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Description of the fault of the electromagnetic flowmeter during operation

After the initial commissioning and normal operation for a period of time, the faults that occur during the operation are: the adhesion layer on the inner wall of the flow sensor, the lightning strike, and the environmental conditions.

1. Inner wall adhesion layer
Since the electromagnetic flowmeter measures much more than the other flow meters when measuring the suspended solid phase or the dirty body, the probability of failure of the inner wall adhesion layer is relatively high. If the conductivity of the adhesion layer is close to the liquid conductivity, the meter can output the signal normally, but only change the flow area to form a hidden fault of the measurement error; if it is a high conductivity adhesion layer, the electromotive force between the electrodes will be short-circuited; if it is an insulating adhesion layer The surface of the electrode is insulated to disconnect the measuring circuit. The latter two phenomena will make the three instruments inoperable.

2, lightning strike
Lightning strikes induce transient high voltages and surge currents in the line, and entering the meter can damage the meter. There are three ways to introduce the lightning damage meter: the power line, the flow signal line between the sensor spoon converter and the excitation line. However, from the analysis of damaged components in lightning faults, the induced high voltage and surge currents that cause faults are mostly introduced from the control room power line, and the other two approaches are less. It was also learned from the scene of the lightning strike that not only the electromagnetic flowmeter was faulty, but also other instrumentation in the control room often had lightning strikes at the same time. Therefore, the user must know the importance of setting up the lightning protection facilities of the control room instrument power cord. The current team has been able to identify and explore this issue in the design unit team.

3. Changes in environmental conditions
The main reason is the same as the fault environment in the commissioning period of the previous section, except that the interference source does not appear during the commissioning period and then intervenes during the operation. For example, an electromagnetic flowmeter whose grounding protection is not ideal is not normal due to factory disturbance, and the instrument is operating normally. However, new interference sources appear during operation (such as pipelines near the measuring point or pipeline welding at a remote location). When running, there is a large fluctuation in the output signal.

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