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.
Compressed air flowmeter installation requirements
Keywords: compressed air flow meter, compressed air vortex flowmeter, air flowmeter
First, the compressed air vortex flowmeter installation requirements
1. The upstream of the compressed air vortex flowmeter should avoid installing the regulating valve or the semi-opening valve. The regulating valve or the semi-opening valve is installed after the downstream 8DN of the sensor.
2. The straight pipe section where the flowmeter is installed should be as close as possible to the sensor diameter. If it is not consistent, a pipe diameter slightly larger than the sensor diameter should be used, and the error should be ≤3% and not more than 5mm.
3. When the measured medium contains more impurities, the filter should be installed outside the length required for the straight pipe section upstream of the sensor.
4, the sensor should be avoided on the pipeline with mechanical vibration, and try to avoid strong electromagnetic field interference. When vibration cannot be avoided, consider adding a bracket to the straight pipe section about 2DN before and after the sensor.
Second, choose from the type of flow meter
Various flow meters, such as volumetric flowmeters, speedmeters, and differential pressuremeters, have different characteristics. Different flowmeter types have different turndown ratios. The turbine flowmeter has a turndown ratio of 1:20 to 1:30, the Roots flowmeter has a turndown ratio of 1:20 to 1:160, and the film gauge has a turndown ratio of 1: 160 (The error characteristic curves of these three kinds of flow meters are shown in Figure 1), and the appropriate flow meter should be selected according to the actual situation.
By comparing the error characteristics of the above flowmeters, it can be seen that the starting flow of the membrane meter and the Roots flowmeter is small, the initial flow of the turbine meter is relatively large, and the membrane surface exhibits a positive deviation in the small flow state. The Roots flowmeter exhibits a negative deviation. At low flow rates, the gas supply company is more willing to select a membrane meter for metering.