3000PB, 3700B, 4500B, 3000PVB, 3700VB, 4500VB User Manual 2: Description
02250216-786 R01
Subject to EAR, ECCN EAR99 and related export control restrictions. 17
2.7 Air inlet system, functional 
description 
Refer to Figure 2-6. The compressor inlet system con-
sists of a dry-type air filter, a restriction gauge and an air 
inlet val
ve.
The restriction gauge (located on the air filter) indicates 
the
 condition of the air filter by showing red when filter 
maintenance is required. 
The poppet-type modulating air inlet valve directly con-
trols the amount of air intake to the compressor in 
r
esponse to the operation of the pressure regulator. 
Refer to Section   on
 page 15. The inlet valve also acts as 
a check valve, thus preventing
 reverse rotation when the 
compressor is shut down.
 WARNING
“The Plastic Pipe Institute recommends against 
the use of thermoplastic pipe to transport com-
pressed air or other compressed gases in 
expo
sed above ground locations, e.g. in exposed 
plant piping.”
1
Sullube
®
 should not be used with PVC piping sys-
tems. It may affect the bond at cemented joints. 
Cer
tain other plastic materials may also be 
affected. 
1
Plastic Pipe Institute, Recommendation B. Adopted 
January 19, 1972.
Figure 2-6: Air inlet system
1. Air inlet filter 4. Separator/sump tank
2. Air inlet 5. Restriction indicator
3. Compressor unit