Section Ii - Description; General Description; The Compression Cycle - Quincy QSI-90 Instruction Manual

Section II - Description

•

General Description

•

The Compression Cycle

• Air Flow
• Cooling System
• Capacity Control System
• Controller Options
• Standard Control Lights, Indicators
& Gauges
• Operating Modes
• Electrical System
General Description
The QSI line of rotary screw compressors
covers a horsepower range of 20 to 350
hp. These truly direct drive compressors
have standard full load pressure ratings
of 100, 125 and 150 PSIG. The large,
120/127mm rotors allow Quincy to operate
these compressors at lower speeds than
competitive makes.
The compressor is a single stage, positive
displacement, fl uid-fl ooded rotary screw
type unit, consisting of two precision-
machined rotors. The male rotor is driven
through a coupling arrangement.
All components are attached to a
heavy-duty steel frame. Controls and
indicators are arranged on a control panel.
Acoustical cabinets are standard on QSI
compressors. QSI-90, 120 and 140 units
are available mounted on a 120 gallon
receiver tank.
INLET PORT
A) INTAKE
4
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 or fi ve lobes that mesh
with six fl utes 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 fl ute, progressively
reducing the space thereby raising the
pressure. Compression continues until
the lobe and fl ute pass the discharge port.
The compressed air is then discharged into
the air/fl uid reservoir. There are four or
fi ve complete compression cycles for each
complete rotation of the male rotor.
CYLINDER
FEMALE ROTOR
B) COMPRESSION
Compression Cycle
MALE
ROTOR
DISCHARGE PORT
C) DISCHARGE