Failure and Cause Analysis of Split Electromagnetic Flowmeter

The common faults encountered in the use of split electromagnetic flowmeters, including the faults in the debugging stage, are mainly caused by the selection or unreasonable setting of tools, installation errors, etc. The split electromagnetic flowmeter of this type of fault is related to the initial debugging, but once the fault is improved, it will generally not occur again under the same conditions. Common faults are mainly related to the installation and debugging period, environmental interference, and the influence of fluid characteristics.

(1) Pipeline system installation, etc.

Common electromagnetic flow sensor installation position is not correct fault, common examples are flow sensor installed in the gas pipeline network to facilitate the accumulation of high retention; the flow sensor has no pressure, the liquid is directly discharged into the atmosphere, forming a complete measuring pipe; installed in the vertical line due to dirty, there may be air, the installation of the flow meter is special, because the potential underwater to ensure that there is no floating.

(2) Environment

Main pipeline stray current interference, space electromagnetic wave interference, large motor magnetic field interference, etc. Pipeline stray current interference usually takes good grounding protection to get satisfactory individual measurement, but in the case of pipelines with strong stray current (such as electrolysis workshop assembly line), it cannot be overcome, and special measures should be taken between the flow sensor and the pipeline. Electromagnetic wave-space signal cable introduction, usually single or multiple shielding protection, but also encountered shielding protection can not be overcome.

(3) Fluid

Liquids containing tiny bubbles are usually evenly distributed and do not affect normal measurement. Only the volume flow of liquid and gas is combined; bubbles will increase the fluctuation of the output signal. If large bubbles cover the entire flow through the electrode surface, causing the electrode signal to instantly disconnect the circuit, the output signal will produce larger fluctuations.

When a low-frequency (50/16 Hz-50/6 Hz) rectangular wave excitation split electromagnetic flowmeter measures a slurry containing more than a certain amount of solids in the liquid, it will generate noise and the output signal will also fluctuate to a certain extent.

In a process pipeline where two or more liquids are mixed, if the 2 liquids have a difference in conductivity (or between their respective electrodes and potential) even before they are mixed into the flow sensor, the output signal will fluctuate.

The matching of electrode materials and the test, the generation of passivation or oxidation chemistry, the formation of insulating films on the electrode surface, and electrochemical polarization phenomena will all interfere with normal measurements.