Anybody.....

What does the ASME Section VIII Div. 1 code say about alignment holes near the bolt circle of a flange. The alignment hole will be used to put a small rod in so alignment of the mating flange will be maintained. The alignment hole is inside the bolt circle, not the outside.

I am guessing that the "meat" under the alignment hole has to also be greater than tr (required flange thickness).

Does the rod have to be a tight friction fit to be assumed a part of the flange, and therefore not require any consideration???

Would appreciate any help on this matter.

Hello Jim,

I suppose we are talking about an App. 2 flange (in any case after you have drilled an additional hole). As far as I remember you will not find any information on alignment holes here. The question is: Are the rules applicable although such an additional weakening is not considered?
Assuming that the alignment hole is relative small in comparision to the bolt holes and that the hole is a very localized discontinuity, in my opinion an App. 2 calculation is acceptable without additional considerations.

Regarding the rod: It is not a part of the flange.

Best regards
Michael

Thanks Michael.....appreciate it

Localised discontinuities generate high stresses. I would not recommend it when you could have fatigue issues.
AFAIR such holes are not provided for in B16.x, rendering such a flange non-standard. UG-44 does not apply to them.

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Konrad Anikiel

Thanks Konrad....appreciate it

Hello Konrad,
You are right, as usual fatigue requires special examinations. However, even with cyclic loadings I would not be worried, supposed the local discontinuity "alignment hole" is less severe than the local discontinuity "bolt hole". Especially since the hole is not in an area governed by primary stresses.

Michael

Sure Michael, I don't know whether this is going to be a problem. It's up to Fernandez whether he gives any consideration. And whether the stresses will be high- it actually depends on proportion of diameters and exact location. It could be roughly estimated from table of stress concentration factors, but without a proper FEA it is a guess only.
By the way: Professor O.C.Zienkiewicz just died on 2nd Jan...

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Konrad Anikiel