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Features of electromagnetic flowmeters: ① Electromagnetic flowmeters operate based on Faraday’s law of electromagnetic induction. Therefore, only the flow rate of conductive liquids can be measured; the flow rates of gases, vapors, and liquids containing a large amount of gas cannot be measured. ②Electromagnetic flowmeters have no moving parts or flow-blocking components, so there is virtually no pressure loss, allowing them to measure two-phase flows such as slurry and wastewater containing solid particles. ③In electromagnetic flowmeters, only the pipe lining and electrodes come into contact with the liquid being measured; therefore, by selecting appropriate materials for the electrodes and lining, it is possible to achieve corrosion and wear resistance when dealing with liquids such as slurry, hydrochloric acid, and hydric acid. ④It is easy to install; as long as the pipe is full, with the upper straight section being ≥5D and the lower straight section being ≥2D, it can be installed horizontally, vertically, or at an angle. ⑤It features high measurement accuracy, reaching 0.5%, and can be used for metering in tank filling, truck loading, etc. ⑥The range ratio is large, typically 1:20; on-site, the range can be expanded or reduced as needed without the need to stop the operation. Selection and Installation of Electromagnetic Flow Meters The selection and installation of electromagnetic flow meters are very important steps that require a high level of expertise; the following is a detailed explanation: Applicable media: Whether an electromagnetic flow meter can be used depends first on the conductivity of the medium, with the conductivity of the medium to be measured needing to be greater than 20μs/cm. The flow rate of media with lower conductivity can be measured using electromagnetic flowmeters with ceramic linings and platinum electrodes, but the ceramic linings are fragile, resulting in suboptimal performance. Orifice size selection: The orifice size of the flow meter does not necessarily have to be the same as the pipe diameter; it should be determined based on the flow rate. In the process industry, liquids with low viscosity such as water are transported; the typical flow velocity in pipes is the economic range of 1.5–3 m/s. Electromagnetic flowmeters can be used in such pipes, and the sensor diameter needs to be the same as that of the pipe ； For fluids dealing with substances that tend to adhere, deposit, or form scale, the flow velocity should be no less than 2 m/s; it is preferable to increase it to 3–4 m/s, which helps with self-cleaning and prevents adhesion and deposition ； For highly abrasive fluids such as slurry, the recommended flow rate should be below 2-3 m/s in order to reduce wear on the lining and electrodes ； When measuring liquids with low conductivity near the threshold, it is advisable to use a lower flow rate (0.5–1 m/s), as an increase in flow rate raises flow noise and leads to fluctuations in the output. Material selection for overcurrent components: The components of the sensor that come into contact with the liquid include linings, electrodes, grounding rings, and sealing gaskets. Common lining materials for electromagnetic flowmeters include fluoroplastics, polyurethane rubber, neoprene, and ceramics. The wear resistance, corrosion resistance, and maximum operating temperature of these materials affect the instrument’s suitability for various liquids. Fluoroplastics possess excellent resistance to chemical corrosion, but have poor wear resistance; they cannot be used for measuring slurry, and their operating temperature is below 180 degrees℃ ； Neoprene is used for non-corrosive or mildly corrosive liquids such as industrial water, wastewater, and weak acids and bases, and it is the cheapest option ； Polyurethane rubber has excellent wear resistance, but its resistance to acid and alkali corrosion is poor; it is suitable for use with media such as coal slurry and mineral slurry, provided that the temperature of such media is below 40°C–60°C/70℃ ； Alumina ceramics possess excellent wear resistance and corrosion resistance to strong acids and bases, making them suitable for use with corrosive slurries. However, they are brittle and prone to breaking during installation and clamping; they can be used at relatively high temperatures (120°C–140°C/180°C). The corrosion resistance of the electrode pair in an electromagnetic flowmeter to the measuring medium is the primary factor considered when selecting materials; secondary considerations include whether surface effects such as passivation occur and the noise generated as a result. Electrodes for electromagnetic flowmeters are required to have high corrosion resistance; corrosion is not allowed, or more precisely, only an extremely low rate of corrosion is permissible, as this would otherwise compromise the seal between the electrode and the lining. Common metal materials used include molybdenum-containing acid-resistant steel, Hastelloy, titanium, tantalum, and platinum-iridium alloys, which can handle almost all types of chemical liquids. In addition, there are low-noise electrodes suitable for use with slurries, such as conductive rubber electrodes, conductive fluoroplastic electrodes, porous ceramic electrodes, or metal electrodes coated with these materials. The grounding rings of electromagnetic flowmeters are installed at both ends of the flow sensor, where it is connected to plastic pipes or metal pipes with insulating linings. Their corrosion resistance requirements are lower than those of the electrodes; they can tolerate a certain degree of corrosion and can be replaced periodically. Acid-resistant steel or Hastelloy is usually used for these rings. Metal process pipes in direct contact with fluids do not require a grounding ring. Piping and installation: Improper piping installation for electromagnetic flowmeters can lead to fluctuations in the meter’s output, unstable zero points, a shortened service life, and even damage to the instrument. The following principles should be followed primarily: ① The upstream side of the sensor should not be located close to valves, elbows, or other devices that affect fluid flow ； Pumps cannot be installed on the downstream side to prevent the creation of negative pressure ； Throttling instruments such as control valves should be installed downstream of the flow meter, especially in pipelines used for emptying tanks or tank cars. ②When designing the piping for electromagnetic flowmeters, it is necessary to ensure that the measurement tube is filled completely, with straight pipe sections of 5D and 2D upstream and downstream. ③Attention should be paid to the installation direction: when measuring the flow rate of liquid-solid two-phase media, it is advisable to install the sensor vertically. This helps prevent uneven distribution or phase separation of the two phases at lower flow rates, thereby reducing the additional errors that can arise from this. Secondly, it allows for more even wear of the lining around the sensor; when installed vertically, the flow direction should be from bottom to top, so as to ensure that the electromagnetic flowmeter sensor remains always filled with the medium. When installed horizontally, the connection between the two electrodes of the sensor should be horizontal; this prevents issues such as an open circuit at the input of the converter when bubbles are present in the medium or when precipitation occurs. ④In some operating conditions, chemicals need to be injected into the pipeline, and this injection leads to uneven conductivity of the liquid, thereby interfering with the output signal of the electromagnetic flowmeter. To address this, it can be injected downstream of the flow meter; if injection is required upstream, the injection point should be kept at a certain distance from the flow meter to ensure uniform mixing of the liquid. ⑤A grounding ring must be used when installing on the plastic pipe or lined pipe of an electromagnetic flowmeter. For more information, please visit the company’s official website at http://www.yb1518.com/. Please retain this link when reproducing the content! http://www.yb1518.com/UploadFiles/2012717174126829.jpg