The process of industrialization in China has been accelerating. The problem of environmental pollution has become increasingly serious. The voice of society for sustainable development has also been increasing. The concept of a harmonious symbiosis between man and nature has been accepted by people, and pollution control has become more urgent. In the sewage treatment process, it is necessary to measure and control the discharge of sewage, additives, and sludge. Flow measurement is very important.
1. Characteristics of Electromagnetic Flowmeter Electromagnetic flowmeter is not affected by external factors such as temperature, pressure, viscosity, etc., and there is no pressure loss due to shrinkage or projection inside the measuring tube. In addition, the flow element detects the initial signal, which is an average flow velocity with the fluid. The precise linearly varying voltage, which has nothing to do with the other properties of the fluid, has great advantages. Sewage has characteristics such as large flow variation, impurities, low corrosiveness, certain electrical conductivity, etc. Measuring the flow of sewage, electromagnetic flowmeter is a good choice. It is compact and small in size. Installation, operation, and maintenance are convenient, and the measurement system adopts an intelligent design, and the overall seal is strengthened, so it can work normally in harsh environments. The vortex flowmeter technology reasons, caliber is difficult to make large, quality, pipeline-type ultrasonic flowmeter price phase electromagnetic lack of competitive advantage. In the water and sewage industry, electromagnetic flowmeters, especially large-diameter electromagnetic flowmeters, have great advantages and have become very popular.
SKLD series electromagnetic flowmeter has powerful functions and simple operation. The specific features are as follows:
1 There are no obstructed flow components in the measuring pipe, no pressure loss, and the straight pipe section requires bottom.
2 Lining is available in hard rubber, polyurethane, PTFE, PFA and many other materials.
3 transmitter DC power supply / AC power supply, four-wire / two-wire system, explosion-proof / non-explosion-proof, economic / standard and other subdivision to meet your different needs.
4 Measurements are not affected by variations in fluid density, viscosity, pressure, temperature, and conductivity.
5 light-sensitive keys, can be opened without cover; Chinese menu display, more convenient for domestic users.
6 Quick setting menu, guide to complete the parameter setting, convenient and quick.
7 High measurement reliability, good repeatability, and long-term maintenance-free. Up to 1000:1 ratio
8 provides current, frequency, pulse, Hart, profibus-PA, profibus-DP, FF and other output modes for selection.
2. Measurement principle The working principle of electromagnetic flowmeter is based on Faraday's law of electromagnetic induction. When the conductive metal rod moves perpendicular to the direction of the magnetic force line at a certain speed, an induced voltage is generated.
In the electromagnetic flowmeter, the conductive medium in the measuring tube is equivalent to the conductive metal rod in the Faraday test, and two electromagnetic coils at the upper and lower ends generate a constant magnetic field. When there is a conductive medium flowing, an induced voltage is generated. Two electrodes inside the pipe measure the induced voltage. The measuring pipe is made of nonconductive lining rubber and Teflon etc. achieves electromagnetic isolation from the fluid and the measuring electrode.
The magnetic field strength B generated by the electromagnetic induction coil is constant, and the induced voltage Ue is proportional to the fluid velocity v. The cross-sectional area A of the pipeline is known, and the volume flow rate Qv can be calculated as follows:
Electromagnetic flowmeter consists of flow sensor and transmitter. The sensor measuring tube is equipped with excitation coils on the upper and lower sides, generates a magnetic field through the measuring tube through the excitation current, and a pair of electrodes contact the inner wall of the measuring tube with the liquid to draw out the induced potential and send it to the transmitter. Excitation current is provided by the transmitter. According to the transmitter and sensor assembly methods, there are two types of separation and integration. In the sewage treatment process, large-diameter flowmeters are mostly split type, with one part installed and the other part. Small caliber is more of a one-piece type.
The electromagnetic flowmeter function in the market is also very different, simple to measure one-way flow, only output the analog signal to drive the rear instrument; multi-function instrument has to measure the two-way flow, range switching, upper and lower limit flow alarm, empty pipe and power off alarm, Small signal cutting, flow display and total calculation, automatic check and fault self-diagnosis, communication with the host computer and motion configuration. Some models of instrument serial digital communication function can choose a variety of communication interfaces and special chip ASIC to connect HART protocol system, PROFTBUS, MODBUS, FF field bus and so on.
The scope of electromagnetic flowmeter is wider than other types of flowmeters. Suko Instruments Co., Ltd. of Jiangsu Province provides SKLD type electromagnetic flowmeters for water and sewage, chemical, food, and pharmaceutical industries. The diameter ranges from 20mm to 2m. Accuracy can be 0.5%, 1.0% two options. Measurable positive and negative bi-directional flow, can also measure pulsating flow.
The use of electromagnetic flowmeters is based on the premise that the fluid to be measured must be electrically conductive and must not fall below the threshold, ie the lower limit value. Conductivity lower than the threshold will produce measurement error until it can not be used, more than the threshold change can also be measured, the indication error does not change much, general-purpose electromagnetic flowmeter threshold between 10-4 ~ 5 × 10-6S/cm, depending on the model and different. When it is used, it also depends on the length of the flow signal line between the sensor and the converter and its distributed capacitance. The manufacturer's instruction manual usually specifies the length of the conductivity signal line.
Industrial water and its aqueous solution conductivity greater than 10-4S/cm, acid, alkali, salt liquid conductivity 10-4 ~ 10-1S/cm, use no problem, low distilled water is 10-5S/cm problem . Electromagnetic flowmeters cannot measure liquids with very low conductivity, such as petroleum products and organic solvents. Can not measure gas, steam, and liquids containing more large bubbles. From the data, it was found that some pure liquids or aqueous solutions had low conductivity, and they were considered unusable. In actual work, they encountered instances where impurities could be used, and such impurities were favorable for increasing the conductivity. Aqueous solution, the conductivity of the data is measured with pure water ratio laboratory, the actual use of aqueous solution may use industrial water ratio, conductivity will be higher than the investigation, but also conducive to flow measurement.
3. Installation requirements SKLD series electromagnetic flowmeters provide protection class IP67 dust and flood protection or IP68 dust and anti-submarine protection. Most large-diameter flowmeter sensors in wastewater treatment plants are installed. It is recommended to choose IP68 anti-dive and anti-dive class. Usually electromagnetic flow has all the following requirements for the installation site:
1 When the mixed phase fluid is measured, the selection does not cause the phase separation site; when measuring the two-component liquid, the loading and mixing are not yet uniformly downstream; when measuring the chemical reaction pipeline, it is necessary to install the reaction to fully complete the downstream of the segment; Less than 5D and 2D;
2 easy to implement sensor separate place;
3 Avoid high concentrations of corrosive gases in the surrounding environment as much as possible;
4 As far as possible to avoid the negative pressure in the measuring tube;
5 Avoid large electric motors, large transformers, etc. in the vicinity to avoid electromagnetic interference;
6 Choose a small place for vibration, especially for integrated type instruments;
7 As far as possible, avoid direct sunlight. 4. Application and effect Sewage treatment process The main bio-oxidation, flocculation, sedimentation and other processes reach the goal of sewage purification. Each stage needs a certain amount of meter to measure. Sewage treatment process, the need for process requirements, configure the corresponding detection instrument, constitute a reliable control system. A water treatment plant in the following process detection process is equipped with a flow meter: 1 inlet pipe; 2 primary sedimentation tank to the mud pool mud detection; 3 sludge pumping room surplus, sludge flow detection; 4 sludge return sludge pump room Flow detection; 5 Second settling tank with wells outflow detection; 6 Digestion tank into mud detection; 7 Digestion pond out of the mud detection; 8 flocculant pool into the amount of detection and so on.
1. Characteristics of Electromagnetic Flowmeter Electromagnetic flowmeter is not affected by external factors such as temperature, pressure, viscosity, etc., and there is no pressure loss due to shrinkage or projection inside the measuring tube. In addition, the flow element detects the initial signal, which is an average flow velocity with the fluid. The precise linearly varying voltage, which has nothing to do with the other properties of the fluid, has great advantages. Sewage has characteristics such as large flow variation, impurities, low corrosiveness, certain electrical conductivity, etc. Measuring the flow of sewage, electromagnetic flowmeter is a good choice. It is compact and small in size. Installation, operation, and maintenance are convenient, and the measurement system adopts an intelligent design, and the overall seal is strengthened, so it can work normally in harsh environments. The vortex flowmeter technology reasons, caliber is difficult to make large, quality, pipeline-type ultrasonic flowmeter price phase electromagnetic lack of competitive advantage. In the water and sewage industry, electromagnetic flowmeters, especially large-diameter electromagnetic flowmeters, have great advantages and have become very popular.
SKLD series electromagnetic flowmeter has powerful functions and simple operation. The specific features are as follows:
1 There are no obstructed flow components in the measuring pipe, no pressure loss, and the straight pipe section requires bottom.
2 Lining is available in hard rubber, polyurethane, PTFE, PFA and many other materials.
3 transmitter DC power supply / AC power supply, four-wire / two-wire system, explosion-proof / non-explosion-proof, economic / standard and other subdivision to meet your different needs.
4 Measurements are not affected by variations in fluid density, viscosity, pressure, temperature, and conductivity.
5 light-sensitive keys, can be opened without cover; Chinese menu display, more convenient for domestic users.
6 Quick setting menu, guide to complete the parameter setting, convenient and quick.
7 High measurement reliability, good repeatability, and long-term maintenance-free. Up to 1000:1 ratio
8 provides current, frequency, pulse, Hart, profibus-PA, profibus-DP, FF and other output modes for selection.
2. Measurement principle The working principle of electromagnetic flowmeter is based on Faraday's law of electromagnetic induction. When the conductive metal rod moves perpendicular to the direction of the magnetic force line at a certain speed, an induced voltage is generated.
In the electromagnetic flowmeter, the conductive medium in the measuring tube is equivalent to the conductive metal rod in the Faraday test, and two electromagnetic coils at the upper and lower ends generate a constant magnetic field. When there is a conductive medium flowing, an induced voltage is generated. Two electrodes inside the pipe measure the induced voltage. The measuring pipe is made of nonconductive lining rubber and Teflon etc. achieves electromagnetic isolation from the fluid and the measuring electrode.
The magnetic field strength B generated by the electromagnetic induction coil is constant, and the induced voltage Ue is proportional to the fluid velocity v. The cross-sectional area A of the pipeline is known, and the volume flow rate Qv can be calculated as follows:
Electromagnetic flowmeter consists of flow sensor and transmitter. The sensor measuring tube is equipped with excitation coils on the upper and lower sides, generates a magnetic field through the measuring tube through the excitation current, and a pair of electrodes contact the inner wall of the measuring tube with the liquid to draw out the induced potential and send it to the transmitter. Excitation current is provided by the transmitter. According to the transmitter and sensor assembly methods, there are two types of separation and integration. In the sewage treatment process, large-diameter flowmeters are mostly split type, with one part installed and the other part. Small caliber is more of a one-piece type.
The electromagnetic flowmeter function in the market is also very different, simple to measure one-way flow, only output the analog signal to drive the rear instrument; multi-function instrument has to measure the two-way flow, range switching, upper and lower limit flow alarm, empty pipe and power off alarm, Small signal cutting, flow display and total calculation, automatic check and fault self-diagnosis, communication with the host computer and motion configuration. Some models of instrument serial digital communication function can choose a variety of communication interfaces and special chip ASIC to connect HART protocol system, PROFTBUS, MODBUS, FF field bus and so on.
The scope of electromagnetic flowmeter is wider than other types of flowmeters. Suko Instruments Co., Ltd. of Jiangsu Province provides SKLD type electromagnetic flowmeters for water and sewage, chemical, food, and pharmaceutical industries. The diameter ranges from 20mm to 2m. Accuracy can be 0.5%, 1.0% two options. Measurable positive and negative bi-directional flow, can also measure pulsating flow.
The use of electromagnetic flowmeters is based on the premise that the fluid to be measured must be electrically conductive and must not fall below the threshold, ie the lower limit value. Conductivity lower than the threshold will produce measurement error until it can not be used, more than the threshold change can also be measured, the indication error does not change much, general-purpose electromagnetic flowmeter threshold between 10-4 ~ 5 × 10-6S/cm, depending on the model and different. When it is used, it also depends on the length of the flow signal line between the sensor and the converter and its distributed capacitance. The manufacturer's instruction manual usually specifies the length of the conductivity signal line.
Industrial water and its aqueous solution conductivity greater than 10-4S/cm, acid, alkali, salt liquid conductivity 10-4 ~ 10-1S/cm, use no problem, low distilled water is 10-5S/cm problem . Electromagnetic flowmeters cannot measure liquids with very low conductivity, such as petroleum products and organic solvents. Can not measure gas, steam, and liquids containing more large bubbles. From the data, it was found that some pure liquids or aqueous solutions had low conductivity, and they were considered unusable. In actual work, they encountered instances where impurities could be used, and such impurities were favorable for increasing the conductivity. Aqueous solution, the conductivity of the data is measured with pure water ratio laboratory, the actual use of aqueous solution may use industrial water ratio, conductivity will be higher than the investigation, but also conducive to flow measurement.
3. Installation requirements SKLD series electromagnetic flowmeters provide protection class IP67 dust and flood protection or IP68 dust and anti-submarine protection. Most large-diameter flowmeter sensors in wastewater treatment plants are installed. It is recommended to choose IP68 anti-dive and anti-dive class. Usually electromagnetic flow has all the following requirements for the installation site:
1 When the mixed phase fluid is measured, the selection does not cause the phase separation site; when measuring the two-component liquid, the loading and mixing are not yet uniformly downstream; when measuring the chemical reaction pipeline, it is necessary to install the reaction to fully complete the downstream of the segment; Less than 5D and 2D;
2 easy to implement sensor separate place;
3 Avoid high concentrations of corrosive gases in the surrounding environment as much as possible;
4 As far as possible to avoid the negative pressure in the measuring tube;
5 Avoid large electric motors, large transformers, etc. in the vicinity to avoid electromagnetic interference;
6 Choose a small place for vibration, especially for integrated type instruments;
7 As far as possible, avoid direct sunlight. 4. Application and effect Sewage treatment process The main bio-oxidation, flocculation, sedimentation and other processes reach the goal of sewage purification. Each stage needs a certain amount of meter to measure. Sewage treatment process, the need for process requirements, configure the corresponding detection instrument, constitute a reliable control system. A water treatment plant in the following process detection process is equipped with a flow meter: 1 inlet pipe; 2 primary sedimentation tank to the mud pool mud detection; 3 sludge pumping room surplus, sludge flow detection; 4 sludge return sludge pump room Flow detection; 5 Second settling tank with wells outflow detection; 6 Digestion tank into mud detection; 7 Digestion pond out of the mud detection; 8 flocculant pool into the amount of detection and so on.