Characteristics and structural classification of turbine flowmeter

The turbine flowmeter sensor is a new generation of turbine flowmeter that absorbs advanced technology of flow meters at home and abroad and is optimized and designed. It has the characteristics of simple structure, light weight, high precision, good reproducibility, sensitive response, easy installation, maintenance and use. It is widely used to measure liquids with kinematic viscosity less than 5×10-6m2/s at working temperature in closed pipelines. It has no corrosion effect on stainless steel 1Cr18Ni9Ti, 2Cr13, corundum Al2O3, and hard alloy, and has no impurities such as fibers and particles. For liquids with kinematic viscosity greater than 5×10-6m2/s, the flowmeter can be calibrated with real liquid before use. If it is matched with a display instrument with special functions, it can also be calibrated. According to the

sensor structure classification

1. Axial type (ordinary type), the center of the impeller shaft coincides with the axis of the pipeline. It is the leading product of turbine flowmeter, with (DN10~DN600).
2. Tangential type. The impeller shaft is perpendicular to the axis of the pipeline, and the angle of attack of the fluid flowing to the blade plane is 90°, which is suitable for small-caliber and micro-flow measurement. 3. Mechanical type
. The rotation of the impeller directly or through magnetic coupling drives the mechanical counting mechanism to indicate the total amount of accumulation. The measurement accuracy is slightly lower than that of the sensor for electrical signal detection, but its sensor and display instrument are integrated for easy use.
4. Downhole special type. Suitable for downhole operations and transportation of oil production. The measuring medium includes mud and oil and gas flow. The volume of the sensor is limited and it needs to withstand high pressure, high temperature and fluid impact.
5. Self-correcting twin turbine type. It can be used to measure the flow rate of natural gas and other gases. The sensor consists of a main and auxiliary double impeller, and the change of flow characteristics can be automatically corrected by the speed difference of the two turbines.
6. Wide viscosity type. On the basis of the Porter type floating rotor pressure balance structure, the diameter of the upper cone and the lower cone are enlarged, and the viscosity compensation wing and pressure-bearing blade are added. Structural measures make the sensor suitable for high-viscosity liquids (such as heavy oil, with a viscosity of 30mm2/s).
7. Insertion type. It consists of a measuring head, an insertion rod, an insertion mechanism, a converter and an instrument housing, etc. It has a simple structure and light weight. The manufacturing cost is low when the diameter is large.

Features of turbine flowmeter

1. High accuracy, liquid is generally ±(0.25~0.5)%R, high-precision type can reach ±0.15%R, gas is generally ±(1~1.5)%R, special type is ±(0.5~1)%R. Turbine flowmeter is the most accurate among all flowmeters.
2. Good repeatability, short-term repeatability can reach 0.05%~0.2%. It is precisely because of the good repeatability that high accuracy can be obtained by frequent calibration or online calibration, so it is the preferred flowmeter in trade settlement.
3. The output is a pulse frequency signal, which is suitable for total volume measurement and connection with a computer, without zero drift and strong anti-interference ability. The frequency can be as high as 4kHz, and the signal resolution is strong.
4. Wide range, medium and large diameter can reach (40:1)~(10:1), small diameter is (5:1)~(6:1).
5. Compact and lightweight structure, easy installation and maintenance, large flow capacity.
6. Suitable for high-pressure measurement, the instrument housing does not need to be opened, and it is easy to make a high-pressure instrument.
7. There are many structural types, which can meet the needs of various measurement objects.
8. The calibration characteristics cannot be guaranteed for a long time, and regular calibration is required. For liquids with poor lubricity, the liquid contains suspended matter or abrasiveness, which causes problems such as bearing wear and jamming, limiting its application range. After using carbide shafts and bearings, the situation is improved compared with graphite bearings. For trade storage and transportation and high-precision measurement requirements, it is best to equip on-site calibration equipment, which can be calibrated regularly to maintain its characteristics.
9. When the viscosity of the liquid increases, the lower limit of the flowmeter measurement increases, the range is reduced, and the linearity deteriorates. For high-viscosity liquids, a high-viscosity special type must be used to maintain the measurement characteristics.
10. The physical properties of the fluid (density, viscosity) have a greater impact on the characteristics of the flowmeter. Gas flowmeters are easily affected by density, and liquid flowmeters are sensitive to changes in viscosity. Since the physical properties of the fluid are closely related to pressure and temperature, the pressure and temperature fluctuate greatly during on-site use, and appropriate compensation measures must be taken to maintain a high measurement accuracy.
11. The flow meter is greatly affected by the velocity distribution and the rotating flow, so a longer straight pipe section is required on the upstream and downstream sides of the sensor. If the installation space is limited, a flow regulator (rectifier) ​​can be installed to shorten the length of the straight pipe section.
112. Due to the high requirements for the cleanliness of the medium, auxiliary equipment (filters, degassers) can be installed to expand the scope of use, but this will bring side effects such as increased pressure loss and increased maintenance.
13. The flow characteristics of small-diameter (DN50 or less) instruments are seriously affected by physical properties, and it is difficult to improve the performance of the instrument. (end)