QT 7.5 Parts Manual

QT-7.5 Industrial Quincy Compressor
2022207901, June 2018 11
Item Part
# Qty. Number Description
1 1 2024108000 serial number & nameplate
2 1 2024107202 decal, CAUTION!, MANUAL
3 1 2024107203 decal, DANGER!,"Air from this...."
DECALS
WARNING !
Installation
The pilot valve is mounted directly into the air tank.
Compressors in the field, not equipped with these
controls, can be converted. Consult your local Quincy
distributor for assistance with conversion procedures.
Service
If a change in pilot valve operation is detected, remove
the pilot valve from the air tank and check the screen
in the inlet of the pilot valve for obstructions. Clean
the screen if necessary.
Adjustment
The unloading pressure is adjustable and is regulated
by turning the unload adjustment hex nut (refer to
pilot valve illustrations). Turn the hex nut clockwise
to increase and counterclockwise to decrease the
unloading pressure.
The differential (difference between unloading and
loading pressure) is set by turning the differential
adjustment hex nut (refer to pilot valve illustrations).
Increase the differential pressure by turning the hex
nut clockwise - decrease by turning counterclockwise.
Make all adjustments in small increments. Tighten
the locknuts after adjustment.
SUCTION VALVE UNLOADER
ASSEMBLIES
Description
The Quincy suction valve unloader assembly consists
of unloading assemblies on the suction valves, hav-
ing a plunger to contact the suction valve reed and
an unloader pilot valve (20239116xx or 20239121xx
series) to automatically regulate the passing of air
tank pressure to the unloading arrangement.
Continuous Run Operation
Suction valve unloader assemblies are recommended
for use on Quincy compressors where the compres-
sor is to run continuously and a constant pressure
is to be maintained. The purpose is to automatically
unseat the suction valve of the compressor when the
air supply is greater than the demand.
Unloading occurs when air tank pressure is suf-
ficient to overcome pilot valve spring pressure. The
check ball is then unseated, allowing air tank pressure
to pass to the unloader assemblies. The compressor
will run unloaded until the air tank pressure drops
to a predetermined level. At this time, the action of
the ball is reversed, shutting off air tank pressure to
the unloader assemblies and venting the unloader to
atmosphere. This allows the compressor to load. The
drive, either electric motor or engine, runs continu-
ously and must be started and stopped manually.
20239116xx series pilot valves feature a toggle lever
which can be flipped to provide manual unloading.
Dual Control Operation
Dual control operation is designed to provide
a choice between "start/stop" or "continuous run"
operation. The 20239121xx series pilot valve can be
set for "start/stop" operation by turning the knurled
knob at the end of the pilot valve (refer to illustration
for 20239121xx series pilot valve) clockwise until it
stops. Under these circumstances, a pressure switch
is required to stop the motor. Failure to use a pressure
switch, with the pilot valve locked out, will result in
unsafe conditions.
A pressure switch must be incorporated whenever
20239121xx series pilot valve is employed as part of the
control system.
The compressor will operate in the continuous run
mode if the knurled knob is turned counterclockwise
until it stops.
3
2
1
Decals