How Many Cleaning Methods for Electromagnetic Flowmeters Do You Know?

 Electromagnetic flowmeter: If the medium being measured remains relatively dirty over an extended period, dirt will build up on the electrodes after the flowmeter has been in operation for some time. When the conductivity of the fouling material differs from that of the measured medium, measurement errors can occur. The adhesion of sludge or oil to the electrodes can also cause the meter output to fluctuate and drift. In such cases, regular maintenance and cleaning of the electromagnetic flowmeter electrodes are necessary. Let us introduce several methods for cleaning electromagnetic flowmeter electrodes below.

1. Mechanical Cleaning Method

The mechanical cleaning method involves installing special mechanical structures on the electrodes to achieve cleaning. There are currently two forms: one uses a mechanical scraper, made of stainless steel with a thin shaft, which is led out through a hollow electrode. When the thin shaft is rotated from the outside, the scraper rotates tightly against the electrode end face, scraping off the dirt. This scraper can be operated manually or automatically driven by a motor via the thin shaft.

2. Electrochemical Method

Metal electrodes exhibit electrochemical phenomena in electrolyte fluids. It has been found that most inorganic anions are surface-active substances with typical ion adsorption behavior, while the surface activity of inorganic cations is very low. Therefore, the electrochemical cleaning of electrodes only considers the adsorption of anions. The adsorption of anions is closely related to the electrode potential, and adsorption mainly occurs in the potential range more positive than the zero-charge potential, i.e., on the electrode surface with opposite charge. On a surface with the same charge, when the residual charge density is slightly larger, the electrostatic repulsion exceeds the adsorption force, and the anions are quickly desorbed; this is the principle of electrochemical cleaning.

3. Ultrasonic Cleaning Method

Apply an ultrasonic voltage of 45–65 kHz generated by an ultrasonic generator to the electrodes, so that the ultrasonic energy is concentrated on the contact surface between the electrode and the medium. The ultrasonic energy then breaks up the dirt, achieving cleaning purposes.

4. Electrical Breakdown Method

This method uses periodic high-voltage alternating current applied between the electrode and the medium, typically 30–100 V. Due to the attachment on the electrode, its surface contact resistance increases, and the applied voltage is almost entirely concentrated on the attached matter. The high voltage breaks down the attached material, which is then washed away by the fluid. For safety reasons, the electrical breakdown method must be used only when the flowmeter is not measuring, the signal lines between the sensor and the converter are disconnected, and the power is off, with the AC high voltage applied directly to the sensor's signal output terminals for cleaning.

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