Case Studies on Alarm Handling and Out-of-Range Issues in Electromagnetic Flowmeter Systems

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Fault analysis of electromagnetic flowmeter. Location: Longmen. Date: 3-23-2017. Subject: Electromagnetic flowmeter (with on-site integrated display). Diameter: DN200. Faults: Over-range indication on the on-site display and system alarm (range is 450, but the on-site display shows 480). Resolution process: All parameter settings were checked and found to be correct; upon opening the back cover, water ingress was detected. First, disconnect the power supply, then loosen the screw connecting the meter head to the sensor in order to check whether water has entered the wiring connections. After opening it, I found that quite a bit of water had gotten in, but thanks to the waterproof sealing of the sensor, the water did not reach the coils. I used a hair dryer to dry the areas that were wet. Upon checking the wiring, it was found that there were signs of crushing at the short circuit in the excitation coil; the crushed area was wrapped up again with tape, and the screws were carefully reinstalled. After powering it on again, the meter display showed a flow rate of over 200; the flow alarm had been resolved and the flow meter was operating normally. Problem analysis: The wire was accidentally crushed during manufacturing, and combined with the rainy weather, water got into the meter’s gauge. Grounding of the excitation wire triggers a system alarm, generating an error signal that results in an out-of-range condition.