Because all kinds of ultrasonic flowmeters can be installed outside the pipe, non-contact flow measurement, the cost of the instrument is basically independent of the size of the pipe to be tested, while other types of flowmeters increase with the increase in caliber, so the cost is increased. The flowmeter is superior to the other functions of the same type of flowmeter. It is considered to be a good large-diameter flow measuring instrument. The Doppler ultrasonic flowmeter can measure the flow of two-phase medium, so it can be used for the measurement of dirty sewage such as sewers and sewage. In power plants, the use of portable ultrasonic flowmeters to measure large pipe diameters such as turbine water inflow and turbine circulating water is much more convenient than in the past. Ultrasonic flow juice can also be used for gas measurement. Pipe diameters range from 2cm to 5m, from a few meters wide open channels, culverts to 500m wide rivers.
In addition, the accuracy of the flow measurement of the ultrasonic measuring instrument is almost independent of the temperature, pressure, viscosity, density and other parameters of the measured fluid, and can be made into non-contact and portable measuring instruments, so it can solve the problem that other types of instruments are difficult to measure. Flow measurement problems for corrosive, non-conductive, radioactive, and flammable and explosive media. In addition, in view of the non-contact measurement characteristics, coupled with reasonable electronic circuits, one instrument can adapt to a variety of pipe diameter measurements and a variety of flow range measurements. The adaptability of ultrasonic flowmeters is also unmatched by other instruments. Ultrasonic flowmeters have some of the above advantages, so it has received more and more attention and has been developed into a series of products and generalization. It has been made into standard, high-temperature, explosion-proof and wet instruments of different channels to adapt to different media. Flow measurement for occasions and different pipeline conditions.
The installation position and installation method of the ultrasonic flowmeter.
Installation location
Selecting the installation pipe segment has a great influence on the test accuracy. The selected pipe segment should avoid the interference and eddy current, which have great influence on the measurement accuracy. Generally, the pipe segment should meet the following conditions:
1. Avoid installing the machine in the pump, high-power radio, frequency conversion, that is, where there is strong magnetic field and vibration interference;
2. Select the pipe section where the pipe should be uniform and dense, and it is easy to transmit ultrasonic waves;
3, to have a long straight pipe section, the upstream straight pipe section of the installation point must be greater than 10D (Note: D = diameter), downstream is greater than 5D;
4, the installation point upstream distance pump should have a distance of 30D;
5. The fluid should be filled with pipes;
6. There should be enough space around the pipeline to facilitate the operation of the on-site personnel. The underground pipeline needs to be a test well. The test well is as follows:
Installation method
Ultrasonic flowmeters generally have two types of probe installation methods, namely Z method and V method.
However, when D < 200mm and the site condition is one of the following conditions, it can also be installed by the Z method:
1. When the measured fluid has high turbidity, when the V method is used to measure the signal or the signal is weak;
2. When the inner wall of the pipe is lined;
3. When the service life of the pipeline is too long and the inner wall is fouled seriously;
For those with better pipeline conditions, even if D is slightly larger than 200mm, in order to improve the measurement accuracy, the V method can be used for installation.
Ultrasonic flowmeter common problems (2)
5, the external clip type ultrasonic flowmeter signal is low?
This depends on the technical content of the instrument itself. After a large number of test cases on the spot, it proves that the long-term pipeline, serious scaling and large diameter, the Aitulel AFTU-2W series is better than other external-clip ultrasonic flowmeters. The signal is very fast and the signal is very stable. .
Solution: For large diameter and serious scaling, it is recommended to use a good quality external clamp type ultrasonic flowmeter. The pipe at the probe installation should be cleaned, and the air between the probe and the workpiece surface should be removed with a coupling agent or coupling piece to make the ultrasonic wave. It can be effectively introduced into the pipeline to ensure sufficient sound intensity transmission on the detection surface.
6. Occasionally, there are bubbles in the measurement medium. Does the ultrasonic flowmeter with the time difference method have any influence?
Today's Aitulel AFTU-2W series external clip type ultrasonic flowmeter has dual mode. When there is air bubble, it can be automatically transferred to Doppler mode to measure. When the bubble disappears, it will automatically turn into the time difference method.
7. The meter cannot be used under strong interference on the spot?
On-site inverter or high voltage cable field strong electromagnetic interference
Recommendation: Keep away from the inverter or high voltage cable field electromagnetic interference
8. What is the minimum diameter of the externally clamped ultrasonic flowmeter on the market? What is the highest temperature?
Answer: Now only the minimum diameter of the AFTU-2W series in the world can be measured to 6mm, the temperature can be measured at 550 °C, such as the measurement of molten salt and heat transfer oil, which is not possible with other brands of flowmeters. of.
9. How to choose a suitable ultrasonic flowmeter?
Answer: Pipe material, pipe wall thickness and pipe diameter; fluid type, contain impurities, air bubbles and full pipe; fluid temperature, flow meter type, portable or fixed online.