Feb. 05, 2020
Case 1: The flow value jitters seriously.
Analysis: There is pump tightly closed to the flow meter on the spot. When the liquid flows through the flow meter, it will be in the turbulent condition, which exists strong interference in measurement. That is why the value of flow meter always jitters.
Solution: Be far away from the pump and choose the straight pipe distance, at least five times of pipe diameter longer, to guarantee the flow steady.
As below is the similar case that is installed closed to valves.
Case 2: The measurement is always not correct. Sometimes ATC alarm and lower limit alarm will occur sometimes.
Analysis: From the picture above, there is half pipe of water inside, which means it isn’t full pipe measurement for electromagnetic flow meters. That is why its measurement is not correct.
Solution: reduce and extend the pipe, let the liquid fulfill the pipe.
Case 3: The electromagnetic flow meters always damage.
Analysis: If installed in the places where there is water immersion risk, the flow meters have to be IP68.
Solution: choose IP68
Why is the installation of electromagnetic flow meters so strict?
1. The measurement principle of electromagnetic flow meters is based on Faraday induction, conducting medium’s cutting magnetic line generates inductive emf, and the signal is collected by the electrodes in the central axis.
That is why the liquid has to be fulfilled in the pipe, otherwise, limit alarm or Atc alarm will occur.
In which conditions will guarantee the liquid is fulfilled in the pipe?
It is surely full pipe in the vertical pipe. It is also full pipe in the horizontal pipe if installed correctly.
2. The flow velocity of liquid through the pipe has to be uniform and stable. Why? The flow measurement is actually the product value of velocity and pipe CSA. Then if velocity is not steady, the flow measurement will jitter.
That is why we choose to install the flow meters as far as possible. Certainly, there has to be long enough straight pipes, whose function is gentling the flow velocity and let the liquid go through the flow meters uniformly and steadily. (5 times of pipe diameter longer upstream and 5 times of pipe diameter longer downstream)