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The advantages of electromagnetic flowmeter in sewage treatment industry.
- Apr 24, 2018 -

With the acceleration of China's industrialization, environmental pollution is increasingly serious, society of sustainable development is becoming more and more high, the concept of harmonious coexistence between man and nature to accept by people, to all sorts of pollution of more urgent. In the process of sewage treatment, it is necessary to measure and control the discharge of sewage, additives and sludge, so the flow measurement is very important. The electromagnetic flowmeter is the absolute advantage in the many flowmeter products used in the measurement of sewage, which is the best in principle and precision.  

The electromagnetic flowmeter consists of two parts: flow sensor and transmitter. Sensor tube fitted with excitation coil, excitation current to produce magnetic field through the measuring tube, a pair of electrodes in measuring tube wall in contact with the liquid phase, which leads to the induction electric potential, sent to the transmitter. The excitation current is provided by the transmitter. According to the converter and sensor assembly mode classification, there are two types of separation and one body type. The large diameter flowmeter in the sewage treatment process is divided into two parts, one part is installed underground and the other part is on the ground. Small caliber is more than one style. The principle of electromagnetic flowmeter is based on Faraday's law of electromagnetic induction. When a conductive metal rod moves at a certain speed perpendicular to the direction of the magnetic force, it will generate an inductive voltage. If the magnetic field intensity is B, the length of the rod is L, and the velocity is v, then the induced voltage is generated.  

At present, the function of electromagnetic flowmeter in the market is very different, so it is simple to measure the one-way flow, only to output the analog signal to drive the latter instrument; Intelligent electromagnetic flowmeter can measure the bidirectional flow switch range, upper and lower flow alarm, atc, and power cutting off alarm, cut of small signal, flow display and the total calculation, automatic checking and fault self-diagnosis, communicate with PC and motion configuration, etc. Some types of electromagnetic flowmeter serial digital communication function can choose a variety of communication interfaces and special chips (ASIC) to connect HART protocol system, PROFTBUS, Modbus, FF field bus, etc. Using electromagnetic flowmeter is the premise of measured liquid must be electrically conductive and conductivity is lower than the threshold will produce measurement error until you can't use, more than threshold value can be measured, even change a little change of error. The conductivity of industrial water and its aqueous solution is greater than 10-4s /cm, and the conductivity of acid, alkali and salt is between 10-4 ~ 10-1s /cm. There is no problem with the use of water, and there is no problem with low-grade distilled water of 10-5s /cm. Usually, the sewage is highly conductive, because it contains more ions, which is one of the advantages of the electromagnetic flowmeter to measure the sewage, which is determined by its measuring principle.  

In addition, some characteristics of the electromagnetic flowmeter also determine that it is more suitable for the measurement of sewage than other flowmeter products. Electromagnetic flowmeter is not affected by the influence of external factors such as temperature, pressure, viscosity, measurements of the interior of the tube without shrinkage or bulge caused by the pressure loss, in addition, the flow element to detect the original signal, is an average flow velocity and fluid into precise linear change voltage, it has nothing to do with the other properties of the fluid, has the very big superiority. Based on the characteristics such as high flow rate, impurities, small corrosion, and certain conductivity, the discharge of sewage is measured, and the electromagnetic flowmeter is the best choice.  

And electromagnetic flowmeter is of compact structure, small size, installation, operation and maintenance is very convenient, measurement system using intelligent design, whole sealing, can work normally under the harsh environment. Compared with other flowmeter products, vortex flowmeter is very difficult to make large and quality because of technical reasons, and the quality and pipeline ultrasonic flowmeter have no competitive advantage in price relative to electromagnetism. Therefore, in the field of drainage and sewage treatment, electromagnetic flowmeters, especially large diameter electromagnetic flowmeters, have great advantages and are widely used.  

The wastewater treatment process is mainly through biological oxidation, flocculation, precipitation and other processes to achieve the purpose of sewage purification, and a certain flowmeter is required to be measured at each stage. In the process of sewage treatment, the corresponding measuring instruments should be configured according to the process requirements, which can form a reliable control system. General sewage treatment plants need to be equipped with flowmeter in the following process testing process:

(1) inlet pipe;  

(2) the initial sedimentation tank to the mud volume detection;  

(3) residual and sludge flow detection of sludge pump room;  

(4) flow test of sludge pump room reflux sludge;  

(5) detection of water flow rate of the second sedimentation tank with well;  

(6) detection of sludge in the digester;  

(7) detection of sludge in the digester;