Faults that occur during the initial installation and commissioning of the electromagnetic flowmeter, once improved and eliminated, will generally not reoccur under the same conditions in the future.
Causes and solutions for electromagnetic flowmeter failures during the commissioning period:
Faults that occur during the initial installation and commissioning of the electromagnetic flowmeter, once improved and eliminated, will generally not reoccur under the same conditions in the future. Common faults during commissioning are mainly caused by environmental interference, fluid effects, and improper installation.
1. Environmental aspects
Mainly include pipeline stray circuit interference, space electromagnetic wave interference, large motor magnetic field interference, etc. Stray current interference in pipelines can usually be measured satisfactorily with good single grounding protection. However, if there is a strong stray current in a pipeline (such as an electrolytic workshop pipeline), it may not be able to overcome it. Measures must be taken to isolate the flow sensor from the pipeline edge. Space electromagnetic wave interference is generally introduced through signal cables and is usually protected by single or multi-layer shielding. However, there have been cases where shielding protection cannot be overcome.
2. In terms of fluids
Fluids containing uniformly distributed fine bubbles usually do not affect normal measurement. However, when the measured volume flow is the sum of liquid and gas, the output signal will fluctuate due to the increase of bubbles. If the bubbles enter the flow Overcurrent covers the entire electrical surface, causing the electrical signal loop to be instantly disconnected, and the output signal will produce greater fluctuations.
When two or more liquids are mixed in a pipeline, if there is a difference in the conductivity of the two liquids (or the potential between each liquid and the electric potential), they will enter the flow sensor for flow measurement before the mixture is uniform. The output signal will also fluctuate. Low-frequency (50/16~50/6Hz) rectangular wave excitation electromagnetic flowmeter will produce liquid noise when the solid content in the measured liquid exceeds a certain level, and the output signal will also fluctuate to a certain extent.
Poor selection of the electrical material and the medium to be measured will produce chemical effects such as passivation or oxidation, the formation of a thin film on the electrical surface, and electrochemical neutralization phenomena, etc., which will hinder normal measurement.
3. Piping system and installation aspects
Faults are usually caused by incorrect installation position of the electromagnetic flow sensor. Common ones include installing the flow sensor at a high point in the pipe network where trapped gas is likely to accumulate; there is no back pressure behind the flow sensor. , the liquid is discharged directly into the atmosphere, causing the measuring tube to be less than full; when installed on a vertical pipe that flows from top to bottom, emptying and other reasons may occur.
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