1, flow control instrument system failure analysis (1) When the indicated value of the flow control instrumentation system reaches the minimum, the on-site inspection instrument is first checked, and if it is normal, the failure is displayed on the instrument. When the on-site detection instrument indicator 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 fault between the regulating valve and the regulator. When the on-site detection instrument indicates the minimum, and the opening of the regulating valve is normal, the cause of the malfunction is likely to be caused by insufficient system pressure, digital display controller system pipeline blockage, pump failure, medium crystallization, improper operation, and other reasons. If the instrument is faulty, the reasons are: the orifice differential pressure flowmeter may be a positive pressure induction conduit plug; the differential pressure transmitter positive pressure chamber leakage; the mechanical flowmeter is a gear stuck or a filter plug. (2) When the indicated value of the flow control instrument system reaches the maximum, the detection instrument will often indicate the maximum value. At this point you can manually control the valve to open large or small, if the flow can be reduced, it is generally caused by the process operation. If the flow rate does not fall, it is the cause of the instrument system. Check whether the regulating valve of the flow control instrumentation system is active. Check if the instrument measures the pressure-adjusting system. Check whether the instrument signal transmission system is normal. (3) The flow control instrumentation system indicates that the value fluctuates more frequently, and the control can be changed to manual. If the fluctuation is reduced, it is the reason of the instrument or the instrument control parameter PID is not suitable. If the fluctuation is still frequent, it is the process operation. Caused by. 2, level control instrument system failure analysis (1) When the indicating value of the liquid level control instrument system changes to the maximum or minimum, you can first check the detection instrument to see if it is normal. If the indication is normal, change the liquid level control to the manual remote liquid level to see the change of the liquid level. If the liquid level can be stabilized in a certain range, the fault is in the liquid level control system; if the liquid level cannot be stabilized, it is generally a fault caused by the process system, and the cause must be looked up from the process. (2) When the differential pressure type liquid level control instrument indicator and on-site direct-reading indicator instrument indicator are not on, first check whether the direct-reading indicator instrument is normal. If the indicator is normal, check the negative pressure guide of the differential pressure level instrument. If there is leakage, refill the liquid and adjust the zero point; if there is no leakage, the negative migration amount of the instrument may be wrong. Adjust the migration amount to make the indicator normal. (3) When the indicating value of the liquid level control instrumentation system changes frequently and fluctuates frequently, it is necessary to first analyze the capacity of the liquid level control object to analyze the cause of the failure. The large capacity is generally caused by instrument failure. The first thing to do is to analyze whether there is any change in the process operation. If there is any change, the process may cause frequent fluctuations. If no change may be caused by instrument failure. 3, 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. 4, pressure control instrument system failure analysis (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. The above is only the site of the four common parameters alone control instrument field failure analysis, the actual scene there are some complex control loops, such as cascade control, split control, program control, interlock control and so on. The analysis of these failures is even more complex and requires detailed analysis. Solution: Exclusion 1. When the system is under control, the determination should also be the same. Determining the fault after each part is independent makes it easy to identify problems. 2. It is only the instrument displayed in the field. It is suspected that the data is not normal. The data can be estimated according to the process environment. Too far away, it is only necessary to check and adjust the instrument. 3. The on-site control instrument doubts that the data is not normal. It can automatically disconnect, observe and fix the data of the process conditions, and can determine whether the collected data is normal. If the control result is not stable, it is also first to determine whether the data acquisition is normal. The method is the same as above, because the data acquisition is not normal, and the control result will certainly not work. After the above problem is judged, the actuator is started normally when checking the soft manual output. Finally adjust the PID parameters. Optical Rotary Sensor,Custom Encoder,Optical Encoder 6Mm Shaft,Handwheel Pulse Generator Jilin Lander Intelligent Technology Co., Ltd , https://www.landerintelligent.com