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ASME B31.8 calculation

ASME B31.8 calculation

Dear fellows,
Is there any excel reinforcement calculation available for welded branches according to ASME B31.8? I've been assigned to perform a reinforcing area calculation for internal pressure of a 2" XS weldolet SA 350 LF2, welded to a 20" header API 5L X65 t=11,9mm.
Thanks in advance.

RE: ASME B31.8 calculation

Hello vitalis77,

Weld-o-lets and other integrally reinforced branch connection fittings carry their own reinforcing - THEY DO NOT NEED ADDITIONAL REINFORCEMENT (but pay close attention to the information sheet from Bonny Forge to get the welding correct).  However, there are stress analysis issues that must be addressed when you add a branch to any piping system and you must be sure to use the correct branch stress intensification factor when the stress calculations are performed.

Regarding spreadsheets, I think the very useful "Piping Office" suite of piping design spreadsheets (by Ben Nottingham) includes fabricated branch connection reinforcement calculations.  They are not unlike the calculations for B31.3 branch connections but you must be aware of the differences in the material allowable stresses between these two Codes.  If you look in B31.3, Appendix "H" you will find a tutorial with several examples of branch reinforcement calculations.  However, as I mentioned previously, weld-o-lets do not need reinforcement.

With all due respect, you would do well to look for some education as you are obviously in need.  Get a copy of the ASME text book by Dr. Charles Becht or a copy of the CASTI book by Woods and Baguley.

Regards, John.

RE: ASME B31.8 calculation

Dear John,
Thank you for fast reply,
I'm aware of the issues you brought up throughout your answer, the only thing I was searching for was a simple excel file. I've already set up a excel file for reinforcing calculations acc. to ASME VIII, 31.3, 31.4. You pointed out this calcution is pretty much the same as ASME B31.3 apart from the allowable stress values and that conforts me a lot. Your book references are indeed quite helpful and they are in my possession for a couple of years now. Finally, do you believe that an o lets integrally reinforcement, covers the required reinforcing needs of a welded branch and if so how can I prove this with a calculation. To be more specific, how can I calculate the A3 area?
Thanks in advance,

RE: ASME B31.8 calculation


In B31.8, look at Section 831.4, there is a table (831.42) that corresponds to the text.  I fashined a nifty Excel spreadhseet from that.

Greg Lamberson, BS, MBA
Consultant - Upstream Energy

RE: ASME B31.8 calculation

I think there is a real possibility here that I am completely missing the point of this question.  But, I will expand upon my original comments.  If I am completely off base here please just ignore me.

The entire purpose for using "X"-o-let fitting products is that they are self reinforcing.  The fittings are designed to provide all the needed reinforcement and to place it within the "zone of reinforcement".  You must specify the NPS and schedule of the run pipe and the NPS and schedule of the branch pipe when you procure the fitting - Bonny Forge has already done the calculation.  When you use these fittings (and assuming the fabrication meets the Code  requirements) there is no need to perform reinforcement calculations.  It is much the same as using a B16.9 TEE fitting - it too is designed to not need additional reinforcement, and so calculations are not required.

B31.8 paragraph 831.42(c) says that the REINFORCEMENT MEMBER may be a pad type (for which area replacement calculations must be done)or one of several othere types, or it may be a welding outlet fitting.  If you use the welding outlet fitting, the calculations have already be done.

If you are convinced that you want to do calculations to show that using the fitting provides the area replacement required by B31.8 Appendix F, simply slice a weld-o-let in half longitudinally and sketch the zone of reinforcement (as defined in Appendix F) on the sectioned fitting with a "Sharpie" and measure the dimensions of the reinforcement provided in the reinforcement zone by BF.  Then use the rules of Appendix F.  Alternately, call Bonny Forge and ask them to email you a certification that in fact the fitting provides the necessary reinforcement.  

Regards, John.

RE: ASME B31.8 calculation


My apologies, I may have inadvertently clouded the issue.  I was adrressing the 1sr part of the question referring to branch reinforcement calculations with an Excel spreadsheet.  

I should have been more clear.  

Greg Lamberson
Consultant - Upstream Energy

RE: ASME B31.8 calculation

Yes John,
Now you hit to the core of my query!!!
Thumbs up!!!

RE: ASME B31.8 calculation

Dear All,
I read through this thread and find it very usefull.
I would appreciate if you could help me with this problem:
I have a pipeline test head that has to be verified according to ASME Div VIII, as per client request.
We have selected a weldolet that is certified from the manufactur to comply with ASME 31.8 calculation. We also checket this by calculation and it is true, it actually comply with 31.8 requirements.
The problem is that it does not comply with the requirement set forth in ASME div VIII for welded fittings and openings in pressure vessels.
Basing on this, we should not use this weldolet but instead a reinforced plate.
We found this very strange, that a standard item such as a weldolet does not comply with all ASME codes.
Did you ever come across such question?
Any help would much appreciated.


RE: ASME B31.8 calculation

Hi iuston,

First of all, you "high-jacked" a discussion thread with a slightly "off-topic" question and you should have started a new thread with your question.

It is difficult to understand your client's motives.  If you are designing a piping system you should/shall (depending upon your local jurisdiction) comply with the applicable PIPING CODE.  If you are designing a pressure vessel you should/shall (depending upon your local jurisdiction) comply with the applicable PRESSURE VESSEL CODE.

Therefore, if you are designing a Gas Transmission Pipeline then B31.8 would be the applicable Code of choice (or "required Code" - see also the Code of Federal Regulations).  Applying B31.8 rules, the weldolet would be the fitting to use for a branch connection.

Similarly, if you are working with a ASME Section VIII, Division 1 Unfired Pressure Vessel, (e.g., putting in a new nozzle) you will find that the WFI Vesselet or Nozzlet products DO comply with the ASME B&PV Code.  You can contact WFI and they will help you with all the documentation that you need.

Vesselet - Integrally reinforced, contoured-insert type branch connection ideally suited for cyclical and for high pressure/temperature services. Patented circular design reduces weld volume, permits automatic welding and lends itself to Non-Destructive Examination. Available in butt-weld, socket-weld and flanged configurations.

Nozzlet - A traditional insert welding outlet contoured to fit the inside diameter of the run pipe vessel wall. Available in butt-weld and flanged configurations.

Regards, John.

RE: ASME B31.8 calculation

Hi JohnBreen,
sorry about being off topic. I didn't really start a new thread because my question raised from your previous answer of 14Dec06, where you stated:


If you are convinced that you want to do calculations to show that using the fitting provides the area replacement required by B31.8 Appendix F, simply slice a weld-o-let in half longitudinally and sketch the zone of reinforcement (as defined in Appendix F) on the sectioned fitting with a "Sharpie" and measure the dimensions of the reinforcement provided in the reinforcement zone by BF.  Then use the rules of Appendix F.  Alternately, call Bonny Forge and ask them to email you a certification that in fact the fitting provides the necessary reinforcement

I proceeded as you suggested, measuring a 'slice' of a BonneyForge weldoled, and I verified that it complies with the requirements of Asme B31.8, but not with those of a ASME Div VII.
We are talking about a Pipeline Temporary Test Head, that has to be itself pre-tested prior being connected to the pipeline. So it can be regarded as a pressure vessel, and this is were our client requirement comes from.
So I found it strange that I couldn't find a weldolet that comply with ASME Div VIII.
Actually, I also contacted BonneyForge for clarification, and they answered me that their weldolet do comply with ASME DivVIII, and that calcultations can be provided when ordering the item.

But honestly, basing on the weldolet dimentions derived from Bonney Forge and WFI catalog, I couldn't verify the requirements of ASME Div VIII, so I'm still wondering what I'm doing wrong upsidedown

I hope I've been clear enough, because my english is quite poor, and thanks a lot for you answers always very interesting thumbsup


RE: ASME B31.8 calculation

Hello again iuston,

Have no fear my friend, your English is quite understandable.  Thank you for "making the stretch" to communicate with us in English.  Your effort is appreciated.

The dimensions provided by the manufacturer's of "branch connection fittings" is very limited.  I have never found enough data in the catalogs to do the branch "area replacement" calculations.  Years ago I did make the effort to slice the fittings and accurately measure them for the purpose of making finite element models.  This worked out for me.  

If you were to slice a B16.9 welding TEE and measure all the metal in the "reinforcing zone" and then apply the B31 rules for "area replacement" for branch reinforcement the TEE's would not "pass" the test.  These ASME B16.9 welding fittings are qualified by burst tests, not by B31 rules (however B31 Codes accept this method so without calculations the fittings are "qualified".  Generally speaking, if you were to accurately measure and model the actual geometry of a "branch connection fitting" and make an FEA model for analysis (using the ASME B&PV Code Section VIII, DIVISION 2 (with its allowable stresses)) you would find that the fittings are qualified.  I can assure you that the only way you will get the real dimensions is to cut and measure the fittings - manufacturers consider this to be proprietary information.

What you are saying surprises me.  I would have thought that any "branch connection"  calculation done to the B31 rules would have also "passed" using the ASME B&PV Code Section VIII, DIVISION 1 rules.  I will have to look into that when time allows.

And so to bed........

Regards, John.

RE: ASME B31.8 calculation

Thanks JohnBreen, your clarification was really helpfull.

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