Section Ii - Description General Description; The Compression Cycle - Quincy QGB Series Instruction Manual

Section II - Description
• General Description

• The Compression Cycle

• Air Flow
• Cooling System
• Capacity Control System
• Electrical System
General Description
The QGB line of rotary screw compressors
™
covers a horsepower range of 20 to
60. These belt driven compressors
have standard full load pressure ratings
of 00, 25 and 50 PSIG. The large,
27mm rotors allow Quincy to operate
these compressors at lower speeds than
competitive makes.
The compressor is a single stage, positive
displacement, fluid-flooded rotary screw
type unit, consisting of two precision-
machined rotors. The drive rotor is driven
through a v-belt arrangement.
All components are attached to a
heavy-duty steel frame. Controls and
indicators are arranged on a control panel.
Acoustical cabinets are available to reduce
sound levels.
INLET PORT
A) INTAKE
6
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The Compression Cycle
The compression cycle of a rotary screw
compressor is a continuous process from
intake to discharge with no reciprocating
mechanisms starting and stopping as
found in reciprocating compressors. The
compressor consists of two rotors in
constant mesh, housed in a cylinder with
two parallel adjoining bores. The male
drive rotor has four lobes that mesh with
six flutes in the female rotor. All parts are
machined to exacting tolerances.
As the rotors rotate, (male-clockwise as
viewed from the power input end) air is
drawn into the cylinder through the inlet
port located at the power input end. A
volume of air is trapped as the rotor lobes
pass the inlet cut off points in the cylinders.
Compression occurs as the male rotor
rolls into the female flute, progressively
reducing the space thereby raising the
pressure. Compression continues until
the lobe and flute pass the discharge port.
The compressed air is then discharged
into the air/fluid reservoir. There are four
complete compression cycles for each
complete rotation of the male rotor.
CYLINDER
FEMALE ROTOR
B) COMPRESSION
Compression Cycle
Quincy Compressor-QGB
MALE
ROTOR
DISCHARGE PORT
C) DISCHARGE
™