How to clean the electrodes of electromagnetic flowmeter

If the medium measured by the electromagnetic flowmeter is relatively dirty for a long time, the electrodes of the electromagnetic flowmeter will scale after working for a period of time. When the conductivity of the scaling material is different from the conductivity of the measured medium, it will cause measurement errors. The adhesion of sludge and oil to the electrodes will also cause the output of the instrument to swing and drift. Therefore, in this case, we need to regularly maintain and clean the electrodes of the electromagnetic flowmeter. This article introduces several methods for cleaning the electrodes of electromagnetic flowmeters.

1. Electrochemical method

There are electrochemical phenomena in metal electrodes in electrolyte fluids. According to the principle of electrochemistry, there is an interfacial electric field between the electrode and the fluid, and the interface between the electrode and the fluid is caused by the double electric layer between the electrode/fluid phase. Studies on the interfacial electric field between the electrode and the fluid have found that the molecules, atoms or ions of the substance have enriched or poor adsorption phenomena at the interface, and that most inorganic anions are surfactants with typical ion adsorption laws, while the surface activity of inorganic cations is very small. Therefore, electrochemical cleaning of electrodes only considers the adsorption of anions. The adsorption of anions is closely related to the electrode potential, and the adsorption mainly occurs in the potential range that is more positive than the zero charge potential, that is, the surface of the electrode with opposite charges. On the surface of the electrode with the same charge, when the residual charge density is slightly larger, the electrostatic repulsion is greater than the adsorption force, and the anions are quickly desorbed. This is the principle of electrochemical cleaning.

2. Mechanical removal method

A. Use a mechanical scraper. A scraper with a thin shaft is made of stainless steel, and the scraper is led out through the hollow electrode. A mechanical seal is used between the thin shaft and the hollow electrode to prevent the medium from flowing out, thus forming a mechanical scraper. When the thin shaft is rotated from the outside, the scraper rotates close to the plane of the electrode end to scrape off the dirt. This scraper can be manually or automatically scraped by a motor-driven thin shaft.

B. A wire brush for cleaning dirt is installed in the tubular electrode, and the shaft is wrapped in a sealed "O" ring to prevent fluid leakage. This cleaning device requires someone to frequently pull the wire brush to clean the electrode, which is not very convenient to operate.

3. Ultrasonic cleaning method

The ultrasonic voltage of 45~65kHz generated by the ultrasonic generator is added to the electrode, so that the energy of the ultrasonic wave is concentrated on the contact surface between the electrode and the medium, thereby using the power of the ultrasonic wave to break up the dirt and achieve the purpose of cleaning.