoir and Air/Fluid
Separator Element
The air/fluid reservoir containing the airend is a
pressure vessel performing several functions. Air and
fluid from the compressor is directed through a
discharge pipe to the axial air inlet tunnel which serves
as a ditTuser causing the air/fluid mixture to impact
against the reservoir flange. This action forces much of
the fluid to fall down into the reservoir. Additional
baffling within the reservoir causes the remaining
air/fluid mixture to change directions thus impacting
more fluid from the air. The remaining fluid mist
coalesces in a separator element as the air passes
through. This fluid collects on the bottom and is forced
through an fluid scavenge line back to the compressor.
Compressed air leaving the reservoir contains very little
fluid. The air/fluid resemoir is equipped with a
pressure relief valve, a fluid fill opening and a sight
fluid level gauge.
Capacitv Control System
Functional schematic drawings for the capacity control
system are shown in figures 2-3 through 2-8
Continuous Run with Modulation
As the motor starts turning the compressor rotors, air is
drawn in, compressed and discharged into the airlfluid
reservoir. When the air pressure in the air/fluid
reservoir exceeds 100 PSIG, the full load pressure, the
differential pilot valve opens, passing a controlled
volume of air to the inlet valve air cylinder. (Note:
Other pressure settings are available.)
! CAUTION!
The set screw with locknut located on the inlet
valve is used to allow adequate air flow during
no load operation for proper fluid circulation
This setting is preset at factory and no
adjustment is necessary. DO NOT ADJUSTOR
TAMPER WITH THIS SETTING.
The air forces a piston to move within the cylinder,
...
closing the inlet valve. The compressor
will
continue to
run matching air demand with air delivery by
constantly adjusting the position of the inlet valve. The
inlet valve regulates compressor capacity between 1000/0
and 0°/0of rated delivery.
When maximum pressure has been obtained in the air
system, compressor unloading occurs. The pressure
switch located in the control panel breaks contact.
The 4-way solenoid located on the back of the control
panel opens, venting the residual pressure to the
blowdown valve and allows the air/fluid reservoir to
vent through the blowdown mufller. At the same time,
control air, from the air/fluid reservoir check valve is
directed through the 4-way solenoid to the inlet valve
air cylinder. The inlet valve is held in a closed
position. When the system pressure drops the
wye-delta solenoid closes and the inlet valve opens. In
units with across the line control starters, the solenoid
remains in an open position.
Auto/Dual - Optional
The Auto/Dual system offers two choices of controlling
the Quincy QMA compressor. With the selector switch
in the continuous position, the compressor will operate
in the Continuous Run mode.
When the Auto Dual is selected, a solid state timer is
activated when the pressure switch contacts open. The
timer is adjustable within a ten (10) minute range.
When the timer reaches the end of its delay period, the
compressor will automatically shut down and assume a
"stand-by" mode. Upon a drop in system air pressure,
the pressure switch contacts close, restarting the
compressor automatically. The timer should be set
during unit start-up, for a minimum of six (6) minutes.
During the unloaded./timing out mode, if plant pressure
should drop causing the pressure switch contacts to
close, the compressor will continue to operate, resetting
the timer and instructing the inlet valve to re-open.
When operation in the Auto mode allows the
compressor to start and stop more than five (5) times
per hour select the continuous mode and allow the unit
to operate continuously. Excessive motor starts will
shorten motor life.
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