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Flow meter classification and working principle

Flow meter classification and working principle


First, the classification of flow meter


According to the principle of measurement, there are: mechanical principles, thermal principles, acoustic principles, electrical principles, optical principles, principles of atomic physics.


According to the structural principle of the flow meter, it is divided into a volumetric flowmeter, a differential pressure flowmeter, a float flowmeter, a turbine flowmeter, an electromagnetic flowmeter, a fluid oscillation flowmeter, mass flow meter, and insert type. Flow meter, probe flowmeter.


Second, the working principle and application of ordinary flow meter


1. Turbine flow meter


The turbine flow meter is a major type of speed flow meter that uses the multi-blade rotor (turbine) to sense the average flow rate of the fluid and obtain flow or total amount. Typically, it consists of two parts, sensors, and display instruments, or a single type.

Application: Turbo flow meter is widely used in oil, organic liquids, inorganic liquids, liquefied gases, natural gas and low temperature fluids.


2. Electromagnetic flowmeter


The electromagnetic flowmeter is a meter of conductive liquid according to the Faraday electromagnetic induction.


Application: Electromagnetic flow meter has a series of excellent features, which can solve other difficult flow meters, such as dirty flow and corrosion flow measurements. Electromagnetic flow meters is widely used in applications. Large diameter instruments are widely used in water supply and drainage projects. Small and medium-sized calibers are usually used for high demand or difficulty to measure, such as steel industrial blast furnace air tunnel cooling water control, paper industry measuring pulp and black liquor, and strengthening technology. Corrosive liquids, pulp of non-ferrous metallurgical industries; small diameters, small-diameter commonly used in the medical industry, food industry, biochemistry, etc. have hygienic requirements.


3. Vortex flow meter


Application: The vortex flow meter has developed rapidly and has become a universal flowmeter.

What are the requirements for installing vortex flow meter?

The vortex flow meter is a fluid oscillation flowmeter manufactured according to the principle of "Kamen Vortex". Vortex flow meters are widely used in metallurgy, coal, oil, transportation, agriculture and other fields.


1. Avoid using strong power equipment, high frequency equipment and powerful switching power supplies as much as possible. The power of the instrument is separated from these devices as much as possible.


2. Avoid direct impact on high temperature heat sources and radiation sources. If you must install, heat insulation and ventilation must be performed.


3. Avoid high humidity environments and strong corrosive gas environments. If you have to install, you need to ventilate.


4. For pipes with large vibration, avoid using vortex flow meters as much as possible. The pipe fastening device is installed in upstream and downstream 2D, and the anti-vibration mat is added to enhance the anti-vibration effect.


5. Instruments should be installed indoors. Waterproof should be installed in outdoor. Please pay special attention to bending the cable into a U shape at the electrical interface to prevent water from entering the amplifier housing along the cable.


6. There should be sufficient space around the instrument mounting point to connect to regular maintenance.


4. Ultrasonic flowmeter


The ultrasonic flow meter is based on geometric principle design, that is, the speed of ultrasonic waves propagating in the flow medium is equal to the average flow rate of the medium and the speed of the sound wave itself. It also measures flow rate to reflect the flow rate. According to the measurement principle, the ultrasonic flowmeter can be divided into time difference and Doppler type.


Application: Cleaning the propagation time method of single phase liquid and gas. Typical applications include factory wastewater, singular liquid, liquefied natural gas, etc .; natural gas applications have a wealth of experience in high-pressure natural gas; Doppler method is suitable for two-phase fluids with low polyphetoidin content, such as unprocessed sewage, factory wastewater, Dirty process fluids are usually not suitable for very clean liquids.


5. Mass Flow meter


Quality flow gauges are directly and indirect. The direct mass flow meter is measured by the principle of directly related to mass flow; the indirect mass flow meter multiplies the volume flow using a densitometer to obtain mass flow.


Application: In the case of high temperature and high pressure in modern industrial production, the application of direct mass flow meter is difficult due to material and structural reasons, and indirect mass flow meters are limited by humidity and pressure range. This is not practical.

6.Differential pressure flowmeter


Differential flow gauges are meter of flow based on differential differences, known fluid states and detecting members and tubes installed in the pipeline, and the overall size of the conduit.


Application: Differential pressure flow meter has a wide range of applications. It can be applied to all kinds of objects in closed pipelines, such as fluids: single phase, mix phase, cleaning, dirt, viscous flow, etc .; moderate pressure, high pressure, vacuum, normal temperature, high temperature, low temperature, etc. : From a few millimeters to a few meters; flow: oral sound, sound wave, pulsation flow. It uses about 1/4 to 1/3 of the total flowmeter in various industrial sectors.


7. Poopstone flowmeter


The float flowmeter is also referred to as a rotor flowmeter, which is a variable area flowmeter. In a vertical cone expanded from the bottom to the top, the gravity of the circular cross-section buoy is absorbed by the liquid power such that the float can rise and fall in the cone.


Application: The float flowmeter is the most widely used flow meter after differential pressure flow meters, especially small and micro flow.


8. Volume flow meter


Volume flow meter, also referred to as a fixed displacement flowmeter, called a PD flowmeter, is the most accurate type in the flowmeter. Depending on the measurement results, it uses the mechanical measurement assembly to continuously divide the fluid into a single known volume fraction. Reversely fill the chamber and discharges multiplier fluid to measure the total volume of the fluid.


Application: The volumetric flowmeter, the differential pressure flowmeter, and the float flowmeter are listed as flow meters of three maximum dosages. They are usually used for expensive media (oil, natural gas, etc.).


9. Inserted flowmeter


The working principle of the inserted flow meter is based on the Law of Faraday Iron Magnetic Sense. In the electromagnetic flow meter, the conductive medium in the measuring tube corresponds to a constant magnetic field to generate a constant magnetic field in the upper end and the two electromagnetic coils in the upper end and the lower end. When the conductive medium flows, an induced voltage is generated. The two electrode measurements generated in the conduit are generated. The measuring tube is electrically isolated from the fluid and the measuring electrode by non-conductive liner (rubber, Teflon, etc.).


Applications: power generation and thermal cogeneration, heating industry; aviation, aerospace, shipbuilding, nuclear energy and weapons industry; machinery, metallurgy, coal mining and automobile manufacturing; oil, chemical industry; pharmaceutical, food and smoke manufacturing; agriculture and light industrial.


10. Probe flowmeter


The basic principle of the probe flow gauge is to conduct the total static pressure to differential pressure and pressure sensors by probe holes and pressure catheters. As long as the probe hole is not blocked, the pressure can be transmitted accurately even if there is debris or dirt. Does not affect accuracy. Since the medium in the conductive tube does not flow, foreign objects are difficult to enter and block, so it can maintain high precision for a long time.


Application: extensive application. First, the wide range of media: water vapor (saturated, overheating), air, gas, gas, various chemical raw materials, liquid, water, various solutions, oil, etc., medium temperature can be as high as 650 degrees Celsius, the highest pressure can be 25MPa. Second, the applicable flow range is wide: the lowest medium flow can be measured to be 0.1 ton / hour, and the maximum measurable value is 5,000 tons / hour. Third, it is suitable for various cross-sectional shapes of the medium tube: the flow rate is not required for the cross-sectional geometry of the medium tube, such as circular, elliptical, square, rectangular, diamond, and the like.

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