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Electromagnetic flowmeter device piping request description

1. Measured medium
The liquids measured by the electromagnetic flowmeter are individually low-viscosity (individually less than 15×10-6 m2/s) and low-erosion liquid. Although there are electromagnetic flowmeters for various media measurements, the measurement of low temperature, high viscosity, and strong erosive media still requires careful consideration and appropriate measures. When the viscosity v of the medium is greater than 15×10-6 m2/s, the meter factor of the flowmeter must be calibrated by solid liquid, otherwise a large error will occur.
2, device piping request
The condition of the flow meter has a great influence on the measurement accuracy of the flow meter.
1 The uneven distribution of flow velocity and the presence of secondary flow in the tube are the main factors affecting the accuracy of electromagnetic flowmeter measurement. Therefore, the electromagnetic flowmeter has a certain request for the upper and upper straight pipe sections. Regarding industrial measurements, individual requests upstream 20D, upstream 5D straight tube length. In order to clear the secondary activity, it is best to install a rectifier on the upstream side. If the upstream end can guarantee a straight pipe section of about 20D and a rectifier is installed, the measurement accuracy of the flowmeter can reach the correctness level of the calibration.
2 The electromagnetic flowmeter has a high request for the cleanliness of the fluid, and a filter must be installed in front of the flowmeter to ensure the fluid is clean. The filter can be funnel-shaped, its own cleanliness, and the differential pressure change at both ends can be measured.
3 In order to ensure that the liquid passing through the flowmeter is single-phase, that is, air or steam cannot be allowed to enter the flowmeter, and a gas trap should be installed upstream of the flowmeter if necessary. Regarding the easily gasified liquid, it is necessary to ensure a positive back pressure upstream of the flow meter. The back pressure can be taken as twice the pressure drop of the volume sensor at the maximum flow rate and 1.2 times the vapor pressure of the liquid to be measured at the lowest temperature.
3, signal transmission line
In order to ensure that the display instrument is sufficiently sensitive to the pulse signal input by the turbine sensor, the signal to noise ratio is improved. For this reason, various electrical disturbance scenes, namely electromagnetic induction, electrostatic and capacitive coupling, should be avoided in the installation. Therefore, when configuring the signal transmission line, you must pay attention to the following points:
1 Limit the maximum length of the signal line. The maximum length of the signal line is L=dV; where V is the effective value of the input voltage of the sensing coil at the minimum flow rate, mV; d is the coefficient, m/mV, and its value can be: V<1000mV, d=1.0 When 1000 mV<d<5000 mV, d=1.5; when V>5000 mV, d=2.0.
2 Signal transmission lines should be shielded cables to prevent inductive noise from the inside. Request the transmission cable to shield the ground at the display instrument side. The transmission cable can't be close to strong electromagnetic equipment, and it is not allowed to arrange with energy.
4, operation protection
1 When the pipe of the electromagnetic flowmeter needs to be cleaned, it is necessary to open the bypass, and the cleaning liquid cannot pass through the flowmeter.
2 When the pipeline system starts, it is necessary to open the bypass first to avoid the flow rate suddenly increasing, causing the turbine to rotate too much and destroy.
3 The electromagnetic flowmeter bearings should be changed during the current period, and the wear of the bearings can be inspected according to the change of the small flow characteristics.

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