Reasons for bubbles appearing in the use of electromagnetic flowmeter

Electromagnetic flowmeter is a common flow meter, which is widely used in industry. It can measure the flow of acid, alkali, salt solution, water, sewage, corrosive liquid, mud, ore pulp, paper pulp and other fluids with conductivity ≥5μs/cm. However, there will be a lot of bubbles in the process of measuring liquid, which often leads to errors in flowmeter measurement and affects its use.

Generally, the fluid measured by electromagnetic flowmeters will contain some bubbles. If these bubbles are evenly distributed, they will not affect the measurement. However, once the bubbles become larger, they can cover the entire electrode when rubbing against the electrode, causing the flow signal input circuit to open instantly, resulting in the output signal shaking.

How to judge whether the measurement error of electromagnetic flowmeter is caused by bubbles in the measured liquid? How to deal with this situation? Let us briefly introduce it.

When the measurement results show fluctuations, immediately cut off the excitation circuit current of the magnetic field. If the instrument still has a display and is unstable at this time, it means that it is mostly caused by bubbles.

After determining that a large number of bubbles affect the measurement results of the electromagnetic flowmeter, relevant solutions must be found. If it is determined that a large number of bubbles are caused to merge into the liquid due to the installation position, such as the electromagnetic flowmeter is installed at a high point in the pipe system and the stored gas or the air inhaled from the outside causes the flowmeter to shake, changing the installation position is the most effective solution.

However, in many applications, the diameter is large or the installation position is not easy to change. It is recommended to install a gas collection bag and an exhaust valve upstream of the electromagnetic flowmeter to remove excess gas, reduce the factors that affect the measurement results, and ensure the accuracy of the measurement.