Overlapping Welds for Lethal service in accordance to ASME BPVC Section VIII Div. 1

[ElCidCampeador]

Hello,

I have a vertical vessel in Lethal Service, construction code ASME VIII Div.1, material SS 316/316L from plate, fully radiographed.
This vessel has many stub-end connections and 3 legs with reinforcement pads as support.
I have to choose where to put the longitudinal weld of the shell.
Only 2 choices (I can't change nozzles' placement):
1) Longitudinal weld which intersects 2 stub-end nozzles, so it will be interrupted, BUT full visible
2) Longitudinal weld which doesn't intersect any nozzles, BUT is covered for a small section by a reinforcement pad of the legs.
Longitudinal weld is fully radiographed, even the section under the pad.
Are both solutions above accepted by ASME? In what article is written?
See also interpretation BPV VIII-1-17-11 and this thread

http://www.eng-tips.com/viewthread.cfm?qid=411171

Thank you

 

[r6155]

1)and 2) are not acceptable.
Good engineering practice in lethal service: all pressure welds must be pass leak test (Helium…..).
Delete the pad of the legs. Try to use 4 legs instead of 3 to reduce stresses, if necessary.

Regards
r6155

 

[ElCidCampeador]

1)and 2) are not acceptable.

Not acceptable according to...? ASME? Or only to good engineering practice?

 

[r6155]

If longitudinal weld is covered by a pad then leak test can not be made. Hence is not acceptable by ASME.
Please, read more about lethal service.

Regards
r6155

 

[Jano6924]

Take a look into this link:

https://pveng.com/lethal-service-notes/

Maybe you can find what you are looking for.

Regards.

 

[Trestala]

You can always change the nozzle placement to avoid the longitudinal weld. Why exactly is it limited? Are the nozzles placed in between leg pads? With this situation, you can talk to your piping engineer to re-arrange the attached piping. Just explain that you have no choice but to comply with the requirements.

 

[ElCidCampeador]

I can't change nozzle placement because is fixed by client (the vessel will be assembled on a skid).

I think the only solution could be 1): in this case all the seam will be full visible, although interrupted.

r6155 why 1) is not acceptable?

 

[r6155]

Some type of defects can not be detected when fabrication is under 1)
Clean design is mandatory for lethal service, like nuclear.
Your design under 1) is wrong for normal service too.
Sorry, you are not in conditions to design for lethal service.

Regards
r6155

 

[ElCidCampeador]

My client wants to know where in ASME code it's written that is prohibited this kind of design. Sorry if I insist, but it's new for me and I don't want to make any mistake.