Figure 8-5. - Typical screw type of air compressor.

and to cool the air during the compression cycle. Oil is removed from the compressed air by an oil separator before it leaves the service valves.

SCREW TYPE OF COMPRESSOR

The screw type of air compressor is an oil-injected, helical screw, direct drive, positive displacement air compressor. It maybe single or dual stage (fig. 8-5). The design is relatively simple, being a pair of precisely matched spiral-grooved rotors (fig. 8-6) turning within a single-piece twin-bore cylinder. The rotors provide positive-displacement-internal compression-smoothly, without surging. The matched rotors, one lobed and one grooved, intermesh in the twin bores of the single-piece cylinder. As the rotors turn and unmesh at one end, air is taken in, compressed, and moved through the twin-bore cylinder by the rotors as they rotate. Figure 8-7 shows the steps of airflow past the rotors; figure 8-8 shows aside view of the airflow through the compressor. Compression takes place within the twin-bore cylinder

Figure 8-6. - Male and female screw type of air compressor rotors (matched set).

Figure 8-7. - The compression cycle of a screw type of air compressor.