Electromagnetic flow meters is a volumetric flow meter that measure the voltage created when conductive liquids move through a magnetic field. It can measure liquid such as sewage, paper pulp, slurry and mineral slurry which has an electrical conductivity greater than 5 μS/cm. In order to obtain consistent and accurate flow measurement, it is important to understand and meet the installation requirements. Here are some installation requirements and guidelines:
Low Conductivity Medium
Electromagnetic flow meters will not work with:
- Hydrocarbons: Refers to an organic chemical compound that is composed exclusively of hydrogen and carbon atoms. Hydrocarbons are are highly combustible and form the basis of crude oil, natural gas, coal, and other important energy sources.
- Distilled water: Distilled water is water that has been boiled into steam and then, through cooling, reverted back into a liquid state and collected.
- Non-aqueous solutions: The solution in which any liquid other than water acts as a solvent is called non-aqueous solution. Common examples are benzene, alcohol, ether, carbon disulphide, acetone etc.
- Deionized water: Also known as demineralized water, is water wherein all of its mineral ions, such as sodium, iron, calcium, copper, chloride, and sulfate, are removed.
Installation Location
Flow meter should be installed away from external interference eg. currents, static electricity, electromagnetic waves, magnetic fields, etc. on the pipeline.
Flow meter should be installed in a dry and ventilated place, with sufficient space for installation and maintenance in the future.
Pipe Configuration
Flow meter should always be filled with the medium all the time. Direction of the medium is the same as direction of the flow meter. Flow disturbances (distortion and swirl) can occur if the flow meter is installed incorrectly.
Straight pipe length requirement is 5DN length of piping upstream and 3DN downstream from the meter (measured from the center of the tube).
Mounting
- Horizontal mounting: Flow meter must not be mounted at the highest point of the pipe system or in free outlets, where gravity could empty or partially empty the pipe.
- Vertical mounting: When flow meter is mounted vertically, the flow direction should always be upwards. This will ensure pipe is always full and reduce bubbles significantly.
Flow direction for vertically mounted flow meter should not be downwards in front of a free outlet where gravity could partially empty the pipe. The “waterfall” effect in the pipe could result in pockets of air, and this would cause poor meter reading. - Pump/Valve installation: In a longer pipe system, a pump should be installed at the upstream of the flow meter. A cut off valve should be installed at the downstream of the flow meter.
- To avoid negative pressure, the flow meter should not be installed at the suction side of the pump (pump inlet).
Grounding Connection
Grounding connection helps eliminate electrical noise or interference that affects the measurement accuracy of the flow meter.
Establishing a process ground is one of the most important installation details. Proper process grounding ensures that the sensor and medium are at the same potential so that only the induced flow signal is measured.
Tightening Torque
Check maximum tightening torque [Nm] before installation. Over-tightening may cause deformation or fractures. Under-tightening risk leakage and vibration.
