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.