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8. STANDARD COMPONENTS AND SUBSYSTEMS [Capacity Control System]
Vacuum valve
1st-stage
airend
Intercooler
Check valve
Aftercooler
To the
Atmosphere
Blowoff
valve
Pressure sensor
Control Line Filter
NC
NO
COM
NC
NO
COM
NC
NO
COM
20U
3
20U
2
20U
1
PS
Control air flow
2nd-stage
airend
Compressed Air Discharge
Check valve
NO
NC
COM
20U
4
NC
NO
COM
20US
STARTING
UNLOADING
RELOADING
STOPPING
Suction throttle valve (STV) closed
START button ON
Airend starts rotation to
compress minor amounts of air
Starts in no load
Changes to full voltage delta connection
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
3-way solenoid valve (20Ux)
switched over to pressurize
Chamber (A)
STOP button ON
Suction throttle valve
(STV) closes
Blowoff valve opens
Internal air in discharge pipe
is exhausted to atmosphere
Compressor stops
To Chamber (B)
To Chamber (A)
3-Way Solenoid Valve (4)
3-Way Solenoid Valve (20US)
3-Way Solenoid
Valve (1)
Starting/Stopping
Loading
Unloading
For 20 seconds
after starting with
a star-delta starter.
3-Way Solenoid
Valve (2)
3-Way Solenoid Valve (3)
NC-COM connected for
5 seconds after reactor
is changed over to a
fullvoltage connection.
Suction Throttle Valve
Chamber
(C)
Chamber (B)
Chamber (A)
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 solenoid
valve (20Ux), changing its port to port connection. The
control air is now flowing to and pressurizing chamber
(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. When the pressure sensor (PS)
detects the low pressure, 3-way solenoid valve (20Ux),
suction throttle valve (STV), and blowoff valve work in
reverse action and the airend reloads.
8.4.1 Standard Load-Unload Operation
