ASME VIII stub-end calculation
ASME VIII stub-end calculation
(OP)
Hi all,
I have a question concerning the calculation of lap-joint flanges according to ASME VIII div. 1 appendix 2.
Concerning the loose flange the code is very clear and tells to calculate it as a loose flange with G being the center of the contact between loose ring and stub end (image 1 from appendix 2).
Concerning the stub-end the code doesn't give any recommendations, accept that the lap joint has to be checked for shear stress if shear stress can occur.
But now: How to calculate the stub-end?
In my opinion:
- calculate the stub-end as a fixed or loose flange type, just as a normal slip-on flange, but with the bolt circle being the center of the contact between loose ring and stub end.
This is also the method described in the European code EN-13445.
This however creates thick stub-ends and flanges like the Van-Stone flange can't be calculated this way.
Can somebody please give me some more insight in the calculation of stub-ends according to ASME VIII appendix 2?
Thanks in advance for your reply.
With regards,
Corné
I have a question concerning the calculation of lap-joint flanges according to ASME VIII div. 1 appendix 2.
Concerning the loose flange the code is very clear and tells to calculate it as a loose flange with G being the center of the contact between loose ring and stub end (image 1 from appendix 2).
Concerning the stub-end the code doesn't give any recommendations, accept that the lap joint has to be checked for shear stress if shear stress can occur.
But now: How to calculate the stub-end?
In my opinion:
- calculate the stub-end as a fixed or loose flange type, just as a normal slip-on flange, but with the bolt circle being the center of the contact between loose ring and stub end.
This is also the method described in the European code EN-13445.
This however creates thick stub-ends and flanges like the Van-Stone flange can't be calculated this way.
Can somebody please give me some more insight in the calculation of stub-ends according to ASME VIII appendix 2?
Thanks in advance for your reply.
With regards,
Corné





RE: ASME VIII stub-end calculation
You are correct that it is difficult to use a Van-Stone type flange with ASME work due to the thicknesses required. It is generally difficult to get sufficient lap thickness. To compound the problem, the surface of the lap joint will require a machine finish, and that further reduces the thickness.
A possible solution for you would be to weld an ID/OD ring to a pipe (fabricated stub end) where you are unable to find an acceptable pre-made fitting. This usually happens with very thick pipe or uncommon materials.
Let me know if you need a sketch.
RE: ASME VIII stub-end calculation
I understand what you mean, but the problem is that I need to design a lap joint flange. The stub-end will be very large if the method according to ASME VIII div 1 appendix 2 is followed.
Also the code doesn't mention how to calculate a stub end.
So my actual question is how do you calculate a stub-end according to ASME VIII?
The Van-Stone flange is just an example. The ring you mention will have the same problem, it will be too thin to be used as a stub-end.
RE: ASME VIII stub-end calculation
Regards
StoneCold
RE: ASME VIII stub-end calculation
Regards,
Mike
RE: ASME VIII stub-end calculation
@SnTMan: Only thing those images show is (in image 1a I believe) that tl >= t. Which means the stubend must be evenly thick or thicker as the pipe wall. However these images explicitely give a full face gasket underneath the stubend. If I have a smaller gasket this reference is not valid in my opinion because there will be a bending moment in the stub end flange.
I would like to here more / other opinions regarding this issue. Especially also from people who are also working with the EN-13445 code which gives this explicit calculation method for a stub end (comes down to use the fixed flange method).
Regards, Corné
RE: ASME VIII stub-end calculation
True, no explicit calculation seems to exist for the stub end. I make them at least equal to the neck and go on.
After all, commercial stub ends are not restricted as to type of gasket.
Regards,
Mike
RE: ASME VIII stub-end calculation
Commercial stub ends, as in ASME B16.5, have a thickness more or less equal to the loose ring thickness. And are thus much thicker than the pipe wall thickness.
RE: ASME VIII stub-end calculation
ASME B16.5 (2009) 6.4.3.1 states: The finished thickness of the
lap shall be no less than nominal pipe wall thickness.
Generally, when fabricating from plate, I like to leave a healthy machining allowance, since I am allowed to be thicker.
RE: ASME VIII stub-end calculation
Still it is strange that all European codes (EN-13445, DIN2505, AD-Merkblatt B5, RToD) calculate the stub-end the same as a fixed flange. ASME VIII seems to be the only one not explicitely telling anything about the thickness accept that it must be larger than the pipe wall thickness. Normally the German code gives thinner parts as the ASME code.
And I still can't find any justification to not calculate the stub-ends bending moment and flange thickness.
RE: ASME VIII stub-end calculation
Regards,
Mike
RE: ASME VIII stub-end calculation
RE: ASME VIII stub-end calculation
As for interpretation, I think the previous posts illustrate that.
Regards,
Mike
RE: ASME VIII stub-end calculation
RE: ASME VIII stub-end calculation
Think of the flange as a punch die trying to punch a washer out of the stub end.
Hope this helps
RE: ASME VIII stub-end calculation
Think of the flange as a punch die trying to punch a washer out of the stub end.
Hope this helps.
RE: ASME VIII stub-end calculation
In my opinion the stub end will have to withstand bending forces too.
RE: ASME VIII stub-end calculation