Introduction to specific measurements of electromagnetic flowmeters

As one of the measuring instruments commonly used in industry, electromagnetic flowmeter can effectively measure and calculate the data you want.

At the same time, the measurement accuracy level and functions of the electromagnetic flowmeter can be selected according to the measurement requirements and usage occasions, so as to be truly economical and cost-effective.

For example, when used for trade settlement, product handover and energy measurement, a higher accuracy level should be selected, such as level 1.0, 0.5, or higher;

For process In control situations, choose different accuracy levels according to the control requirements;

Some are just measuring and detecting the process flow. In situations where precise control and measurement are not required, you can choose a slightly lower accuracy level, such as 1.5, 2.5 level, even level 4.0.

This series of electromagnetic flow meters are good helpers for measurement in industry, agriculture and other industries. You can choose it according to your specific needs.

1. The electromagnetic flowmeter measures liquid containing bubbles

The tiny bubbles mixed into the bubble flow can still work normally, but the mixed volume flow rate containing the bubble volume is measured;

If the gas content increases to form a bullet (block) flow, the electrode may be covered by the gas, causing the circuit to be instantly disconnected, resulting in output shaking or even failure to work properly.

2. Electromagnetic flowmeter measures solid-liquid two-phase flow liquids

Solid-liquid two-phase fluids containing non-ferromagnetic particles or fibers can also measure the volume flow rate of the two phases. Fluids with high solid content, such as drilling mud, drilling cement slurry, paper pulp, etc., are actually non-Newtonian fluids.

Since the solid flows together in the carrier liquid, there is sliding between the two, and there is a difference in speed. If the single-phase liquid calibration instrument is used for solid-liquid two-phase fluid, additional errors will occur.

There are reports abroad that the error is within 3% when the solid content is 14%; the test report of the Water Conservancy Science Institute of the Yellow River Water Conservancy Commission in my country said;

Measuring water with high sand content The flow rate, sand content volume ratio is 17% to 40% (sand median particle size is 0.35mm), and the instrument measurement error is less than 3%.

If larger particles in the slurry rub against the electrode surface, peak-like slurry noise will be generated in the electromagnetic flowmeter with low frequency rectangular excitation, making the flow signal unstable;

It is necessary to choose a higher frequency instrument or an instrument with a strong ability to suppress slurry noise. You can also choose an instrument with mains AC excitation or a dual-frequency excitation instrument.

3. Electromagnetic flowmeter measures liquids containing ferromagnetic substances

For ordinary electromagnetic flowmeters, the magnetic permeability in the measuring tube is affected by the difference between ferromagnetic substances and ferromagnetic substances. Changes in content will cause measurement errors.

However, the electromagnetic flowmeter EMF with magnetic flux detection coil compensation is placed in the magnetic circuit. Can reduce the influence of mixed ferromagnets.

The test report shows that the water contains iron ore concentrate with a liquid-to-solid weight ratio of about 4:1 and a particle size of ≤0.15mm.For slurry, use an 80mm caliber instrument to conduct a comparative flow test between clean water and slurry;

Usually the indicated value of the instrument changes by 7% to 10%. For instruments equipped with magnetic flux detection coils, the indication error is ±2%Fs Within.

4. Electromagnetic flowmeter measuring slurry

For the application of slurry containing ore particles, attention should be paid to the degree of wear of the sensor lining. The expansion of the inner diameter of the measuring tube will produce additional errors.

In this case, a ceramic lining or polyurethane rubber lining with better wear resistance should be used. It is also recommended that the sensor be installed on a vertical pipe to make the pipe wear even and eliminate the shortcomings of serious local wear in the lower half of the horizontal installation. .

A nozzle-shaped sheath can also be installed at the inlet end of the sensor to extend the service life.