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Industry Information
Balanced flowmeter with high linearity and good repeatability
2012-2-16 10:15:09

由于其特殊的结构设计,使其具有特殊的性能,它可以进行气液两相,各种混合气体(如瓦斯、沼气、煤气等等)、各种低温气体(如LNG、液氮、液氧、液氩、液氢、液氯、液化乙烯、液化石油气等等)、气液两相介质(如湿气)、浆料、多相水流、震动水流、电磁干扰介质和双向流(因为平衡流量计左右完全对称)。 Due to its special structure design, the balance flow meter has special performance. It can perform gas-liquid two-phase, various mixed gases (such as gas, biogas, coal gas, etc.), and various low-temperature gases (such as LNG, liquid nitrogen). , Liquid oxygen, liquid argon, liquid hydrogen, liquid chlorine, liquefied ethylene, liquefied petroleum gas, etc.), gas-liquid two-phase media (such as moisture), slurry, multiphase water flow, vibrating water flow, electromagnetic interference media and two-way flow (Because the balanced flow meter is completely symmetrical from left to right).

The balance flow meter is a third-generation throttling device. It is a new type of flow meter designed and invented by the NASA-Marshall Aviation Flight Center (NASA-MSFC) for the measurement of liquid oxygen in the main engine of the space shuttle. Is a balanced flow meter. The measurement accuracy of this flow meter is 5 to 10 times that of traditional throttling devices, the flow noise is reduced to 1/15, the permanent pressure loss is about 1/3, and the pressure recovery is 2 times faster. The minimum straight pipe section can be less than 0.5D. The movable parts are very convenient and simple to install and use, which can save large straight pipe sections and greatly reduce the energy consumption required for fluid operation. It is an energy-saving instrument with broad application prospects. The balanced flow meter has greatly improved the traditional throttling device, and changed the principle of throttling from edge throttling to balanced throttling. It is a revolutionary differential pressure flow meter. The balanced flow sensor is a porous disc throttle rectifier, which is installed on the cross section of the pipeline. The size and distribution of each hole are customized based on unique formulas and test data, called function holes. When the fluid passes through the function holes of the disc, the fluid will be balanced and adjusted, and the vortex will be minimized to form an approximately ideal fluid. Through the conventional pressure taking device, a stable differential pressure signal can be obtained, and the volume flow rate is calculated according to Bernoulli's equation. ,Mass Flow. The ingenious design of the balanced flow meter is to combine the porous rectifier and the measurement orifice plate into one, which can adjust the flow field balance to the ideal state to the maximum extent, so as to exert the advantages of the differential pressure flow meter to the extreme. Supported by huge space research funding, from 2000 to 2004, NASA and QMC have organized a large number of flow technical experts, invested 10 million US dollars, conducted a large number of tests on balanced flow meters, and about 100,000 sets of flow measurement data reflected the test. The results are good and the product performance is comforting. The balanced flow meter is suitable for almost all fluid measurement. It is a revolution in fluid measurement technology. Its processing, manufacturing and installation can be standardized like orifice plates. Verification is also easy to achieve dry standard. It is expected to become a new international standard for throttling devices. NASA has won a series of patents for product inventions in 2004 and the invention award from the President in 2006. The traditional throttling device has only one flow aperture, and the fluid loses its ideal state after throttling. The balanced flowmeter has multiple function apertures, which can balance the flow field into an ideal fluid to the maximum extent, thereby reducing the pressure of the differential pressure flowmeter. Give full play to the advantages. The balanced flow meter is suitable for almost all fluid measurement. It is a revolution in fluid measurement technology. At present, the balanced flow meter has been widely used in petroleum, chemical, metallurgy, power, natural gas, water treatment and other industries. Product Principle Balanced flow meter is a revolutionary differential pressure flow meter. Its working principle is the same as other differential pressure flow meters. It is based on the principle of energy conversion in a sealed pipeline: the flow in the pipeline under the condition of an ideal fluid. It is proportional to the square root of the differential pressure; the flow in the pipeline can be calculated by measuring the differential pressure according to Bernoulli's equation. The balanced flow sensor is a porous disc throttle rectifier, which is installed on the cross section of the pipeline. The size and distribution of each hole are customized based on special formulas and test data, called function holes. When the fluid passes through the function holes of the disc, the fluid will be balanced and rectified, and the vortex will be minimized to form an approximately ideal fluid. Through the pressure taking device, a stable differential pressure signal can be obtained. The volume flow rate is calculated according to Bernoulli's equation, Mass flow. Characteristics of balanced flowmeter 1. Measurement accuracy is 5 to 10 times that of standard orifice plate 2. Flow noise is 1/15 of standard orifice plate 3. Permanent pressure loss is 1/3 of standard orifice plate 4. Pressure recovery 2 times faster than standard orifice plates5, the smallest straight pipe section can be less than 0.5D

First, high linearity and good repeatability

传感器具有对称多孔结构特点,能对流场进行平衡,降低了涡流、振动和信号噪声,流场稳定性大大提高,使线性度比孔板提升了5~10倍,重复性提高了54%,为0.15%,从其综合性能来看,平衡流量计属于高档流量计行列。 The balanced flowmeter sensor has the characteristics of symmetrical porous structure, which can balance the flow field, reduce eddy current, vibration and signal noise, greatly improve the stability of the flow field, make the linearity 5 to 10 times higher than the orifice plate, and improve the repeatability. 54% is 0.15%. From its comprehensive performance, balanced flowmeters belong to the ranks of high-end flowmeters.
5: 1 range ratio, linearity can reach ± 0.3%;
7: 1 range ratio, linearity can reach ± 0.5%;
10: 1 range ratio, linearity can reach ± 1.0%

2. Low requirements for straight pipe sections

The balanced flow sensor has a stable flow field, and the pressure recovery is twice as fast as the orifice plate, which greatly shortens the requirements for straight pipe sections. The straight pipe sections before and after are generally 3D before 1D, and the minimum can be less than 0.5D, thereby eliminating a large number of straight pipe sections. , Especially pipes of particularly expensive materials.

Third, reduce permanent pressure loss

The porous symmetrical balance design reduces the formation of turbulent shear forces and vortices, and reduces the loss of kinetic energy. Under the same measurement conditions, it reduces the permanent pressure loss by 2.5 times compared with the orifice plate, thereby saving considerable The large operating energy cost is an energy-saving instrument, which is worthy of extensive promotion.

Fourth, dirt resistance is not easy to block

The porous and symmetrical balance design reduces the turbulent shear force and the formation of eddy currents, thereby greatly reducing the formation of stagnant dead zones, ensuring that the dirty medium smoothly passes through multiple holes, and reducing the chance of fluid holes being blocked.

Five, can directly replace the orifice plate

It has the same use method and appearance as the orifice plate, so it can be replaced directly without any changes in piping and related instruments. It is very suitable for changing the orifice plate to a balanced flow meter in the whole plant energy measurement transformation.

Wide flow measurement range

According to the test results, we learned that: the performance of the flow meter is balanced so that the flow rate can be from the minimum to the speed of sound; its minimum Reynolds number can be less than 200, the maximum Reynolds number is greater than 107; and the beta value can be selected from 0.25 to 0.90.

Good long-term stability

Because its turbulent shear force is significantly reduced, the direct friction between the medium and the throttle is greatly reduced. Its β value remains unchanged for a long time. The entire instrument has no moving parts, so it can maintain stability for a long time.

Eight, can measure high temperature and high pressure medium

As with orifices and other throttling devices, the working temperature and pressure depend on the materials and grades of the pipes and flanges. The working temperature can reach 850 ° C and the working pressure can reach 42MPa.

Nine, measurable medium of complex working conditions

Due to its special structural design, it has special properties, it can perform gas-liquid two-phase, various mixed gases (such as gas, biogas, coal gas, etc.), and various low-temperature gases (such as LNG, liquid nitrogen, liquid oxygen) , Liquid argon, liquid hydrogen, liquid chlorine, liquefied ethylene, liquefied petroleum gas, etc.), gas-liquid two-phase media (such as moisture), slurry, multiphase water flow, vibrating water flow, electromagnetic interference media and bidirectional flow (because of equilibrium The flow meter is completely symmetrical from left to right).

Technical indicators:
Pipe diameter range: DN15 ~ DN3000

Accuracy: ± 0.3%, ± 0.5%, ± 1%

Straight pipe requirements: 0.5D ~ 2D

Permanent pressure loss: 1/3 ~ 1/4 of orifice plate

Range ratio: 10: 1, suitable working conditions data can be wider.

Repeatability: 0.1%

Re range: 200 ~ 107

β range: 0.25 ~ 0.9

Temperature range: The temperature that the metal pipeline can withstand, up to 850 ° C.

Pressure range: the pressure that the metal pipeline can withstand, up to 42MPa.

Dirt resistance: special design and calculation

Can measure bidirectional flow


Differential pressure flowmeters [1] are widely used, and the standard throttling device is a preferred instrument for flowmeter selection. At present, the throttling components that can be selected for the throttling differential pressure flowmeter are usually orifice plates, nozzles, venturi tubes, averaging tubes, wings and so on. Among them, the orifice principle of the orifice plate and the nozzle is the edge restriction; the principle of the venturi pipe is the reduction of the pipe; the principle of the equalizing pipe is the double-chamber throttle; the principle of the wing's throttle is the wing Throttling. Each type of throttling element has its advantages and disadvantages. The designer's flowmeter manufacturer should choose a throttling element that is more suitable for the working condition according to the needs. With the advancement of technology and the continuous improvement of throttling elements, a balanced differential pressure throttling device has passed tests and has been gradually applied to petrochemical devices. The flowmeter using this throttling element is called a balanced flowmeter. This technology was designed and invented by NASA's Marshall Aviation Flight Center. It obtained a patent for product invention series in 2004 and the invention award from the president in 2006. .

Performance advantages of balanced flow meters

是一种革命性的差压式流量仪表[2],其传感器是一个多孔的圆盘节流整流器,安装在管道的截面上,每个孔的尺寸和分布基于独特的公式和测试数据定制,称为函数孔。 The balanced flow meter is a revolutionary differential pressure flow meter [2]. Its sensor is a porous disc throttling rectifier, which is installed on the cross section of the pipeline. The size and distribution of each hole are based on unique formulas and tests. Data customization, called function holes. When the fluid passes through the function holes of the disc, the fluid will be balanced and adjusted, and the vortex will be minimized to form an approximately ideal fluid. Through the pressure taking device, a stable differential pressure signal can be obtained. The volume flow rate is calculated according to Bernoulli's equation. Mass Flow. The performance characteristics of a balanced flow meter will be explained in detail below. Balance the flow field and reduce the vortex. The standard throttling device that is widely used today has only one flow hole. The dead zone on both sides of the hole generates a lot of vortex, which consumes the kinetic energy of the fluid, which will cause a large permanent pressure loss. The formed noise causes fluctuations in the signal at the pressure taking point, which reduces the linearity and repeatability of the measurement; the structure of a hole requires a long straight pipe section to organize the flow field and restore the pressure. The balanced flow meter can perform fluid balance measurement cleverly through a porous disc throttling rectifier, which can significantly reduce the formation of vortex, reduce the dead zone effect, reduce the loss of fluid kinetic energy, reduce the fluctuation of the signal of pressure taking point caused by vortex, and reduce the permanent pressure loss The balanced and porous symmetrical design of the balance flow meter reduces the formation of eddy currents and turbulent friction, and reduces the loss of kinetic energy. Under the same measurement conditions without reducing the differential pressure value, it can reduce the permanent flow by 2.5 times compared with the traditional throttling device. Pressure loss, which reduces large operating energy costs, is an energy-saving instrument. The straight pipe section has low requirements and is convenient for measuring two-way flow. The balanced flow meter can adjust the flow field balance and stability, and the pressure recovery is twice as fast as the traditional throttling device of the liquid turbine flow meter, which greatly reduces the requirements for the straight pipe section. In most cases, the straight pipe section can be as small as 0.5D. Using a balanced flow meter can save a large number of straight pipe sections, especially for pipes of special expensive materials. In addition, the balanced flow meter is completely symmetrical from left to right, so it can be easily measured in both directions. Other performance advantages. A) High measurement accuracy and wide range. Due to the symmetrical porous structure of the balanced flowmeter, it can balance the flow field, reduce eddy current, vibration and signal noise, and greatly improve the stability of the flow field. The meter body uses special precision pipes and special pressure taking devices to make the linearity better than traditional The throttling device is increased by 5-10 times. After real-flow calibration, the accuracy can reach ± 0.3% to ± 0.5%, which is suitable for trade measurement occasions; the geometric dimension inspection, the accuracy can reach ± 0.5% to ± 1.0%, which is suitable for process control occasions. According to the experimental results, the speed of sound can be reached by balancing the flow rate of the flowmeter; its minimum Reynolds number can be lower than 200, and its maximum Reynolds number is greater than 107; the beta value can be selected from 0.25 to 0.90. Wide range ratio, good repeatability and long-term stability. Compared with the traditional throttling device, the balanced flowmeter greatly improves the measurement range ratio. The results of research in the United States show that when the Reynolds number is greater than 5 × 104, the appropriate aperture parameter is selected, and the range ratio of the differential pressure throttling device has no upper limit. According to the practical application of industrial measurement, the conventional measurement range ratio is 10: 1. Selecting appropriate parameters can achieve 30: 1, 50: 1 or higher. The balanced flow meter can balance the flow field and make the repeatability greatly improved, up to 0.1%. Balanced differential pressure throttling device. Multiple flow holes are distributed and stressed, and there is no acute-angle wear. Its β value can be maintained for a long period of time, and the long-term stability is very good. The device is extended 5 to 10 times. Dirt resistance is not easy to block and has a wide range of applications. The porous symmetrical balance design of the balance flow meter reduces the formation of turbulent shear forces and vortices, thereby greatly reducing the formation of stagnant dead zones, ensuring that dirty media can smoothly pass through multiple holes, and reducing the chance of fluid holes being blocked. The working temperature and pressure of the balanced flowmeter depend on the materials and grades of the pipes and flanges, which can reach 850 ° C and 42MPa, respectively. Suitable for gas-liquid two-phase, slurry, and even solid particle measurement. The comparison of balanced flowmeters and other differential pressure throttling devices combined with the performance characteristics introduced above can be used to compare the balanced flowmeters and other differential pressure throttling devices. Applications and conclusions of balanced flowmeters, August 2007 in Guangzhou Petrochemical In the reconstruction of 5Mt / a atmospheric and vacuum decompression device, American A + K balanced flow meter was used for gas measurement in and out of the device. After several months of use, the product has stable readings, high accuracy, large range ratio, and small pressure loss. Compared with other traditional differential pressure flow meters, the performance has been significantly improved.
According to the performance analysis of the electromagnetic flowmeter manufacturer on the balanced flowmeter, it can be seen that the balanced flowmeter is a new type of flowmeter. The measurement accuracy of this flow meter is 5-10 times that of traditional throttling device, the flow noise is reduced to 1/5, the permanent pressure loss is about 1/3, the pressure recovery is 2 times faster, and the minimum straight pipe section can be as small as 0.5D. It has no moving parts and is very convenient and simple to install and use. It can save a large number of straight pipe sections and greatly reduce the energy consumption of fluid movement. It is an energy-saving instrument with broad application prospects. Balanced flow meters are now widely used in the US natural gas, refining, gas industries, chemical plants, steel plants, power plants, and pharmaceutical plants. At the end of 2006, A + K balanced flowmeter was introduced into the Chinese market for large-scale promotion.