If the electromagnetic flowmeter measurement medium is relatively dirty for a long time, then the electromagnetic flowmeter in the work of a period, the electrode will produce scaling. When the conductivity of the fouled material and the measured medium conductivity is different, it will bring about the measurement error. Moreover, the electrode will make the meter output oscillate and drift by sludge, oil, and dirt adhesion to the electrode. In this case, consequently, we will need to maintain and clean the electromagnetic flow meter’s electrodes periodically. Therefore, we have come to introduce several electromagnetic flowmeter electrode cleaning methods for your reference.
The following methods are commonly used for electrode cleaning：
1. Electrochemical methods
Metal electrodes exist electrochemically in an electrolyte fluid. According to electrochemical principles, an interfacial electric field exists between the electrode and the fluid, and the interface between the electrode and the liquid is caused by a double electric layer between the electrode/fluid phase. Studies of the electrode-fluid interfacial electric field have found that molecules, atoms, or ions of substances are adsorbed at the interface in an enriched or depleted manner, and it has been found that most inorganic anions are surface-active substances with typical ionic adsorption patterns, while inorganic cations have little surface activity. Therefore electrochemically cleaned electrodes are only considered for anion adsorption. The adsorption of anions is closely related to the electrode potential, with adsorption occurring mainly in a potential range more positive than the zero charge potential, i.e., on the surface of electrodes with a different charge. Among the same quantity of orders on the electrode surface, when the remaining charge density is a little larger, the electrostatic repulsion is greater than the adsorption force. The negative anions are quickly desorbed, which is the principle of electrochemical cleaning.
2. Mechanical removal method
Mechanical removal is achieved by attaching unique mechanical structures to the electrodes for electrode removal. Two forms are currently available.
2.1 Mechanical scrapers are used.
A mechanical scraper is used. A scraper with a fine shaft made of stainless steel is led through a hollow electrode, and a mechanical seal is used between the shaft and the hollow electrode to prevent the media from flowing out, thus forming an automated scraper. When the beam is rotated from the outside, the scraper rotates against the electrode plane and scrapes off the dirt. A motor with a fine shaft can manually or automatically drive this scraper. The domestic electromagnetic flowmeter scraper type has such performance and is stable and easy to operate.
2.2 The tubular electrode is fitted with a wire brush for removing dirt, 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 and not as convenient as the scraper-type electromagnetic flowmeter.
3. Ultrasonic cleaning methods
The 45-65 kHz ultrasonic voltage generated by the ultrasonic generator is applied to the electrodes so that the ultrasonic energy is focused on the contact surface of the electrodes and the medium, thus using the ability of ultrasonic waves to break up the dirt and achieve the purpose of cleaning.
4. Electrical Breakthrough Method
This method uses AC high-voltage electricity regularly added to the electrode and the medium between, generally add 30 ~ 100 V. As the electrode is attached, its surface contact resistance becomes large, the added voltage is almost concentrated on the attachment, the high voltage will be attached to the breakdown, and then washed away by the fluid. In summary, the electric shock method must be used to disconnect the signal line between the sensor and the converter when the flowmeter interrupts the measurement and clean the AC high voltage directly at the signal output terminals of the sensor during a power failure.
The scraper-type electromagnetic flowmeter comprises a display instrument, shell, upper coil, lower coil, electrode assembly, etc. The electrode assembly is a removable scraper-type electrode structure. This structure is the signal electrode through the sleeve in the scraper rod with scraper, there are signal electrode and scraper rod fixed in the electrode cup, the electrode cup is welded solid in the inner table body, signal electrode and inner table body, electrode cup, compression nut between through. When the signal electrode needs maintenance, the operator needs to open the cover, turn the handle by hand, drive the scraper rod to rotate, and make the scraper close to the signal electrode to scrape off the dirt on the surface of the signal electrode. After cleaning, turn the direction of the scraper to the direction of fluid flow. The operation is very convenient.
Electromagnetic flowmeter media contamination cleaning method
Several unique media on the electrode after the pollution of the cleaning method (only for electromagnetic flowmeter can be inserted under the electrode applicable)
(1) For inorganic contamination, the electrode can be immersed in 0.1 mol/L dilute hydrochloric acid for 30 minutes, cleaned with pure water, then immersed in 3.5 MOL/L potassium chloride solution for 6 hours before use.
(2) dipped in 4% hydrogen fluoride solution for 3 to 5s, removed and rinsed with distilled water, then dipped in 0.1 mol/L hydrochloric acid solution for several hours, rinsed with distilled water, and calibrated
(3) for organic oil and oil film pollution, available detergent cleaning platinum or gold surface after cleaning with pure water, and then immersed in 3.5MOL / L potassium chloride solution soaked in 6 hours after use.
(4) platinum surface contamination of deep oxide film formation, available toothpaste on the platinum or gold surface polishing, then cleaned with pure water, and then immersed in 3.5MOL/L potassium chloride solution soaked in 6 hours after use.
The above electromagnetic flowmeter electrode maintenances and cleaning methods, if we can fully consider the future measurement medium that will produce pollution to the electrode in the early selection, then you should choose the scraper type electromagnetic flowmeter, which can be very convenient for electrode maintenance and cleaning, save a lot of trouble.
