Henzy1977
Mechanical
- May 8, 2019
- 7
Hi all,
maybe you can help me finding an exception/rule about a uncommon design here below!
Thanks in advance, I do not know what to do.....
I have a VERY thick ASME VIII Div.1 pressure vessel with internal diameter "di", and on one point there is a drilling "d1" through the thickness as per attached image. OD/ID=2.
The thickness of the vessel is overdesigned, but I do not find any rule in the ASME for an exception in the local area of the thickness "t1".
Shall the thickness "t1" follow the minimum thickness required by the calculation of UG-27 or we can consider a different rule because it is local and only in one point of a vessel with high OD/ID ratio??
The problem now is that I have geometrical condition now that should consider a fix location of the "d1" hole, this position allow a thickness above 25% of the min thickness but locally I cannot guarantee the UG-27 min thk there.
We performed a verification acc.to Div.2 / Annex 5 and the stress is low (below the ASME II-D max allowable stress in the local area around the hole) but I cannot use Div.2 for this vessel.
Can you suggest me it there is any exception I can use or evaluate? Maybe because of the OD/ID ratio?
Shall I change the geometry and keep the UG-27 minimum thickness everywhere?
Thanks!
maybe you can help me finding an exception/rule about a uncommon design here below!
Thanks in advance, I do not know what to do.....
I have a VERY thick ASME VIII Div.1 pressure vessel with internal diameter "di", and on one point there is a drilling "d1" through the thickness as per attached image. OD/ID=2.
The thickness of the vessel is overdesigned, but I do not find any rule in the ASME for an exception in the local area of the thickness "t1".
Shall the thickness "t1" follow the minimum thickness required by the calculation of UG-27 or we can consider a different rule because it is local and only in one point of a vessel with high OD/ID ratio??
The problem now is that I have geometrical condition now that should consider a fix location of the "d1" hole, this position allow a thickness above 25% of the min thickness but locally I cannot guarantee the UG-27 min thk there.
We performed a verification acc.to Div.2 / Annex 5 and the stress is low (below the ASME II-D max allowable stress in the local area around the hole) but I cannot use Div.2 for this vessel.
Can you suggest me it there is any exception I can use or evaluate? Maybe because of the OD/ID ratio?
Shall I change the geometry and keep the UG-27 minimum thickness everywhere?
Thanks!
