| Control system
for ammonia refrigeration system.
SUMMARY:
A programmable logic controller (PLC) and operator interface
terminal (OIT) were used to control the suction and discharge
pressures of an ammonia refrigeration system for a cola bottling
facility.
DESCRIPTION :
Eleven ammonia compressors, each with a number of unloading solenoids,
are controlled by the PLC in order to maintain compressor suction
pressure. Two condenser units, each with two two-speed fans,
are controlled by the PLC in order to maintain compressor discharge
pressure. As the plant filler starts and stops, the PLC loads
and unloads the compressors and sequences the condenser in order
to provide consistent cooling capacity to the filling process.
Through the OIT, the operator can change setpoints and view process
status.
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