Due to its wide adaptability and intelligent development trend, flow sensors have gradually become an indispensable part of the chemical production process. They can be applied to various chemical scenarios, including high temperature and high pressure, strong corrosiveness, solid-liquid two-phase flow, etc.
Selection method of flow sensors
1. Measuring medium
The selection of flow sensors must first consider the properties of the measuring medium, including the type of medium (liquid, gas, steam), physical properties (density, viscosity, temperature, pressure) and chemical properties (corrosiveness, toxicity). For example, for high viscosity or corrosive media, flow sensors made of corrosion-resistant materials should be selected, such as metal tube float flowmeters or electromagnetic flowmeters.
2. Measurement accuracy
The output signal should have as wide a dynamic range and good response characteristics as possible; the output signal should have a high enough resolution to obtain information about small changes in the measured object; the output signal should have a relatively high signal-to-noise ratio; the appropriate measurement accuracy must be selected according to application requirements. High-precision measurement is particularly important for occasions where the raw material ratio needs to be precisely controlled. For example, in the production process of synthetic resins, the mass flowmeter or electromagnetic flowmeters should be able to monitor the flow of raw materials in real time to ensure the accuracy of the ingredients.
3. Working environment
Whether the working environment is good or not determines whether the sensor can truly reflect the measured value, and has a direct impact on the entire test system. The working environment includes temperature, pressure, vibration, etc., and the medium in the pipeline also has single-phase flow, solid-liquid two-phase flow, etc. For example, the vortex flowmeter has poor vibration resistance and is not suitable for use in a large vibration environment; high temperature and high pressure resistant flow sensors should be selected in high temperature and high pressure environments, such as metal tube float flowmeters or high temperature resistant electromagnetic flowmeters.
4. Installation conditions
The installation conditions include pipeline size, straight pipe length, vibration, etc. For example, the electromagnetic flowmeter has a lower requirement for the length of the straight pipe section before the meter, but it needs to be avoided to be installed in a strong electromagnetic field and vibration place; when installing an ultrasonic flowmeter, it is necessary to ensure that the upstream of the straight pipe section is greater than 10D (D is the diameter of the installation pipe) and the downstream is greater than 5D.
5. Economy
When selecting a flow sensor, it is also necessary to consider economy, including equipment cost, maintenance cost and service life. For example, although the volumetric flowmeter has high measurement accuracy, it has a complex structure and a large volume, which is suitable for small and medium flow measurement; the vortex flowmeter has a simple structure and is easy to maintain, which is suitable for large flow measurement.