Compressor Principle; Air Flow In The Compressor System; Lubrication, Cooling And Sealing; Compression Cycle - Gardner Denver Electra-Screw EDEQHF Operating And Service Manual

SECTION 1
GENERAL INFORMATION
FIGURE 1-1 - COMPRESSION CYCLE
COMPRESSOR - The Gardner Denver@ compressor
is a single stage, positive displacement rotary machine
using meshing helical rotors to effect compression. Both
rotors are supported between high capacity roller bear-
ings located outside the compression chamber. Single
width cylindrical roller bearings are used at the inlet end
of the rotors to carry part of the radial loads. Tapered
roller bearings at the discharge end locate each rotor
axially and carry all thrust loads and the remainder of the
radial loads.
COMPRESSION PRINCIPLE (Figure 1-1) - Compres-
sion is accomplished by the main and secondary rotors
synchronously meshing in a one-piece c Iinder. The
main rotor has four (4) helical lobes 90 apart. The
secondary rotor has six (6) matching helical grooves 60°
apart to allow meshing with main rotor lobes.
The air inlet port is located on top of the compressor
cylinder near the drive shaft end. The discharge port is
near the bottom at the opposite end of the compressor
cylinder. Figure 1-1 is an inverted view to show inlet and
discharge ports. The compression cycle begins as the
rotors unmesh at the inlet port and air is drawn into the
cavity between the main rotor lobes and the secondary
rotor grooves (A). When the rotors pass the inlet port
cutoff, air is trapped in the interlobe cavity and flows
axially with the meshing rotors (B). As meshing con-
tinues, more of the main rotor lobe enters the secondary
rotor grove, normal volume is reduced and pressure
increases.
Oil is injected into the cylinder to remove the heat of
compression and seal internal clearances. Volume
reduction and pressure increase continues until the
air/oil mixture trapped in the interlobe cavity by the
rotors passes the discharge port and is released to the
oil reservoir (C). Each rotor cavity follows the same
"fill-compress-discharge" cycle in rapid succession to
produce a discharge airflow that is continuous, smooth
and shock free.
AIR FLOW IN THE COMPRESSOR SYSTEM (Figure
5-1, page 1, Section 5) - Air enters the air filter and passes
through the inlet unloader valve and on into the com-
pression chamber where oil is injected into the air. After
compression, the air/oil mixture passes into the oil reser-
voir where most of the entrained oil is removed by
velocity change and impingement and drops back into
the reservoir. The air and remaining oil then passes
through piping and the air/oil separator. The air then
passes through the minimum pressure/check valve, the
aftercooler and the moisture separator and into the plant
air lines.
LUBRICATION, COOLING AND SEALING - Oil is
forced by air pressure from the oil reservoir through the
oil cooler, thermostatic mixing valve, and oil filter and
discharged into the compressor main oil gallery. A por-
tion of the oil is directed through internal passages to
the bearings, gears and shaft oil seal. The balance of the
oil is injected directly into the compression chamber to
remove heat of compression, seal internal clearances
and lubricate the rotors.
13-8-610 Section 1 Page 1