As an important instrument in the field of modern industrial measurement and control, the accuracy and stability of electromagnetic flowmeter is crucial for the continuity of the production process and product quality. The electrode, as the core component of the electromagnetic flowmeter, is responsible for sensing the change of conductivity in the fluid, which is then converted into an electrical signal for flow measurement. However, due to impurities in the fluid, sediments and chemical reactions and other factors, the electrode surface often accumulates a variety of dirt, affecting the measurement accuracy or even lead to instrument failure. Therefore, regular cleaning of electromagnetic flowmeter electrodes is one of the key measures to ensure its long-term stable operation.
Mechanical cleaning method
Mechanical cleaning is the direct physical removal of dirt from the electrode surface. This method is suitable for the electrode surface dirt is relatively loose or less stubborn. According to the different ways of operation, mechanical cleaning method can be divided into two categories: manual scraping and mechanical scraper.
Manual scraping method:
Use a soft scraper or plastic scraper to gently scrape off the dirt on the electrode surface. This method is simple and easy to use, but requires manual operation, relatively low efficiency, and may cause minor damage to the electrode surface. Therefore, special care needs to be taken during operation to avoid excessive force.
Mechanical scraper method:
Part of the electromagnetic flowmeter is equipped with a mechanical scraper device, which can automatically scrape off the dirt on the electrode surface on a regular basis. Mechanical scraper is usually made of stainless steel, through the hollow electrode lead, thin shaft and hollow electrode between the use of mechanical sealing to prevent media outflow. When the shaft is rotated from the outside, the scraper rotates against the electrode tip and removes the dirt. This method is straightforward and effective in removing thick layers of dirt, but again there is a risk of damage to the electrode surface and it is not suitable for cleaning viscous or hard dirt.
Chemical Cleaning
Chemical cleaning method is to use chemical solvents to remove the electrode surface dirt by dissolving, emulsifying and dispersing. This method is suitable for electrode surface fouling that is complex or difficult to remove physically. According to the different types of dirt, chemical cleaning method can be divided into three categories: solvent cleaning, acid cleaning and alkaline cleaning.
Solvent cleaning:
Use organic solvents such as alcohol, acetone, etc. to clean the electrode surface. These solvents have good solubility and volatility, and can quickly remove greasy dirt. However, it should be noted that organic solvents may cause corrosion of the electrode material, so the concentration and cleaning time need to be strictly controlled when used.
Acid cleaning:
Use dilute hydrochloric acid, nitric acid and other acidic solutions to remove rust scale and inorganic salt dirt on the electrode surface. Acid washing can quickly dissolve and strip the dirt, restore the surface finish of the electrode. However, the acid washing process may produce harmful gases and is corrosive to the electrode material, so it needs to be fully tested and evaluated before use.
Alkaline Cleaning:
Alkaline solutions such as sodium hydroxide and sodium carbonate are used to remove greasy dirt. Alkaline cleaning has the advantages of easy operation and good cleaning effect, but it is more corrosive to the electrode material, so it is necessary to strictly control the concentration of alkaline solution and cleaning time.
Ultrasonic cleaning method
Ultrasonic cleaning method is to use ultrasonic cavitation effect in the cleaning solution, stripping the electrode surface dirt. This method is applicable to electrodes of various shapes and complex structures, especially the dirt that is difficult to remove by mechanical methods. The ultrasonic cleaning machine generates high-frequency vibration through the ultrasonic generator, which makes the micro-bubbles in the cleaning liquid expand and rupture rapidly, generating a strong impact force and stripping the dirt from the electrode surface. Ultrasonic cleaning method has the advantages of good cleaning effect, easy operation and little damage to electrode materials, but the equipment cost is high and prolonged use may cause tiny mechanical damage to the electrode.
Electrolysis method
Electrolytic degreasing method removes greasy dirt on the electrode surface by electrolysis. An electrolytic solution, such as phosphate or silicate solution, is added to the cleaning tank, and the electrode is connected to the power supply so that it becomes the anode or cathode of the electrolytic tank. After starting the electrolysis process, the grease dirt is decomposed or detached under the action of electrolysis. Electrolytic degreasing method has the advantages of good cleaning effect and non-corrosive to electrode materials, but it requires specific electrolytic equipment and electrolytic solution, and harmful gas may be generated during the electrolysis process.
Recoil cleaning method
Backflush cleaning method is to use the reverse flow of fluid to rinse the electrode surface. This method is simple to operate, requires no additional equipment, and is suitable for situations where the fluid contains solid impurities such as sand and small particles. Close the downstream valve of the flowmeter and open the upstream valve to reverse the flow of fluid and flush the electrode surface. However, it should be noted that the backwash cleaning method can only remove loose dirt on the surface, the cleaning effect is limited, and the reverse flow may cause damage to the internal structure of the flowmeter.
Combined mechanical and ultrasonic cleaning method
The combined mechanical and ultrasonic cleaning method combines the advantages of mechanical cleaning and ultrasonic cleaning, first removing most of the dirt by mechanical means and then removing the residual dirt by ultrasonic cleaning. This method can give full play to the advantages of the two cleaning methods and improve the cleaning effect, but the operation is relatively complicated and the cost of the equipment is high.
Cleaning Precautions
When selecting the cleaning method, comprehensive consideration should be made according to the type of dirt, the material and structure of the electrode, and the cleaning conditions at the site. Meanwhile, the following points should be noted during the cleaning process:
1. Protect the electrode material: avoid using cleaning agents and solvents that are corrosive to the electrode material.
2. Control the cleaning time: too long cleaning time may cause damage to the electrode, too short may not clean thoroughly.
3. Properly dispose of the waste liquid: For the waste liquid generated by chemical cleaning and electrolysis methods, it needs to be properly disposed of to prevent environmental pollution.
4. Periodic maintenance: Regular visual inspection and maintenance of the electromagnetic flowmeter to ensure that the electrodes and sensors work properly.
Cleaning Examples
The following are some specific cleaning examples for reference:
1. Inorganic contamination: Immerse the electrode in 0.1mol/L dilute hydrochloric acid for 30 minutes, clean it with pure water and then immerse it in 3.5mol/L potassium chloride solution for 6 hours before use.
2. Organic contamination: After cleaning the surface of the electrode with detergent, clean it with pure water and then immerse it in 3.5mol/L potassium chloride solution for 6 hours before use.
3. Grease-type dirt: use electrolytic degreasing method or ultrasonic cleaning method to remove grease-type dirt.
4. Platinum surface oxidation: use toothpaste to polish the surface of platinum, and then clean it with pure water, and then immerse it in 3.5mol/L potassium chloride solution for 6 hours after use.
In summary, the electromagnetic flowmeter electrode cleaning is a complex and important work. Choosing the appropriate cleaning method and following the correct operating steps and precautions can ensure the long-term stable operation of the electrode and improve the measurement accuracy and service life of the instrument.
Hangzhou Economic Development Area，Hangzhou 310018，China
