Chinese name
Vortex precession flowmeter
Foreign name
Vortex precession flowmeter
Vortex precession flowmeter is widely used in petroleum, chemical industry, electric power, metallurgy, urban gas supply and other industries to measure various gas flows, and it is the first choice for oil field and urban natural gas transmission and distribution measurement and trade measurement.
Environmental conditions of use
Ambient temperature: -30℃ ~+55℃
Relative humidity: 5% ~ 95%
Atmospheric pressure: 86 kPa ~ 106 kPa
Conditions of use
Medium temperature range: -20℃ ~+70℃
Nominal pressure: 1.6, 2.5, 4.0 and 6.3MPa
major constituent
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Vortex precession flowmeter consists of two parts: sensor and converter.
product classification
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Vortex precession flowmeter is a new gas flowmeter with advanced micro-processing technology, which has the advantages of strong function, wide flow range, simple operation and maintenance, convenient installation and use, and its main technical indicators have reached the advanced level of similar products abroad.
Because of the uniqueness of vortex precession flowmeter, it must constantly adapt to the development of mechanical manufacturing level in the process of development, so vortex precession flowmeter is divided into "intelligent vortex precession flowmeter" and "steam vortex precession flowmeter" according to different measurement objects.
Intelligent precession vortex street gas flowmeter adopts advanced micro-processing technology, which has the advantages of strong function, wide flow range, simple operation and maintenance, convenient installation and use, and its main technical indicators have reached the advanced level of similar products abroad. It can be widely used for measuring various gases in petroleum, chemical industry, electric power, metallurgy, coal and other industries.
The steam vortex precession flowmeter adopts the advanced technology of double-probe precession flow sensor, which has strong anti-interference ability, high precision, no mechanical rotating parts, no corrosion, compact structure, high reliability, good stability and less maintenance.
Intelligent vortex precession flowmeter can measure all kinds of gases, while steam vortex precession flowmeter can only measure steam.
main feature
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1, no mechanical moving parts, corrosion resistance, stability and reliability, long service life, long-term operation without special maintenance;
2. The mechatronics is realized, and there is no need for manual attendance in the daily metering process;
3. The installation conditions are not harsh. Compared with orifice plate and vortex flowmeter, the upstream and downstream straight pipe sections of the instrument can be greatly shortened;
4. The measurement accuracy of the system can meet the current trade measurement requirements (≤1.5%);
5. The flow measurement range is wide (qmax/qmin = 15 ~ 20), which can effectively work in some small flow areas where orifice plates and vortex flowmeter can't get involved;
6. Small size, light weight and easy off-line calibration;
7. The measurement signal can be displayed locally or transmitted remotely as required;
8. Instrument managers do not need professional training, and the measurement parameters such as flow, pressure and temperature can be read directly from the meter head without conversion;
9. Regularly change the parameters of the battery (micro power consumption) and the measured medium.
10, with large pressure loss;
When the flowing medium is gas, the pressure loss is about 3 ~ 4 times that of vortex flowmeter.
principle of operation
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When the fluid passes through a vortex generator composed of spiral blades (see figure 1), the fluid is forced to rotate violently around the axis of the generator to form a vortex. When the fluid enters the diffusion section, the vortex is affected by the backflow and starts to rotate for the second time, forming a gyro vortex precession phenomenon. The precession frequency is proportional to the flow velocity and is not affected by the physical properties and density of the fluid. When the detecting element measures the precession frequency of the secondary rotation of the fluid, the flow rate can be known. But also can obtain good linearity in a wide flow range. The calculation formula of flowmeter is:
Vortex precession flowmeter
K=f/q
Where: k- flowmeter coefficient l/m&; sup3
F- vortex frequency Hz
Q- volume flow m&m;; sup3/s
The instrument coefficient of the flowmeter is within certain structural parameters and specified Reynolds number range, and has nothing to do with the temperature, pressure, composition and physical properties (density and viscosity) of the fluid.
The flowmeter consists of a sensor and a conversion display.
1. The sensor includes vortex generator, detection element, rectifier and shell.
The vortex generator consists of special spiral blades, which are fixed at the front end of the contraction section of the shell, forcing the fluid to produce strong vortex.
The detection element is installed near the throat of the expansion tube, and thermal, piezoelectric, strain, capacitance or optical fiber detection elements can be used to detect the frequency signal of vortex precession.
The rectifier is fixed at the outlet of the flowmeter body, and its function is to eliminate eddy current, so as to reduce the influence of downstream flow pattern on instrument measurement.
The shell is designed as a flow channel with a certain shape, which makes eddy current form, fixes and protects the components installed inside, and is connected with the pipeline through the flange.
2, conversion display instrument
After being amplified, filtered and shaped, the weak voltage signal detected by the piezoelectric sensor becomes a pulse signal whose frequency is proportional to the flow rate, and then it is counted and displayed by the display instrument. The display instrument is equipped with an output interface which can output various signals. The measured gas medium can be compensated for temperature and pressure, converted into volume flow under standard conditions and displayed.
Main features:
1. Built-in pressure, temperature and flow sensors have high safety performance, compact structure and beautiful appearance.
2. On-site display of temperature, pressure, instantaneous flow and cumulative flow.
3. Using new signal processing amplifier and unique filtering technology, the interference signals caused by pressure fluctuation and pipeline vibration are effectively eliminated, and the anti-interference ability of the flowmeter is greatly improved, so that the small flow rate has excellent stability.
4. Unique time display and real-time data storage function can ensure that internal data will not be lost under any circumstances and can be stored permanently.
5. The power consumption of the whole machine is extremely low, and it can run with built-in battery for a long time, so it is an ideal local display instrument without external power supply.
6. Reliable anti-theft function and password protection to prevent parameter change.
7. The meter head can rotate at will 180 degrees, which is convenient for installation.
Matters needing attention
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Any measuring instrument has its particularity, and intelligent vortex precession flowmeter is no exception. In order to make the instrument better serve the flow measurement, the practical experience in the production site shows that the following precautions should be paid enough attention by the relevant management and use departments.
(1) Pay attention to instrument selection. When the instrument type has been selected (such as intelligent vortex precession flowmeter), the selection of instrument specifications and its supporting components is very important. In short, if you choose well, you can use it well. Therefore, two basic principles should be grasped in the process of type selection; Namely: first, to ensure the accuracy of use, and second, to ensure the safety of production. In order to achieve this, three selection parameters must be realized, namely, the maximum, minimum and common instantaneous flow in the near and long term (mainly used to select the size and specification of the instrument), the design pressure of the measured medium (mainly used to select the nominal pressure grade of the instrument) and the working pressure (mainly used to select the pressure grade of the instrument pressure sensor).
② On the one hand, the calibration before use takes into account that there are still some difficulties in the field verification of such instruments at present. In addition, if the purchase intention is to apply the instrument to more important metering occasions, such as large-flow trade metering or controversial metering points, and the application site does not have the conditions for online flow calibration, then in this case, it is too early to easily judge that all the performance of the instrument is qualified only by a factory certificate provided by the manufacturer at the time of purchase. Therefore, in order to ensure the reliability and accuracy of the measurement results in the future work, before the formal installation, it needs to be sent to a department with verification ability and qualification in this field for system verification within the full flow range.
(3) Do a good job in process installation. Although this instrument does not have too many special requirements for process installation and use environment, any flow measuring instrument has such a * * * attribute, that is, it tries to avoid vibration and interference with flow components (such as compressors, separators, pressure regulating valves, large and small heads, manifolds, elbows, etc.). ) In the high temperature environment, keep the inner wall of the straight pipe section before and after the instrument smooth and straight, and ensure that the measured medium is a clean single-phase fluid.
④ Strengthening post-management Although the instrument has many automatic disposal functions and micro-power consumption characteristics, it still needs to strengthen management after it is put into operation. For example, in order to ensure the accuracy and reliability of the long-term operation of the instrument (to avoid accidental shutdown and data loss), the system should be calibrated regularly (every 1 ">~ 2 years), copy the header data (daily or weekly), change the medium parameters (monthly or quarterly), and check the battery status, instrument coefficient and lead seal from time to time.
⑤ Pay attention to internal maintenance If it is necessary to regularly check or clean the measuring cavity and its components of the instrument due to impure temperament or other reasons, then one thing must be paid special attention to: for vortex precession flowmeter with the same specification, its core components such as vortex generator and deflector cannot be interchanged, otherwise it is necessary to recalibrate the measuring coefficient of the instrument and systematically correct its temperature and pressure sensors.
application area
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The application of flow measurement technology and instruments has the following aspects.
First, the industrial production process.
Flowmeter is one of the main types of process automation instruments and devices. Widely used in metallurgy, electric power, coal, chemical industry, petroleum, transportation, construction, textile, food, medicine, agriculture, environmental protection and people's daily life. It is an important tool to develop industrial and agricultural production, save energy, improve product quality, improve economic benefits and management level, and occupies an important position in the national economy. Among the process automation instruments and devices, the flowmeter has two functions: as a detection instrument for the process automation control system and as a master instrument for measuring the quantity of materials.
Second, energy measurement.
Energy is divided into primary energy (coal, crude oil, coalbed methane, liquefied petroleum gas and natural gas), secondary energy (electricity, coke, artificial gas, refined oil, liquefied petroleum gas and steam) and energy-carrying working medium (compressed air, oxygen, nitrogen, hydrogen and water). Energy measurement is an important means to manage energy scientifically, save energy and reduce consumption, and improve economic benefits. Flowmeter is an important part of electric energy metering instrument. Water, artificial gas, natural gas, steam and oil all use a huge number of flowmeters, which are indispensable tools for energy management and economic accounting.
Third, environmental protection projects.
The discharge of flue gas, waste liquid and sewage seriously pollutes the atmosphere and water resources and seriously threatens the living environment of human beings. The country regards sustainable development as a national policy, and environmental protection will be the biggest topic in the 2 1 century. To control air and water pollution, management must be strengthened, and the basis of management is quantitative control of pollution.
China is a country with coal as its main energy source, and millions of chimneys all over the country continuously emit smoke into the atmosphere. Smoke emission control is an important project to eliminate pollution. Each chimney must be equipped with smoke analyzer and flowmeter to form a continuous emission monitoring system. The velocity of flue gas has great difficulties, such as large chimney size and irregular shape, changeable gas composition, wide velocity range, dirt, dust, corrosion, high temperature and no straight pipe section.
Fourth, traffic.
There are five ways: railway, highway, aviation, water transportation and pipeline transportation. Although pipeline transportation has existed for a long time, its application is not universal. With the prominent environmental problems, people began to pay attention to the characteristics of pipeline transportation. Pipeline transportation must be equipped with flowmeter, which is the eye of control, distribution and scheduling, and also an essential tool for safety monitoring and economic accounting.
Verb (abbreviation of verb) biotechnology
2 1 century will usher in the century of life science, and the industry characterized by biotechnology will develop rapidly. There are many substances that need to be monitored and measured in biotechnology, such as blood and urine. The development of instruments is extremely difficult and diverse.
Sixth, scientific experiments.
The flowmeters needed for scientific experiments are not only numerous, but also various. According to statistics, a large part of 100 flowmeters are used for scientific research. They are not mass-produced and sold in the market. Many scientific research institutions and large enterprises have set up special groups to develop special flowmeters.
Seven. Marine meteorology, rivers and lakes
These areas are open channels, so it is generally necessary to measure the flow and then calculate the flow. The physical principle and fluid mechanics foundation of current meter and flowmeter are the same, but the principle, structure and use conditions of the instrument are very different.
The content is a bit long, I hope it will be useful to you.