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8. STANDARD COMPONENTS AND SUBSYSTEMS [Capacity Control System]
8.4 Capacity Control System
The unloading process occurs when the compressed air
demand decreases and the discharge pressure rises as
high as cut-out pressure. The pressure sensor (PS)
detects the high pressure and energizes the 3-way sole-
noid valve (20Ux), changing its port to port connection.
The control air is now flowing to and pressurizing cham-
ber (A) of the suction throttle valve (STV), consequently
closing the suction throttle valve (STV) and unloading
the airend while the blowoff valve opens and exhausts
the internal compressed air to atmosphere.
The loading process occurs when the compressed air
demand increases and the discharge pressure dropped as
low as cut-in pressure. The pressure sensor (PS)
detects the low pressure and 3-way solenoid valve
(20Ux), suction throttle valve (STV), and blowoff valve
work in reverse action and the airend reloads.
Valve 2
NC
NO
COM
NO
NO
NC
NC
NC
COM
COM
COM
NO
20U2
20U4
20US
20U
3
COM
NC
NO
Air Exhaust Valve
20U1
PS
Valve 1
(Vacuum Valve)
Blowoff air cooler
To Chamber (B)
To Chamber (A)
Blowoff Valve
3-Way Solenoid
Valve (20US)
Chamber
(B)
Chamber
(A)
Chamber
(C)
Suction Throttle Valve
NC-COM connected for 5 seconds
after reactor is changed over to a
fullvoltage connection.
3-Way Solenoid
Valve (3)
1st-Stage
Air End
Intercooler
Check Valve
2nd-Stage
Air End
Orifice
Check Valve
Aftercooler
Compressed Air Discharge
Pressure Sensor
Control Line Filter
3-Way Solenoid
Valve (2)
3-Way Solenoid
Valve (4)
3-Way Solenoid Valve (1)
For 20 seconds after starting
with a star-delta starter.
For 15 seconds after starting
with reactor starter.
Control Air Flow
Starting/Stopping
Loading
Unloading
To the
Atmosphere
STARTING
△switch (Reactor short)
UNLOADING
RELOADING
STOPPING
Suction throttle valve (STV) closed
START button ON
Airend starts rotation to
compress minor amounts of air
Starts in no load
3-way solenoid valve (20Ux)
switched over to connect
Chamber (A) & Chamber (C)
Suction throttle valve (STV) opens
Loading
Air demand decreases
Discharge pipe pressure rises
Pressure sensor (PS) operates
3-way solenoid valve (20Ux)
switched over to pressurize
Chamber (A)
Suction throttle valve
(STV) closes
Blowoff valve opens
Internal air in discharge pipe
is exhausted to atmosphere
Air demand increases
Discharge pipe pressure drops
Pressure sensor (PS) operates
3-way solenoid valve (20Ux)
switched over to pressurize
Chamber (B)
Suction throttle valve
(STV) opens
Blowoff valve closes
Loading
STOP button ON
3-way solenoid valve (20Ux)
switched over to pressurize
Chamber (A)
Suction throttle valve
(STV) closes
Blowoff valve opens
Internal air in discharge pipe
is exhausted to atmosphere
Compressor stops
8.4.1 Standard Load-Unload Operation
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