Electrode cleaning method for multi-electrode electromagnetic flowmeter

Multi-electrode electromagnetic flowmeter product introduction:

It can obtain the average liquid velocity of multi-phase flow. It is an effective tool for non-invasive measurement of multi-phase flow. It is suitable for use in various pipelines and containers and various multi-phase flows. flow measurement field. Multi-electrode electromagnetic flowmeters can be used in conjunction with electrical impedance tomography EIT to calculate void fraction within a fluid cross-section and are also able to provide void fraction based flow rates by comparing the propagation of phase distribution images from upstream and downstream layers.

The electrode cleaning methods of multi-electrode electromagnetic flowmeters usually include the following:

1. Ultrasonic cleaning method:

The ultrasonic cleaning method uses the principle of high-frequency ultrasonic vibration to apply the ultrasonic voltage of 45~65kHz generated by the ultrasonic generator to the electrode, so that the energy of the ultrasonic wave is concentrated on the contact surface between the electrode and the medium, thereby utilizing the power of the ultrasonic wave. Ability to break dirt into pieces and achieve the purpose of cleaning.

2. Electrical breakdown method:

This method uses AC high-voltage electricity to be regularly added between the electrode and the medium, generally 30~100V. Because the 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 sake of total safety, the electric breakdown method must be used when the flowmeter interrupts measurement, the signal line between the sensor and the converter is disconnected, or there is a power outage by applying AC high-voltage power directly to the sensor signal output terminal for cleaning.

3. Mechanical cleaning method:

The mechanical cleaning method achieves electrode cleaning by installing a special mechanical structure on the electrode. There are currently two 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 turned from the outside, the scraper rotates close to the electric surface and scrapes away the dirt. This scraper can be used manually, or it can be scraped automatically with a motor-driven thin shaft. Among domestic electromagnetic flowmeters, the scraper type electromagnetic flowmeter of Xi'an Yunyi has such performance, and its performance is stable and easy to operate.

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. It is not very convenient to operate and is not as convenient as the scraper type electromagnetic flowmeter of Xi'an Cloud Instrument.

4. Electrochemical method:

The metal electrodes of multi-electrode electromagnetic flowmeters have electrochemical phenomena in the electrolyte fluid. According to the principle of electrochemistry, there is an interface electric field between the electrode and the fluid. The interface between the electrode and the fluid is caused by the electric double layer existing between the electrode/fluid phase. Research on the electric field at the interface 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 typicalType ion adsorption rules, 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. 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.