I am trying to calculate massflow (

[coolcando]

I am trying to calculate massflow (of ethane)from our supplier.

They measure this flow using coriolis massflow meter.
However the Reference Gravity used for their calculation(in DCS control logic) is not same as we use on our end.Our Reference Gravity is about 10% lower to their RG.

What difference can this make ?

 

[Latexman]

I think the answer is it makes no difference, because a properly calibrated coriolis meter has a signal and displays an absolute mass flow, like kg/min, and there is no reference to another fluid.

Good luck,
Latexman

 

[Latexman]

. . . because a properly calibrated coriolis meter has a signal [red]that is proportional to[/red] and [red]a display that reads[/red] an absolute mass flow . . .

Sorry!

Good luck,
Latexman

 

[jmw]

Unless, of course, you need the standard volume which, historically because of the many volumetric meters, may be the case. If so then you need the density to continuously calculate the standard volume volume at reference temperature). Mass meters do also measure density but not all mass meters measure to the same degree of accuracy (they are optimised for mass flow performance, not density) and they will use density to determine volume from mass flow.

None the less, one should never disregard any anomaly.
10% is a big difference and presumably the reference gravity has some significance somewhere or it would not be reported by both parties.
So the questions are:
[ul][li] do you need standard volume?[/li]
[li] what is the significance of reference gravity?[/li]
[li] why do the values differ?[/li]
[li] how does each party determine the reference gravity?[/li]
[li] what is the standard that defines how it should be determined?[/li][/ul]
If you don't need it in any way then have it removed from both parties records as it is obviously only going to cause ongoing confusion.

JMW

http://www.ViscoAnalyser.com

 

[dcasto]

You need to visit with your rthane supply purchaser and see what the contract says on measurement. Ethane is normally sold by the gallon. It is measured by mass and then the contract will specify what and how to convert pounds to gallons.

The coriolis meters measures density at flowing conditions ie under pressure. Because you are above the criticle point when measureing, the ethane has a high compressibility. So, the density at flowing is going to be more dense that at standard conditions.

The gospal for ethane measurement standards is the GPA publications GPA2154-03. It list pure ethane as having a density of 2.9716 lb/gallon. Your contract may stipulate this density or even adjust for the 1.5% methane and .5% propane in the mixture.