9 replies to this topic

[fallah]

Dear All,
Can we install orifice plate (for measuring flow) in vertical run of a gas line?.If so,any reference/practice/standard?
Regards

[smalawi]

Dear All,
Can we install orifice plate (for measuring flow) in vertical run of a gas line?.If so,any reference/practice/standard?
Regards

Hi,

I must say that most orifice meters I've seen where in horizontal lines. I dont know excatly why ! prehaps better access. I've seen some on vertical lines, I dont see whay it will matter. Make sure the lead lines are properly designed and self draning into the process, ie. transmitter is better be elevated, or use diaphrams or sealent lead line.

I dont recall the practice for such installations, but the only guide I have is best keep 5 pipe dia and 10 after the orifice to avoid excessive noize in the readings. The API's might have a referance or other standards, do a google search. Prehaps other in this from have better expriance.

cheers,

sm

[djack77494]

fallah,
I see no reason why not if proper care is taken. With small differentials measured, it can be quite important that everything about the high and low pressure impulse lines be as close to identical as possible. It is not possible to achieve identical tubing runs for a vertical installation simply because the taps are not at the same elevation. It is possible to achieve essentially identical runs with a horizontal installation. As the measured differential increases, the small differences in impulse lines rapidly becomes insignificant. All things considered, I think it preferable to do a horizontal installation but think a vertical installation is acceptable if carefully done.

[fallah]

fallah,
I see no reason why not if proper care is taken. With small differentials measured, it can be quite important that everything about the high and low pressure impulse lines be as close to identical as possible. It is not possible to achieve identical tubing runs for a vertical installation simply because the taps are not at the same elevation. It is possible to achieve essentially identical runs with a horizontal installation. As the measured differential increases, the small differences in impulse lines rapidly becomes insignificant. All things considered, I think it preferable to do a horizontal installation but think a vertical installation is acceptable if carefully done.

Thanks a lot. As per your above explanations, I think using an orifice in a vertical run, in the case of a gas line, may have higher possibility and accuracy. Am i right?

[djack77494]

Thanks a lot.As per your above explanations,i think using orifice in vertical run in the case of gas line may have higher possibility and accuracy.Am i right?

Based on your response I do not think you understood my point. I prefer installing the orifice in a horizontal run, but concede that a successful measurement can be made with the orifice carefully installed in a vertical run.

Using Imperial units, a typical flow measuring orifice might be calibrated for 0 to 100 inches of water column (or in.W.C.). Such an instrument would likely function fine in either a vertical or horizontal run. If pressure is low or pressure drop is critical, then perhaps a low range transmitter (say 0 to 10 in. W.C.) might be used. Now very small errors caused by the presence of trapped condensate or any one of hundreds of other possibilities could significantly affect the measurement's accuracy. Under these circumstances, I would opt for the horizintal run installation.

[Qalander (Chem)]

Dear fallah,

Kindly do consider that (although I am not a mechanical engineer and somebody may correct if wrong) the stability grade level wise is easily manageable for horizotal pipeline runs in comparision to vertical runs and occassionaly the verticality/alignment may falter during longer periods of time or where some inherent vibration may be present in the operated system.

hope this helps
best regards
qalander

[fallah]

Based on my previous post, i think i may didn't describe my point properly. Therefore, I will try to clarify the matter more than before.

If in any case we have to install a flow measuring orifice in vertical run, based on your previous post about the necessity of identical tubing runs, for gas flow (with respect to liquid flow) higher possibility and accuracy may be attained.

[smalawi]

Hi,

I think all posts tend to support horizontal line installtion is safer, but, when you dont have the option, a vertical installtion will also work. You simply need to put more care into the design.

The lead (impluse) lines will not by symitirical in vertical installtion, but the error for gas is small and a transmitter with 100 WC span properly desinged for accurate range will give good readings.

The possibility of liquid accumelation in the line either by gravity or condnesation of the gas should be considered. The lines should be self draning back to the process.

One trick that also works well, is using diphram type transmitters to aviod the possibility of liquid all togather and calibrate the transmeter for this condidtions.

Sure you can use vertical flow orifice type, simply design for it.

cheers,

sm

[djack77494]

I think sm has nicely summarized the important points of this thread. My sole remaining recommendation is to not use an extremely low differential pressure instrument for a vertical installation. Also, I do not concur with the "trick" of using diaphragm seals for your dP instruments. They have their own problems, including an unavoidable loss of accuracy. Again, use with care.

[Zauberberg]

If you take a look at the websites of different orifice/flow element measuring device vendors, you'll see that vertical orifices can be used without any problems - if sufficient care is taken during design stage (this kind of care is required for horizontal orifices as well). This thread offers some really good points of view - all coming from applying the common sense in engineering and design; I believe you simply cannot make that much big mistakes, if you evaluate your system correctly and make the right conclusions out of those observations.

http://www.burmt.de/...4_e_Oriflow.pdf
http://www.spiraxsar.../IM/p176_05.pdf
http://www.emersonpr...5-0100-4792.pdf