adjust full scale in an orifice flowmeter

[elisosky]

Hi everybody!
I hope somebody can help me...

We are using a plate orifice to measure water feed to a reboiler; the pipeline size is 1" and the orifice was initially designed for 0-1800 kg/h of water, with a maximum pressure drop of 1000 mm water. As water feed doubles may I simply change pressure drop - by doubling the higher value of scale - to obtain water flow?


Thank you ( ang forgive for my bad english...)

[JRPB]

Considering that water has virtually no viscosity and the changes in rheology due to pressure and temperature are negligible, I'd say you could assume a linear relationship between pressure drop and volumetric flow.

This is not the case for other fluids: oil-based and gases (water vapor included).

EDIT: I'm not sure what a "reboiler" is: I'm assuming that a single-phase fluid (clean liquid water) is flowing through your orifice meter. If you're dealing with more than one phase (suspended solids, gases), you won't get a reliable measurement using an orifice plate meter.

[FredGarvin]

Ummm...the flow rate through an orifice is a function of the square root of the delta P. You might want to rethink that aspect. You will, most likely, introduce a bot more error by keeping the flow coefficient constant, but it shouldn't be a very large amount.

http://upload.wikimedia.org/math/a/3/5/a3505472b47bfd95e0dbe97620e24001.png