2. 1 advantages
USF can be used for non-contact measurement. As long as the sensor is installed outside the existing pipeline, the clamp sensor USF can be installed without stopping the flow and cutting the pipeline. This is the unique advantage of USF in industrial flowmeter, so it can be used to measure fluidity (that is, non-fixed installation) and is suitable for the evaluation and determination of flow conditions in pipe network.
USF is a measurement method without flow obstacle and extra pressure loss.
The instrument coefficient of flowmeter can be calculated from the actual geometric dimensions of measuring pipe and sound channel, and can be calibrated by dry method. Except for measuring pipe section, it is generally unnecessary to verify the actual flow.
USF is suitable for large circular and rectangular pipes, and it is not limited by pipe diameter in principle, and the cost is basically independent of pipe diameter. It is not only convenient for large pipelines, but also the first choice when it is impossible to verify the real flow.
Doppler USF can measure liquids with high solid content or bubbles.
USF can measure non-conductive liquid, which is a supplement to electromagnetic flowmeter in unobstructed flow measurement.
Because it is easy to be combined with testing methods (such as velocity-area method and tracer method). ) can solve some special measurement problems, such as the measurement of serious distortion of velocity distribution and the measurement of non-circular cross-section pipes.
Some propagation time methods USF have the function of measuring the propagation time of sound waves, that is, judging the type of liquid by measuring the sound speed of liquid. For example, when a tanker pumps oil ashore, it can check whether it is measuring oil or bottom water.
2.2 Shortcomings and limitations
The propagation time method USF can only be used to clean liquids and gases, and cannot measure liquids with suspended particles and bubbles exceeding a certain range. On the other hand, Doppler USF can only be used to measure liquids with a certain phase difference.
USF of external transducer can not be used for pipes with thick lining or scale, nor can it be used for pipes with lining (or rust layer) peeling off from the inner wall of the pipe (if there is gas in the interlayer, the ultrasonic signal will be seriously attenuated) or seriously corroded (changing the ultrasonic propagation path).
In most cases, the measurement accuracy of Doppler USF is not high.
The existing varieties produced in China cannot be used for pipelines with a diameter less than dn 25 mm