Page
9
KRSL series
2.2 THE COMPRESSION CYCLE
The rotary screw oil-injected vacuum pump is a specific form
of rotary positive displacement pump using a dual screw
airend as the principal element in air compression.
The compressor housing contains of two rotors; Male and
Female rotor. The male rotor has five lobes and female rotor
has six flutes. They are constantly and precisely meshed and
housed in the cylinder with two parallel adjoining bores. All
parts are machined to exacting tolerances. The rotors provide
positive-displacement internal compression smoothly and
without surging. As the rotors rotate, air is drawn into the
cylinder through the inlet port. A volume of air is filled and trapped as the rotor lobes pass the
inlet port 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/oil
separator tank. There are five complete compression cycles for each complete rotation of the
male rotor.
When the compressor is operating, a partial vacuum is produced at the compressor inlet. Fluid is
injected into the compressor unit and mixed with the air. The fluid has three basic functions:
•
As a coolant, it controls the rise in air temperature normally associated with the heat of
compression.
•
It seals the leakage paths between the rotors and stator and between the rotors themselves.
•
It acts as a lubricating film between the rotors allowing one rotor to directly drive the
other, which is an idler.
After air/fluid mixture is discharged from compressor to the reservoir, fluid is separated from the
air in the separator tank. Compressed air then flows through the after-cooler for moisture
removal while the lubricant is being cooled by the fluid-cooler for re-injection.
2.3 MOTOR
The main motor is a variable speed induction motor. Operating conditions of the variable speed
motor are as follows (may vary with different countries).
Ambient temperature
≤
40
℃
Altitude
≤
1000m
