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Hi, your industrial control assistant is here as promised. Last time, we explained the classification of flow meters in detail from the perspective of their principle and structure; some of you asked for a summary of flow meter classifications based on accuracy requirements. Given the wide variety of flow meters and their numerous applications, it would likely require a specialized book on mechanical engineering to provide a comprehensive overview of their classification. Therefore, today we will briefly categorize the common flow meters by their applications – let’s take a look together. Firstly, flow meters used in different applications certainly vary, and the requirements for them also differ. Let’s take a look at some of the most commonly used flow meters. 1. Elliptical gear flow meters can be widely used for measuring liquids such as lubricating oil, diesel, and alcohol. They are capable of measuring the flow rate of highly viscous fluids, but it is important to ensure that the fluid is clean, free of solid particles and gases. Furthermore, the temperature of the measuring medium should not be too high; otherwise, it will affect the accuracy of measurement or cause the gears to get stuck. 2. Electromagnetic flowmeters can be widely used in industries such as environmental protection, metallurgy, chemicals, pharmaceuticals, water supply, food, and papermaking. Meters are less constrained by the physical properties of the medium; they have a simple structure, good stability, high sensitivity, no pressure loss, and very high accuracy. However, some issues must also be taken into account; for example, electromagnetic flowmeters are susceptible to interference from electromagnetic fields, and they cannot be exposed to rain and sunlight. 3. An ultrasonic flow meter is a flow meter with high performance, high reliability, and low cost, and it is particularly suitable for measuring media with large diameters and high flow rates. It is widely used in industries such as petrochemicals, power generation, and metallurgy. Ultrasonic flowmeters can measure fluids that cannot be measured by conventional flowmeters, such as highly corrosive, radioactive, flammable, and explosive fluids, as well as non-conductive fluids for which electromagnetic flowmeters are not suitable. It also has a long service life and is extremely easy to maintain. 4. The rotary piston flow meter is also a type of positive displacement flow meter; its measurement is not affected by the viscosity of the medium or by particles present in the fluid. It also has the capability for remote transmission of data, offers a wide measurement range, and provides high measurement accuracy. It is mainly composed of components such as a housing and a piston mechanism. 5. In terms of classification, twin-rotor flowmeters belong to the same category as rotary piston flowmeters, namely volume flowmeters, but there are still significant differences between the two. Double-rotor flowmeters can be used for heavy oil, light oil, crude oil with high water content, and so on. The requirements for the viscosity range of the medium are also relatively low. It has a long wired transmission distance and low pressure loss. It is a flow meter with excellent performance. 6. Liquid turbine flowmeters are also a common type of flowmeter. These types of flowmeters have a simple structure, are easy to carry, and have high sensitivity; they are a type of velocity-type flowmeter. It is widely used in fields such as chemicals, petroleum, metallurgy, and scientific research. When in use, be careful to keep the sensor of the liquid vortex flow meter away from magnetic fields during installation, and pay attention to waterproofing. There is a lot to know about choosing and installing, and we have already covered some of it; more will be discussed in the future. 7. Target flowmeters are widely used in industries such as petrochemicals, pharmaceuticals, power generation, environmental protection, and metallurgy. It has unique advantages in the measurement of highly viscous, low-Reynolds-number liquids. It features high sensitivity and accuracy, has no moving parts, and a long service life. 8. Orifice plate flow meters are widely used in industries such as petrochemicals, water supply, metallurgy, power generation, light textiles, and agriculture. Since the standard throttle element is universal, it does not require recalibration based on the actual flow rate. This is one of the advantages that other flowmeters do not possess. Structurally, the orifice plate flow meter features a simple design that makes maintenance and replacement easy; its body is durable, its performance is stable, and it is affordable. However, there are also certain issues, such as high pressure loss, a relatively narrow measurement range, the inability to measure corrosive, dirty, or particulate-containing liquids, and high requirements for straight pipe sections. 9. Vortex flowmeters are not affected by factors such as the density, viscosity, temperature, or pressure of the liquid; they have no moving mechanical parts, which gives them high reliability and makes maintenance easy. It also has advantages such as low pressure loss, low power consumption, durability, and easy installation. However, there are requirements for the straight pipe sections upstream and downstream of the installation. It is also necessary to avoid environments with vibrations, corrosion, high temperatures, radiation, high frequencies, etc., as these will affect the measurement results. 10. The Coriolis mass flow meter measures by using vibrating fluid tubes to generate a deflection corresponding to the mass flow rate. Coriolis flowmeters can be used to measure the mass flow rate of liquids, slurries, gases, or steam. High precision. However, the pipe walls need to be regularly maintained to prevent corrosion. Applications in different scenarios: 1. Wastewater treatment. Wastewater is divided into domestic wastewater and industrial wastewater. Wastewater is a solid-liquid mixture; industrial wastewater, due to its complex composition and corrosive nature, is difficult to measure, and most instruments are unable to handle such measurements. Theoretically, ultrasonic waves can be used; however, time-difference ultrasonic flowmeters are rarely employed due to their poor measurement performance in practice ； Doppler ultrasound is only suitable for measuring wastewater that is non-corrosive and free of large particles and impurities; its accuracy is low, which is why it is rarely used. The main instruments used in wastewater treatment are electromagnetic flowmeters, along with a small number of open-channel flowmeters. 2. Chemical industry: The chemical industry is the sector where flow meters are used most extensively; various types of flow meters have their own appropriate applications. 1. When measuring viscous oil-based media, positive-displacement instruments offer excellent performance and measurement accuracy ； 2. When measuring gases such as air and steam, vortex flowmeters are the most commonly used; DP instruments such as V-cones and orifice plates are also employed ； 3. For measuring various types of light oils, such as diesel, gasoline, and non-corrosive chemical solvents, turbine flowmeters are the preferred choice ； 4. For ammonia liquid and liquefied gas measurement, orifice plates and V-cones are the most commonly used; larger enterprises employ mass flow meters ； 5. Metal rotor flowmeters are also widely used in the chemical industry, mainly for measuring low-flow rates and for process control purposes ； 6. In the measurement of chemical wastewater, electromagnetic flowmeters are currently the only option available. *Explosion protection is a necessity for all chemical measurement instruments. 3. Food and pharmaceutical industries 1). Sanitary electromagnetic flowmeters are primarily used for measuring clean water, fruit juices, emulsions, pharmaceutical solutions, etc. It is usually connected using clamps, which facilitates disassembly and cleaning ； The material is stainless steel, with a high-temperature resistant lining made of FEP, PFA, etc. Due to its structure, which has no dead corners, it is easy to disinfect at high temperatures, making it the most widely used. 2). Vortex flowmeters are mainly used to measure steam, water, beer, edible oil, etc. It is made of stainless steel and is secured using flanges, making it easy to use; the downside is that its accuracy is slightly lower compared to electromagnetic flowmeters. 3). Currently, some manufacturers produce sanitary turbine flowmeters; most of these are fitted using flanges, while there are also those with a clamp-type design. Their measurement accuracy is comparable to that of electromagnetic flowmeters. Due to the oil-prohibition requirement, sealed bearings must be used, and these bearings need to be replaced regularly. 4). Mass flow meters are also used in applications where very high measurement accuracy is required. For example, in filling processes for measuring CO2, sanitary thermal mass flow meters are often employed. Characteristics of flow meters in the food and pharmaceutical industry: 1. High requirements for measurement accuracy ； 2. The material of the table body is stainless steel, which is resistant to corrosion and rust ； 3. The quick-install structure facilitates cleaning and maintenance.