Electromagnetic Flow Meters are based on FARADAY'S LAW INDUCTION. These meters are also called as Magflow or Electromagnetic Flow Meters. A magnetic field is applied to the metering tube, which results in a potential difference proportional to the flow velocity perpendicular to the flux lines.
The physical principle at work is Electromagnetic Induction and mathematically defined as E=k*B*D*V. where,
- E = Induced Voltage (Linear with velocity)
- K = Proportionality Constant
- B = Magnetic Field Strength (Coil Inductance)
- D = Distance between electrodes
- V = Velocity of process fluids
The induced voltage (E) is directly proportional to the velocity (V) of the fluid moving through the magnetic field (B). The induced voltage is carried to the transmitter through the electrode circuit. The transmitter then converts this voltage into a quantifiable flow velocity. The volumetric flow rate of the fluid is calculated using this known velocity along with the area of the pipe.
When a flowmeter is installed and activated, its operations begin with a pair of charged magnetic coils. As energy passes through the coils, they produce a magnetic field that remains perpendicular to both the conductive fluid being measured and the axis of the electrodes taking measurements. The fluid moves along the longitudinal axis of the flowmeter, making any generated induced voltage perpendicular to the field and the fluid velocity. An increase in the flow rate of the conductive fluid will create a proportionate increase the voltage level.
The meter features flanged construction and is available with choice of liner and electrode material. All meters consist of a sensor and a converter that may be mounted integral to the sensor or remotely either with a field mount kit.
Selection of Flow meter type
- Integral type and Remote type displaying Flow Rate & Totaliser on same Screen / Display Unit
- Integral type compact structure can observe the Flow on site on the pipeline without wiring etc.
- Remote type in harsher applications, such as high temperature fluids, environments, open space, pipe line at high.
- Line Size: DN 25 – DN 3000 mm
- Nominal Pressure: 0.6 - 1.6 Mpa (2.5Mpa/4.0Mpa/6.4Mpa…Max 42Mpa)
- Accuracy: +/-0.5%(Standard)
- Liner: PTFE, Hard Rubber
- Electrode: SS 316L, Hastelloy C, Tantalum
- Type : Integral type, Remote type with 10 mtr. cable
- Medium Temperature: -20~+80 deg C (Integral type)
- Remote type (Hard Rubber) -10~+80degC Remote type (PTFE) -10~+160degC
- Ambient Humidity : 5-100%RH (relative humidity)
- Conductivity: >15us/cm
- Protection Class : IP65 (Standard); IP68 (Optional for remote type)
- Process Connection: Flange (Standard), Wafer, Thread, Tri-clamp etc (Optional)
- Output Signal: 4-20mA (Standard) / Pulse (Optional)
- Communication : RS485(Standard),GPRS/GSM (Optional)
- Power Supply: Integral - 24 V DC , AC 220V Remote - 24 V DC (Standard) , SMPS AC 220V (Optional)
- Power Consumption: <20W
Main Performances of the Electrode Materials
Applicable in Water, Sewage and Low corrosive medium
Be resistant to oxidable acid such as nitric acid, mixed acid as well as oxidable salt such as Fe+++,Cu++ and sea water
Having strong resistance to corrosive mediums that is similar with glass. Almost applicable in all chemicals mediums except for hydrofluoric acid, oleum and alkali
- The obstruction to the flow is almost nil and therefore this type of meters can be used for measuring heavy suspensions, including mud, sewage and wood pulp.
- There is no pressure head loss in this type of flow meter other than that of the length of straight pipe which the meter occupies.
- They are not very much affected by upstream flow disturbances.
- They are practically unaffected by variation in density, viscosity, pressure and temperature.
- Electric power requirements can be low (15 or 20 W), particularly with pulsed DC types.
- These meters can be used as bidirectional meters.
- The meters are suitable for most acids, bases, water and aqueous solutions because the lining materials selected are not only good electrical insulators but also are corrosion resistant.
- The meters are widely used for slurry services not only because they are obstruction less but also because some of the liners such as polyurethane, neoprene and rubber have good abrasion or erosion resistance.
- They are capable of handling extremely low flows.
- These meters can be used only for fluids which have reasonable electrical conductivity.Accuracy is only in the range of ± 1% over a flow rate range of 5%.
- The size and cost of the field coils and circuitry do not increase in proportion to their size of pipe bore. Consequently, small size meters are bulky and expensive.
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