Application technology of electromagnetic flowmeter in water supply system

With the continuous development of China's water supply industry, it is required that water supply flow measurement be more accurate in order to provide accurate references for water supply and distribution, and it is also an important means to improve the economic efficiency of water supply enterprises. The application of electromagnetic flow meters in water supply systems is becoming increasingly widespread. They are independent of conductivity, pressure, and temperature, and are not affected by these parameters, resulting in high measurement accuracy and reliability. Electromagnetic flow meters require the integration of computer information technology to collect, convert, and analyze signals, and then simulate them to analyze flow changes. Its advantages include easy operation, high accuracy, and reduced manual identification processes.

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The basic principle of electromagnetic flowmeter

Electromagnetic flowmeter is based on the law of electromagnetic induction, which treats fluid as a conductor. When passing through magnetic field lines, it cuts the magnetic field and generates electromotive force. Induced electromotive force E=K × V × B × D, where E refers to the induced electromotive force, K is the instrument constant, V is the average flow velocity, B refers to the magnetic induction intensity, and D is the inner diameter of the measuring tube. The fluid flows perpendicular to the direction of the magnetic field, and the induced electromotive force is positively correlated with the unit volume voltage or average flow velocity. By measuring the signal of the induced voltage and processing it with an amplifier, it is converted into a unified output signal.

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Research on the Application of Electromagnetic Flow Meter in Water Supply System

Main technical characteristics and installation requirements of electromagnetic flowmeter

2.1.1 Main technical characteristics of electromagnetic flowmeter

The technical characteristics of electromagnetic flow meters mainly include five aspects: * *, no obstruction in the measuring tube, low pressure loss, and less interference in water supply flow measurement. Due to the fact that the measurement results are not affected by certain factors such as temperature, pressure, etc., this can ensure high accuracy and stability. Thirdly, only electricity and pipelines come into contact with the measured liquid, so their impact on electricity is not significant. By selecting appropriate wear-resistant and corrosion-resistant materials, the reliability of electrical operation can be ensured. Fourthly, the flow rate in both directions can be measured. Fifth, the output signal method is very flexible and can be selected according to the characteristics of the working environment, such as current, frequency, pulse, etc.

2.1.2 Requirements for the Use and Installation of Electromagnetic Flowmeters

The use and installation of electromagnetic flow meters require strict requirements, generally starting from four aspects. There are clear regulations for upstream and downstream pipelines: for straight pipes with a length exceeding 5 times the pipe diameter upstream, and for straight pipes with a length exceeding 3 times the pipe diameter downstream, the length of the upstream and downstream pipelines should be increased when encountering special working environments. Strictly control the grounding resistance, usually below 10 ohms. Thirdly, it is necessary to avoid external electromagnetic interference with the electromagnetic flowmeter. Fourthly, install valves in upstream pipelines, especially at locations that severely affect flow characteristics such as right angle bends and butterfly valves. Install rectifiers to stabilize water flow and ensure accurate measurement.

Online calibration of 2.2 electromagnetic flowmeter

The electromagnetic flowmeter has been verified by the manufacturer before purchase, but the environment of the water supply system is complex and there are various factors that can interfere, resulting in significant differences between the production environment and the usage environment. Once put into use on site, the components of the electromagnetic flowmeter are affected by many factors and may malfunction. Routine on-site calibration is required before use, but the electromagnetic flowmeter is installed in the water supply pipeline and difficult to disassemble, requiring online calibration. Online verification mainly includes five aspects. Firstly, conducting copper resistance testing on the excitation coil. Under the same ambient temperature, the resistance value is consistent with the original factory value. Secondly, test the insulation of the excitation coil, with an insulation resistance value exceeding 20 megaohms. Thirdly, test the electrical resistance of the sensor to ground. If the resistance value is between 2-20kv, multiple tests are required to obtain a stable test value. Only when there is a charging and discharging phenomenon and the two resistance values are close can it be qualified. Fourthly, when testing the excitation current of the converter, the original current value and output value of the converter should be observed. If the error is less than 0.25mA, it is considered qualified. Fifthly, test the analog output and frequency output of the converter. When the linear error of * * is less than 0.5, it is considered qualified.

Application of Electromagnetic Flow Meter in Water Supply System

2.3.1 Used for regional measurement

Electromagnetic flow meters are widely used in urban pipeline networks, especially in the measurement and distribution of water supply, which plays a crucial role in facilitating water scheduling and configuration. Taking the water supply situation in a certain urban area as an example, some pipeline materials are DN600 and DN800, which are new, have high flow rates, and do not have serious leakage. Therefore, it is necessary to choose electromagnetic flow meters with high sensitivity and a wide measurement range.

2.3.2 Used as a settlement water meter

One important purpose of water supply flow measurement is water meter settlement, and electromagnetic flow meters are used as settlement water meters and have important reference functions. The management program for flow meters is to analyze the requirements of electromagnetic flow meters, such as model, quantity, etc., and then purchase, archive, install, use, verify, etc. Regular maintenance is required.

2.3.3 Used for water quantity measurement in water plants

Electromagnetic flow meters are widely used in current water plants, laying a solid foundation for water allocation and scheduling, providing data reference for production management, and facilitating water purification and chemical treatment. This allows for the calculation of consumption, chemical consumption, electricity consumption, and other data, facilitating cost control and water purification treatment. The water supply system may also experience some degree of malfunction, which can lead to inaccurate measurement. Electromagnetic flow meters can promptly respond to unit abnormalities or water supply pipeline bursts and other faults. Electromagnetic flow meters provide reference for the scheduling of urban pipeline networks, and the long water pressure and flow meters work together to provide data reference for unit operation. Electromagnetic flow meters have good stability and high measurement accuracy, but require imported flow meters of the same accuracy level for verification and setting the verification time to better control errors.

Difficulties and Solutions in the Use of Electromagnetic Flowmeters

The environment in which the water supply system is used is relatively complex, requiring electromagnetic flow meters to have high stability and reliability. However, there are also various problems and difficulties in practical use. The following is a brief analysis.

(1) The installation conditions for the flowmeter are not met. The installation of electromagnetic flowmeter requires high requirements for the straight pipe section, but it is difficult to install in old water supply systems, which will affect the stability of measurement. The flow characteristics can be improved by installing rectifier tubes.

(2) The flow rate of the tested water is too low. The water flow velocity is proportional to the induced electromotive force, but if the water flow velocity is too low, it will affect the measurement accuracy, especially at the end of the pipeline network. The corresponding method is to open the valves on both sides of the boundary as much as possible.

(3) The surface of the sensor should be clean and free of sludge. If there is sludge, it will affect the measurement due to the conductivity of the sludge. When selecting electricity, a scraper type electricity can be used, and a maintenance plan should be developed to reduce electrical interference factors, ensure electrical stability, and ensure its normal operation.

(4) If there is water vapor in the pipeline, it will disturb normal measurements and affect the measured values. When water vapor appears in the pipeline, it is necessary to promptly identify the cause and take corresponding measures. If necessary, an exhaust valve can be installed to remove the water vapor.

(5) The inlet pipeline of the electromagnetic flowmeter should be kept unobstructed and free of debris, otherwise it will affect the flow characteristics of the electromagnetic flowmeter, affect the measurement accuracy, and cause measurement errors. Therefore, it needs to be cleaned up in a timely manner.

(6) Lightning damage to electromagnetic flow meters is a common accident, and even minor ones can affect their performance, such as signal interference. Especially in relatively open suburban areas, thunderstorms cover a large area and can have a significant impact on electromagnetic flow meters, requiring the installation of corresponding lightning protection devices. When dealing with such issues, it is necessary to take measures such as power protection and grounding protection. The work of lightning protection is very important, usually by installing grounding grids, lightning rods, and building houses on electromagnetic flowmeter wells, which can significantly improve the lightning protection capability of electromagnetic flowmeters. If such problems cannot be fundamentally solved, separation protection is needed to reduce losses.