How to Install Electromagnetic Flowmeter?
The electromagnetic flowmeter is a volumetric flowmeter without any moving parts. It is ideal for wastewater applications or any conductive or water-based dirty liquids. The electromagnetic flowmeter is also ideal for applications requiring low-pressure drop and low maintenance costs.
Electromagnetic flow meters are not normally suitable for hydrocarbons, distilled water, and many non-aqueous solutions.
How does an electromagnetic flowmeter work?
Electromagnetic flowmeters use a magnetic field to generate and direct the flow of liquid through the pipe. When a conductive fluid flows through the magnetic field of the flowmeter, a voltage signal is generated. The faster the fluid flows, the greater the voltage signal generated. An electrode sensor located on the wall of the flow pipe receives the voltage signal and sends it to an electronic transmitter, which processes the signal to determine the flow rate of the fluid.
There are three types of electromagnetic flowmeters.
The specific requirements of your application will determine which type of electromagnetic flowmeter is best:
Insertion type electromagnetic flowmeter – best suited to large pipeline applications
In-line electromagnetic flowmeter – best suited to applications requiring high accuracy or higher flow rates
Low-flow magnetic meters – best suited to low-flow applications
How to install an electromagnetic flowmeter?
Installation considerations for insertion type electromagnetic flowmeter.
Choose a location for the sensor where the flow curve is fully expanded and free from any interference. A minimum of 10 pipe diameters upstream and a minimum of 5 pipe diameters downstream is recommended. In some cases, it may be necessary to use 20 times or more the pipe diameter upstream to ensure that the turbulence curve is fully developed. Insertion-type electromagnetic flowmeters are sensitive to air bubbles on the electrodes. If there is any doubt about the absolute filling of the pipe, install the sensor at an angle of 45 to 135 degrees.
Electromagnetic flow sensors are sensitive to the electrical noise present in most piping systems. In plastic piping systems, the fluid carries a lot of static electricity and must be earthed for optimum electromagnetic flowmeter performance. The installation manual contains instructions on how to ground the electromagnetic flowmeter optimally.
Electromagnetic flow meters are susceptible to air bubbles, which can cause the electromagnetic flowmeter to read high. The flowmeter should be oriented to ensure that the flowmeter is filled with water. If there is any question that the pipe may not be absolutely full, install the sensor at an angle of 45 to 135 degrees to avoid compromising the accuracy of the flow measurement.
To make sure the flow meter working stably, improve the measuring accuracy, and not be disturbed by outside parasitic electric potential, the sensor should use an independent earth line—Earthing resistance<10Ω. If the pipeline is plastic or is covered with an insulating coating, the sensor should be equipped with an earthing ring or earthing electrode.
- Ways of earthing on the metal pipe: The internal wall of the metal pipe has no insulating barrier
- Ways of earthing on the plastic pipe or other insulating pipe—use an earthing ring or earthing electrode. Earthing ring should be installed between two flanges at the inlet side of sensors to make the measured mediums connect with the ground, with zero electric potential. Otherwise, electromagnetic flowmeters cannot work normally. Please refer to the following left figure.
Straight pipe requirements for electromagnetic flowmeter
To improve the effects of eddy current and malformation of current fields, there are certain requirements to the length of front and back straight pipe of flow meters. Otherwise, the measuring accuracy will be affected (the power converter can be installed but must avoid being installed near or after the regulation and half-open valve).
|Pipe Installation Types||Installation Instruction |
|Standard- pipe Type|
|Front straight pipe L||Back straight pipe S|
|Bent pipe||Picture a||10D||5D|
|Horizontal pipe||Picture b||5D||3D|
|Backward position of the valve||Picture c||10D||5D|
|Flaring pipe||Picture d||10D||5D|
|Backward position of mercury||Picture e||15D||2D|
|Shrinkage pipe||Picture f||5D||2D|
|Mixed liquid||Picture g||30D||3D|
Requirements to Craft Pipe
Electromagnetic flow meters have certain requirements for upstream and downstream craft pipes. Otherwise, the measuring precision will be affected.
- The inner diameter of upstream and downstream craft is the same as that of the sensor, and it should meet the needs: 0.98DN≤ D≤1.05DN (in the equation DN: inner diameter of the sensor, D: inner diameter of craft pipe)
- Craft pipe and the sensor must be concentric; deviation of the same axis should be no more than 0.05DN
Requirements to by-pass tube
To conveniently examine and repair flow meters, installing a bypass tube for flow meters is better. Additionally, to those heavily polluted fluxes and flow meters need to be cleaned while the flux cannot be stopped, bypass tube must be installed.
- The convenience of examination and repair of flowmeters
- In terms of heavily polluted flux, a by-pass tube must be installed
- Fluid cannot be stopped while the flowmeters need to be cleaned
Installation requirements of flow meters on the pipeline