Overview and Installation of Electromagnetic Flow Meters

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Introduction to electromagnetic flowmeters: http://upload.gongkong.com/Upload/gongkong/technicalDataImage/202007/27/4d1ab01382de452e856b25af09e93aae_w.jpg Electromagnetic flowmeters (EMF for short) are a new type of flow measurement instrument that developed rapidly in the 1950s and 1960s alongside the progress of electronic technology. An electromagnetic flowmeter is an instrument that utilizes the principle of electromagnetic induction to measure the flow rate of conductive fluids, based on the electromotive force generated when such fluids pass through an external magnetic field. The electromagnetic flowmeter is a new type of flow measurement instrument that developed rapidly in the 1960s alongside the advancement of electronic technology. It is based on Faraday’s law of electromagnetic induction and is used to measure the volumetric flow rate of conductive fluids. Due to its unique advantages, it is widely used in the measurement of various conductive liquids in industry. For example, it is used to measure corrosive liquids such as various acids, bases, and salts ； Various flammable and explosive substances ； Various industrial wastewater, pulp, sludge, etc. The measurement principle is based on Faraday’s law of electromagnetic induction. That is, when a conductive liquid flows through an electromagnetic flowmeter, a voltage is generated in the conductive liquid that is proportional to the average flow velocity V (volumetric flow rate). This induced voltage signal is detected by two electrodes in contact with the liquid, transmitted via cables to an amplifier, and then converted into a standardized output signal. Based on the measurement principle of electromagnetic flowmeters, the flowing liquid is required to have a minimum level of conductivity. Features of electromagnetic flowmeters: The transmitter of an electromagnetic flowmeter has a simple structure; it contains no moving parts nor any throttling elements that could impede fluid flow. As a result, no additional pressure loss occurs as the fluid passes through it, and issues such as wear or blockage do not arise. It is particularly suitable for measuring two-phase fluids containing solid particles, such as slurry and wastewater, as well as various viscous slurries. Additionally, due to the absence of moving parts in its design, it is possible to equip it with corrosion-resistant insulating linings and electrodes made from corrosion-resistant materials, thereby providing excellent corrosion resistance and enabling its use in measuring various corrosive media. Installation notes for electromagnetic flowmeters: 1. Length of straight pipe sections – For vortex flowmeters, it is important to avoid components that can generate vortices, such as valves, elbows, and bypasses. Try to increase the length of the straight pipe sections upstream and downstream of the flowmeter. If necessary, install straightening tubes. The upstream straight pipe section should be at least 5 DN (the diameter of the measurement tube), while the downstream section should be at least 2 DN. 2. The liquid conductivity must be uniform and stable; do not install the flow meter in areas where the conductivity of the fluid being measured is highly uneven. If different media are injected upstream, it will lead to non-uniform conductivity and affect the measurements. In this case, it is recommended to move the injection port downstream ； If injection from upstream is necessary, it should be done as far away from the flow meter as possible. It is advisable to maintain a distance of at least 20 DN to ensure thorough and even mixing of the liquid. 3. Keep the electrode axis level. The connection of the electromagnetic flowmeter should comply with the installation guidelines. Note: If restricted by on-site installation conditions, keep the allowable tilt angle ≤ 45°. 4. Bubble-free gas flow meter: When designing the pipeline for installing the flow meter, it is necessary to ensure that no bubbles are formed. 5. The flowmeter pipeline is full; the flowmeter can be installed horizontally, vertically, or at an angle. However, the piping design must ensure that the measuring tube is always filled with liquid (full tube). When designing the piping, make sure there are no bubbles in the measurement section; otherwise, it will lead to unstable measurements and large deviations. 6. Selection of installation method: If the medium to be measured contains solid particles or slurry, it is recommended to install it vertically (with the flow direction from bottom to top) to prevent solid particles from depositing inside the meter’s measuring tube. When the flow meter is installed horizontally or at an angle, its electrode axis should be in a horizontal position. If the electrode axis is perpendicular to the ground, bubbles tend to accumulate near the upper electrode. 7. Pipeline installation: Avoid misalignment or tilting of the pipelines upstream and downstream of the flow meter, and ensure alignment with the flanges on those pipelines. Before installation, remove welding residues and protrusions, and place shims. After an electromagnetic flowmeter is installed on a pipeline, welding operations must be prohibited on that section of the pipe to prevent damage to the lining.