Electromagnetic Flow Meters: Design Considerations and Solutions

“If you can’t measure it, you can’t manage it.” An often heard quote in industry and particularly relevant to flow measurement. Simply stated, there is an increasing need to monitor more flow and often with more speed and accuracy. There are a few areas where industrial flow measurement is important, such as residential waste. With more and more focus on protecting our environment, the disposal and monitoring of waste is critical as we strive to create a cleaner and less polluted world. Humans are consuming vast quantities of water and this will continue as the world population grows. Flow meters are critical in both monitoring the residential effluent waste as well as being an integral part of the process control system in wastewater treatment plants.

Flow meters also find homes in many industrial control processes, including chemical/pharma, food and beverage, and pulp and paper. Such applications often have the need to measure flow in the presence of high levels of solids—not easily achieved by most flow technologies.

High end flow meters are needed in the area of custody transfer, which deals with the transfer and payment of a product transfer between two parties. An example would be oil transfer through a large pipeline. Here, even a small change in the accuracy of the flow measurement over time can result in significant revenue lost or gained for one of the parties.

Why Is Electromagnetic Induction Technology a Good Fit for Liquid Flow Measurement?

This technology has a number of advantages when it comes to liquid flow measurement. The sensors are generally inserted in line into the pipes’ diameter, and are therefore designed such that they do not disturb or restrict the flow of the medium under measurement. As the sensors are not directly immersed in the liquid—there are no moving parts—there are no wear and tear concerns.

The electromagnetic method measures the volume flow, which means the measurement is insensitive to changes in effects such as fluid density, temperature, pressure, and viscosity. Once the electromagnetic flow meter is calibrated with water, it can be used to measure the other types of conductive fluid—with no additional correction. This is a significant advantage that other types of flow meters don’t have.

Electromagnetic technology is particularly suitable for measuring within a solid-liquid two-phase medium, such as a liquid with suspended dirt, solid particles, fibers, or viscosity within a heavily conductive medium such as slurry. It can be used to measure the sewage, mud, ore pulp, paper pulp, chemical fiber slurry, and other media. This makes it particularly suitable, for example, to the food and pharmaceutical industry, where it can measure the flow of corn syru