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AGA 3 Basic Orifice Factor (Fb) Value

AGA 3 Basic Orifice Factor (Fb) Value

AGA 3 Basic Orifice Factor (Fb) Value

AGA #3 Report, Table B1 Basic Orifice Factor (Fb).
For flange taps, 7.981-inch pipe, and 5.575-inch orifice plate bore, my copy of the AGA 3 Report lists the Basic Orifice Factor (Fb) in Table B1 as 7830.2.  A workbook that I've been using for years (developed and written by myself) computes the value as 7233.97.

I've compared several other Table B1 listed values with that of the workbook with no differences (nearly a perfect match).

I'm inclined to believe their is a typographical error within the AGA #3 Report.

Will those individuals knowledgeable with the AGA #3 calcs conduct a calculation and advise of their results.  I do not have the old DOS program anymore . . .


RE: AGA 3 Basic Orifice Factor (Fb) Value

Not likely a misprint

RE: AGA 3 Basic Orifice Factor (Fb) Value


i'd like to review your analysis.  i've compared several bores and plate sizes using the workbook results & the values in Table B1 with NO differences.


RE: AGA 3 Basic Orifice Factor (Fb) Value

you are out of date, there is no FsubB in AGA 3 anymore.

RE: AGA 3 Basic Orifice Factor (Fb) Value


I've not used the AGA you've coded (used hand calcs back in the day) and believe that there has been a recent update based on a thorough re-evaluation of the flow lab data used for the original AGA 3.

The AGA calcs were closely checked and re-checked, used for contact sales etc., and no one has reported the discrepancy you report. Suspect a calculation error. That will take a bit of sorting out.

Did you prepare a curve fit from the AGA Tables or did you have access to their correlations?


RE: AGA 3 Basic Orifice Factor (Fb) Value

If you have a copy of the Spink's flow meter handbook, the Fb factor was developed as Fb=338.178Ko*d^2 where Ko is described in his Appendix...that correlation is still pretty good, though out of sync with the current standards.

Miller's handbook (worked under Spink) is probably a good starting point.

good luck in your pursuit


RE: AGA 3 Basic Orifice Factor (Fb) Value


I found an old DOS program and executed the program.  The DOS program returned the same results as what my workbook computed.  The Tabular Data in Table B1 for a 7.981-inch meter bore with a 5.575-inch orifice plate is definitely a typographical error (I'm convinced).  I possess the 1985 Edition of "Comparison Analysis of Orifice Metering of Natural Gas & Other Related Hydrocarbon Fluids", which provides the calculation details for all Factors used in determining flow by an orifice meter (pipe &/or flange taps).  I am confident about the my workbook calcs.

Yes, my copy of AGA #3 is pre-1989 (I left the AGA #3 at home today) and I've since noted a more recent version is available.  I also found a couple of shareware programs and noted that the Fb factor (Basic Orifice Factor) is not computed; but rather a Composite Orifice Factor (a combination of several orifice meter factors).

dcasto, fyi, I am not out of date, but rather there is a more updated or current version of the AGA Report which simplifies the flow calcs as noted by hacksaw.

I will obtain the more recent AGA Report and proceed from there.

Thanks folks!

RE: AGA 3 Basic Orifice Factor (Fb) Value

ASME and API studied orifice plates and other flow elements and updated their publicaions in about 1989.  My copy of ASME MFC-3M is dated 1989 reflecting a revision to the 1985 edition.  Most of my API MPMS documents reflect an update in 1995 and reaffirmed in 2002.  My copy of ISO 5167 is dated 2003.

RE: AGA 3 Basic Orifice Factor (Fb) Value


I did the number plugs on Spink's correlation, and get


the AGA 2 table shows 7830.0

I'm not seeing the discrepancy you report.

The newer correlations should be comparable,  

RE: AGA 3 Basic Orifice Factor (Fb) Value

API Chapter 14 "Natural Gas Fluids Measurement," Section 3, "Concentric, Square-Edged Orifice Meters," Part 3, "Natural Gas Applications" of the Manual of Petroleum Measurement Standards, Third  Edition, August 1992

3-D-1-Basic Orifice Factors (Fb) for PIPE Taps

RE: AGA 3 Basic Orifice Factor (Fb) Value


are you referencing the proper AGA base condition?

some calculations are performed on a 32 F (0 C) basis, some on 60 F basis, and the AGA on 70 F basis.

for what its worth

RE: AGA 3 Basic Orifice Factor (Fb) Value


the Basic Orifice Factor is independent of base conditions.  the two factors that are dependent upon base conditions are Fpb & Ftb.  The AGA #3 Report is using 60°F and 14.73-psia as base conditions as is the workbook I've developed.

I conducted the calcs again using pencil, paper, and calculator (sorry slide rule era seasoned engr's) and the results match my workbook calcs.  Again, the Basic Orifice factor is for flange taps (not pipe taps, which result in a higher Fb factor).

I'll be contacting the AGA this week about this matter and obtaining the more recent AGA #3 Part 3 report.  I am baffled . . .  i may even contact Daniels and have someone conduct an analysis.


RE: AGA 3 Basic Orifice Factor (Fb) Value


The basic orifice factor in question is not a discharge coefficient in AGA terminology. If it were you'd be absolutely correct. Rather it is specific to natural gas at 60F, 14.73 psia, a specific grav of 1.00, for infinite Renolds number and unity expansion factor...

Suggest that you use the calculation you've developed and plot a family of curves with the diameter ratio, beta, as a parameter. It will help narrow down just where the AGA coefficients depart from your curves.

good luck on your pursuits. You might pick up a copy of R.W. Millers book or meter sizing software.

RE: AGA 3 Basic Orifice Factor (Fb) Value


finally, after loosing more hair, the problem has been resolved.

It bears worth repeating the problem and I have attached a photo of the Table B1 in question.

AGA #3 Report, Table B1 Basic Orifice Factor (Fb).
For flange taps, 7.981-inch pipe, and 5.575-inch orifice plate bore, the table lists Fb factor of 7830.2.  To verify the table, the calcs were done by a workbook, developed by me, and by long-hand arithmetic.  The results using both methods is 7233.97; yet the table lists 7830.2.

I consulted the matter with an AGA committee member.  He initially told me the Table value is correct, but after a minute or so of discussion, we both noted the error simultaneously.  The error lies in the Orifice Plate bore size listed Table B1.  The Fb value listed, 7830.2, is correct for a 5.75-inch (not a 5.575-inch).  Please see attached document.

So, for those individuals still using the AGA #3 Report, please make this correction.

btw, the current issue of the now AGA #3 Report contains 4 parts and they are available from the AGA.

thanks to all whom participated in this discussion.

RE: AGA 3 Basic Orifice Factor (Fb) Value

persistence pays off, good work! (and lots of it) tracking it down

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