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Mag Flow and Magflow Elements: Obstructionless Electromagnetic Volumetric Metrology

Quick Answer: Mag flow meters measure conductive liquid volume without moving parts or inline obstruction. Silver Automation Instruments supplies these meters for water, wastewater, chemicals, food, and marine lines from DN15 to DN3000. Send your pipe size, flow range, fluid conductivity, temperature, and pressure for a matched model and price.

Mag flow meters rely on electromagnetic induction. The flow tube generates a magnetic field. Two electrodes measure the voltage created by the moving conductive fluid. That voltage is proportional to volumetric flow. There is no orifice, no gear, and no turbine inside the pipe. This is why engineers call it an obstructionless electromagnetic volumetric measurement method.

In practice, the meter works best with water, acids, slurries, and any fluid with conductivity above 5 µS/cm. Oils, solvents, deionized water, and most gases do not work with this technology. So we ask about conductivity early in the selection process. It saves time and avoids a wrong quote.

What Are Magflow Elements in a Mag Flow Meter

Magflow elements are the parts that make the measurement repeatable. The key elements are the flow tube, liner, electrodes, excitation coils, and the transmitter. The flow tube can be carbon steel or stainless steel. The liner protects the tube from corrosion. Common liner materials are PTFE, hard rubber, and polyurethane. Electrodes pick up the induced voltage. Electrode materials include 316L stainless steel, Hastelloy C, titanium, tantalum, and platinum iridium.

The excitation coils create the magnetic field. The transmitter converts the electrode signal into a 4-20 mA HART output, a pulse output, or a Modbus RTU signal. Most engineers skip this part during initial sizing. But the liner and electrode material selection decides the meter life in aggressive fluids. We have seen this on customer sites many times. A cheap natural rubber liner fails fast in hot caustic, while PTFE works fine up to 150 °C.

Obstructionless Electromagnetic Volumetric Metrology in Real Plants

A desalination plant in Saudi Arabia uses DN500 rubber lined mag flow meters on the seawater feed line. The meters run at 2.1 m/s and send 4-20 mA signals to the control room. There is no pressure drop across the meter. For reverse osmosis brine, the plant uses Hastelloy C electrodes and PTFE liners. Brine conductivity is above 50,000 µS/cm, so signal strength is excellent.

A water treatment contractor in Surabaya, Indonesia installed DN300 mag flow meters for raw water intake. The specification was simple. Accuracy is 0.5 percent of reading. Electrodes are 316L. Liner is hard rubber. The transmitter is remote mounted with IP68 protection. The line pressure was 6 bar. The meter body had no moving parts. Maintenance was limited to annual electrode cleaning.

For chemical dosing in a paint plant in Binh Duong, Vietnam, we supplied DN15 and DN25 mag flow meters with PTFE liners and tantalum electrodes. The fluid was a water based titanium dioxide slurry. Flow range was 0.3 to 3.0 m/s. The customer wanted a fast batch pulse output. We configured the transmitter for 100 pulses per liter. That made batching easy for the PLC.

Which Mag Flow Meter for Your Application

Silver Instruments offers two common mag flow configurations. The SA-MAG 2100 is a compact electromagnetic flow meter for water, wastewater, and utility lines. It suits DN15 to DN600. Accuracy is 0.5 percent of rate. Liner options include hard rubber and PTFE. Electrode options include 316L and Hastelloy C. Process temperature can reach 120 °C for hard rubber and 180 °C for PTFE.

The SA-MAG 4100 is a remote transmitter model for harsh or hard to reach installations. It covers DN15 to DN3000. It supports 4-20 mA HART, pulse, RS485 Modbus, and optional Profibus D