What Is Magnetic Flow Meter?
The magnetic flow meter is a transducer device that measures the fluid flow using the voltage induced due to that fluid flow across a magnetic field. A magnetic flow meter is also known as an electromagnetic flow meter or a magmeter. The magnetic field is established inside the metering tube, which creates a potential difference that is proportional to the velocity of the fluid flow and upright with the flux lines.
The working principle of the magnetic flow meter is based on electromagnetic induction. A magnetic flow meter needs a conducting liquid like water with ions and an electrically insulated pipe covering like a steel tube with rubber lines to function accurately.The potential difference created inside the tube is difficult to differentiate from the induced potential due to the liquid flow for the constant magnetic field path, electrochemical reaction, and other effects.
The magnetic field is permanently reversed in the modern meters to show the difference; this cancels the electromagnetic voltage difference and never changes its direction with the magnetic space. It furthermore discourages using PM ( permanent magnet ) in the magnetic flow meter.
How Magnetic Flow Meter Works?
The magnetic flow meters work on Faraday's law of electromagnetic induction, which says when a conductor moves through a magnetic field, a voltage will be induced in it.
The magmeters or electromagnetic flow meters consist of a sensor and a transmitter that work together to measure the liquid flow. The sensor of the magnetic flow meter is set up in line with the fluid flow and measures the induced voltage created during the fluid flow through the pipe.
The transmitter part of the meter conveys the voltage generated by the sensor, then changes the voltage into flow measurement, and finally transmits the flow measurement to the installed control system.
Magnetic Flow Meter Installation Guidelines:
The flow detector sensor of the magnetic flow meter should be installed in a place free from hindering devices like pumps, TS, valves, bends, etc., to secure a laminar flow of the liquid towards the flow sensor.
That is why the flow sensor should be installed inside a straight pipe. The minimum distance of sensor placement from the hindering devices should be (3×DN upstream) and ( 2×DN downstream).
Note: All valves should be installed on the downside of the sensor.
If you need to utilize reducers, the inner slope should not exceed a 7.5° angle. You can use the below formula to check the minimum length required to maintain an angle below 7.5°.
Formula
L = (D-d)×7.63
Where d= the small diameter and D= the big diameter of the reducer.
How To Check Magnetic Flow Meter?
Regular checking of the magnetic meter is necessary for some installation. A visual inspection is the first step to finding the defective magnetic flow meter. The various parameters and readings of the magnetic flow meters should fit the plant standards. The necessary elements for proper meter functioning are the coil resistance of the sensor, grounding resistance, and insulation resistance between the signal cables. However, the verification process is performed through a verification tool provided by the magnetic flow meter manufacturing company in the following method:
Step 1: First, you need to check out the authentic tag and the serial number of the flow meter. Then place the verification tool around the converter of the flow meter.
Step 2: After that, switch off the converter's power supply. Then open the software provided with the meter by the manufacturer and select the connected flow meter. The validation tool will automatically collect all of the relevant data.
Step 3: Perform a reconnection test after the verification. You must turn off the power supply of the flow meter converter and disconnect all of the wires from the converter.
Step 4: The above steps will set the magnetic flow meter at starting condition. In this step, you have to reconnect the cables again. Press on the reconnection tab to generate a detailed statement of the process.
Step 5: At last, turn on the device with which the magnetic flow meter is connected to start the regular flow meter operation again.
Where Magnetic Flow Meter is Used?
The magmeter is one kind of volumetric flow gauge which has no moving parts, so it is suitable for measuring wastewater and other dirty fluid flow measurement which is conductive.
The performance of the magnetic flow meter is not curtailed due to material properties such as viscosity, corrosiveness, density, pressure, alkalinity, and acidity. So the meter can calculate the flow of fluids, water slurries, pastes, wastewater, dairy, chemical, fertilizer, pharmaceutical, medical, iron, mining, steel, paper, and agricultural enterprises. They are also used in power plants and steel plants to calculate cooling water flow. They can measure the flow of sludge, clean water, effluent, etc., in environmental and pollution control.
Why Magnetic Flow Meter Need Grounding?
The grounding is essential to confirm that the fluid and the sensor are at the same voltage or potential. The potential stability ensures the meter will only measure the induced flow signal. The magmeter grounding arrangement depends primarily on the type of pipe in which the meter is installed.
There are two types of magmeter grounding, I.e., grounding by ground rings and by ground electrodes. Magnetic flow meter ring grounding is essential for some users who usually don't measure sharp corrosive media and use nonmetallic pipes. For those users, ring grounding is a must.
Ring grounding is also essential for electromagnetics. In general, a grounding ring is used in a nonmetallic piping system. The grounding ring is suitable for nonmetallic pipelines. The grounding ring is not used in the metallic pipeline because it is expensive. In strong corrosive metallic channels, three electrodes are used to replace the grounding ring.
Two electrodes work for measuring, and one for grounding. In this process, fasten the flow meter flange with the pipeline and ground it. This method is also suitable for large-diameter systems because the large diameter needs the most extensive and costly grounding rings.
What is K Factor in Magnetic Flow Meter?
The K-factor of a magnetic flow meter is the way of liquid flow measurement that flows through the meter and is assigned by the manufacturer. K-factor is the number of vibrations or pulses determined per volumetric unit of liquid going through a magnetic flow meter. It is generally experienced when negotiating with a pulse signal.
K-factor value 100 means 100 pulses are created for each gallon of liquid.
