Cause Analysis and Countermeasures of Instrument and Control System Failure of Refrigeration Unit
In view of the high failure rate of instrument and control system in the operation of freezing unit in styrene plant,the causes are analyzed,including improper design selection of on-site detection instrument,low reliability of single point interlocking instrument,unstable power supply of on-site programmable controller(PLC),nonredundant design of PLC CPU,input/output module(I/O unit),communication unit and power supply module,and poor on-site operation environment of PLC.By taking measures such as improving the design of on-site detection instrument,changing the single pointinter locking logic to two out of two interlocking logic,changing the unit control from PLC to decentralized control system(D)and changing the power supply of on-site instrument to uninterruptible power supply(UPS),the number of unplanned shutdowns caused by instrument and control system failure of freezing unit has been reduced to zero,providing a guarantee for the stable and long operation of styrene plant.
unit instrumentcontrol systeminstrument power supplyanalysis of causescountermeasure
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