Electromagnetic flow meter is a flow meter widely used in industrial production. It measures the flow of liquid or gas through the principle of electromagnetic induction. Although it has the advantages of accuracy, reliability, and stability, it also has some situations where it is not applicable. This article will discuss the situations in which electromagnetic flow meter are not applicable from the following aspects.

Measurement of small or extremely trace flows

The measurement range of the electromagnetic flow meter is usually between 0.1~10m/s. For the measurement of small flow or extremely trace flow, the sensitivity of the electromagnetic flow meter is insufficient, and large measurement errors may occur. At this time, other measurement methods can be considered, such as mass flow meters, positive displacement flow meters, etc.

There are bubbles, particles and other impurities in the liquid medium

When impurities such as bubbles and particles exist in the liquid medium, these impurities may block the measurement pipe or electrode of the electromagnetic flow meter, resulting in a decrease in measurement accuracy or measurement failure. At this time, other flow meters suitable for measuring impurity-containing media can be used, such as ultrasonic flow meters, Vortex flow meters, etc.

Not applicable for measuring pipe dimensions

Electromagnetic flow meter are usually suitable for measuring the flow of liquid or gas in pipes with diameters ranging from 10mm to 2000mm. When the pipe size is too large or too small, the measurement accuracy of the electromagnetic flow meter will decrease. At this time, you can consider using other flow meters suitable for large or small size pipes, such as differential pressure flow meters, thermal flow meters, etc.

Not applicable for measuring the conductivity of the medium

Electromagnetic flow meter measure flow based on the conductivity of liquid or gas. When the conductivity of the medium is not within the applicable range of the electromagnetic flow meter, the flow cannot be accurately measured. At this time, you can consider using other flow meters suitable for measuring low or high conductivity media, such as capacitive flow meters, thermal flow meters, etc.

Not applicable to the temperature and pressure of the measuring medium

The measurement accuracy of the electromagnetic flow meter is affected by factors such as the temperature and pressure of the medium. When the temperature and pressure of the medium exceed the applicable range of the electromagnetic flow meter, its measurement accuracy will be adversely affected and may even lead to measurement failure. Therefore, in practical applications, it is necessary to select an appropriate electromagnetic flow meter based on the characteristics of the medium and working conditions to ensure the accuracy and reliability of its measurement.

For media whose temperature exceeds the range, the main influencing factors are the thermal expansion coefficient and thermal distortion of the internal components of the electromagnetic flow meter, as well as the sensitivity of the electromagnetic flow meter to the medium temperature. Generally speaking, the applicable temperature range of electromagnetic flow meter is -20°C~+60°C. If the temperature of the medium exceeds this range, other flow meter suitable for high-temperature media need to be used, such as thermal flow meter, Vortex flow meter, etc.

For media whose pressure exceeds the range, the main influencing factors are the strength and stability of the internal components of the electromagnetic flow meter, and the sensitivity of the electromagnetic flow meter to the medium pressure. Generally speaking, the applicable pressure range of electromagnetic flow meter is 0~4MPa. If the pressure of the medium exceeds this range, other flow meter suitable for high-pressure media need to be used, such as differential pressure flow meter, ultrasonic flow meter, etc.

In addition,Electromagnetic flow meter may not be suitable for special media such as corrosive media, high-viscosity media, and media that are prone to crystallization.The special properties of these media will cause corrosion, wear and other damage to the internal components of the electromagnetic flow meter, thus affecting its measurement accuracy and lifespan. At this time, it is necessary to select an appropriate flow meter according to the characteristics of the medium to meet the actual measurement requirements.

When choosing an electromagnetic flow meter,The flow state of the medium also needs to be considered. For low speed, small flow, closed pipeline, etc., the measurement accuracy of the electromagnetic flow meter will be greatly affected, so other suitable flow meter need to be used. In addition, for pipes with smaller diameters, electromagnetic flow meter may not be suitable because their measurement accuracy will be affected by flow field disturbances, resulting in large measurement errors.

In short, as a widely used flow meter, electromagnetic flow meter has many advantages, such as high measurement accuracy, fast response speed, high reliability, etc., and is suitable for many occasions. However, there are some limitations and exclusions that need to be noted. When using an electromagnetic flow meter, comprehensive consideration needs to be given to the properties of the medium, flow range, pipe size, environmental conditions, etc. to ensure its normal operation and accurate measurement. Electromagnetic flow meter can only perform optimally if these limitations and requirements are understood and followed.