The magnetic flow meter market is one of the largest among flow meters, namely because of the large installed base of magmeters worldwide. They were first introduced for commercial use in 1952, years before Coriolis (1977), ultrasonic (1963) and vortex (1969). Because they were introduced so early, these meters have had more time to penetrate markets in Europe, North America and Asia.

Liners Available in Many Different Types

One growth factor for magnetic meters is the availability of many types of liners, including  dominant liners such as PFA, PTFE and hard rubber. These liners increase the durability and reliability of magnetic flow meters and make it possible to use them with almost any type of liquid. No other flow meter that measures liquids has such versatility when it comes to the material in the flow meter that makes contact with the liquid.

The variety of liner types also makes these meters especially attractive for the pharmaceutical, food & beverage and chemical industries, which often require sanitary linings. Some caustic chemicals require highly durable linings that can withstand contact with these types of liquids. Magnetic flow meters are also very popular in the water and wastewater industry, where they can handle both clean and dirty water applications.

Companies Improving Magnetic Flow Meter Technology

Although magnetic meters boast strong applications for liquids, they cannot measure nonconductive liquids, barring their use in the oil & gas and refining industries without an unforeseen technological breakthrough. However, suppliers have succeeded in reducing the amount of conductivity required to measure flow with a magnetic meter. To do so, they have boosted the amount of power used to excite the magnetic coils, creating a stronger signal. By pushing back the boundaries of conductivity, suppliers are making magnetic meters usable in a broader range of applications.

Other technological advances are developing related to electrical currents. Magnetic flow meters generate a magnetic field when AC or DC electric current passes through wound wire coils contained within the magmeter. As a result, its classification as AC or DC refers to the current in the coils, not necessarily the type of current that powers the meter. When the meters were first introduced, they were primarily AC. Because of noise and additional voltages that may be present in the environment of the meter, these meters need to be zero-calibrated. To do this properly, the meter needs to be full of process fluid and at a no-flow condition. Some users had difficulty with this calibration process, and as a result, they found unsatisfactory results from their magnetic meters.

Partially because of the noise and calibration issues with AC types, suppliers introduced pulsed DC meters that do not require zero calibration and handle noise better. Still, AC magnetic meters are far from an outmoded technology. In reality, AC varieties are better able to handle certain types of difficult applications that include slurries and liquids with solids content. DC meters, on the other hand, excel with cleaner liquids.

For more information about Flow Research’s work on magnetic meters, visit www.flowmags.comJesse Yoder, Ph.D., is president of Flow Research Inc. in Wakefield, Massachusetts, a company he founded in 1998. He has 28 years of experience as an analyst and writer in instrumentation. He holds a U.S. patent on a dual-tube meter design and is the author of The Tao of Measurement, published by ISA. Dr. Yoder also founded the Flowmeter Recalibration Working Group, addressing the topic of recalibration frequency. He may be reached at jesse@flowresearch.com.