How to ensure the proper operation of electromagnetic flowmeters

Thread Content

Units using electromagnetic flowmeters need to conduct a comprehensive inspection once a year. The inspection items include: visual inspection, converter performance testing, calibration of measurement values, measurement of voltages at various points, measurement of insulation resistance, and verification of the circuit. When checking and adjusting electromagnetic flowmeters, zero drift makes it very important to adjust the zero point (\"on-line zero adjustment\" requires the flow of the medium being measured to stop, which is difficult to achieve in practice). 　 Therefore, online inspections often omit checks related to the operation of sensors, and only perform calibration of the converter in order to compare the results of the online inspection with historical data and determine whether the instrument should be continued in use, repaired, or replaced. As for the sensors, whether to replace them is decided based on the degree of degradation in the insulation resistance of the measured excitation coils. Verify whether there are any abnormalities in the electromagnetic flowmeter through online inspection. 　 For pipelines where the medium flow cannot be stopped, the flow sensors and converters are checked separately; the converters are tested using analog signal generators and other standard instruments, and they exhibit high calibration accuracy (which depends on the accuracy of the analog signal generators). 　 The inspection of electromagnetic flowmeter sensors involves indirect methods such as testing the electrode contact resistance, checking the insulation resistance and copper resistance of the excitation coil including the excitation connection cables, as well as examining the excitation current output by the converter and verifying the magnetic field strength. For pipelines where the medium flow can be stopped, access can be obtained through the geotextile membrane holes pre-installed near the sensor to inspect and clean the electrodes and lining for dirt/deposition.