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Purge Air Valve - The purge valve is a normally closed two-way air actuated valve that admits purge air
from the final discharge manifold to the compressor to counteract the oil knock that occurs in oil-flooded
rotary screw compressors when they are completely unloaded with pressure in the oil reservoir. This
valve is controlled by the same control pressure which controls the inlet valve.
Figure 4-5 – BLOWDOWN VALVE
Blowdown Valve (Figure 4-5) - The blowdown valve is a two-way solenoid valve which is piped into the
air/oil reservoir outlet ahead of the minimum pressure valve. When the solenoid is de-energized, the
valve opens and the coolant system is blown down. When the solenoid is energized, the valve closes to
allow the coolant system to pressurize. A control air check valve is provided to ensure that the inlet valve
is closed during blowdown.
System Pressure Transducer - This transducer is connected after the minimum pressure valve. It
converts the pressure in the plant air system into an electrical signal for use by the “AutoSentry” controller
for modulation and control.
Reservoir Pressure Transducer - This transducer is connected to the coolant system. Its signal is
used to prevent loaded starts, monitor oil pressure, and monitor the condition of the separator.
Air Filter Vacuum Switch - This switch is used to monitor air filter condition and alert the user if the
filter requires service or replacement.
Discharge Thermistor - This sensor is located directly in the compressor discharge. Its signal is used
to monitor compressor temperature and shut down the compressor if a coolant problem is detected.
Reservoir Thermistor - This sensor is located in the reservoir / separator housing and is used to
monitor temperature and shutdown the compressor if temperature problems occur at the separator.
Emergency Stop Pushbutton - This is a maintained pushbutton, and removes power from the
controller outputs regardless of controller status. It is located on the upper section of the panel, next to
the keypad. This should be used for emergency purposes only - use the keypad [STOP/RESET] for
normal controlled stopping.
WARNING
Automatic restarting or electrical shock can cause injury or death. Open,
lockout and tagout main disconnect and any other circuits before servicing
unit.
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