When analyzing the temperature control instrumentation system failure, first of all: the system instrumentation mostly uses electric instrumentation for measurement, indication, and control; the system instrumentation measurement often has a large lag. The indication value of the temperature instrumentation system suddenly changes to the maximum or minimum, which is generally a malfunction of the instrumentation system. Because the temperature measuring system has a large measurement lag, no sudden change will occur. The faults at this time are mostly caused by broken thermocouples, thermal resistors, compensation wires or transmitter amplifiers. The temperature control instrument system indicates a rapid oscillation phenomenon, which is mostly caused by improper adjustment of the control parameter PID. The temperature control instrumentation system indicates that the large and slow fluctuations are likely to be caused by changes in the process operation. If the process operation does not change at that time, it is likely that the instrumentation control system itself is faulty. The failure analysis steps of the temperature control system itself: check whether the input signal of the control valve changes, the input signal does not change, the control valve operates, and the diaphragm of the control valve is leaking; 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, and it is the fault of the regulator itself.
When the pressure control system instrument indicates that rapid oscillation fluctuations occur, first check whether there is a change in the process operation. This change is mostly caused by the poor operation of the process operation and regulator PID parameters. Pressure control system instrument indicates dead line, the process operation changes the pressure indication or does not change, the general fault occurs in the pressure measurement system, first check whether the measurement pressure guiding catheter system is blocked, check the output of the pressure transmitter. Whether the system is changed or not, the fault lies in the controller measurement and indication system.
When the indicated value of the flow control instrument system reaches the minimum, first check the on-site detection instrument. If normal, the fault is displayed on the instrument. When the indication of the on-site testing instrument is also the smallest, check the opening degree of the regulating valve. If the opening degree of the regulating valve is zero, it is often a failure between the regulating valve and the regulator. When the on-site testing instrument indicates the smallest and the opening degree of the regulating valve is normal, the failure may be caused by insufficient system pressure, system pipeline blockage, pump failure, medium crystallization, and improper operation. If it is a fault in the instrument, the reasons are: the orifice plate differential pressure flowmeter may be blocked by a positive pressure induced pressure conduit; the differential pressure transmitter positive pressure chamber is leaking; the mechanical flowmeter is blocked by gears or blocked by a filter.