Common flowmeter classification and principle
Common flowmeter classification and principle
Meters measuring fluid flow are collectively referred to as flow meters or flow meters. Flowmeter is one of the most important instruments in industrial measurement. With the development of industrial production, the requirements for the accuracy and range of flow measurement are getting higher and higher, and the flow measurement technology is changing with each passing day. In order to adapt to various uses, various types of flow meters have come out one after another. At present, more than 100 flow meters have been put into use.
Each product has its specific applicability and it also has its limitations. According to the principle of measurement, there are mechanics principle, thermal principle, acoustic principle, electrical principle, optical principle and atomic physics principle.
According to the structure principle of the flow meter to classify: Volumetric flowmeters, differential pressure flowmeters, floater flowmeters, turbine flowmeters, electromagnetic flowmeters, vortex flowmeters in mass flowmeters, mass flowmeters, and plug-in type Flow meter.
According to the measurement object, there are two types of closed pipes and open channels; according to the purpose of measurement, it can be divided into total measurement and flow measurement, and the meters are called total meters and flow meters, respectively. Aggregate meters measure the flow through a pipeline over a period of time, expressed as a quotient of the total amount of flow through a pipeline for a short period of time divided by that time. Actually, a flow meter is usually equipped with an accumulative flow device for use as a total gauge. The total volume table also has a traffic signalling device. Therefore, dividing the flow meter and the total amount table in a strict sense has no practical significance.
First, classified by measuring principle
1. Mechanics: The instruments belonging to this type of principle include differential pressure type and rotor type utilizing Bernoulli's theorem, impulse type and movable tube type using momentum theorem, direct mass method using Newton's second law, and fluid momentum. The target of the principle, the turbine type using the angular momentum theorem, the vortex type and the vortex type using the fluid oscillation principle, the Pitot tube type using the total static pressure difference, and the volumetric type enthalpy, trough and so on.
2. Electrical principles: Instruments used for this type of principle include electromagnetic, differential capacitance, inductive, and strain resistive.
3. Acoustic principle: Ultrasonic type is used for flow measurement using acoustical principle. Acoustic type (shock wave type) etc.
4. Thermal principle: The use of thermal principles to measure the flow of the thermal type, direct calorimeter, indirect calorimeter and so on.
5. Optical principle: Laser type, photoelectric type, etc. are instruments that belong to this type of principle.
6. Atomic Physics: Nuclear magnetic resonance, nuclear radiation, etc. are instruments that fall into this category.
7. Other principles: Marking principle (tracing principle, nuclear magnetic resonance principle), related principles, etc.
Second, according to the structure of the flow meter structure classification
According to the actual situation of current flow meter products, according to the structure principle of the flow meter, it can be roughly classified into the following types:
1. differential pressure flowmeter
The differential pressure flowmeter is a meter that calculates the flow rate based on the differential pressure generated by the flow detection element installed in the pipeline, the known fluid condition, and the geometry of the detection element and the pipeline.
The differential pressure flowmeter consists of a primary device (test piece) and a secondary device (differential pressure conversion and flow display instrument). Differential pressure flowmeters are often classified in the form of test pieces, such as orifice flowmeters, venturi flowmeters, and equal velocity tube flowmeters.
The secondary device is a variety of mechanical, electronic, electromechanical integrated differential pressure gauges, differential pressure transmitters and flow display instruments. It has developed into a large-scale instrument with a high degree of specification, serialization, generalization and standardization. It can measure flow parameters as well as other parameters (such as pressure, level, density, etc.) ).
Differential pressure flow meter detection parts according to its role can be divided into: throttling device, hydraulic resistance type, centrifugal, dynamic pressure head type, dynamic pressure head gain type and jet type several categories.
Detectors can be divided into two categories according to their degree of standardization: standard and non-standard.
The so-called standard test pieces are designed, manufactured, installed, and used as long as they are in accordance with standard documents. They can be determined without real-flow calibration, and their estimated flow errors and estimated measurement errors.
Non-standard test pieces are of poor maturity and have not been included in international standards.
Differential pressure flowmeter is one of the most widely used flowmeters, and it ranks first in the use of various types of flow meters. In recent years, due to the advent of various new flowmeters, the percentage of its use has gradually declined, but it is still the most important type of flowmeter.
advantage:
(1) The most widely used perforated plate flowmeter has a strong structure, stable and reliable performance, and long service life;
(2) A wide range of applications. No flowmeters have yet been compared;
(3) The detection parts, transmitters and display meters are produced by different manufacturers respectively, which is convenient for economies of scale production.
Disadvantages:
(1) The measurement accuracy is generally low;
(2) The range is narrow, generally only 3:1~4:1;
(3) High requirements for on-site installation conditions;
(4) Large pressure loss (finger plates, nozzles, etc.).
Application Overview:
Differential pressure flowmeters have a particularly wide range of applications and have applications in flow measurement of closed pipes, such as fluids: single-phase, mixed-phase, clean, dirty, viscous flow, etc.; working conditions: normal pressure, high pressure , vacuum, room temperature, high temperature, low temperature, etc.; pipe diameter: from a few mm to several m; flow conditions: subsonic, sonic, pulsating flow. Its consumption in various industrial sectors accounts for about 1/4 to 1/3 of the total flow meter usage.
1.1 orifice flowmeter
advantage:
(1) The standard throttling device is universal in the world and has been approved by the international standard organization. It can be used without real-time calibration, and it is also unique in the flowmeter.
(2) The structure is easy to copy, simple, firm, stable and reliable, and low in price;
(3) It has a wide range of applications, including all single-phase fluids (liquid, gas, steam), and partially mixed-phase flows. The pipe diameters and working conditions (temperature, pressure) of the general production process are all products.
(4) The test piece and differential pressure display instrument can be produced separately from different manufacturers, and it can be produced with professional scale;
Disadvantages:
(1) The repeatability and accuracy of the measurement are intermediate in the flowmeter, and the accuracy is difficult to improve due to the intricacies of numerous factors.
(2) The range is narrow. Since the flow coefficient is related to the Reynolds number, the general range is only 3:1 to 4:1.
(3) There is a long straight pipe length requirement that is generally difficult to meet. Especially for larger diameters, the problem becomes more pronounced;
(4) Large pressure loss;
In order to maintain the normal operation of an orifice meter, the pump requires additional power to overcome the orifice pressure loss. This additional power consumption can be determined directly from pressure loss and flow calculations. It takes about tens of thousands of kilowatt hours a year, equivalent to tens of thousands of yuan. The following table lists the energy consumption calculations for the orifice plate under normal pressure loss conditions. The number of days of operation is calculated on the basis of 350 days, and the price of electricity is calculated on the basis of 0.35 yuan/degree. From the calculation of power consumption data in the table, it can be seen that the additional operating cost of the orifice plate is extremely high, while the operating cost of the elbow flow meter is zero!
(5) The precision of the hole is ensured by the acute angle of the inner hole, so it is sensitive to corrosion, abrasion, scaling, and dirt. It is difficult to ensure the long-term use accuracy. It is necessary to remove the strong inspection once a year.
(6) Flange connection is easy to cause running, running, drip and leakage problems, which greatly increases the maintenance workload.
2. Float flowmeter
A float flowmeter, also known as a rotameter, is a type of variable area flowmeter. In a vertical conical tube that expands from bottom to top, the gravity of a float of circular cross-section is subjected to hydrodynamic forces, thereby allowing the float to float. It can rise and fall freely in the cone.
The float flow meter is the second most widely used type of flow meter after the differential pressure flow meter, and plays an important role in the small and micro flow.
In the mid-1980s, sales in Japan, Western Europe, and the United States accounted for 15% to 20% of the flow meters. China's production in 1990 was estimated at 12 to 140,000 units, of which more than 95% were glass cone floater flowmeters.
Features:
(1) The glass cone floater flowmeter has a simple structure and is easy to use. The disadvantage is that the pressure resistance is low and there is a large risk that the glass tube is fragile.
(2) Suitable for small diameter and low flow rate;
(3) Low pressure loss.
3. volumetric flowmeter
Volumetric flowmeters, also known as fixed displacement flowmeters, referred to as PD flowmeters, are the most accurate type in flow meters. It uses a mechanical measuring element to continuously divide the fluid into a single known volume fraction, measuring the total volume of fluid according to the number of times that the measurement chamber fills and discharges the volume fraction of fluid one after another.
Volumetric flowmeters are classified according to their measuring components and can be divided into oval gear flowmeters, scraper flowmeters, dual-rotor flowmeters, rotary piston flowmeters, reciprocating piston flowmeters, disk flowmeters, liquid-sealing tumbler flowmeters. Wet gas meter and film gas meter.
advantage:
(1) High measurement accuracy;
(2) Installation pipeline conditions have no effect on the measurement accuracy;
(3) can be used for the measurement of high viscosity liquids;
(4) Wide range;
(5) Direct-reading meters can be directly accumulated, total, clear, and easy to operate without external energy.
Disadvantages:
(1) The result is complex and bulky;
(2) The types of medium to be measured, the caliber, and the working status of the medium are more limited;
(3) Not suitable for high and low temperature applications;
(4) Most meters are only suitable for clean single-phase fluids;
(5) Generate noise and vibration.
Application Overview:
Volumetric flowmeters and differential pressure flowmeters and float flowmeters are listed as the three most used flowmeters, and they are often applied to the measurement of the total amount of expensive media (oil products, natural gas, etc.).
In industrialized countries, the sales flow of PD flowmeters (excluding domestic gas meters and household water meters) accounted for 13%~23% of the flow meters in recent years; China accounted for about 20%, and the 1990 production (excluding domestic gas meters) was estimated at 340,000. Taiwan, with elliptical gears and waist wheels, accounts for about 70% and 20% respectively.
4. Turbine flow meter
Turbine flowmeters, which are the main types of speed flowmeters, use a multi-blade rotor (turbine) to sense the average flow rate of the fluid and to derive a flow or total meter.
It is generally composed of two parts: a sensor and a display. It can also be made into an integral type.
Turbine and positive displacement flowmeters and Coriolis mass flowmeters are called three types of repeatability and precision in flowmeters. As one of the ten types of flowmeters, their products have been developed into multi-species, multi-series batches. The scale of production.
advantage:
(1) High precision, among all flow meters, the most accurate flow meter;
(2) good repeatability;
(3) zero-zero drift, good anti-interference ability;
(4) Wide range;
(5) Compact structure.
Disadvantages:
(1) The calibration feature cannot be maintained for a long time;
(2) The fluid properties have a great influence on the flow characteristics.
Application Overview:
Turbine flowmeters are widely used in several measurement objects: petroleum, organic liquids, inorganic liquids, liquefied gas, natural gas, and cryogenic fluids. In Europe and the United States, turbine flow meters are the second only to the natural measurement of orifice flow meters. Instruments, only the Netherlands in the natural gas pipeline on the use of more than 2,600 various sizes, pressure from 0.8 ~ 6.5MPa gas turbine flow meter, they have become an excellent natural gas meter.
5. Vortex Flowmeter (USF)
The vortex flowmeter is a non-streamlined vortex generator placed in the fluid, and the fluid is alternately separated on both sides of the generator to release two series of regularly staggered vortex vortex meters. When the flow cross section is constant, the flow rate is proportional to the flow volume of the lead volume. Therefore, measuring the oscillation frequency can measure the flow. Vortex flowmeter according to the frequency detection method can be divided into: stress type, strain type, capacitive type, thermal type, vibration type, photoelectric type and ultrasonic type. This flow meter was developed and developed in the 70's. Because it has the advantages of no rotating parts and pulsed digital output, it has a promising future.
advantage
(1) The vortex flowmeter has no movable parts and the measuring element has a simple structure, reliable performance and long service life.
(2) Vortex flowmeter has a wide measuring range. The range ratio can generally reach 1:10.
(3) The volumetric flow rate of vortex flowmeters is not affected by thermal parameters such as temperature, pressure, density, or viscosity of the fluid being measured. Generally do not need to be calibrated separately. It can measure the flow of liquids, gases or steam.
(4) It has a small pressure loss.
(5) High accuracy, repeatability of 0.5%, and low maintenance.
Shortcomings
(1) The volumetric flow rate of the vortex flowmeter is not affected by the thermal parameters such as temperature, pressure, and density of the measured fluid, but the final measurement result of the liquid or steam should be the mass flow. For the gas, the final measurement result should be Is the standard volume flow. Mass flow or standard volumetric flow must be scaled by fluid density. Fluid density changes due to changes in fluid conditions must be considered.
(2) The main causes of flow measurement error are: measurement error caused by uneven flow velocity of the pipeline; inability to accurately determine the density of the medium when the fluid working conditions change; and to assume that wet saturated steam is measured as dry saturated steam. If these errors are not limited or eliminated, the total measurement error of vortex flowmeters will be large.
(3) Poor vibration resistance. External vibrations can cause vortex flowmeters to produce measurement errors, and may not even function properly. The impact of high flow velocity in the channel fluid will cause additional vibration in the cantilever of the vortex generator body, which will reduce the measurement accuracy. The influence of large diameter is even more pronounced.
(4) poor adaptability to measure dirty media. The body of the vortex flowmeter is easily contaminated by dirt or dirt, changing the size of the geometry and greatly affecting the measurement accuracy.
(5) High requirements for straight sections. Experts pointed out that the vortex flowmeter straight pipe section must ensure 20D before the first 40D to meet the measurement requirements.
(6) Poor temperature resistance. Vortex flowmeters typically measure only fluid flow below 300°C.
USF entered industrial applications in the late 1960s, and it accounted for 4% to 6% of the sales amount of flow meters in various countries since the late 1980s. In 1992, the world's estimated sales volume was 3.548 million units, and domestic products were estimated to be 8,000-9,000 units during the same period.
6. Electromagnetic flowmeter (EMF)
Electromagnetic flowmeters are meters that measure conductive liquids based on Faraday’s electromagnetic induction law.
Electromagnetic flowmeter has a series of excellent characteristics, which can solve the problems that other flowmeters are not easy to apply, such as the measurement of dirty flow and corrosion flow.
In the 70s and 80s, there was a major technological breakthrough in electromagnetic flow, making it a widely used type of flow meter, and the percentage of its use in flow meters has been rising.
advantage:
(1) The measurement channel is a smooth, straight section of tubing that will not block and is suitable for the measurement of liquid-solid two-phase fluids containing solid particles, such as pulp, mud, sewage, etc.;
(2) No pressure loss caused by flow detection, and good energy saving effect;
(3) The measured volume flow is virtually unaffected by changes in fluid density, viscosity, temperature, pressure, and conductivity;
(4) Large flow range and wide caliber range;
(5) Corrosive fluids may be applied.
Disadvantages:
(1) The application of the electromagnetic flowmeter has certain limitations. It can only measure the liquid flow of the conductive medium, and it cannot measure the flow of non-conductive medium, such as gas and water heating water. In addition, its lining needs to be considered under high temperature conditions.
(2) The electromagnetic flowmeter determines the volumetric flow under working conditions by measuring the velocity of the conductive liquid. According to the measurement requirements, for the liquid medium, the mass flow should be measured. The measurement of the medium flow should involve the density of the fluid. Different fluid media have different densities and change with temperature. If the electromagnetic flowmeter converter does not consider the fluid density, it is not appropriate to give only the volumetric flow rate at room temperature.
(3) The installation and commissioning of electromagnetic flowmeters are more complex than other flowmeters and require more stringent requirements. Transmitters and converters must be used together. Two different types of meters cannot be used between them. When installing the transmitter, from the choice of installation site to the specific installation and commissioning, must strictly follow the product specification requirements. There must be no vibration and no strong magnetic field at the installation site. The transmitter and pipe must have good contact and good grounding during installation. The potential of the transmitter is equal to the fluid being measured. In use, the gas remaining in the measuring tube must be drained, otherwise it will cause a larger measurement error.
(4) When the electromagnetic flowmeter is used to measure viscous liquid with dirt, stickies or deposits adhere to the inner wall or electrode of the measuring tube, so that the output potential of the transmitter changes, brings about measurement error, and the dirt on the electrode reaches a certain degree. Thickness may cause the meter to fail to measure.
(5) Fouling or abrasion of the water supply pipe to change the inner diameter size will affect the original flow rate value and cause measurement error. For example, if the diameter of a 100mm diameter meter changes by 1mm, it will bring about 2% additional error.
(6) The transmitter's measurement signal is a very small millivolt potential signal. In addition to the flow signal, it also contains some signals that are not related to flow, such as phase voltage, quadrature voltage, and common-mode voltage. In order to accurately measure the flow rate, various interference signals must be eliminated to effectively amplify the flow signal. The performance of the flow converter should be improved. Microprocessor type converters should be used to control the excitation voltage. The excitation mode and frequency should be selected according to the nature of the fluid to be measured, and the in-phase and quadrature interferences can be excluded. However, the improved meter structure is complex and the cost is high.
(7) Higher prices
Application Overview:
Electromagnetic flowmeters have a wide range of applications. Large diameter instruments are used in water supply and drainage projects; medium and small diameters are often used in demanding or unpredictable applications, such as the control of cooling water in blast furnace tuyere in the iron and steel industry, pulp and black liquor in the paper industry, chemical industry Strong corrosive fluid, non-ferrous metallurgical industry pulp; small diameter, small diameter is often used in the pharmaceutical industry, food industry, biochemical and other health requirements. Since EMF entered the industrial application in the early 1950s, the use of the field has been expanding. Since the late 1980s, it has accounted for 16% to 20% of the sales amount of flow meters in various countries. China's rapid development in recent years, 1994 sales estimated at 6500 to 7500 units. China has produced ENF with a maximum diameter of 2~6m, and has a real-life calibration capability of 3m.
7. Ultrasonic flowmeter
Ultrasonic flowmeters are based on the geometrical principle of the speed at which ultrasonic waves travel in a flowing medium equal to the average flow velocity of the medium being measured and the velocity of the sound waves themselves. It is also measured flow rate to reflect the size of the flow. Ultrasonic flowmeters appeared in the 70s, but because they can be made into non-contact type, and can be measured in conjunction with ultrasonic water level meter opening flow measurement, the fluid does not produce disturbance and resistance, so very happy.
Ultrasonic flowmeter according to the principle of measurement can be divided into time difference and Doppler
The time-difference type ultrasonic flowmeter manufactured using the time-difference principle has received extensive attention and use in recent years, and is an ultrasonic flowmeter that is currently used most frequently by enterprises.
Ultrasonic Doppler flowmeters manufactured using the Doppler effect are used to measure the medium with a certain amount of suspended particles or bubbles, and their use has certain limitations, but it solves the problem that time-lapse ultrasonic flowmeters can only measure single clear fluids. It is also considered as an ideal instrument for non-contact measurement of two-phase flow.
advantage:
(1) Ultrasonic flowmeter is a non-contact measuring instrument, which can be used to measure the fluid flow and large-diameter flow that are difficult to contact and difficult to observe. It does not change the flow state of the fluid, does not generate pressure loss, and is easy to install.
(2) The flow of highly corrosive and non-conductive media can be measured.
(3) Ultrasonic flowmeter has a large measuring range, ranging from 20mm to 5m in diameter.
(4) Ultrasonic flow meters can measure various liquid and wastewater flows.
(5) The volumetric flow rate measured by the ultrasonic flowmeter is not affected by the thermal physical parameters such as temperature, pressure, viscosity, and density of the measured fluid. Can be made in both fixed and portable forms.
Disadvantages:
(1) Ultrasonic flowmeters do not have a high temperature measurement range and generally only measure fluids with temperatures below 200°C.
(2) Poor anti-interference ability. It is susceptible to interference from ultrasonic noises such as air bubbles, scaling, pumps, and other sound sources, affecting the measurement accuracy.
(3) Straight pipe sections are strictly required for the first 20D and the last 5D. Otherwise, the dispersion is poor and the measurement accuracy is low.
(4) Uncertainty of installation will bring greater error to flow measurement.
(5) The fouling of the measuring pipeline will seriously affect the accuracy of the measurement and bring about significant measurement error. Even when the pipeline is serious, the instrument will show no flow.
(6) The reliability and accuracy grades are not high (generally about 1.5 to 2.5 grades), and the repeatability is poor.
(7) Short service life (General accuracy can only be guaranteed for one year).
(8) Ultrasonic flow meters determine the volumetric flow rate by measuring the fluid velocity. The mass flow rate of the liquid should be measured. The mass flow rate measured by the instrument is obtained by multiplying the volume flow rate by the artificially set density. When the fluid temperature changes, The density of the fluid is variable. Artificially setting the density value does not guarantee the accuracy of the mass flow. The fluid density can only be measured at the same time as the fluid velocity is measured, so that the true mass flow value can be obtained through calculation.
(9) Higher prices.
Application Overview:
(1) The propagation time method is applied to clean, single-phase liquids and gases. Typical applications include factory effluents,: strange liquids, liquefied natural gas, etc.;
(2) Good experience has been used in the field of high-pressure natural gas for gas applications;
(3) The Doppler method is applicable to biphasic fluids with relatively low out-of-phase contents, such as untreated sewage, factory discharge fluids, and dirty process fluids; it is generally not suitable for very clean fluids.
8. Mass flow meter
Since the volume of the fluid is influenced by parameters such as temperature and pressure, the volume of the flow is used to indicate the size of the medium. In the case of continuous changes in the media parameters, it is often difficult to achieve this requirement, resulting in distortion of the instrument display value. Therefore, mass flow meters have been widely applied and valued. Mass flow meter is divided into direct and indirect two. The direct mass flow meter uses the principle directly related to the mass flow to measure. At present, mass flow meters such as calorimetric, angular momentum, vibratory gyro, Magnus effect, and Coriolis force are commonly used. An indirect mass flow meter uses a density meter and a volumetric flow rate to obtain a mass flow.
In modern industrial production, the operating parameters such as temperature and pressure of the working fluid are continuously increasing. In the case of high temperature and high pressure, due to the reasons of material and structure, the application of the direct mass flowmeter has encountered difficulties and indirect quality. Flowmeters are often not practical because they are limited by the range of application of humidity and pressure. Therefore, temperature and pressure compensated mass flow meters are widely used in industrial production. It can be regarded as an indirect mass flowmeter, instead of using a density meter, but using the relationship between temperature, pressure and density, and using temperature and pressure signals to calculate the density signal by function and multiplying it with the volumetric flow rate to obtain Mass Flow. At present, temperature and pressure compensation mass flowmeters have been put into practical use. However, when the measured medium parameters vary widely or rapidly, correct compensation will be difficult or impossible. Therefore, further study of the applicable mass flow in actual production is made. Meters and densitometers are still a topic.
8.1 Thermal mass flow meter (differential temperature difference TMF)
advantage:
(1) Ball valve installation, easy installation and removal. And can be installed with pressure.
(2) Direct measurement of mass flow based on King's law. The measured value is not affected by pressure and temperature.
(3) rapid response.
(4) Large measuring range, pipeline-type installation can measure the flow of 8.8mm pipeline, the maximum can be measured to 30''
(5) Plug-in type flow meters, one flow meter can be used to measure a variety of pipe diameters.
Disadvantages:
(1) The accuracy is not as good as other types of flowmeters, typically 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.
8.2 Coriolis Mass Flow Meter (CMF)
Coriolis mass flowmeter (hereinafter referred to as CMF) is a direct type mass flow meter made by using the Coriolis force principle which is proportional to the mass flow when a fluid flows in a vibrating tube.
The application of China's CMF started relatively late. In recent years, several manufacturing plants (such as Taihang Instrument Factory) have developed their own supply markets; several factories have also established joint ventures or used foreign technology to produce serial meters.
The foreign CMF has developed more than 30 series. The development of each series is focused on the technical aspects: design and innovation of the structure of the flow detection and measurement tube; improvement of the performance of instrument zero point stability and accuracy; increase of measurement tube deflection, increase of sensitivity; improvement of the measurement tube stress Distribution, reduce fatigue damage, strengthen anti-vibration interference capabilities.
9. Open channel flow meter
Different from the previous ones, it is a flow meter that measures the natural flow of a free surface in a non-full tubular open channel.
The waterway that is not full-pipelined is called an open channel, and the flow measurement of the open channel flow is called an open channel flowmeter.
In addition to circular flow meters, there are U-shaped, trapezoidal, rectangular and other shapes.
The open channel flowmeter applies all the urban water diversion canals; the power plant diversion and drainage, the sewage treatment inflow and discharge canals; the industrial and mining enterprises water discharge and irrigation works and irrigation channels. Some people estimated that 1995, accounting for about 1.6% of the overall flow instrument, but there is no estimated data for domestic applications.
10. Electrostatic flowmeter
The Tokyo Institute of Technology develops an electrostatic flowmeter for low conductivity liquid flow measurement in oil transmission pipelines.
The metal measuring tube of the electrostatic flowmeter is connected to the pipe system in an insulated manner, and the charge on the measuring pipe can be known by measuring the electrostatic charge on the capacitor. They conducted solid-flow tests on metal and plastic measuring tube instruments with internal diameters of 4 to 8 mm, such as copper and stainless steel. The tests showed that the flow and charge were close to linear.
11. Combined effects meter (combined effects meter)
The working principle of the instrument is based on the fluid's momentum and pressure acting on the instrument body's cavity deformation, measuring the composite effect of the deformation of the flow. The instrument was developed by the American GMI School of Engineering and Management and has applied for two patents.
12. Tachometer flowrate sensor (tachmetric flowrate sensor)
It was developed by the Russian Scientific and Engineering Center Industrial Instrumentation Corporation and was developed based on the suspension effect theory. The instrument has been successfully applied in several fields (for example, more than 2,000 sets of hot water flow are measured in nuclear power plants and used continuously for 8 years), and it is still being improved to expand the application field.
Details:
1. Use: to the firm straight plate lifting
2. 2. Loading range: 0 to 8ton.
3. It is manufactured by low-carbon hi-quality alloy steel
4. To test one of the rated load and lifting operations alone, or supporting the use of two.
5. Only hang a steel plate at the same time, the locking handle must be up to make the spring tense. When the load is cancelled, the locking handle must be down. After he spring is loosened, the clamp and the steel plate can be separated.
6. Test load is the max, operation load of 2 times.
7. Don`t overload to use.
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