Sewage flow meter selection recommendations

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　　Overview: Flow meters are one of the few instruments that are harder to use than they are to make. When selecting a sewage flowmeter, the effects of caliber size, physical properties of the medium (corrosiveness, dirtiness, abrasion), fluid dynamics, operating pressure, medium temperature, etc. should be considered. 　　Waste liquids and sewage are discharged into rivers and lakes, causing serious damage to water resources. This makes the already tight water resources even worse. The control and management of sewage discharge is an urgent task. Environmental protection has become a basic national policy for the sustainable development of our country’s economy. * * Driven by environmental protection policies, enterprises are paying more and more attention to environmental protection work, and the measurement and control of sewage flow has become an important part of enterprise work. 　　Because sewage pumping stations and sewage treatment plants are mostly located in urban areas, their construction area is limited, so the straight pipe section ratio required to install a flow meter is limited. The diameter of sewage pipes is relatively large, and most of them are underground. It is impossible to build a large instrument well to install a flow meter and matching stop valve. At the same time, sewage, especially untreated sewage, is not only highly corrosive, but also contains a large amount of debris, such as sediment, plastic sheeting and other floating objects, which makes many flowmeters not very suitable. The flow range of sewage also varies greatly, which is a difficulty in its measurement. There is a large difference between rainy days and sunny days, and between peak drainage and normal flow rates, which requires the flowmeter to have a wide range ratio. 　　Flow meters are one of the few instruments that are harder to use than they are to make. When selecting a sewage flow meter, the effects of pipes, caliber size, physical properties of the medium (corrosiveness, dirtiness, abrasion), fluid dynamics, operating pressure, medium temperature, etc. should be considered. According to the characteristics of sewage, the commonly used sewage flowmeters are roughly as follows: 1. Electromagnetic flowmeter The electromagnetic flowmeter is not affected by external factors such as temperature, pressure, viscosity, density, etc., and there is no pressure loss in the contraction or protruding part of the measuring tube. The initial signal detected by the flow element is a voltage that changes accurately linearly with the average flow rate of the fluid. It has nothing to do with other properties of the fluid and has great advantages. According to the characteristics of large changes in sewage flow, many impurities, and certain electrical conductivity, using an electromagnetic flowmeter to measure sewage is a good choice. 　　The electromagnetic flowmeter is suitable for measuring sewage pipe diameters from DN15 to DN3000, and the range ratio can reach 1: 10. Only the front 5D and back 3D straight pipe sections are required. It is simple to install, easy to use, has high measurement accuracy, compact structure, small size, and is very convenient for installation, operation and maintenance. It can work normally in harsh environments. A polytetrafluoro lining can be used to measure sewage, and a 316L electrode can meet the measurement requirements. 　　2. External clamp-on ultrasonic flowmeter External clamp-on ultrasonic flowmeter is suitable for large pipe diameters, can be installed online without cutting the pipe, is easy to disassemble and assemble, and can measure high temperature, high pressure, and highly corrosive media. It has a wide measuring range, is easy to install and use, the cost has nothing to do with the caliber size, and has strong versatility. After a certain pipe is used, it can be removed and installed in another pipe. The accuracy of ultrasonic wave is lower than that of electromagnetic wave, and it is often used for sewage measurement of very large pipe diameters. 　　3. Open channel flowmeter Open channel flowmeter is mainly used to measure the flow of sewage discharged through open channels instead of closed pipes. Due to the large flow rate in open channels, the fluid is often corrosive or has increased impurities. It is difficult to achieve ideal measurement results using ordinary flow meters, and it is also very difficult to implement. Open channel flow refers to setting up weirs and grooves according to certain standards on the waterway through which the fluid flows. Through the single-valued functional relationship between the fluid flow rate in the weirs and grooves and its liquid level, the liquid level is measured to calculate the flow rate. It requires low maintenance, is simple to use and has high accuracy. 　　4. Vortex flowmeter The vortex flowmeter is cheap, simple and convenient to install, has small pressure loss, wide range ratio, and high measurement accuracy. When measuring sewage, pay attention to the corrosiveness of the sewage. If it is highly corrosive, it can be lined with polytetrafluoroethylene. The sewage cannot contain flocs such as plastic cloth. Once these flocs are hung on the vortex generator, they will affect the frequency of vortex generation, thus affecting the measurement of the instrument. 　　To sum up, the selection of sewage flow meter needs to select an instrument suitable for the site according to the pipeline, discharge mode, temperature, corrosiveness, dirtiness of the medium, etc.