Electromagnetic flowmeter electrode four physical cleaning methods

Electrochemical phenomena exist in electromagnetic flowmeter metal electrodes in electrolyte fluids. According to the principle of electrochemistry, there is a contact electric field between the electrode and the fluid, and the contact between the electrode and the fluid is caused by the double electric layer existing between the electrode fluids. Research on the electric field in contact between electrodes and fluids has found that molecules, atoms or ions of substances have enriched or depleted adsorption phenomena at the interface, and it has been found that most inorganic anions are surface-active substances with typical ion adsorption rules, while the surface of inorganic cations Very little activity. Therefore, electrochemical cleaning of electrodes only considers the adsorption of anions. The adsorption of anions is closely related to the electrode potential. Adsorption mainly occurs in a potential range that is more positive than the zero charge potential, that is, on the electrode surface with an opposite charge. On the surface of electrodes with the same charge, when the remaining 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.

There are currently four forms: one is to use a mechanical scraper. A scraper with a thin shaft is made of stainless steel, and the scraper is led out through a 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 electrode-end plane to scrape off dirt. This scraper can be used manually, or it can be scraped automatically with a motor-driven thin shaft.

The other is to install a wire brush for removing dirt 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 electrodes, which is not very convenient to operate.

The third method of ultrasonic cleaning adds the 45~65kHz ultrasonic voltage generated by the ultrasonic generator to the electromagnetic flowmeter electrode, so that the ultrasonic energy is concentrated on the contact surface between the electrode and the medium, thereby utilizing ultrasonic waves The ability to crush dirt to achieve the purpose of cleaning.

The fourth method, electrical breakdown method, uses AC high-voltage electricity to be regularly applied between the electromagnetic flowmeter electrode and the medium, generally 30~100V. Since the electromagnetic flowmeter electrode is attached, its surface contact resistance becomes larger, and the applied voltage is almost concentrated on the attachment. The high voltage will breakdown the attachment and then be washed away by the fluid. For the first time, when using the electrical breakdown method, the flow meter must interrupt the measurement work, the signal line between the sensor and the converter is disconnected, and the AC high-voltage power should be directly applied to the sensor signal output terminal for cleaning.