The instruments used to measure fluid flow are collectively referred to as flow meters or flow meters. Flow meter is one of the important instruments in industrial measurement. With the development of industrial production, the requirements for accuracy and range of flow measurement are becoming increasingly high. Flow measurement technology is advancing rapidly, and in order to adapt to various applications, various types of flow meters have emerged one after another. Currently, more than 100 types of flow meters have been put into use.
Flow meters are applied in various industries
Each product has its specific applicability and limitations. According to measurement principles, it can be divided into mechanical principles, thermal principles, acoustic principles, electrical principles, optical principles, atomic physics principles, etc.
According to the structural principle of flow meters, there are volumetric flow meters, differential pressure flow meters, float flow meters, turbine flow meters, electromagnetic flow meters, vortex flow meters in fluid oscillation flow meters, mass flow meters, and insertion flow meters.
According to the measurement object, there are two main categories: closed pipelines and open channels; According to the measurement purpose, it can be divided into total measurement and flow measurement, and their instruments are called total meter and flow meter respectively. A total flow meter measures the flow rate through a pipeline over a period of time, expressed as the quotient of the total amount flowing over a short period of time divided by that time. In fact, flow meters are usually equipped with cumulative flow devices for use as total flow meters, and total flow meters are also equipped with flow signaling devices. Therefore, strictly distinguishing between flow meters and total meters has no practical significance.
Flow meters classified according to measurement principles
- Mechanics principle: Instruments belonging to this type of principle include differential pressure and rotor type instruments that utilize Bernoulli’s theorem; The impulse equation and movable tube equation using the momentum theorem; Using the direct mass formula of Newton’s second law; Target based on the principle of fluid momentum; Turbine type using the angular momentum theorem; Vortex type and vortex street type utilizing the principle of fluid oscillation; Utilize pitot tube type, volumetric type, weir, trough type, etc. that utilize the total static pressure difference.
- Electrical principles: Instruments used for this type of principle include electromagnetic, differential capacitive, inductive, strain resistance, etc.
- Acoustic principles: There are ultrasonic and acoustic (shock wave) methods that use acoustic principles for flow measurement.
- Thermal principles: There are various methods for measuring flow rate using thermal principles, such as calorimetry, direct calorimetry, indirect calorimetry, etc.
- Optical principles: Laser, photoelectric, and other instruments belong to this type of principle.
- Atomic physics principles: Nuclear magnetic resonance, nuclear radiation, and other instruments belong to this type of principle.
- Other principles: including labeling principles (tracing principles, nuclear magnetic resonance principles), related principles, etc.
Classified by the principle of flow meter structure
Based on the actual situation of current flowmeter products and the structural principle of flowmeters, they can be roughly classified into the following types:
Differential pressure flowmeter is an instrument that calculates flow based on the differential pressure generated by the flow detection component installed in the pipeline, known fluid conditions, and the geometric dimensions of the detection component and the pipeline.
The differential pressure flowmeter consists of a primary device (detection component) and a secondary device (differential pressure conversion and flow display instrument). Differential pressure flow meters are usually classified in the form of detection components, such as orifice flow meters, Venturi flow meters, and averaging tube flow meters.
The secondary device includes various mechanical, electronic, and electromechanical integrated differential pressure gauges, differential pressure transmitters, and flow display instruments. It has developed into a large category of instruments with a high degree of standardization (serialization, generalization, and normalization) and a wide range of types and specifications. It can measure both flow parameters and other parameters (such as pressure, level, density, etc.).
The detection components of differential pressure flow meters can be divided into several categories according to their operating principles: throttling device, hydraulic resistance type, centrifugal type, dynamic pressure head type, dynamic pressure head gain type, and jet type.
Testing items can be divided into two categories based on their standardization level: standard and non-standard.
The so-called standard test piece is designed, manufactured, installed, and used according to standard documents, without the need for actual flow calibration to determine its flow value and estimate measurement errors.
Non standard testing components are those with poor maturity and have not yet been included in international standards.
Differential pressure flowmeter is the most widely used type of flowmeter, with its usage ranking first among various flow meters. In recent years, due to the emergence of various new types of flow meters, their usage percentage has gradually decreased, but they are still the most important type of flow meter at present.
advantage:
(1) The most widely used orifice plate flowmeter has a sturdy structure, stable and reliable performance, and a long service life;
(2) It has a wide range of applications and there is currently no type of flow meter that can be compared to it;
(3) The detection components, transmitters, and display instruments are produced by different manufacturers, facilitating economies of scale production.
Disadvantages:
(1) The measurement accuracy is generally low;
(2) Narrow range, generally only 3:1~4:1;
(3) High requirements for on-site installation conditions;
(4) High pressure loss (referring to orifice plates, nozzles, etc.).
Application Overview:
Differential pressure flowmeter has a wide range of applications, including flow measurement in closed pipelines for various objects such as fluids: single-phase, mixed phase, clean, dirty, viscous flow, etc; In terms of working conditions: normal pressure, high pressure, vacuum, normal temperature, high temperature, low temperature, etc; In terms of pipe diameter: from a few millimeters to a few meters; in terms of flow conditions: subsonic, sonic, pulsating flow, etc. It accounts for approximately 1/4 to 1/3 of the total usage of flow meters in various industrial sectors.
orifice flowmeter
advantage:
Standard throttling components are widely used worldwide and have been recognized by international standard organizations. They can be put into use without the need for actual flow calibration and are the only instrument in flow meters that is easy to replicate in structure. They are simple, sturdy, stable and reliable in performance, and cost-effective;
Widely applicable, including all single-phase fluids (liquid, gas, steam) and some mixed phase flows, with products available for pipe diameters and working conditions (temperature, pressure) in general production processes.
The detection components and differential pressure display instruments can be produced separately by different manufacturers, facilitating specialized scale production;
Disadvantages:
The repeatability and accuracy of measurements are at a moderate level in flow meters, but due to the complex influence of numerous factors, it is difficult to improve accuracy.
The range is narrow, and due to the correlation between flow coefficient and Reynolds number, the general range is only 3:1 to 4:1. There are long requirements for the length of straight pipe sections, which are generally difficult to meet. Especially for larger pipe diameters, the problem becomes more prominent;
The pressure loss is large, and usually in order to maintain the normal operation of an orifice flowmeter, the water pump needs additional power to overcome the pressure loss of the orifice plate. The additional power consumption can be directly determined by pressure loss and flow calculation, which requires tens of thousands of kilowatt hours of electricity consumption per year, equivalent to tens of thousands of yuan.
The sharp angle line inside the orifice plate is used to ensure accuracy, so it is sensitive to corrosion, wear, scaling, and dirt. Long term use makes it difficult to guarantee accuracy, and it needs to be removed and inspected once a year. Using flange connections can easily lead to issues such as running, emitting, dripping, and leaking, greatly increasing maintenance workload.
Float flowmeter, also known as rotor flowmeter, is a type of variable area flowmeter. In a vertical conical tube that expands from bottom to top, the gravity of the circular cross-section float is supported by liquid dynamics, allowing the float to freely rise and fall inside the conical tube.
Float flowmeter is the most widely used type of flowmeter, second only to differential pressure flowmeter, and plays a crucial role in small and micro flow.
In the mid-1980s, sales in Japan, Western Europe, and the United States accounted for 15% to 20% of flow meters. The estimated production in China in 1990 was between 120000 and 140000 units, of which over 95% were glass cone tube float flowmeters.
characteristic:
(1) The glass cone tube float flowmeter has a simple structure and is easy to use, but its disadvantage is low pressure resistance and a high risk of glass tube fragility;
(2) Suitable for small diameters and low flow rates;
(3) Low pressure loss.
Positive displacement flowmeter
Positive displacement flowmeter, also known as fixed displacement flowmeter, abbreviated as PD flowmeter, is the most accurate type of flow meter. It uses mechanical measuring elements to continuously divide the fluid into individual known volume parts, and measures the total volume of the fluid based on the number of times the measuring chamber repeatedly fills and discharges that volume part of the fluid.
Volumetric flow meters can be classified according to their measuring components, including elliptical gear flow meters, scraper flow meters, dual rotor flow meters, rotary piston flow meters, reciprocating piston flow meters, disc flow meters, liquid sealed rotary cylinder flow meters, wet gas meters, and membrane gas meters.
advantage:
(1) High measurement accuracy;
(2) The installation of pipeline conditions does not affect the measurement accuracy;
(3) Can be used for measuring high viscosity liquids;
(4) Wide range;
(5) Direct reading instruments do not require external energy sources and can directly accumulate data. The total amount is clear and easy to operate.
Disadvantages:
(1) The results are complex and bulky;
(2) There are significant limitations in the type, diameter, and working state of the tested medium;
(3) Not suitable for high and low temperature environments;
(4) Most instruments are only suitable for clean single-phase fluids;
(5) Generate noise and vibration.
Application Overview:
Volumetric flow meters, differential pressure flow meters, and float flow meters are among the three most widely used types of flow meters, commonly used for measuring the total amount of expensive media such as oil and natural gas.
In recent years, the sales amount of PD flow meters (excluding household gas meters and household water meters) in industrialized countries has accounted for 13% to 23% of flow meters; China accounts for about 20%, with an estimated production of 340000 units in 1990 (excluding household gas meters), of which elliptical gear type and waist wheel type account for about 70% and 20% respectively.
Types of sewage flow meters
Sewage flow meters are classified according to their measurement principles:
- Flow meters include throttling flow meters, pitot tube flow meters, averaging tube flow meters, rotor flow meters, and target flow meters. These flow meters use the Bernoulli equation principle to reflect flow by measuring fluid differential pressure signals;
- Flow meters include turbine flow meters, vortex street flow meters, electromagnetic flow meters, Doppler ultrasonic flow meters, and hot wire speed measurement flow meters, which reflect flow rate by measuring fluid flow velocity;
- Flow meters include gear flow meters, scraper flow meters, and rotary piston flow meters, which reflect flow rates by measuring small volumes of standard volumes;
- Flow meters include thermal mass flow meters, differential pressure mass flow meters, impeller mass flow meters, Coriolis mass flow meters, and indirect mass flow meters, which reflect flow by measuring fluid mass;
- The flow meter has a weir type flow meter, which reflects the flow rate by measuring the liquid level.
Characteristics of sewage flowmeter:
- The sewage flowmeter has a simple structure, is sturdy and reliable, and has a long service life.
- There are no moving parts or resistance parts inside the measuring tube, no pressure loss, no blockage, reliable measurement, strong anti-interference ability, small size, light weight, easy installation, low maintenance, and wide measurement range; The measurement is not affected by changes in fluid temperature, density, pressure, viscosity, conductivity, etc. It can be retrofitted and installed by drilling holes on old pipelines, with simple construction and installation and small engineering quantities.
Turbine flowmeter is the main type of velocity flowmeter, which uses a multi blade rotor (turbine) to sense the average flow velocity of the fluid and derive the flow rate or total amount from it.
Generally, it consists of two parts: sensors and displays, or it can be made as a whole.
Turbine flow meters, volumetric flow meters, and Coriolis mass flow meters are known as the three types of flow meters with the best repeatability and accuracy. As one of the top ten types of flow meters, their products have developed into a large-scale production of multiple varieties and series.
advantage:
(1) High precision, among all flow meters, it belongs to the most accurate flow meter;
(2) Good repeatability;
(3) Yuan zero drift, good anti-interference ability;
(4) Wide range;
(5) Compact structure.
Disadvantages:
(1) Unable to maintain calibration characteristics for a long time;
(2) Fluid properties have a significant impact on flow characteristics.
Application Overview:
Turbine flow meters are widely used in measuring objects such as petroleum, organic liquids, inorganic liquids, liquefied gases, natural gas, and low-temperature flows.
Turbine flowmeter is a natural measuring instrument second only to orifice flowmeter in terms of usage. In the Netherlands alone, more than 2600 gas turbine flowmeters of various sizes and pressures ranging from 0.8 to 6.5 MPa are used in natural gas pipelines, making them excellent natural gas measuring instruments.
A vortex flowmeter is an instrument that places a non streamlined vortex generator in a fluid, and the fluid alternately separates and releases two series of regularly arranged vortices on both sides of the generator. When the flow cross-section is constant, the flow velocity is proportional to the volumetric flow rate. Therefore, measuring the oscillation frequency can determine the flow rate. Vortex flowmeters can be classified according to frequency detection methods, such as stress type, strain type, capacitance type, thermal sensitive type, vibration type, photoelectric type, and ultrasonic type. This type of flowmeter was developed and evolved in the 1970s, and due to its advantages of having no rotating parts and pulse digital output, it has great potential for development.
advantage
(1) Vortex flowmeter has no movable parts, simple measuring element structure, reliable performance, and long service life.
(2) The vortex flowmeter has a wide measurement range. The range ratio can generally reach 1:10.
(3) The volumetric flow rate of a vortex flowmeter is not affected by thermal parameters such as temperature, pressure, density, or viscosity of the fluid being measured. Generally, there is no need for separate calibration. It can measure the flow rate of liquids, gases, or vapors.
(4) It causes minimal pressure loss.
(5) High accuracy, repeatability of 0.5%, and low maintenance.
shortcoming
(1) The volumetric flow rate of a vortex flowmeter during operation is not affected by thermal parameters such as temperature, pressure, and density of the fluid being measured. However, the final measurement result for liquids or vapors should be mass flow rate, and for gases, the final measurement result should be standard volumetric flow rate. Both mass flow rate and standard volume flow rate must be converted based on fluid density, taking into account changes in fluid density caused by variations in fluid operating conditions.
(2) The main factors causing flow measurement errors are: measurement errors caused by uneven flow velocity in pipelines; Unable to accurately determine the medium density when fluid conditions change; Assuming wet saturated steam as dry saturated steam for measurement. If these errors are not limited or eliminated, the total measurement error of the vortex flowmeter will be significant.
(3) Poor anti vibration performance. External vibrations can cause measurement errors in vortex flowmeters, and even prevent them from functioning properly. The high flow velocity impact of the channel fluid will cause additional vibrations in the cantilever of the vortex generator, resulting in a decrease in measurement accuracy. The impact of larger pipe diameters is more pronounced.
(4) Poor adaptability to measuring dirty media. The generating body of vortex flowmeter is easily contaminated by the medium or entangled by dirt, which changes the geometric dimensions and greatly affects the measurement accuracy.
(5) The straight pipe section requires high standards. Experts point out that the straight section of the vortex flowmeter must ensure the first 40D and the last 20D to meet the measurement requirements.
(6) Poor temperature resistance. Vortex flow meters can generally only measure fluid flow rates of media below 300 ℃.
USF entered industrial applications in the late 1960s and has accounted for 4% to 6% of the sales revenue of flow meters in various countries since the late 1980s. In 1992, the estimated global sales volume was 354800 units, while the estimated domestic products during the same period were between 8000 and 9000 units.
The electromagnetic flowmeter is an instrument for measuring conductive liquids made based on Faraday’s law of electromagnetic induction.
Electromagnetic flowmeters have a series of excellent features that can solve problems that are difficult to apply with other flowmeters, such as the measurement of dirty flow and corrosive flow.
In the 1970s and 1980s, electromagnetic flowmeters made significant technological breakthroughs, making them a widely used type of flowmeter. The percentage of their usage among flowmeters has been continuously increasing.
Advantages:
(1) The measurement channel is a smooth straight pipe that will not be blocked and is suitable for measuring liquid-solid two-phase fluids containing solid particles, such as pulp, slurry, sewage, etc.
(2) It does not cause pressure loss due to flow detection and has a good energy-saving effect.
(3) The measured volumetric flow rate is actually not significantly affected by changes in fluid density, viscosity, temperature, pressure and electrical conductivity.
(4) Wide flow range and wide diameter range;
(5) Corrosive fluids can be applied.
Disadvantage:
(1) The application of electromagnetic flowmeters has certain limitations. They can only measure the liquid flow of conductive media and cannot measure the flow of non-conductive media, such as gas and well-treated hot water supply. In addition, the lining needs to be considered under high-temperature conditions.
(2) Electromagnetic flowmeters determine the volumetric flow rate under working conditions by measuring the velocity of conductive liquids. According to the metrological requirements, for liquid media, the mass flow rate should be measured. The measurement of the medium flow rate should involve the density of the fluid. Different fluid media have different densities and they change with temperature. It is inappropriate to only provide the volume flow rate at normal temperature if the electromagnetic flowmeter converter does not take the fluid density into account.
(3) The installation and commissioning of electromagnetic flowmeters are more complex and have stricter requirements than those of other flowmeters. The transmitter and the converter must be used in combination. Two different types of instruments cannot be used in conjunction with each other. When installing the transmitter, from the selection of the installation site to the specific installation and commissioning, it must be carried out strictly in accordance with the requirements of the product manual. The installation site must be free from vibration and strong magnetic fields. When installing, it is necessary to ensure that the transmitter and the pipeline have good contact and good grounding. The potential of the transmitter is equal to that of the fluid being measured. When in use, all the gas remaining in the measuring tube must be completely discharged; otherwise, it will cause significant measurement errors.
(4) When an electromagnetic flowmeter is used to measure viscous liquids with dirt, the sticky substances or sediment adhere to the inner wall of the measuring tube or the electrode, causing changes in the output potential of the transmitter and resulting in measurement errors. When the dirt on the electrode reaches a certain thickness, it may cause the instrument to be unable to measure.
(5) Scaling or wear of water supply pipes that changes the inner diameter size will affect the original flow value and cause measurement errors. For instance, a 1mm change in the inner diameter of a 100mm caliber instrument will result in an additional error of approximately 2%.
(6) The measurement signal of the transmitter is a very small millivolt-level potential signal. Besides the flow signal, it also contains some signals independent of the flow, such as phase voltage, orthogonal voltage and common mode voltage, etc. In order to accurately measure the flow rate, it is necessary to eliminate various interference signals and effectively amplify the flow signal. The performance of the flow converter should be improved. It is best to use a microprocessor-type converter to control the excitation voltage. Select the excitation mode and frequency according to the nature of the fluid being measured, which can eliminate in-phase interference and orthogonal interference. However, the improved instrument has a complex structure and a relatively high cost.
(7) Relatively high price.
Application Overview:
Electromagnetic flowmeters have a wide range of applications. Large-diameter meters are more commonly used in water supply and drainage projects. Medium and small diameters are often used in high-demand or difficult-to-measure situations, such as the control of cooling water at blast furnace vents in the steel industry, the measurement of pulp and black liquor in the paper industry, strong corrosive liquids in the chemical industry, and pulp in the non-ferrous metallurgical industry. Small-bore and micro-bore are often used in places with hygiene requirements such as the pharmaceutical industry, food industry, and biochemistry. Since EMF entered industrial applications in the early 1950s, its application fields have been expanding increasingly. Since the late 1980s, it has accounted for 16% to 20% of the sales amount of flow meters in various countries.
China has developed rapidly in recent years. The estimated sales in 1994 were 6,500 to 7,500 units. Domestically, ENF with the largest diameter ranging from 2 to 6 meters has been produced, and there is also the capacity to verify equipment with a real-flow diameter of 3 meters.
Ultrasonic flowmeters are designed based on the principle that the speed of ultrasonic waves in a flowing medium is equal to the geometric sum of the average flow velocity of the measured medium and the speed of the sound wave itself. It also reflects the flow rate by measuring the flow velocity. Although ultrasonic flowmeters only emerged in the 1970s, they have become very popular because they can be made in a non-contact form and can be linked with ultrasonic water level meters for open flow measurement without causing disturbance or resistance to the fluid.
Ultrasonic flowmeters can be classified into time difference type and Doppler type according to their measurement principles.
The time-difference ultrasonic flowmeter manufactured based on the time-difference principle has received extensive attention and application in recent years and is currently the most widely used ultrasonic flowmeter in enterprises and institutions.
Ultrasonic Doppler flowmeters made by utilizing the Doppler effect are mostly used to measure media with certain suspended particles or bubbles. Their application has certain limitations, but they solve the problem that time-difference ultrasonic flowmeters can only measure a single clear fluid. They are also regarded as ideal instruments for non-contact measurement of two-phase flow.
Advantages:
Ultrasonic flowmeters are non-contact measuring instruments that can be used to measure the flow of fluids that are difficult to contact and observe, as well as the flow of large pipes. It does not change the flow state of the fluid, does not cause pressure loss, and is easy to install.
(2) It can measure the flow of strongly corrosive media and non-conductive media.
(3) Ultrasonic flowmeters have a wide measurement range, with pipe diameters ranging from 20mm to 5m.
(4) Ultrasonic flowmeters can measure the flow of various liquids and sewage.
(5) The volumetric flow rate measured by ultrasonic flowmeters is not affected by the thermal physical parameters of the fluid being measured, such as temperature, pressure, viscosity and density. It can be made in two forms: fixed and portable.
Disadvantage:
The temperature measurement range of ultrasonic flowmeters is not high. Generally, they can only measure fluids with a temperature below 200℃.
(2) Poor anti-interference ability. It is susceptible to ultrasonic noise interference from bubbles, scale, pumps and other sound sources, which affects the measurement accuracy.
(3) The requirements for the straight pipe section are strict, with 20D at the beginning and 5D at the end. Otherwise, the discreteness is poor and the measurement accuracy is low.
(4) The uncertainty of installation can cause significant errors in flow measurement.
(5) If the measuring pipeline is clogged with scale, it will seriously affect the measurement accuracy, cause significant measurement errors, and in severe cases, the instrument may not display the flow rate.
(6) The reliability and accuracy grades are not high (generally around 1.5 to 2.5 grades), and the repeatability is poor.
(7) Short service life (generally, the accuracy can only be guaranteed for one year).
(8) Ultrasonic flowmeters determine volumetric flow by measuring the fluid velocity. For liquids, their mass flow should be measured. The instrument measures the mass flow by multiplying the volumetric flow by the artificially set density. When the fluid temperature changes, the fluid density also changes. Artificially setting the density value cannot guarantee the accuracy of the mass flow. Only when the fluid velocity is measured simultaneously with the fluid density can the true mass flow rate value be obtained through calculation.
Application Overview:
The propagation time method is applied to clean, single-phase liquids and gases. Typical applications include factory discharge liquids, strange liquids, liquefied natural gas, etc. There has been good experience in the application of gases in the field of high-pressure natural gas.
The Doppler method is suitable for two-phase fluids with not too high heterogeneous content, such as untreated wastewater, factory discharge liquid, and dirty process liquid. Generally, it is not applicable to very clean liquids.
Due to the influence of temperature, pressure, and other parameters on the volume of a fluid, it is necessary to provide the parameters of the medium when using volumetric flow rate to represent the flow rate. In the case of constantly changing medium parameters, it is often difficult to meet this requirement, resulting in distortion of instrument display values.
Therefore, mass flow meters have been widely used and valued. There are two types of quality flow scoring: direct and indirect. Direct mass flow meters use principles directly related to mass flow for measurement. Currently, commonly used mass flow meters include calorimetry, angular momentum, vibration gyroscope, Magnus effect, and Coriolis force. The indirect mass flow meter calculates the mass flow rate by directly multiplying the density meter with the volumetric flow rate.
In modern industrial production, the operating parameters such as temperature and pressure of the flowing working fluid are constantly increasing. Under high temperature and pressure conditions, due to material and structural reasons, the application of direct mass flow meters encounters difficulties, while indirect mass flow meters are often difficult to apply in practice due to the limitations of humidity and pressure range of density meters.
Therefore, temperature pressure compensation mass flow meters are widely used in industrial production. It can be regarded as an indirect mass flow meter, not equipped with a density meter, but using the relationship between temperature, pressure, and density. The temperature and pressure signals are converted into density signals through functional operations, and the mass flow rate is obtained by multiplying them with the volumetric flow rate. At present, although temperature and pressure compensated mass flow meters have been put into practical use, it will be difficult or impossible to compensate correctly when the parameters of the measured medium change widely or rapidly. Therefore, further research on mass flow meters and density meters applicable in practical production is still a topic.
advantage:
(1) Ball valve installation, easy to install and disassemble. And it can be installed under pressure.
(2) Based on King’s Law, directly measure mass flow rate. The measured value is not affected by pressure and temperature.
(3) Respond quickly.
(4) The range is large, and the pipeline installation can measure the flow rate of a minimum 8.8mm pipeline and a maximum of 30.
(5) Plug in type flow meter, one flow meter can be used to measure multiple pipe diameters.
Disadvantages:
(1) The accuracy is inferior to other types of flow meters, generally at 3%.
(2) The scope of application is narrow and can only be used to measure dry non explosive gases such as compressed air, nitrogen, argon, and other neutral gases.
The Coriolis mass flowmeter (CMF) utilizes fluid flow in a vibrating tube. A direct mass flow meter based on the principle of Coriolis force that is proportional to the mass flow rate.
The application of CMF in China started relatively late, and in recent years, several manufacturing plants (such as Taihang Instrument Factory) have independently developed and supplied the market; Several manufacturing plants have formed joint ventures or adopted foreign technology to produce a series of instruments.
More than 30 series of CMF have been developed abroad, with a focus on technological innovation in the design of flow detection and measurement tube structures; Improve the stability and accuracy of instrument zero points; Increase the deflection of the measuring tube to improve sensitivity; Improve the stress distribution of the measuring tube, reduce fatigue damage, and enhance the ability to resist vibration interference.
Unlike the previous methods, it is a flow meter used to measure free surface natural flow in non full tubular open channels.
A waterway with non full pipe flow is called an open channel, and the one that measures the flow rate of water in the open channel is called an open channel flowmeter.
In addition to circular flow meters, open channel flow meters also come in various shapes such as U-shape, trapezoid, rectangle, etc.
The application of open channel flow meters in all urban water supply and diversion channels; Water diversion and drainage channels, sewage treatment inflow and discharge channels in thermal power plants; Water discharge from industrial and mining enterprises, as well as channels for water conservancy projects and agricultural irrigation.