Nozzles Attached on Elliptical Head
Nozzles Attached on Elliptical Head
(OP)
Hi,
I had a discussion with my collegue at work because he thinks that the nozzles attached to an elliptical head must be placed inside a circle of diam = 0.8 Head's OD.
Refering to the ASME code UG-37, I only found that in case the nozzles (with their reinf pad) are included in a 0.8*(Head's OD) circle, then the required thickness of the shell for reinf. calculation would be of that of an spherical head with a corresponding coef. depending on the radius relation of the ellipse.
Since he's a 60 year old man with a lot of experience on PV design and I'm new in this subject, I'm not sure if he's right or wrong.
Can anyone give me his personal opinion?
PS: Sorry, I published the same thread in the piping forum.
I had a discussion with my collegue at work because he thinks that the nozzles attached to an elliptical head must be placed inside a circle of diam = 0.8 Head's OD.
Refering to the ASME code UG-37, I only found that in case the nozzles (with their reinf pad) are included in a 0.8*(Head's OD) circle, then the required thickness of the shell for reinf. calculation would be of that of an spherical head with a corresponding coef. depending on the radius relation of the ellipse.
Since he's a 60 year old man with a lot of experience on PV design and I'm new in this subject, I'm not sure if he's right or wrong.
Can anyone give me his personal opinion?
PS: Sorry, I published the same thread in the piping forum.





RE: Nozzles Attached on Elliptical Head
Please do not cross post.
prex
http://www.xcalcs.com
Online tools for structural design
RE: Nozzles Attached on Elliptical Head
jt
RE: Nozzles Attached on Elliptical Head
A lot of years is not equal to "good experience"
Regards
rhg
RE: Nozzles Attached on Elliptical Head
"... my interpretation has been that there are no specific requirements in the Code when the nozzle and its reinforcement fall outside the 80% limit, i.e. is is a U-2 (g) design, therefore I tend to avoid placing nozzles out there."
It is kind of a question of what you can justify to customers and AI's, and many "old guys" avoid the practice.
As asked, this is my personal opinion.
Regards,
Mike
RE: Nozzles Attached on Elliptical Head
RE: Nozzles Attached on Elliptical Head
in your OP you wrote '...must be placed inside...': if you use that wording, then the answer is 'No, you are not obliged by code to do so'.
If you have the choice, then of course there is no reason to place a nozzle with part (or all) of its reinforcement outside that circle. The point is that sometimes you need to do so.
prex
http://www.xcalcs.com
Online tools for structural design
RE: Nozzles Attached on Elliptical Head
The vessels 12' dia, 16' lg, are designed for FV & 100 psig @ 150°C. There has never been any questions during numerous repairs under the auspices of several AIs' and insurance audits.
The calculations for the original vessels was by hand and when an FEA was done the stresses were within 5% of the calculated around the nozzle.
RE: Nozzles Attached on Elliptical Head
BTW, the phrase "and its reinforcment" to me means the limits of reinforcement and not just a pad. Something to watch when putting a nozzle near the edge.
Regards,
Mike
RE: Nozzles Attached on Elliptical Head
I checked today and found out all the archived historical information that was available for a lot vessels has been discarded, even some that are still inservice. The 6 vessels that I referenced have all been replaced inkind and only have a U1 sheet in the files. There are no calculations or any copy of the FEA study in the any of three sets of files that pertain to the installed equipment.
Unfortunately the engineer that made the original calculations is no longer with us.
I made an inquiry to the current AI to see if perchance he has copy of the FEA file folder that contained both the FEA analysis and the original calculations.
RE: Nozzles Attached on Elliptical Head
Mike
RE: Nozzles Attached on Elliptical Head
You are ok: use "tr" in UG-37 as defined in UG-32(d) when calculate a nozzle outside 0,8D
Regards
rhg
RE: Nozzles Attached on Elliptical Head