The Benefits of Using Electromagnetic Flow Meters

Flow meters are devices used to measure the linear, nonlinear, volumetric, or mass flow rate of a fluid (liquid or gas) moving through a pipeline. These devices are necessary during process operations to ensure consistent product quality, safety, and efficiency. Water, steam, natural gas, oil, and process chemicals are just a few of the fluids monitored continuously by flow meters in various industrial applications.

Not all flow meters are created equal, and no single solution exists for all situations. Endress + Hauser offers a comprehensive range of flow meters to suit the varying needs of any application.

Different fluid properties demand different flow measuring technologies for optimal precision and accuracy. Along with differential pressure or positive displacement flow meters, electromagnetic flow meters are a very common type of flow meter. As their name suggests, electromagnetic models measure flow rates based on the principle of electromagnetic induction.

Features of Electromagnetic Flow Meters

Electromagnetic induction is the production of an electromotive force (voltage) in an electrical conductor through changes in a magnetic field. In short, as a conductive material and a magnetic field move relative to each other, a voltage is generated. This phenomenon is utilized by electromagnetic flow meters to measure the flow of a conductive liquid through a particular section of piping.

Electromagnetic flow meters work by applying a magnetic field across the cross-section of the measuring tube via a pair of electromagnetic coils. Electrodes installed perpendicular to the wall of the tube are used to detect any voltages produced in the system. As the conductive fluid flows in the measuring tube, it passes through the magnetic field to generate an electromotive force, which is detected by the electrodes.

In accordance with Faraday’s law of electromagnetic induction, the voltage generated between the electrodes is directly proportional to the magnetic flux density, the diameter of the measuring tube, and the velocity of the fluid through the magnetic field. This relationship is expressed by the equation: 

img-product-flow
E = kBDv

Where:
k = numerical constant,
B = magnetic flux density,
D = diameter of the measuring tube,
V = flow velocity between the electrodes.

In other words, the greater the flow velocity, the higher the voltage produced between the electrodes.

Based on the laws of electromagnetic induction, the fluid must be conductive in order to produce electricity through the magnetic field. This means that electromagnetic flow meters cannot be used with nonconductive fluids such as some hydrocarbons, alcohols, nonaqueous solutions, and deionized water.

Benefits of Electromagnetic Flow Meters

One of the key benefits of these types of flow meters is the absence of moving parts. The electrodes/sensors are installed in-line into the pipe’s diameter; therefore, they do not obstruct or restrict the flow of the fluid being measured. The lack of moving parts significantly reduces maintenance requirements as there are no wear-and-tear concerns.

Also, since electromagnetic flow meters measure the volume flow, the results obtained by the device are not affected by changes to other fluid properties such as density, temperature, pressure, and viscosity. This means an electromagnetic flow meter calibrated with water can be used to measure any other type of conductive fluid without additional correction or calibration.

Electromagnetic flow meters can also be used to measure flows in liquids containing contaminants and inconsistencies such as solid particles, air bubbles, and fibers. The flow measurement is dependent solely on the movement of charged particles through the electrodes, making this method suitable for liquids such as wastewater, mud, fruit juice, or paper pulp.

Working With Electromagnetic Flow Meters

Electromagnetic flow meters are ideal for highly precise flow measurements in specific fluids that would otherwise be unachievable with other flow measurement technologies. It should be noted, however, that since these meters rely on the principle of electromagnetic induction, they are limited to utilization with conductive fluids only.

Endress + Hauser has sold more than two million electromagnetic flow meters since 1977. To learn more about our electromagnetic flow meters, and how they can improve your operation, please contact us.

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