This article analyzes the six common faults of magnetic flow meters and provides the corresponding solutions.

No.1-Air bubbles in the liquid

Fault phenomenon: Output fluctuation Cause of failure: When the temperature or flow rate changes, the air in the medium will be resolved to form bubbles. If air bubbles are large enough to cover the entire electrode, the electrode will temporarily be open circuit, the output signal will fluctuate.

Solution: Install magnetic flow meters properly. If it is difficult to change the pipeline when flow meters are already installed, we can install exhaust valves, air collection bags upstream of the flow meter, or regulators downstream.

No.2-Electrode corrosion

Fault phenomenon: output fluctuation, or sensor failure (after excluding cause of air bubbles)

Cause of failure: Wrong electrode selected, electrode material is not compatible with the medium

Solution: Remove the flow meter to visually check whether the electrode is corroded, if yes, replace it.

No.3-Low conductivity

Fault phenomenon: No output or inaccurate measurement

Cause of failure: The medium can not form a closed loop thus no induced electromotive force is generated if it is not conductive.

Solution: Use other types of meters instead

No.4-Liner deformation

Fault phenomenon: inaccurate measurement, or sensor damage

Cause of failure: deformed liner destroys the uniformity of flow velocity

Solution: add heat insulation measures between the flange and the coil box, or optimize the installation

No.5-Electrode fouling

Fault phenomenon: the measurement increases or decreases in one direction

Cause of failure: If the attached deposit covered on the electrode is a conductive substance with a higher conductivity than the measured liquid, the measured value will be lower than the actual, and the electrode will be even short-circuited. If the attached deposit is a non-conductive substance with a lower conductivity than the measured liquid, the measured value will be lower than the actual, and the electrode will be even open-circuited.

Solution: descaling, regular maintenance

No.6-Electromagnetic Interference

Fault phenomenon: signal distortion or signal fluctuation

Cause of failure: The flow signal is small and subject to external interference

Solution: Use shielded cables to standardize wiring and grounding; keep away from interference sources

Contact Holykell engineers for more information on electromagnetic type flow meters and more products.