Multiple Nozzle Openings Overlap

[loilfan]

I have two openings close enough together that their limits of reinforcement overlap. One of the nozzles (N1) is a forged HB type and has sufficient reinforcement in the area A2 to pass. The other nozzle (N2) needs A1 and A2 reinforcement to pass.

Am I able to "ignore" the A1 area for N1 (since I don't need it's strength) and give the full limit of reinforcement to N2's A1 area? Or can I only take the limit of N2 up to the shared limit (ratio of their diameters)?

 

[metengr]

Review Figure PG-38.1-1
Example of Two Openings Spaced With Limits of
Reinforcement Overlapping

ASME Section I, 2017 Edition for guidance.

 

[loilfan]

Thanks for the response metengr.

Figure PG-38.1-1 is identical to Figure UG-42(a). I forgot to mention that my question is relative to ASME VIII-1. I didn't see anything else in PG-38 or PG-33 that further clarified my question. Unless there's something I missed, I'll keep my question relative to ASME VIII-1 2017.

I had asked this question before, and it made sense at the time, but I'm having trouble justifying it now.

http://www.eng-tips.com/viewthread.cfm?qid=378595

Apologies for re-hashing a post. I would have messaged prex directly if there was a feature to do so since the original post is closed.

UG-42(a)(1) says
"The available area of the head or shell between openings having an overlap area shall be proportioned between the two openings by the ratio of their diameters"

The wording makes it sound that the maximum limit that I can take for N2 is the shared limit defined by the ratio of their diameters. However, if I choose N1 to have a limit of reinforcement of 0 (i.e. not account for A1), then their is no overlap and I could potentially take the full limit or reinforcement for N2. What prex said had made sense but I would appreciate clarification of this understanding since it isn't explicitly

Based on what prex said and how UG-42(a)(1) is written, I see two possible ways to view this scenario. Which approach should I take?

Option 1:
Consider N1 to have no parallel limit of reinforcement so there is no overlap based on "chosen limits" and N2 can have its full limit of reinforcement.

Option 2:
Consider N2 to have a maximum limit of reinforcement of its shared limit based on the ratio of their diameters.

Note that UG-42(c) is not an option in this example. i.e. I cannot assume a single opening encloses both nozzles.

I reviewed PTB-4, Bednar, Moss, Megyesy and other resources but couldn't find the answer.

 

[SnTMan]

loilfan, you could do it either way. In my class of work there is occasionally a spec requirement that no credit be taken for excess thickness in the shell, A1 = zero. In which case the limits in the shell are irrelevant.

Regards,

Mike



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

 

[MrPDes]

The most important thing is that the Local membrane stress at the edge of each nozzle remains with its allowables. The stress half way between the nozzle can't be greater than allowables if the stress at the nozzle edge is less than allowables.

If you choose to make less area "available" to a nozzle to remove an overlap, I don't see anything wrong with that. I think UG-42(a)(1) is only applicable to any overlapping area that is "required" for reinforcement by both nozzles.

Perhaps consider checking it with Div 2 reinforcement rules (in accordance with Code case 2695) just to make sure you're covered. Div 2 rules are allot less conservative than the clunky old div 1 reinforcement rules.

 

[loilfan]

Thanks for the responses everyone. Without the explicit wording the Code, it's nice to have the opinion of others within this community to make sure I'm not misusing the intent of the Code.