Daily maintenance method of electromagnetic flow meter

Abstract: The daily maintenance method information of electromagnetic flow meter is provided by the excellent flow meter and flow meter production and quotation manufacturers. Generally qualified (truly implementing the ISO9001 quality management system) the general inspection method of the enterprise is: (1), 1/3 is only for online inspection; (2), 1/3 is removed from the pipeline for inspection after cleaning the wetted parts; (3) ), 1/3 offline for flow calibration. Specific operation method: . More flowmeter manufacturers choose models and price quotations. You are welcome to inquire. The following is the article details of the daily maintenance method of electromagnetic flowmeters. Generally qualified (truly implementing the ISO9001 quality management system) the general inspection method of the enterprise is: (1), 1/3 is only for online inspection; (2), 1/3 is removed from the pipeline for inspection after cleaning the wetted parts; (3) ), 1/3 offline for flow calibration. Specific operation method: Operation method 1 The enterprise can conduct a comprehensive inspection of the electromagnetic flowmeter once a year. The inspection contents are: appearance inspection, converter characteristic test, measurement value calibration, voltage measurement of each part, insulation resistance measurement, circuit confirmation, etc. When the instrument is checked and adjusted due to zero drift, it is very important to adjust the zero point (“Online zero adjustment”It is necessary to stop the flow of the measured medium, which is actually difficult to do). Therefore, the online inspection often omits the inspection involving the operation of the sensor, and only carries out the calibration of the converter, so as to compare the online inspection result with the historical data to determine whether the instrument should continue to be used, repaired or updated. For the sensor, according to the measured excitation coil insulation resistance The degree of deterioration determines whether to update or not. Operation mode 2 Verify whether the electromagnetic flowmeter is abnormal through online inspection. Check the flow sensor and the converter separately for pipelines that cannot stop the flow of the medium. Test the converter with an analog annunciator and other general-purpose instruments with high calibration accuracy (this depends on the accuracy of the analog annunciator), and the sensor check is based on the test electrode Wet resistance, check the excitation coil, including the insulation resistance and copper resistance of the excitation connection cable, as well as indirect methods such as checking the excitation current output by the converter and checking the magnetic field strength. For pipelines that can stop the flow of the medium, it can be entered from a preset inlet near the sensor, and the electric level and lining contamination/deposition can be checked and cleaned. Check the electromagnetic flowmeter. In addition to the zero point check, the flow sensor, converter and connecting cable are also carried out separately. 1. Zero point inspection of the whole machine The technical requirements for the zero point inspection of the whole machine are: the flow sensor measuring tube is full of liquid and there is no flow, which is not available in many enterprise sites and gives up the zero point inspection and adjustment of the whole machine, but can be turned to the converter. Do a separate zero check and adjustment. Technically speaking, this has practical significance only after the sensor inspection is completed and the insulation resistance of the excitation circuit and the signal circuit of the sensor is guaranteed to be normal (both including cables), otherwise the whole machine cannot operate normally. Usually the single zero point of the converter is negative and the value is very small; if its absolute value is greater than 5% of the full scale, it needs to be checked first, and then adjusted after confirming the cause. Under normal circumstances, the difference between the zero point of the electromagnetic flowmeter and the individual zero point of the converter is less than 1%. There are many cases where the zero difference value greater than 5% is caused by the user's incorrect zero adjustment operation when the pipeline valve is not closed properly. 2. Inspection of connecting cables The inspection content is to check the continuity and insulation resistance of each core of the signal line and the excitation line, and to check whether the grounding of each shielding layer is in good condition. 3. Converter inspection The inspection content is to use the general instrument and the analog signal device matching the flowmeter model to replace the sensor to provide the flow signal for zero adjustment and calibration. Calibration includes zero check and adjustment, setpoint check, field current measurement, current/frequency output check, etc. It should be noted that the inspection items should be compared with the last inspection value (or factory value) to analyze whether there is a change or whether the change meets the original measurement requirements. 4. Flow sensor inspection The inspection content is: through the inspection of the excitation coil and the excitation current measured by the converter to indirectly evaluate whether the magnetic field strength changes; measure the electrode liquid resistance to evaluate the electrode surface is polluted and the lining adhesion layer Condition; check the insulation resistance of each part to judge the degree of deterioration of the parts to evaluate whether interference will be introduced. For pipelines that can stop the flow of the medium, the thickness of the electrode and lining adhesion layer can be observed and measured to estimate the flow value change caused by the change of flow area before and after cleaning the adhesion layer. (1) Measure the copper resistance of the excitation coil. Use a high-precision digital multimeter or a Wheatstone bridge to measure the coil resistance. If necessary, correct the temperature coefficient and compare it with the instrument file value. Confirm whether the coil is well connected and there is no short circuit between turns. (2) Check the insulation resistance of the excitation coil. After the excitation coil and its terminals are damp, the insulation of the excitation circuit to the ground decreases. It is possible to introduce the excitation signal into the flow signal transmission circuit, so that the electrode adds a larger insulation resistance and signal resistance to the excitation voltage. The voltage divider will form a larger common mode interference signal. When this interference signal exceeds the suppression capability of the converter preamplifier, it will cause the converter zero to drift. When the insulation resistance drop is not very serious, this phenomenon is not easy to detect when the instrument is running. In addition to IP68 no terminal box, due to negligence in practice, the terminal box is not sealed and enters the moisture, and the terminal insulation resistance drops to 5 ~ 6MΩIt is easy to cause malfunction in the following cases. Blow dry the terminal, usually the fault can be eliminated.
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