half of leg support coming on Knuckle region. Acceptable or not in ASME

[inammanj123]

I have a ASME div.1, S.S vertical vessel with 1500 mm I.D. Bottom head is cone, with knuckle at large end.

In the drawing vessel in supported on legs made out of pipe. center of pipe is in line with shell mean diameter, so a part of the pipe will be coming on the knuckle region of cone.

As per my understanding we cannot weld anything on knuckle of head. How can i justify a leg welded on the knuckle region?

Regards,
Inam

 

[MJCronin]

Can you post details from the vessel drawing ?

MJCronin
Sr. Process Engineer

 

[TGS4]

Such a detail is neither specifically permitted nor prohibited. Engineering judgement must be applied.

So, to answer your question - it depends...

 

[Geoff13]

My company has done many column supported pressure vessels with details that sound similar to yours. You just need to determine what your design methodology will be that meets U-1(a)(3).

 

[inammanj123]

i heard someone giving reference of denis r moss book about not putting attachments on knuckle region.. any idea..i searched the book but couldn't find any reference

 

[KevinNZ]

We found a similar problem with an unreinforced tapping in the knuckle region. When we checked this detail with NozzlePro we find the stress riser fails the knuckle under design pressure.

 

[SnTMan]

High stress in the knuckle. Huh.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[TGS4]

Don't get me wrong, there are very high discontinuity stresses in a knuckle, and adding something like a support there will necessitate an FEA to qualify the design.

Just because something is a generally bad idea doesn't mean that it's prohibited. Just that the level of Engineering needed is increased.

 

[r6155]

Centroidal axis of pipes used as legs coincide with the centerlines of the vessel shell eliminates the eccentricity in the column. This is the best design.

Regards
r6155