Measurement of electromagnetic flowmeters in a partially filled pipe

In theory, an electromagnetic flowmeter cannot do it.

Personally, I think it’s impossible to achieve a non-full pipe

Electromagnetic flowmeters cannot meet the installation and usage requirements; these requirements can be satisfied by simply changing the pipe layout!

It’s hard to say; it definitely won’t work. An electromagnetic flowmeter actually measures the flow velocity, which is then converted into volumetric flow rate based on the cross-sectional area. According to the principle of electromagnetic induction, the induced electromotive force is proportional to the flow velocity, with the formula U=BLV. Here, L represents the inner diameter of the pipe when it’s completely filled. However, when the pipe isn’t completely filled, there are two scenarios: if it’s more than 1/2 full, then L remains the inner diameter of the pipe, and the flow velocity V can be calculated from the induced electromotive force. If S represents the cross-sectional area of the pipe, then the volumetric flow rate calculated by the instrument is Q=S*v*3600/s/h. In this case, the value of S used is too large, resulting in inaccurate measurements. Moreover, the actual flow velocity is also affected by the degree to which the pipe is not full; since the actual flow rate Q remains constant, the lower the fill level, the higher the flow velocity. So this cannot be measured ； In another case, the filling degree is less than 1/2; at this time, L is smaller than the inner diameter of the pipe, and this value is unknown. According to the formula U=BLV, the instrument software still assumes that L represents the inner diameter of the pipe, resulting in an inaccurate calculation of V. Moreover, the cross-sectional area is also incorrect, making it impossible to carry out any measurements! In summary, there may be areas where the analysis is incomplete, but the conclusion is that the inductive electromagnetic type cannot perform measurements!

I also think it’s not possible to measure it, but an experienced engineer told me that there should be a method for measurement when the pipe isn’t completely filled; he had seen it in practice. I found it strange as well, and after searching extensively I couldn’t find any information on such a method, so I came here to ask.

It still depends on the actual conditions on site. We have encountered this situation before: the pipe isn’t completely full, but it’s more than half full. Even if an electromagnetic flow meter from Cologne is used, it’s still possible to measure the flow rate; however, the resulting value can only be used as a reference. As mentioned by someone on the 5th floor, if the pipe isn’t even half full, then measurement is definitely not possible.

This post was last edited by taohuajiang on 2011-7-11 12:32. The TIDALFLUX 411PF in Cologne can measure non-full pipes. Accuracy: For non-full pipe, V >= 1 m/s,

The pipes can be modified, for example into a \"concave\" shape; that way, the pipes will be filled, right? ? ? ? O(∩_∩)O Hahaha~

For a concave-shaped pipe, won’t the air in the pipe pass by the flow meter?

Such electromagnetic flowmeters do exist on the market. Their principle involves designing the measuring tube in a format similar to that of a capacitive level gauge, using this to determine the liquid level inside the pipe; from this, the cross-sectional area can be calculated. The pipe flow rate is then determined using the law of electromagnetic induction, and ultimately the flow rate is obtained. Of course, the accuracy of such measurements is quite poor. I haven’t seen any actual use of them in the field yet, but relevant product descriptions can be found in the selection materials provided by some manufacturers