What are Electromagnetic Flow Meters?

Electromagnetic flowmeter is the application of the principle of electromagnetic induction, according to the conductive fluid through the applied magnetic field generated by the electric potential to measure the flow of conductive fluids in an instrument.

Electromagnetic flowmeter is based on Faraday's law of electromagnetic induction for flow measurement. The advantage of an electromagnetic flowmeter is minimal pressure loss and can measure the flow range. The ratio of maximum flow rate and minimum flow rate is generally more than 20:1, applicable to a wide range of industrial pipe diameter, up to 3m. The output signal and the measured flow rate into a linear, high accuracy, can measure the conductivity ≥ 5μs/cm of acid, alkali, salt solutions, water, sewage, corrosive liquids and mud, slurry, pulp, pulp, and other fluid flow. But it can not measure the flow of gas, steam, and pure water.

The structure of the electromagnetic flowmeter is mainly composed of a magnetic circuit system, measuring conduit, electrode, shell, lining, and converter.

Magnetic circuit system:

Its role is to generate a uniform DC or AC magnetic field. DC magnetic circuit with permanent magnets to achieve the advantage of a relatively simple structure, less interference by the AC magnetic field, but it is easy to make the electrolyte through the measurement conduit liquid polarisation, so that negative ions surround the positive electrode, the negative electrode is surrounded by positive ions, i.e., the electrode of the polarisation phenomenon, and lead to the internal resistance between the two electrodes increases, thus seriously affecting the normal operation of the instrument. When the pipe diameter is large, the permanent magnet is correspondingly large, bulky, and uneconomical, so the electromagnetic flowmeter is generally used in the alternating magnetic field, and is generated by 50HZ industrial frequency power supply excitation.

Measuring conduit:

Its function is to allow the conductive liquid being measured to pass through. To make the magnetic lines of force through the measuring conduit when the magnetic flux is shunted or short-circuited, the measuring conduit must be made of non-conducting, low electrical conductivity, low thermal conductivity and a certain degree of mechanical strength of the material made of non-conducting stainless steel, glass fiber reinforced plastic, high-strength plastics, aluminum and so on.

Electrode:

Its role is to lead and be measured proportionately to the induction potential signal. Electrodes are generally made of non-magnetic stainless steel and are required to be flush with the lining so that the fluid is not obstructed when passing through. Its installation position should be in the vertical direction of the pipeline, in order to prevent the accumulation of sediments on it and affect the measurement accuracy.

Housing:

Should be made of ferromagnetic material, it is the outer cover of the excitation coil of the distribution system and isolates it from the interference of the external magnetic field.

Lining:

A complete electrically insulating lining on the inside of the measuring conduit and on the sealing surface of the flange. It is in direct contact with the measured liquid and serves to increase the corrosion resistance of the measuring conduit and to prevent the induced potential from being short-circuited by the metal measuring conduit wall. The lining material is mostly corrosion-resistant, high temperature-resistant, wear-resistant polytetrafluoroethylene plastic, ceramics, and so on.

Converter:

The induced potential signal generated by the liquid flow is very weak, by a variety of interfering factors, the role of the converter is to amplify the induced possible signal and convert it into a unified standard signal and inhibit the main interfering signals. Its task is the electrode detected by the induction potential signal Ex by amplification into a unified standard DC signal.

Electromagnetic flow meter features:

1.Measurement is not affected by changes in fluid density, viscosity, temperature, pressure and conductivity;

2.No obstruction to the flow of parts in the measuring tube, no pressure loss, straight pipe section requirements are low. Unique adaptability to slurry measurement;

3.Reasonable choice of sensor lining and electrode materials, that is, good corrosion and wear resistance;

4.The converter adopts novel excitation method, low power consumption, stable zero point, high accuracy. The flow range degree can reach 150:1;

5.The converter and the sensor can be composed of one body type or separate type;

6.The converter adopts 16-bit high-performance microprocessor, 2x16LCD display, convenient parameter setting, reliable programming;

7.The flow meter is a bidirectional measurement system, built-in three accumulators: total forward, total reverse and total difference; can display the positive and negative flow, and has a variety of output: current, pulse, digital communication, HART;

8.The converter adopts surface mounting technology (SMT) with self-test and self-diagnosis function;

9.Measurement accuracy is not affected by changes in fluid density, viscosity, temperature, pressure and conductivity, the sensor senses a linear relationship between the voltage signal and the average flow rate, so the measurement accuracy is high.

10.Measurement of the pipeline without flow resistance, so there is no additional pressure loss; measurement of the pipeline without moving parts, so the sensor life is extremely long.

11.Because the induction voltage signal is formed in the entire space filled with magnetic field, is the average value on the pipe-carrying surface, so the sensor requires a shorter straight pipe section, the length of 5 times the diameter of the pipe.

12.The converter uses the latest and most advanced international single-chip microcomputer (MCU) and surface mount technology (SMT), reliable performance, high accuracy, low power consumption, zero stability, convenient parameter setting. Click on the Chinese display LCD, display cumulative flow, instantaneous flow, flow rate, flow rate percentage and so on.

13.Two-way measurement system, can measure forward flow, reverse flow. The use of special production processes and high-quality materials to ensure the performance of the product in a long time to maintain stability.

The electromagnetic flow meter on the display is divided into: split electromagnetic flow meter, a body electromagnetic flow meter. Series nominal diameter DN15 ~ DN3000.

Split electromagnetic flow meter is based on Faraday's law of electromagnetic induction to measure the volume flow of conductive media in the pipe inductive instrumentation, the use of single-chip embedded technology to achieve digital excitation, while the electromagnetic flow meter on the use of CAN field bus, the first of its kind in the country, the technology has reached a leading level in China.

Split electromagnetic flow meter to meet the field display at the same time, but also can output 4 ~ 20mA current signal for recording, regulation and control, is now widely used in the chemical industry, environmental protection, metallurgy, medicine, paper making, water supply and drainage and other industrial technology and management departments.

Split electromagnetic flow meter in addition to measuring the flow of general conductive liquids, but also can measure the liquid-solid two-phase flow, high-viscosity liquid flow and salts, strong acid, and strong alkali liquid volume flow.

A body type electromagnetic flow meter is based on Faraday's law of electromagnetic induction, is used to measure the volume flow of conductive fluids. Due to the unique characteristics has been widely used in industry for a variety of conductive liquid measurements. Mainly used in chemical, paper, food, textile, metallurgy, environmental protection, water supply and drainage and other industries, and computer matching can achieve system control.

1. Electromagnetic flow meter has no moving parts, there is no flow stopper, will not cause pressure loss, but also does not cause wear and tear, blockage and other issues.

2. Electromagnetic flow meter is a volume flow measurement instrument in the measurement process is not subject to the measured medium temperature, viscosity, density and conductivity (within a certain range).

3. Electromagnetic flow meter range is wide, up to 1: 100. In addition, the electromagnetic flow meter is only proportional to the average flow rate of the measured medium, and the axisymmetric flow state (laminar or turbulent).

4. Electromagnetic flow meter without mechanical inertia, responsive, can measure the instantaneous pulsating flow, and good linearity, so you can measure the signal directly with the converter linear conversion into a standard signal output.LD-T-type can be on-site instructions, LD-type can be transmitted over long distances.

Lining selection:

Electromagnetic flow meter lining material correct selection method:

Should be based on the measured medium corrosive, abrasive and temperature to select the lining material:

First. Natural rubber (soft rubber)

1, better elasticity, abrasion resistance and tearing force

2, resistance to general weak acid, weak alkali corrosion

3, water measurement, sewage

Second. Acid-resistant rubber (hard rubber)

Resistant to hydrochloric acid, acetic acid, oxalic acid, ammonia, phosphoric acid and 50% sulfuric acid, sodium hydroxide, potassium hydroxide corrosion at room temperature, but does not resist strong oxidant corrosion

Measurement of general acids, alkalis, salt solutions

Third. Chloroprene rubber (Neoprene)

1, excellent elasticity, high degree of tearing force, good abrasion resistance

2, resistant to general low concentration of acid, alkali, salt solution corrosion, but not resistant to oxidative media corrosion

<80℃;

Measurement of water, sewage, mud and slurry

Fourth. Polyurethane rubber (Polyurethane)

1, excellent wear resistance

2, poor resistance to acid, alkali

<40 ℃

Measurement of neutral strong abrasion of coal slurry, mud and slurry

Fifth. Polytetrafluoroethylene (PTFE)

1, boiling hydrochloric acid, sulfuric acid, nitric acid, aqua regia, concentrated alkali and various organic solvents

2, good wear resistance, poor adhesive properties

-80 ~ +180 ℃;

Measurement of concentration, concentrated alkali strong corrosive solutions and sanitary media

WESDOM Group specializes in pipeline fluid systems: R&D, production and sales of valves, pipe fittings, water meters, flow meters, etc. The products cover cast iron, cast steel, stainless steel, copper, plastics and other materials, which are widely used in hydropower stations, heat, buildings, Water supply and drainage, petroleum, chemical industry, electric power, medical and other fields.

Why more and more customers are choosing wesdom valves:

1. There is a professional technical team, and quality is guaranteed

2. Independent factory, more favorable price

3. Extensively trained employees are well-versed in all aspects of flow control technology

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