Quincy Compressor QR-25 Series Instruction Manual page 8

UNLOADER TOWERS
Fig. 2-2 Control Version L
PRESSURE
RELIEF
VALVE
CHECK
VALVE
TO
AIR
RECEIVER
Pix 1155
Fig. 2-3 Control Version L
Variation (Discharge Line
Check Valve & Pressure
Switch)
UNLOADER TOWERS
Pix 1071
Fig. 2-4 Control Version S
*1, 2, or 4 unloader towers are employed depending upon the model of compressor.
QR-25 Series
52201-107, December 2012
for com pressed air. The idea is to create com pressed air on demand, but
to limit the number of times a motor must start the compressor in a given
time period. To prevent motor burnout, the motor should be limited to no
more than six (6) starts per hour.
FROM THE
AIR RECEIVER
Control Version P : Describes a basic compressor with no added control
features.
HYDRAULIC
UNLOADER
Control Version L : Consists of unloader tower(s)
the compres sor, a hydraulic unloader mounted on the bearing carrier, and a
pressure switch. This version is recommended for those applications where
Pix 1069
the compressor will not be required to start more than six (6) times per
Pix 1069
hour. A compressor equipped with control Version L is sometimes referred
to as a "start/stop machine"
The pressure switch detects the demand for compressed air and allows
the unit to start. When the demand is satisfied, the unit stops.
The hydraulic unloader allows the com pres sor to start in an "unloaded"
AUTOMATIC
PRESSURE
state, that is, the compressor starts but does not begin to create compressed
SWITCH
air until oil pressure is established. The hydraulic unloader also guards
against excessive damage in the event of an oil pressure drop.
Control Version L Variation: A variation of Control Version L is illustrated
in Fig. 2-3. It shows how a discharge line check valve, pressure switch, &
pressure relief valve are combined to provide start/stop operation.
Pix 1155
Control Version S : This version is best suited for "continuous run"
applications (whenever the compressor must start more than six [6] times
per hour). If the demand for compressed air is continuous and exceeds one
half or more of the compressor's capacity, Control Version S should be used.
Once the compressor is started, it continues to run until it is manually
turned off. Whenever there is a demand for compressed air, the pilot valve
closes, allowing the un loader in the unloader tower to actuate. At this point,
the compressor starts making com pressed air. As soon as the demand for
com pressed air is met, the pilot valve opens, al lowing air pressure to de-
actuate in the un loader tower. The compressor continues to run but does
UNLOADER PILOT
(110832 series)
not compress air.
Control Version LS: This version consists of a head assembly with unloader
CONNECT TO
tower(s)* a pilot valve and a hydraulic unloader. It is usually applied to gas
AIR RECEIVER
WITH A MINIMUM
OF 3/8" O.D.
or diesel engine driven units. Virtually the same as Control Version S, but
COPPER TUBING.
with a hydraulic unloader added to protect the compressor in the event of
Pix 1071
an oil pressure drop.
Control Version LVD: Unloader tower(s)*, a pilot valve with a manual shut-
off, a hy draulic unloader, a check valve assembly, and a pressure switch make
up the LVD Control Version. This version is recom mended wherever the degree
of demand and usage is variable.
8 3501 Wismann Lane, Quincy IL - 62305-3116
located on the head of
*
Quincy Compressor