A magnetic flow meter is also known as mag
meter or electromagnetic flowmeter is a flow transducer that measures the flow
of fluids by sensing the voltage produced by the fluid. It is, In fact, EM flow
meter is a volumetric flow meter that can be used for clean water and
wastewater management and other wide range of applications. A magnetic water
meter is, therefore, an industrial flow meter used for differential flow
measurement.
The instrumentation of the magnetic water
flow sensor consists of a pipe through which the liquid flows. Two electrodes
are installed at the end walls of this cylindrical pipe and these electrodes
are connected to an electric transmitter. Also, a device used for the
generation of a magnetic field is installed exteriorly in the direction of the
flow of liquid. The size of electromagnetic flow transmitter ranges from 0.125 to
79 inches with a velocity between 0.5 to 10 m/s. Mag flow water meter can be
inline electronic water meter or insertion type electromagnetic flow meter.
Mag flow water meter Principle
Mag flow meter makes use of Faraday's law
of electromagnetic induction as a general principle to measure fluid flow. A
magnetic field is manually applied to a liquid or fluid flowing through a pipe.
If the flowing liquid is a conductor, it follows the Faradays law to measure
the flow. The flow of the conducting fluid through a pipe will create a voltage
difference across the pipe. This voltage is sensed by the two electrodes placed
at the end of the flow tube walls. Now according to Faraday's law, the voltage
generated is directly proportional to the fluid flow, therefore, the greater is
the flow or velocity of the fluid, the more voltage will be generated sensed by
the measuring electrodes. The electrodes are connected to an electronic
transmitter that finds the value of fluid flow.
Magnetic water flow meter Applications
Electromagnetic flow meters have large
applications, because it can choose different lining material and electrodes
material to suit different applications, no matter clean water or dirty water, magnetic
flow metre can all work.
Magnetic flow meter has higher efficacy for
corrosive conditions like abrasives and slurries, it also has a lot
applications in water or wastewater industries primarily. This water management
involves flow measurement of clean water like tap water, drink water, portable
water or dirty water, like effluent water and saline water of seas,
acid
corrosive water.,etc. The water treatment plants use this flow meter to measure
both treated and untreated waste and water and chemical processing. Other less
common uses involve food and beverages, chemical industries, paper, and pulp
industries and other pharmaceutical and mining industries. Although they are
not applicable to oil and gas they are less commonly used in oil and gas
industries for the support of processes.
Pros and cons
These flow meters are 23 % of the total
sold flow meters. However, they also come up with certain pros and cons. These
magnetic flowmeters cannot be used in non-conductive water, like DI water, RO
water, condensate, On the other hand, oils and other non-conductive
fluids are not applicable for measurement. Magnetic water flow meters are accurate.
And the active measurement of less expensive fluids like water is possible with
greater efficacy. Thus they are employed mostly for sanitary use. Lack of
pressure drop and availability of greater line size is another one of its
significance.
Precautionary use
Full bore electromagnetic flow meter is
only used for the fluids that have electrical conductivity of 5μS/cm therefore
liquids with lower conductivity measure zero flow. The obstruction to fluid
flow is almost null so it can be used for sanitary, clean, dirty and corrosive fluids.
Good care is needed to use these flow meters in vacuum services because of the
risk of collapse and damage to the flow meter. While measuring the flow, make
sure that the meter is filled completely with fluid otherwise the precision of
measurement is affected. The vacuum condition and excessive temperature can
damage the meter so these conditions should be avoided.
