The steps of temperature control instrument system failure analysis

When analyzing the failure of the temperature control instrument system, two points should be paid attention to first: The system instruments mostly use electric instruments for measurement, indication, and control; the measurement of the system instruments often lags behind. (1) The indicated value of the temperature instrument system suddenly changes to the maximum or minimum, which is generally a failure of the instrument system. Because the measurement lag of the temperature instrument system is large, no sudden changes will occur. At this time, when the temperature control instrument system is faulty, two points should be paid attention to first: The system instruments mostly use electric instruments for measurement, indication, and control; the measurement of the system instruments often lags behind.　　(1) The indicated value of the temperature instrument system suddenly changes to the maximum or minimum, which is generally a failure of the instrument system. Because the measurement lag of the temperature instrument system is large, no sudden changes will occur. At this time, the fault causes are mostly caused by thermocouple, thermal resistance, compensating wire disconnection or transmitter amplifier failure.　　 (2) The temperature control instrument system indicates rapid oscillation, which is mostly caused by improper adjustment of the control parameter PID.　　 (3) The temperature control instrument system indicates that there is a large and slow fluctuation, which is likely to be caused by changes in the process operation. If there is no change in the process operation at that time, it is likely to be a malfunction of the instrument control system itself. (4) The failure analysis steps 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 acts, and the regulating valve diaphragm is leaked; check whether the input signal of the regulating valve positioner changes, the input signal If there is no change, the output signal changes, and the positioner is faulty; check the input signal of the positioner, and then check whether the output of the regulator has changed. If the input of the regulator does not change, the output changes, this is the fault of the regulator itself.