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Views: 6 Author: Site Editor Publish Time: 2025-06-30 Origin: Site
The advantages of ultrasonic water flow meters are significant, including a wide measuring range, low pressure loss, and adaptability to large diameter pipes. These advantages make it widely used in pipeline flow measurement. Ultrasonic flow meter is mainly composed of three parts, which are electronic circuit, ultrasonic transducer, display and accumulation system. Ultrasonic transducer plays an important role in flow measurement, can be converted into ultrasonic energy, and will be emitted into the fluid, at the same time, the receiver will receive the signal, after the electronic circuit will be converted into electrical signals, which will be converted into flow signals through the calculator.
Noise method ultrasonic flow meter is mainly based on the noise signal and fluid flow rate to realize the measurement. In the completely closed pipeline, there are vortex, nai flow and other phenomena, and has a shear force, will produce the noise associated with the flow rate, this time on the noise data analysis, you can get the flow rate. This type of flowmeter has the advantages of cheap price and easy installation, which is suitable for convenient detection work. However, its detection accuracy level is not high, in the small pipe diameter, low flow velocity in the flow field, can not realize the effective application.
The principle of correlation method ultrasonic flowmeter is that if there is fluid in the pipeline, there will be disturbances, and there will be a uniformity of flow signals, and at this time in accordance with the correlation of the characteristics of the flow rate can be calculated. The detection method for the pipe caliber, ultrasonic rate is not a strict requirement. Therefore, in the small pipeline, small flow has a wide range of applications.
Ultrasonic Doppler flowmeter detection principle based on the Doppler effect, when the distance between the receiver and the source of the wave changes, it will change the frequency of the received wave. Specifically, an increase in the distance between the two will result in a decrease in frequency; conversely, it will result in an increase in frequency. This type of flow meter does not make direct contact during detection, and also does not change the flow field and pressure. However, in actual detection, it is necessary to ensure that there is a certain amount of impurities in the flow field, and if it is a pure fluid, it cannot be detected.
ultrasound in the propagation process, when the medium is a fluid, the propagation speed and fluid speed has a direct correlation, downstream and countercurrent will inevitably be the time difference, at this point, according to the time difference can be obtained from the flow rate of the fluid. According to the difference in the existence of time difference, generally divided into time difference, phase difference, frequency difference of three kinds.
In boiler circulating water pipes, the faster airflow, and the presence of devices such as elbows and valves, creates noise. Therefore, in the design and installation process, it is necessary to pay attention to the impact of noise. In the actual working process, the flow rate, temperature, pressure and other parameter factors will also change, while the compressor will also create noise in the work. All of these factors will have a negative impact on the actual detection of ultrasonic water flow meter. In addition, some pressure-reducing components also create noise. Compared to regulators, low-noise valves have a greater impact, mainly due to their high noise frequency of 20 kHz or more, which is beyond the acceptable hearing range of the human ear. At the same time, this is almost the same as the frequency of ultrasonic water flow meter, which will bring some interference to the flow meter detection.
In boiler circulating water detection, impurities will accumulate on the surface of the pipeline, and even block the probe, which will cause some deviation to the detection data. If a large number of impurities attached to the probe, it will reduce the transmission efficiency of ultrasonic waves, which in turn affects the sensitivity of the probe. Relevant experiments show that in the flowmeter detection process, due to the impact of errors caused by impurities, the final deviation caused by about 0.3%.
In the process of boiler circulating water testing, according to the technical requirements of the relevant regulations, the time of the solid fuel boiler test can not be less than 8h. Before the application of ultrasonic flowmeter to start the test, it is necessary to set the density value, and this will result in a certain measurement error with the actual density value. Therefore, in the boiler test, you need to do a good job of the corresponding measures, such as pipeline and water storage tank insulation, reduce the water temperature difference brought about by the random error and so on.
Wall mounted ultrasonic flowmeter
Handheld ultrasonic flowmeter
If the flow meter is installed downstream of a control valve, it is necessary to ensure that the length of the upstream straight pipe meets the requirements in order to improve the accuracy of the measurement data. In addition, if the noise generated by the control valve is large, it will certainly affect the normal detection work of the flow meter. Therefore, when installing the regulating valve, in order to improve the accuracy of the measurement, it should not be installed in the downstream . Finally, if the pressure difference in the pipeline is obvious, the flow rate is too fast, there will be a variety of noise, and its frequency may be the same as the ultrasonic wave, resulting in the flowmeter in the detection process is interfered with. The propagation path of these noises is variable and may propagate both downstream and upstream. Therefore, when installing the flowmeter, the impact of noise on the performance of the flowmeter should be analyzed in many ways. In order to achieve noise reduction, the propagation channel of noise is generally optimized, and tees, elbows and mufflers are reasonably installed between the regulating valve and the flowmeter.
To effectively reduce the impact of impurities, you need to do a good job of monitoring the boiler circulating water, and regularly implement the cleaning of the flow meter and straight pipe section. After cleaning the inner wall of the flowmeter, if there are still traces of corrosion, it must be calibrated again, in order to effectively avoid the problem of increasing the inner diameter caused by corrosion in the cleaning of the interior. As the size of the flow and the inner diameter has a direct relationship, the larger the inner diameter, the larger the flow. Therefore, the measured flow rate will be smaller than the actual flow rate, resulting in a negative detection error of the flow meter. At this point, it is necessary to carry out another test.
When applying ultrasonic water flow meter, the pressure and temperature values at the experimental site should be emphasized. It is generally necessary to check the pressure and temperature parameters in time to ensure that the display value error of the pressure and temperature transmitter is in accordance with the requirements of the accuracy level. When there is a failure to meet the standard requirements, calibration or replacement should be taken immediately. Furthermore, in order to reduce the impact of temperature changes on the zero position, the pressure transmitter can be covered with a tarpaulin. At the same time, the temperature transmitter should also be well maintained, regularly adding thermal oil. In addition, it is also necessary to pay attention to the maintenance of the protective tube sleeve, regular cleaning and washing. To improve the accuracy of measurement, we must pay attention to the measurement range, to ensure that the measurement range is not less than 10% of the full range, in order to effectively improve the accuracy of measurement and detection.
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