Electromagnetic flowmeter is an instrument for measuring conductive liquids made according to Faraday's law of electromagnetic induction.
The electromagnetic flowmeter has a series of excellent characteristics, which can solve the problems that other flowmeters are not easy to apply, such as the measurement of dirty flow and corrosive flow.
In the 1970s and 1980s, there was a major breakthrough in electromagnetic flow technology, making it a widely used type of flowmeter, and the percentage of its use in flow meters continued to rise.
Electromagnetic flowmeters have a wide range of applications, and large-diameter instruments are mostly used in water supply and drainage projects; medium and small calibers are often used in high-demand or difficult-to-measure occasions, such as blast furnace tuyere cooling water control in the iron and steel industry, measurement of pulp and black liquor in the paper industry, and chemical industry. Strong corrosive liquid, ore pulp in non-ferrous metallurgy industry; small-diameter and micro-diameter are often used in places with hygiene requirements such as pharmaceutical industry, food industry, and biochemistry.
1. The measurement is not affected by changes in fluid density, viscosity, temperature, pressure and conductivity;
2. There are no obstructing flow parts in the measuring tube, no pressure loss, and low requirements for straight pipe sections. Unique adaptability to slurry measurement;
3. Reasonable selection of sensor lining and electrode materials, that is, good corrosion resistance and wear resistance;
4. The converter adopts a novel excitation method, with low power consumption, stable zero point and high accuracy. The flow range can reach 150:1;
5. The converter can be integrated or separated with the sensor;
6. The converter adopts 16-bit high-performance microprocessor, 2x16LCD display, convenient parameter setting and reliable programming;
7. The flowmeter is a two-way measurement system with three built-in totalizers: forward total, reverse total and difference total; it can display forward and reverse flow, and has a variety of outputs: current, pulse, digital communication , HART;
8. The converter adopts surface mount technology (SMT), with self-test and self-diagnosis functions;
9. The measurement accuracy is not affected by changes in fluid density, viscosity, temperature, pressure and conductivity. The sensor induced voltage signal has a linear relationship with the average flow rate, so the measurement accuracy is high.
10. There is no obstruction in the measurement pipeline, so there is no additional pressure loss; there are no moving parts in the measurement pipeline, so the sensor has a very long life.
11. Since the induced voltage signal is formed in the entire space filled with magnetic field and is the average value on the pipeline surface, the straight pipe section required by the sensor is short, and the length is 5 times the pipe diameter.
12. The converter adopts the latest and most advanced single chip microcomputer (MCU) and surface mount technology (SMT) in the world, with reliable performance, high precision, low power consumption, stable zero point and convenient parameter setting. Click on the Chinese display LCD to display the cumulative flow, instantaneous flow, flow rate, flow percentage, etc.
13. Two-way measurement system, which can measure forward flow and reverse flow. The use of special production technology and high-quality materials ensures that the performance of the product remains stable for a long time.
The lining material should be selected according to the corrosiveness, abrasiveness and temperature of the measured medium:
1. Natural rubber (soft rubber)
(1) Good elasticity, wear resistance and tearing force
(2) Resistant to general weak acid and weak alkali corrosion
(3) Measuring water and sewage
2. Acid-resistant rubber (hard rubber)
Resistant to the corrosion of hydrochloric acid, acetic acid, oxalic acid, ammonia water, phosphoric acid and 50% sulfuric acid, sodium hydroxide, potassium hydroxide at room temperature, but not resistant to the corrosion of strong oxidants
Measure general acid, alkali and salt solution
Measure water, sewage, mud and slurries
(1) Excellent elasticity, high breaking force, good wear resistance
(2) It is resistant to corrosion by general low-concentration acid-base and salt solutions, but not resistant to corrosion by oxidative media
4. Polyurethane rubber
Measure neutral and highly abrasive coal slurries, slurries and ore slurries
(1) Excellent wear resistance
(2) Poor acid and alkali resistance
5. Polytetrafluoroethylene (PTFE)
Concentration measurement, concentrated alkali strong corrosive solution and hygienic medium
(1) Resistant to boiling hydrochloric acid, sulfuric acid, nitric acid, aqua regia, concentrated alkali and various organic solvents
(2) Good wear resistance and poor adhesion
Electromagnetic flowmeters are widely used in sewage, fluorine chemical, production water, tap water industry, medicine, steel and many other aspects. Due to the principle, it can only measure conductive liquids. Although it is much better than other types of flowmeters in terms of reliability and stability, customers will still encounter some problems in the actual use process. Let me explain in detail the selection and installation of electromagnetic flowmeters:
First, like other flowmeters, although the electromagnetic flowmeter has a measurement range ratio of 30:1, which is higher than that of vortex flowmeters and differential pressure flowmeters, it is also limited. Comparing it with a water meter, it is thought that it can measure a very low flow rate. Under normal circumstances, it can only measure 0.1m/s. It is difficult for an electromagnetic flowmeter to measure correctly below this flow rate. Therefore, it is necessary to clarify the flow range ratio in the early stage of ordering. When ordering, it is not possible to order according to the original pipe diameter, it is best to determine the diameter of the instrument according to your actual flow.
Second, like other flowmeters, electromagnetic flowmeters also have requirements for straight pipes before and after installation, but they have lower requirements than other types of flowmeters, but the most critical point is to meet: that is, the pipe is full, and then the pipe is full. When the pipe is not full, it is easy to cause the flowmeter to jump randomly:
Third, like other flowmeters, electromagnetic flowmeters also have protection levels. Generally, the integrated protection level is IP65, and the split type is IP68 (for sensors). If the customer has requirements for the installation environment of the instrument, the installation location is underground. In wells or some other wet places, it is recommended that customers choose the split type. In order to avoid damage to the instrument due to wrong selection.
Fourth, the electromagnetic flowmeter can measure corrosive liquids, but at the beginning of the order, the customer should correctly provide other measurement medium properties, so as to avoid errors in the selection of the electrode during the selection, resulting in the sensor being scrapped in the later use process, bringing inconvenience to customers and economic loss.
Fifth, although the electromagnetic flowmeter has good reliability and will not be damaged under normal circumstances, due to its principle, the electrode surface of the sensor has been in contact with the liquid. After a long time, the electrode surface is more likely to be polluted. Therefore, in general, when the electromagnetic flowmeter is dismantled by the customer, it is recommended that the electrode be disassembled and cleaned once a year to one and a half years to ensure the measurement accuracy of the entire flowmeter. Any instrumentation requires "maintenance", and electromagnetic flowmeters are no exception.
Sixth, when the main line is a vertical pipeline, under normal circumstances, the water flow is required to be bottom-up, and try not to be top-down. The latter is likely to cause relatively large flow fluctuations. In addition to the installation of full pipes, this is also very important, followed by the distance between the front and rear straight pipes.
Choose a place that is easy to maintain and easy to move around. The flowmeter should be installed at the back end of the pump, never on the suction side; the valve should be installed on the downstream side of the flow.
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