Flowmeter for custody transfer

[hassanfadil]

Hello
What are the required repeatability and linearity for a flowmeter used for custody transfer?
Also what is "Accuracy" shown on shown on suppliers specification, as i read accuracy is only a qualitative term?

[Shabbir2009]

Hello
What are the required repeatability and linearity for a flowmeter used for custody transfer?
Also what is "Accuracy" shown on shown on suppliers specification, as i read accuracy is only a qualitative term?

Salaam

My understanding for the above is as follows:
The meter minimum performance (accuracy & repeatability) criteria for a gas custody transfer application is defined in relevant insternational measurement standards.
The inherent accuracy of a meter is often published in the manufacturer’s specification, and may be expressed as repeatability and/or linearity. In other words,
accuracy is based on how repeatable and how linear the meter can stay within the manufacturer’s performance specifications.
Manufacturers’ specifications are based on meter operation
within recommended flow ranges, within a narrow
range of pressures, temperatures, and fluid viscosities. For
custody transfer applications, meters with the highest inherent
accuracy should be used and should be proved (mostly for liquid applications)on site .
The meters should operate within the manufacturer’s specifications.

[hassanfadil]

Thanks for the informative reply
Yes that's what am asking but my problems are:
1) the API standard shows that Uncertainty should be +/- 0.027 with 95% level of confidence, which can be achieved by: The typical requirement is that a meter must repeat within +/- 0.05%
in 5 consultative runs. For example, a repeatability of +/ - 0.12% in 10 consecutive runs or a repeatability of +/- 0.17% in 15 consecutive
runs both meet +/- 0.027% at 95% confidence level.
2) The API standard does not show the linearity requirement.

[Shabbir2009]

Thanks for the informative reply
Yes that's what am asking but my problems are:
1) the API standard shows that Uncertainty should be +/- 0.027 with 95% level of confidence, which can be achieved by: The typical requirement is that a meter must repeat within +/- 0.05%
in 5 consultative runs. For example, a repeatability of +/ - 0.12% in 10 consecutive runs or a repeatability of +/- 0.17% in 15 consecutive
runs both meet +/- 0.027% at 95% confidence level.
2) The API standard does not show the linearity requirement.

It's true that API do not define the linearity numbers that should go with the meter. (Probably the reason for this could be with the diffent physical properties for the liquid ( e.g.: phase, viscosity etc) & the variety of fluids fluids to meter (crude, lpg, lng,other refined products) it could be difficult to define a particular number for linearity). Hence for majority of liquid custody transfer applications, this linearity requirement is defined in the contract between buyer & seller with their mutual agreement. Secondly it also depends on the what r the best linearity meters available in the market. For a turbine meter / ultrasonic meter the linearity is typically +/-0.15%.

I hope this answers your query.

[hassanfadil]

Thanks Shabbir2009 you've answered my question, and thanks again for the fast replies ^_^