Choice of caliber
The choice of the diameter of the electromagnetic flowmeter is not necessarily the same as the diameter of the pipe, and should be determined by the flow rate and flow rate. However, as the chemical raw materials and intermediate liquid of Salt Lake, the viscosity is large and the flow rate is low (generally 2.0 to 4.0 m/s). The electromagnetic flowmeter is used on such a pipe, and the diameter of the sensor is the same as the diameter of the pipe. If the flow rate is lower than 1.0m/s, an electromagnetic flowmeter of appropriate flow rate can be selected to ensure measurement accuracy and relatively reduce investment.
Selection of flow rate and range
Basically, they are anti-corrosion plastic pipes, and considering the lining of the flow meter, the flow rate is generally controlled at 2m/s. For some materials that are easy to crystallize (such as sodium carbonate solution, compounding liquid: crystallized mainly boron and magnesium double salt), the flow rate is increased to 3.0 to 4.0 m/s by taking measures. The flow rate will increase the flow noise, and the vibration of the pipeline will affect the measurement accuracy. Under the condition that the electromagnetic flowmeter is installed, the shock absorber should be installed before and after. The full scale of the meter is greater than the expected maximum flow value, which is typically 1.2 times the estimated maximum flow. The normal measurement flow is greater than 50% of the full scale of the meter to ensure a certain measurement accuracy.
The ultrasonic flowmeter is designed based on the geometrical principle that the velocity of the ultrasonic wave propagating in the flowing medium is equal to the average flow velocity of the measured medium and the velocity of the acoustic wave itself. It is also measured by the flow rate to reflect the flow rate. Although the ultrasonic flowmeter appeared only in the 1970s, it is very popular because it can be made into a non-contact type and can be connected to the ultrasonic water level gauge for opening flow measurement without disturbing or resisting the fluid. There are promising flow meters.
Ultrasonic Doppler flowmeters fabricated using the Doppler effect have received widespread attention in recent years and are considered to be ideal gauges for non-contact measurement of two-phase flow.
Fluid oscillating flowmeter
The fluid oscillating flowmeter is designed based on the principle that the fluid will oscillate when flowing under specific flow conditions, and the frequency of the oscillation is proportional to the flow velocity. When the flow cross section is constant, the flow rate is proportional to the flow volume of the pilot volume. Therefore, the flow rate can be measured by measuring the oscillation frequency. This flowmeter was developed and developed in the 1970s. Because it combines the advantages of non-rotating components and pulsed digital output, it has a promising future. At present, typical products include vortex flowmeters and spiral vortex flowmeters.
Ultrasonic flowmeter common problems (1)
1. The ultrasonic flowmeter probe is used for a period of time, and irregular alarms may occur. This problem is more common when there are more impurities in the transport medium. Solution: Clean the probe regularly (recommended once a year).
2. When the ultrasonic flowmeter transport medium contains liquid impurities such as water, the flow metering tube is prone to effusion, and the freezing of the pressure tube may occur when the temperature is low, especially in the northern regions in winter. Solution: Purge or electrify the pressure tube
3, the ultrasonic flowmeter is very strict on the requirements of the pipeline, there can be no abnormal noise, otherwise it will affect the measurement error.
During the propagation of ultrasonic waves, their strength is attenuated due to obstruction or absorption by impurities in the medium and medium. Whether it is an ultrasonic flowmeter or an ultrasonic level gauge, there is a certain requirement for the received sound wave intensity, so various attenuations are suppressed.
4. What is the instantaneous flow fluctuation?
The signal strength is large, and the measured fluid fluctuation is large.
Solution: Adjust the probe position, improve the signal strength, and ensure the signal strength is stable. If the fluid fluctuation is large, the position is not good. Re-select the point to ensure the 5D working condition after the first 10D.