Select the flow sensor measurement method as needed

According to the measurement principle, flow sensors can be divided into rotor flow sensors, throttling flow sensors, slit flow sensors, volume flow sensors, electromagnetic flow sensors, ultrasonic flow sensors, etc.; according to the medium classification: liquid flow sensors and gas flow sensors. When using, first of all, the sensor must be ensured to operate safely, and then strive to improve the accuracy and energy saving of the sensor. To this end, not only should a display instrument that meets the accuracy requirements be selected, but also a reasonable measurement method should be selected according to the characteristics of the measured medium. For example, in the measurement of the main steam flow of a power plant, since it is crucial to the safety and economy of the power plant, a mature standard throttling volume with a differential pressure flow sensor is generally used. The sewage and fuel oil of chemical water treatment belong to dirty flow and low Reynolds number viscous flow, respectively, and standard throttling parts are not suitable. For the measurement of dirty fluids, non-standard throttling parts such as circular orifice plates are generally used with differential pressure gauges or ultrasonic Doppler flow sensors, while viscous flows can be respectively used with volumetric, target or wedge-shaped flow sensors. The flow rate of turbine inlet, condenser circulating water and heat recovery steam of heat recovery unit are all large diameter flow measurement parameters. Due to the difficulty of processing and manufacturing and large pressure loss, standard throttling devices are generally not used. According to the characteristics of the measured medium and the measurement accuracy requirements, insertion flow sensors, speed measuring elements with differential pressure gauges, ultrasonic flow sensors, or non-energy loss methods such as marking method and simulation method are used to measure flow.

To ensure the service life and accuracy of the flow sensor, you should also pay attention to the vibration resistance requirements of the instrument when selecting the model. In hot and humid areas, you should choose a hot and humid type instrument.

Correctly selecting the specifications of the instrument is also an important part of ensuring the service life and accuracy of the instrument. Special attention should be paid to the selection of static pressure and temperature resistance. The static pressure of the instrument is the pressure resistance, which should be slightly greater than the working pressure of the measured medium, generally 1.25 times, to ensure that no leakage or accidents occur. The selection of the range is mainly the selection of the upper limit of the instrument scale. If it is too small, it is easy to overload and damage the instrument; if it is too large, it will hinder the accuracy of the measurement. Generally, it is selected between 1.2 and 1.3 times the maximum flow value in actual operation.

For contact instruments installed on production pipelines and running for a long time, the energy loss caused by the flow measurement element should also be considered. Generally speaking, multiple measurement elements with large pressure loss, such as throttling elements, should not be selected in the same production pipeline.

In short, no flow sensor can adapt to all fluids and flow conditions. Different measurement methods and structures require different measurement operations, usage methods and usage conditions. Each type has its own unique advantages and disadvantages. Therefore, the measurement method of the flow sensor should be selected as needed based on a comprehensive comparison of various measurement methods and instrument characteristics, so as to meet production requirements and ensure safety and reliability.