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Your compressor is either a LG (Low Pressure) or HG (High Pressure) single stage,
positive displacement, oil-flooded screw compressor. There are two basic general
configurations; geared (Figure 1) and non-geared (Figure 2).
Figure 1 - geared compressor Figure 2 -Typical non-geared compressor
Oil-flooding provides cooling, lubrication and sealing in the compressor. The oil must be cooled using either water
or air in a heat exchanger that is properly sized for all operating conditions.
Geared units (Figure 1) come standard with integral gearing to increase or decrease the speed internally, allowing
for direct connection with standard drivers. The drive (input) shaft is an integral extension of the male rotor.
Compressors with gears use an independent input shaft, commonly referred to as a jackshaft, mounted on roller
and/or special deep groove ball bearings. The gear mounted on the jackshaft drives the gear mounted on the male
rotor and the male rotor meshes with and drives the female rotor.
Figure 3 shows the direction of the rotor rotation and
the gas/oil flow through the compressor. Note that
this flow is between the rotors and the inside diameter
(bore of the cylinder).
The uncompressed gas enters the compressor at the
inlet flange, passes into the front bearing retainer, and
enters the cylinder bore at the front (inlet) end. (Figure
3). As the gas passes a predetermined inlet cut-off
point in the cylinder, compression takes place due to
decreasing rotor to cylinder volume as the rotors turn.
Gas at the desired pressure is discharged at the rear
(discharge) end. Oil is injected into the compressor at
specific locations for cooling.
Understanding Your Compressor
Figure 3 - Oil/Gas Flow-Typical
