Three Methods of Cleaning Electromagnetic Flowmeter Electrodes
If there is a conductive substance with a higher electrical reversal rate than the liquid attached, it is easy to measure the fluid that adheres and precipitates the substance on the pipe wall. The signal potential will be short-circuited and cannot work. If it is a non-conductive layer, the contamination of the electrode should be paid attention to first, such as choosing a pointed or hemispherical protruding electrode that is not easy to adhere to, replaceable electrode, scraper-type cleaning electrode, etc.
There are usually three ways to descale the electromagnetic flowmeter
1) Electrochemical method
Metal electrodes exhibit electrochemical phenomena 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 electric double layer existing between the electrode/fluid phase. The study of the electric field at the interface between the electrode and the fluid found that the molecules, atoms or ions of the substance have enriched or poor adsorption at the interface, and found that most inorganic anions are surface active substances with typical ion adsorption laws, while the surface of inorganic cations activity is small. Therefore, the electrochemical cleaning of electrodes only considers the anion adsorption. 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 electrode surface with the opposite sign. On the electrode surface of 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, which is the principle of electrochemical cleaning.
2) Ultrasonic cleaning method
The ultrasonic voltage of 45~65kHz generated by the ultrasonic generator is applied to the electrode, so that the energy of the ultrasonic wave is concentrated on the contact surface between the electrode and the medium, so as to use the ability of ultrasonic wave to crush the dirt and achieve the purpose of cleaning.
3)Electrical breakdown method
This method uses alternating high-voltage electricity to be regularly added between the electrode and the medium, generally adding 30 to 100v. Because the electrode is attached, its surface contact resistance becomes larger, and the applied voltage is almost concentrated on the attached object. The high voltage will break down the attached object and then be washed away by the fluid. For safety, when using the electric breakdown method, it is necessary to interrupt the measurement of the flowmeter, disconnect the signal line between the sensor and the converter, and clean the AC high voltage directly on the signal output terminal of the sensor in the event of a power failure.
