EM Flowmeter-accuracy

What does the manufacturer have to say on the topic?

I have not yet contacted them , manufacturer usually ask about the flow,dia,quality of liquid,flow on which to caliber and they gonna supply according to it.

I have attached a jpg file here for your reference : there are 2 cases which one is going to the best . Suggest me !

Thanks

Without seeing the manufacturer's literature supplied with it, go for the second one, though it does look as though the instrument needs to be selected for a larger line size, in which case it is wrong and needs to be sent back and re-ordered. What is the point of installing a 2in meter in a 4in line, for example <rhetorical question>? It is an electromagnetic flowmeter, not a flippin' orifice plate!

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Doesn't anyone read the instructions and talk to suppliers any more <sigh>? It was all the rage before the damn internet, the iphone and all the other modern technology came along!

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I think your second example is the best with exception. A general rule of thumb is 20 diameters upstream and 10 down.

Agreed - 5D and 2D are useless in this application. If you have turbulent flow you will not get accurate or repeatable readings.

If the OP is using piping as per his 2nd figure, 5 D / 3D should be sufficient. For EM flowmeters 20D/ 10 D are not necessary.

Besides, are you talking about turbulent flow in technical terms? Acording to definition beyond Raynaulds no. 4000, all flows are turbulent. It is very difficult to find the non-turbulent flow with water in actual life. So all water flows are turbulent.

EM flowmeters can very well handle turbulent flows. Better to have well developed flow.

In any case i am not going to take a chance with turbulent flow in my process ,Whether contacting suddenly(1st fig.) or 5D before(2nd fig.) the EM flow meter, by calculating the sudden contraction pressure loss and increase in velocity .

In the case 2, I am going to consider 5D in inlet run and 2D in outlet run ,coz of vendor recommendation and accuracy concerns .

For the 1st fig , i would like to state that this type of arrangement is possible where larger pipe dia is involved there by contracting it to a certain limit ,but if am contracting it suddenly with all precautionary measures within the range of and for Flow meter ,DO I HAVE TO STILL CONSIDER 5D & 2D, IF YES, WHETHER THIS REDUCER AND EXPANDER WILL BE INCLUSIVE IN THE LENGTH .(This is my prime concern).

Thanks in advance.

Again you are misunderstanding about the turbulent flow. Your flow is already turbulent. By any means you can not achieve laminar flow. Most important thing is that there is nothing wrong in turbulent flow. The should be well developed, means the it should be well symmetrical in the pipe line. The velocity profile should be almost same across any cross section along the length.

Then about your configuration 1 & 2.

Don't you think that it is economical to have configuration 2 than 1. In configuration 1 you are bringing bigger pipe line all the way near to flowmeter and then reducing it to flowmeter size.

In configuration 2, you are reducing the size of your line to flowmeter size at far distance and then bringing appropriate size of flowmeter to flowmeter. With this economical solution, automatically you achieve the good working conditions for the flowmeter. Now in this case 5 D and 3 D should be of the straight length of the pipes after reducer expander till center of the flowmeter.

Thanks

The main reason for this too low flow and velocity is because the process is of approx. double capacity which will be attained in later stages and this Flow meter is coming on the header of pumps, 2 pumps are yet to be installed. in the final stage the velocity will be around 1.7-1.8 m/sec,

Both of the ideas are of mine ,i very well know that the economical and better configuration for project & flow meter is indeed 2nd one.Already recommended for the same .

However 1st case is valid too (in what cases ), i just wanted to know the conditions/design parameters in which this works /works properly,

Agreed with your point of 0.5% + 1mm/sec.

Calculate the flow all you want - in all my years in process plants I never saw anything that accurate outside of a design office where they don't know better.

You want reasonable accuracy and repeatability - that is what counts.

Use case 2 only. The reducer and expander sections can NOT be considered in the straight section.

The talk of accuracy is stretching things a bit from my experience. The shorter the runs into and out of the meter the less the repeatability and accuracy.

With what you describe, EM flowmeter should give you good accuracy with your scheme 2 in your another post. Accuracy should be within 0.5% of actual flow + 1 mm/sec. Do not neglect this effect of 1 mm/sec.

Problem in your case seems to be different. Your flow rate is too low for 1000 mm flowmeter. ar your flow rate of 2369 m3/hr. the velocity is just 0.84 m/sec.(I assume this as FS set for the flowmeter)

Now, do not neglect the effect of 1 mm /sec in above formula.

Thus, with above formula the accuracy will be 0.62% of actual flow rate. If your flow rate goes down to 20% of this FS (which is permitted for EM flowmeters.. the accuracy becomes 1.1%