Secti0N - Gardner Denver ELECTRA-SAVER II Service Manual

SECTION 1
GENERAL INFORMATION
FIGURE 1-1. – COMPRESSION CYCLE
COMPRESSOR – The
Gardner- DenveP Electra-Saver 1P
compressor is a single stagei positive displacement rotary
machine using meshing helical rotors to effect compression
The input drive shaft and helical drive gear are supported in
the gear case by high capacity tapered roller bearings The
drive gear meshes with a driven gear mounted on the main
rotor shaft to drive the rotors Both rotors are supported
between large capacity antifriction bearings located outaide
the compression chamber. SingIe-width cylindrical roller
bearings are used at the inlet end of the rotors Heavy duty
tapered roller bearings at the discharge end locate the
rotors axially and carry all thrust loads
COMPRESSION PRINCIPLE (Figure l-l) – Compres
sion is accomplished by the main and secondary rotors
synchronously meshing in a onepiece cylinder. 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 near
the center. 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 compres
sion cycle begins as rotors unmesh at the inlet port and air
is drawn into the cavity between the main rotor lobes and
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 the meshing
continues more of the main rotor lobe enters the second
ary rotor groove 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-discharg&
cycle in rapid succession to produce a discharge air flow
that is continuous smooth and shock-free
AIR FLOW (Figures 2-1 & 3-1) – Air enters the air filter
and passes through the inlet unloader valve to the
compressor. After compression the air/oil mixture passes
into the oil reservoir where most of the entrained oil is
removed by velocity change and impingement and drops
back into reservoir. The air and remaining oil then passes
through the oil separator and the separated oil is returned
to the system through tubing connecting the separator and
compressor. The air passes through the reservoir discharge
manifold discharge check valve minimum pressure valve
and the customer furnished unit shutoff globe valve to the
plant air lines
LUBRICATION, COOLING AND SEALING – Oil is
forced by air pressure from the oil reservoir through the
oil cooler, thermal control (thermostatic mixing) valve and
oil filter and discharges into the compressor main oil gal
Iery. A portion 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 by proprietary means to remove heat of com
pression seal internal clearances and lubricate the rotors
COMPRESSOR OVERHAUL – For compressor overhaul
procedures and rebuilding data including dimensions run
ing clearances and fits see Service Manual 13-10-602.
13-9-630 Section 1
Page 1