电磁流量计运行故障及处理方法

There are generally two types of faults that occur during the operation of electromagnetic flowmeters: one is the fault of the instrument itself, which is caused by the damage of structural components or components of the instrument; the other is the fault caused by external factors, such as poor installation location, high viscosity and corrosivity of the medium, etc. The discussion is as follows.
I. No flow signal output from the instrument 1. Possible cause analysis (1) Abnormal power supply to the instrument; (2) Improper cable connection; (3) Improper installation location; (4) Damaged sensor components or adhesive layer on the measuring inner wall; (5) Damaged converter components.
2. Solution (1): Confirm that the power supply is connected, check whether the output voltages of each circuit on the power circuit board are normal, or try replacing the entire power circuit board to determine if it is faulty.
(2) Check whether the cable is intact and the connection is correct.
(3) Check the direction of liquid flow and whether the liquid inside the pipeline is fully filled. For electromagnetic flowmeters capable of measuring in both forward and reverse directions, if the directions are inconsistent, measurement can still be made, but the set display flow rate will be inconsistent in the forward and reverse directions, which must be corrected. If dismantling the sensor involves a large amount of work, it is also possible to change the direction of the arrow on the sensor and reset the display instrument symbol. The main reason why the pipeline is not fully filled with liquid is due to improper installation of the sensor. Measures should be taken during installation to avoid incomplete filling of the pipeline with liquid.
(4) Check whether the electrodes on the inner wall of the transmitter are covered with a layer of liquid scarring. For measuring liquids that are prone to scarring, regular cleaning is necessary.
(5) If it is determined that the fault is caused by damaged converter components, simply replace the damaged components.
II. Fluctuations in Output Values 1. Possible Causes Analysis: Most of these failures are caused by the influence of the measured medium or external environment, and the faults can be resolved spontaneously after the external interference is eliminated. To ensure measurement accuracy, such failures cannot be ignored. In some production environments, due to significant vibration of the measuring pipeline or liquid, the circuit board of the flowmeter may become loose, which can also cause fluctuations in output values.
2. Solution (1): Confirm whether the pulsation in the fluid is due to process operation. If so, the flowmeter is simply reflecting the actual flow condition. The fault may resolve itself once the pulsation ends.
(2) Electromagnetic interference generated by external stray currents, etc. Check the operating environment of the instrument to see if there are large electrical appliances, welding machines, frequency converters, and other equipment operating. Confirm that the instrument is properly grounded and the operating environment is good.
(3) When the pipeline is not fully filled with liquid or the liquid contains bubbles, both are caused by process reasons. At this time, you can request confirmation from the process personnel. After the pipeline is fully filled with liquid or the bubbles subside, the output value can return to normal.
(4) The transmitter circuit board adopts a plug-in structure. Due to the significant vibration of the measuring pipeline or liquid on site, the power board of the flowmeter may often become loose. If it is loose, the flowmeter can be disassembled and the circuit board re-fixed.
III. Discrepancy between flow measurement value and actual value 1. Possible cause analysis (1) Whether the transmitter circuit board is intact; (2) When the liquid flow rate is too low, the measured liquid contains tiny bubbles, which rise and gradually gather above the pipeline, causing changes in the liquid flow area. When there are many bubbles, interference signals may also be generated, affecting measurement accuracy; (3) Poor connection of the signal cable or decreased insulation performance of the cable during use may cause inaccurate measurement; (4) Inaccurate parameter settings of the converter.
2. Solution (1): Check whether the transmitter circuit board is intact. If the junction box is flooded or corroded by corrosive measured liquid, it may lead to performance degradation or damage of the electrical appliance. In this case, the circuit board should be replaced.
(2) Ensure that the flow rate of the measured liquid in the pipeline is above the minimum flow limit to enable the transmitter to operate normally.
(3) Check the signal cable connections and the insulation performance of the cables to ensure they are intact. If the signal cables are loose, simply reconnect them. If the insulation of the cables is found to be non-compliant with insulation requirements, a new cable needs to be replaced.
(4) Reset the converter's set values and verify its zero point and full-scale value.
IV. Output signal exceeding the full measurement range 1. Possible cause analysis The reasons for such malfunctions are generally as follows: (1) Wiring errors in the signal cable or disconnection of the cable; (2) Incorrect parameter settings of the converter; (3) Incompatibility between the converter and sensor models.
2. Solution (1) Check whether the signal circuit connection is normal. If the signal circuit is disconnected, the output signal will exceed the full-scale value. In this case, the signal cable needs to be reconnected correctly. At the same time, check whether the insulation performance of the cable is intact. If it no longer meets the requirements, a new cable needs to be replaced.
(2) Conduct a detailed inspection to ensure that the parameter settings, zero point, and full scale of the converter meet the specified requirements.
(3) If it is found that the model of the converter does not match that of the sensor, it is necessary to contact the manufacturer for replacement.
5. Zero instability 1. Possible cause analysis (1) The pipeline is not fully filled with liquid or the liquid contains bubbles.
(2) Subjectively, it is believed that there is no flow of the pumped liquid, but in reality, there is slight flow.
(3) Reasons related to the liquid (such as poor uniformity of liquid conductivity, electrode contamination, etc.).
(4) Decreased insulation of the signal circuit.
2. Solution (1): The pipeline not being fully filled with liquid or the presence of bubbles in the liquid are both due to process reasons. Process personnel need to confirm whether to install an exhaust valve or increase pressure, etc. Once the process is normal, the output value can return to normal.
(2) There is a slight flow in the pipeline, which is not a malfunction of the electromagnetic flowmeter.
(3) If impurities are deposited on the inner wall of the measuring tube or scale forms on the inner wall, or if the electrode is contaminated, zero drift may occur. In this case, cleaning is necessary; if the zero drift is not significant, you can also try to reset the zero point.