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Instrument Failure Analysis System Description

1. Temperature Control Instrument System Failure Analysis Steps
When analyzing the temperature control instrument system failure, we must first pay attention to two points: The system instrument uses electrical instrumentation to measure, indicate, and control; the measurement of the system instrument often lags behind.
(1) The indicator value of the temperature meter system suddenly changes to the maximum or minimum, which is generally a failure of the instrument system. Because the temperature meter system measures large lags, sudden changes do not occur. Most of the faults at this time are due to the thermocouple, thermal resistance, wire breakage in the compensation lead, or malfunction of the transmitter amplifier.
(2) Temperature control instrumentation system indicates rapid oscillation, which is mostly caused by improper adjustment of control parameter PID.
(3) The temperature control instrumentation system indicates the occurrence of large and slow fluctuations, which may be due to changes in process operations. If the process operation does not change at that time, it is likely that the instrument control system itself has failed.
(4) Failure analysis procedure of the temperature control system itself: Check whether the input signal of the regulating valve changes, the input signal does not change, the regulating valve is actuated, and the diaphragm of the valve diaphragm is leaked; check whether the input signal of the regulating valve positioner changes, or the input signal No change, the output signal changes, the positioner has a fault; check the positioner input signal changes, and then check whether the regulator output changes, if the regulator input does not change, the output changes, this time is the fault of the regulator itself.
2. Pressure Control Instrument System Failure Analysis Procedure
(1) When the pressure control system instrument indicates rapid oscillation fluctuations, first check whether there is any change in the process operation. This change is mostly caused by the poor setting of the process operation and the PID parameters of the regulator.
(2) The pressure control system instrument indicates dead line, the process operation changes the pressure indication or does not change, the general failure occurs in the pressure measurement system, first check whether the measurement pressure piping system has a plugging phenomenon, no plugging, check the pressure change The transmitter output system has no change, there are changes, the fault is in the controller measurement indicator system.

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