Electromagnetic flow meters, also known as magnetic flow meters, are widely used for measuring conductive liquids in water supply, wastewater treatment, chemical processing, and industrial applications. In practical use, most failures are not caused by the instrument itself, but by improper installation, environmental interference, or unsuitable fluid conditions.

 

Based on field application experience, electromagnetic flow meter failures can generally be divided into commissioning-stage failures and operation-stage failures.

 

1.Commissioning-Stage Failures of Electromagnetic Flow Meters

 Commissioning-stage failures usually occur immediately after installation. These problems are mainly related to application conditions rather than product quality.

 

Installation-Related Problems

Incorrect installation is one of the most common causes of electromagnetic flow meter malfunction. Typical issues include installing the flow sensor at pipeline high points where air accumulates, insufficient back pressure at the outlet causing partially filled pipes, or installing the meter on vertical downward pipelines where empty pipe conditions may occur.

These installation errors often lead to unstable flow readings, signal fluctuation, or intermittent measurement loss.

 

Environmental Interference

Electromagnetic flow meters are sensitive to external electrical interference. Common sources include stray currents in metal pipelines, electromagnetic radiation, and magnetic fields generated by large motors or frequency converters.

 

Proper independent grounding usually resolves most interference issues. However, in environments with strong stray currents, such as electrolysis plants, additional insulation between the flow meter sensor and the pipeline may be required to ensure stable measurement.

 

Fluid Characteristics and Measurement Stability

Small, evenly distributed air bubbles generally do not affect electromagnetic flow meter performance. However, large air bubbles may cause output signal fluctuation. When bubbles pass over and cover the electrodes, the signal circuit may be temporarily interrupted.

 

For slurry applications, low-frequency excitation magnetic flow meters may generate slurry noise, resulting in signal instability. In addition, when two liquids with different conductivity are mixed but not fully homogenized before measurement, the output signal may fluctuate.

 

Improper electrode material selection can also cause corrosion, oxidation, or passivation, forming an insulating layer on the electrode surface and affecting normal operation.

2.Operation-Stage Failures During Long-Term Use

 After a period of stable operation, electromagnetic flow meters may experience new problems caused by changing operating conditions.

 

Deposits on Lining and Electrodes

When measuring liquids containing suspended solids or contaminants, deposits may form on the inner lining or electrodes. If the deposits are conductive, measurement accuracy may gradually drift. If the deposits are insulating, the electrodes may be electrically isolated, resulting in complete signal loss.

 

Lightning and Power Surge Damage

Lightning strikes can induce high transient voltage and surge current in power and signal lines. Field experience shows that most lightning-related damage enters the electromagnetic flow meter through the power supply line rather than the signal cable.

Therefore, surge protection devices and proper grounding of control room power systems are essential for reliable long-term operation.

 

Changes in Installation Environment

Environmental conditions may change after commissioning. New welding operations, added electrical equipment, or degraded grounding systems can introduce interference that did not exist during initial installation, causing severe signal fluctuations.