Section 4
COMPRESSOR SYSTEMS
15
UNLOAD -- IN EXCESS OF 135 PSIG (9.3 BAR)
LINE PRESSURE
When no air is being used,the service line pressure
rises to the setting (cut--out pressure) of the pres-
sure switch. the pressure switch opens, interrupting
the electrical power to the solenoid valve. At this
time, the solenoid valve allows dry sump tank air
pressure to be applied directly to the inlet valve pis-
ton and keep it closed. Simultaneously, the solenoid
valve sends a pneumatic signal to the blowdown
valve. The blowdown valve relieves air pressure to
the compressor reducing the sump pressure to
approximately 20 to 30 psig (1.4 to 2.1 bar). The
check valve in the air service line pressure prevents
line pressure from returning to the sump.
When the line pressure drops to the low setting (cut--
in pressure) of the pressure switch (usually 125 psig
[8.6 bar]), the pressure switch closes, re--energizing
the solenoid valve and allowing the blowdown valve
to close. The re--energized solenoid valve again
prevents pressure from reaching the inlet valve. The
inlet valve is fully open and the compressor delivers
full rated capacity. Should the pressure begin to rise,
the pressure regulator will resume its normal func-
tion as previously described.
4.7 CONTROL SYSTEM, FUNCTIONAL DE-
SCRIPTION- SUPERVISOR II
The purpose of the compressor control system is to
regulate the amount of air being compressed to
match the amount of compressed air being used.
The capacity control system consists of a
solenoid
valve
,
regulator valve
and an
inlet valve
.The
functional description of the control system is de-
scribed below in 4 distinct phases of operation. The
following description text applies to all Series ES--11
compressors with optional Supervisor II. For ex-
planatory purposes, this description will apply to a
compressor with an operating range of 100 to 110
psig (6.9 to 7.6 bar). A compressor with any other
pressure range would operate in the same manner
except stated pressures.
START MODE -- 0 TO 50 PSIG (0 TO 3.5 BAR)
When the compressor
“I” (START)
pad is de-
pressed, the sump pressure will quickly rise from 0
to 50 psig (0 -- 3.5 bar). During this period, both the
pressure regulator and the solenoid valve are
closed, the inlet valve is fully open and the compres-
sor pumps at full rated capacity. The rising compres-
sor air pressure is isolated from the service line in
this phase by the minimum pressure valve set at
approximately 50 psig (3.5 bar).
FULL LOAD MODE -- 50 TO 100 PSIG (3.5 T O 6.9
BAR)
When the compressed air pressure rises above 50
psig (3.5 bar), the minimum pressure valve opens
allowing compressed air to flow into the service line.
From this point on, the line air pressure is continually
monitored by the Supervisor. The pressure regula-
tor and the solenoid valve remain closed during this
phase. The inlet valve is in the fully open position as
long as the compressor is running 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
being used, the service line pressure will rise above
100 psig (6.9 bar). The pressure regulator valve
gradually opens, directing air pressure to the inlet
control valve, reducing air entering the compressor
until it matches the 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 to varying demands from the service
line.
The pressure regulator has an orifice which vents a
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 exceeds 110 psig (7.6 bar), the Supervisor
Control System de--energizes the solenoid valve al-
lowing sump air pressure to be supplied directly to
close the inlet valve. Simultaneously, the solenoid
valve sends a pneumatic signal to the blowdown
valve. The blowdown valve relieves air pressure to
the compressor inlet reducing the sump pressure to
approximately 20 to 30 psig (1.4 to 2.1 bar). The
check valve in the air service line prevents line pres-
sure from returning to the sump.
When the line pressure drops to the low setting (cut--
in pressure; usually 100 psig [6.9 bar] on low pres-
sure [“L”] compressors and 125 psig [8.6 bar] on
high pressure [“H”] compressors, 150 psig [10. bar]
on [“HH”] compressors), Supervisor energizes the
solenoid valve and allows the blowdown valve to
close. The re--energized solenoid valve again pre-
vents line pressure from reaching the inlet control
valve. Should the pressure begin to rise, the pres-
sure regulator will resume its normal function as pre-
viously described.
AUTOMATIC OPERATION
For 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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