Section 5
COMPRES SOR SYSTEMS
19
cooling of air on units with air aftercoolers.
5.5 AIR INLET SYSTEM, FUNCTIONAL DE-
SCRIPTION
The compressor inlet system consists of a dry--
typeairfilterandanaircontrolvalve.Reactingon
apressuresignal,thevalveclosest heintakeforun-
loaded operation. The valve also acts as a check
valve upon shutdown.
5.6 CONTROL SYSTEM, FUNCTIONAL DE-
SCRIPTION
Thepurposeofthecompressorcontrolsystemisto
regulate the amount of air being compressed to
match the amount of compressed air being used.
The capacitycontrolsystemconsistsofasolenoid
valve, regulator valve and an inlet valve.The
functional description of the control s ystem is de-
scribed below in four distinct phases of operation.
The following description text applies to all Series
ES---8 compressors. For explanatory purposes,
this description will apply to a compressor with an
operating range of 100 to 110 psig (6.9 to 7.6bar).
Acompressorwithanyotherpressurerangewould
operate in the same manner, excepting stated
pressures.
START MODE -- 0 TO 60 PSIG (0 TO 4.2 BAR)
When the compressor “I” pad is depressed, the
sump pressure w ill quicklyrise from0 to60 psig(0
--- 4.2 bar). During this period, both the pressure
regulatorand the solenoid valve areclosed, the in-
let valve is fully open, and the compressor pumps
at full rated capacity. The rising compressor air
pressure is isolated from the service line in this
phase by the minimum pressure valve set at
approximately 60 psig (4.2 bar).
FULLLOADMODE -- 60 TO100PSIG(4.2TO6.9
BAR)
When the compressed a ir pressure rises a bove 60
psig (4.2 bar), the minimum pressure valve opens
allowing compressed air to flow into the service
line.From thispoint on, thelineairpressure iscon-
tinually monitored by the Supervisor II .Thepres-
sure regulator and the solenoid valve remain
closedduringthisphase.Theinletvalveisintheful-
ly open position as long as the compressor is run-
ning at 100 psig (6.9 bar) or below.
MODULATING MODE -- 100 TO 110 PSIG ( 6.9
TO 7.6 bar)
If less than the rated capacity of compressed air is
beingused,theservicelinepressurewillriseabove
100 psig (6.9 bar). The pressure regula tor valve
gradually opens, directing air pressure to the inlet
control valve, thus reducing air entering the com-
pressor until it matches t he amount of air being
used. The control system functions continually in
this manner between the limits of 100 to 110 psig
(6.9 to 7.6 bar) in response t o varying demands
from the service line.
Thepressureregulatorhasan orificewhich ventsa
small amount of air to the atmosphere when the
pressure regulator controls the inlet control valve.
The orifice also bleeds any accumulated moisture
from the pressure regulator.
UNLOAD MODE -- IN EXCESS OF 110 PSIG ( 7.6
BAR)
When a relatively small amount or no air is being
used, the service line pressure continues to rise.
When it exceeds110 psig (7.6 bar), the Supervisor
Control System de---energizes the solenoid valve
allowing sump air pressure to be supplied directly
to close the inlet valve. Simultaneously, the sole-
noid valve sends a pneumatic signal to the blow-
down valve. The blowdown valve opens the sump
tothe atmosphere, reducing the sump pressure to
approximately20to30psig(1.4to2.1bar).The
checkvalveintheairservicelinepreventslinepres-
sure from returning to the sump.
When the line pressure drops to the low setting
(cut---in pressure;usually100 psig [6.9 bar] onlow
pressure [“L”] compressors and 125 psig [8.6 bar]
on high pressure [“HH”] compressors, 175 psig
[12.1bar]on[“XH”]compressors),SupervisorII
energizes the solenoid valve and allows the blow-
down valve to close. The re---energized solenoid
valve again prevents line pressure from reaching
theinletcontrolvalve.Shouldthepressurebeginto
rise, the pressure regulator will resume its normal
function as previously described.
AUTOMATIC OPERATION
F or applications with varied periods of time when
there are no air requirements, Supervisor’s AUTO-
MATIC mode allows the compressor to shutdown
(time delayed) when no compressed air require-
ment is present and restart as compressed air is
needed.
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