What is a magnetic flow meter, and how it works?

As the name suggest it is a measuring instrument, used for determining the flow of any liquid in a pipe. Since, it is based on the Law of Electromagnetic Induction as incepted by Faraday; it is referred to as Magnetic or Mag Flow Meter. It generates a magnetic field and channels it into the liquid flowing through the pipe.

The flow of liquid creates voltage signals that are sensible for the electrodes integrated on the tube walls. When the flow of conductive liquid increases, it will instantly result in greater voltage, which also justifies the Faraday's law that says generated voltage is directly proportional to the speed of flowing liquid. Then there is an electronic transmitter also, which is integrated with the instrument to process the voltage signals for determination of liquid flow in a quantitative manner.

Consideration to be made while using magnetic flow meter

One can easily measure the velocity of any fluidic substance like water, caustic, slurries, acids etc by using Magnetic flow meter. However it should be a conductive liquid having electric conductive of more than 5 EC. On the other hand, liquids with lower electric conductivity, like hydrocarbons, de-ionized water, and boiler feed water should be used with a lot of care. Because of low conductivity, the flow meter can get turned off or show zero flow with these types of liquids.

There is an advantage with magnetic flow meter that you can use it to measure pure, corrosive, dirty, as well as abrasive liquids, because it doesn't offer any obstruction in the flow. However, if you are looking to use it with gases and hydrocarbon liquids, then it is totally worthless, as they are non-conductive in nature.

Mag flow meter can be mounted in the short meter run, as it doesn't require a great deal of upstream or downstream straight run. From the plane of electrodes, 3 to 5 times of dia. of up-stream and 0 to 3 times of dia. of down-stream straight run is enough for this instrument.

Usually, this flow meter is used, where the liquid is fed in the tube by the use of gravity. You have to make sure that the orientation of magnetic flow meter is managed in such a way that the instrument is completely filled with the liquid. In case, you failed to ensure these two important things, you must be ready to deal with inaccurate readings from the flow meter.

You have to be more attentive, while using the magnetic flow meter in the vacuum services. There are more possibilities of instrument collapse in such circumstances. If the instrument got sucked in the pipe during vacuum service it can easily cause catastrophic damaging of the flow meter. On the other hand, if the instrument is working with excessive temperature of the liquid, then there are very high chances of permanent damaging in the magnetic flow meter.

Cautions with the instrument

• Magnetic flow meter is a volumetric measuring instrument; that's why you must ensure its proper placement, before using it.
• Make sure about the conductivity of liquid whose flow has to be determined. The meter will not work with DE-ionized water and hydrocarbons, as it is compatible with liquids having conductivity of 5 EC or more.
• Allowance should be given for the change in composition of liquid.
• In typical cases the maximum flow measurable with this instrument is 2 or 3 m/sec. it’s essential to consider the points, which differential pressure restraints, as well as, states of flow-tube that can make the application of common guideline unacceptable.

This post is contributed by SpireMT, a leading supplier of Magnetic Flow meters,Handheld Ultrasonic Flow Meter, digital flow meters, water flow meter,wireless telemetry systems and many more. For more information visit at http://www.spiremt.com