Electromagnetic flowmeter selection

1. Accuracy levels and features

High Accuracy ±0.2% ±0.5% Providing accurate and reliable measurements is critical to process control and optimization.

Accuracy depends on factors such as ambient temperature, length of front and back straight pipe sections, etc. Therefore, selection should be based on product samples and operating conditions. Therefore, selection should be based on a comprehensive comparison of product samples and operating conditions. Electromagnetic flowmeter measurement function is also very different, simple just measuring one-way flow, output analog signal to the control system or instrument display; multi-functional measurement of bi-directional flow, range switching, flow upper and lower limits W: Alarm, empty pipe and power supply cut-off alarm, automatic calibration and self-diagnosis of faults, and the host computer communication and motion configuration. Electromagnetic flowmeter can choose a variety of serial digital communication interface, such as HART protocol, MODBUS RS485, etc.

2. flow rate, full-scale flow rate and caliber

The full-scale flow rate of the electromagnetic flowmeter can be selected within the range of 0.1~12ms liquid flow rate, the range is relatively wide. The upper limit of flow rate is not limited in principle, but it is usually recommended not to exceed 5ms, unless the lining material can withstand the washout of liquid flow.

The caliber of electromagnetic flowmeter ranges from 6 ~ 2200mm. Electromagnetic flowmeter caliber selection.

3. Liquid conductivity

Electromagnetic flowmeter must be used under the premise of conductivity, can not be low threshold, the threshold of the conventional flowmeter is generally 10-4 ~ 10-6 sm, should be based on the model. Organic solvents and petroleum products have a low conductivity, and therefore can not be measured by electromagnetic flowmeter. According to experience, the conductivity of the measured liquid should be at least one order of magnitude larger than the threshold value specified by the instrument manufacturer, otherwise it is easy to cause fluctuations in the measured value.

4. Liquids containing admixtures

When measuring in media containing hard solid particles, attention should be paid to the degree of wear of the sensor lining and to the additional error caused by the expansion of the measuring tube inner diameter. In this case, a ceramic or polyurethane lining with good abrasion resistance should be used. It is also recommended that the sensor be installed in a vertical pipe so that the wear of the pipe will be more uniform, eliminating the disadvantage of severe localized wear in the lower part of the pipe when installed horizontally.

5. Adhesion and deposition

Measurement of fluids easily in the pipe wall adhesion and precipitation of substances, if the adhesion is higher than the liquid conductivity of conductive substances, the signal potential will be short-circuited and can not work, if it is a non-conductive layer should pay attention to the electrode contamination, such as the use of not easy to adhere to the sharp or hemispherical protruding electrodes, replaceable electrodes, squeegee-type scale electrodes and so on.

6. Selection of lining materials

In order to adapt to the measurement conditions of different media, such as fluid medium temperature, pressure, corrosion, wear and other requirements, to choose different lining, electrode materials. If inclined to wear resistance, it is recommended to choose polyurethane rubber material, if inclined to corrosion resistance, it is preferred to choose PTFE material.