Electromagnetic flow measurement


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Electromagnetic flow measurement

  2. 2. Flow measurement is the quantification of bulk fluid movement. Flow can be measured in a variety of ways. It accumulates a fixed volume of fluid and then count the number of times the volume is filled to measure flow.
  3. 3. A magnetic flow meter (mag- meter) is a volumetric flow meter which does not have any moving parts and is ideal for wastewater applications or any dirty liquid which is conductive or water based. Magnetic flowmeters will generally not work with hydrocarbons, distilled water and many non- aqueous solutions). Magnetic flowmeters are also ideal for applications where low pressure drop and low maintenance are required.
  4. 4. The operation of a magnetic flowmeter or mag meter is based upon Faraday's Law, which states that the voltage induced across any conductor as it moves at right angles through a magnetic field is proportional to the velocity of that conductor. •This law states that e= B l v •In of electromagnetic flowmeters, the conductor is the liquid flowing through the pipe, e = B D v
  5. 5. In Magmeter magnetic field is generated using Electromagnets.The magnetic field has to permeate the process liquid through the tube wall, and for that reason the measuring tube should not have ferromagnetic properties.
  6. 6. Electrodes are used over here to sense the EMF generated in the conducting fluid. The electrodes are in direct contact with the process liquid. Their material needs to be adequately resistant to corrosion and must allow good electrical contact with the process liquid. The most commonly used electrode materials are stainless steel grades, Cr-Ni alloys, platinum, tantalum, titanium zirconium.
  7. 7. The Basic components of Electromagnetic flow meter(so called Magmeter) are-  Teflon lined flow tube.  Excitation coils(for generation of magnetic field).  Two electrodes.
  8. 8. •Power usage is relatively low, with electrical power requirements as low as 15 watts for some models. •They are mechanically obstructionless and can be equipped with abrasion-resistant liners, making them effective for measuring slurries and other erosive fluids. • Relatively small amounts of electrode metals are needed for magnetic flowmeters. • They can measure both very low flows and very high volume flow rates, with a minimum diameter of roughly 0.125 inches and a maximum volume of up to 10 cubic feet. • They can usually measure multidirectional flow, either upstream or downstream.
  9. 9. No Moving Parts Very Wide Rangeability Ideal For Slurries Unobstructed Flow Path No pressure drop Flow rate independent of viscosity, temperature, and density Measure dirty liquids with solids Linear output Physical Pressure and Temperature Limits Measure conductive fluids
  10. 10. From this study, the following conclusions can be drawn: • The motion of many fluids, flowing through an electromagnetic flow meter, is not affected by the magnetic field. • The reverse, i.e. charged particles affecting the magnetic field by their motion, can be neglected also. • Most electromagnetic flow meters will be able to measure the exact mean flow rate. • The weight function is non uniform. So local disturbances in the velocity profile can be liable for considerable errors.