"Set in" nozzles versus "Set on" nozzles - pros &cons?
"Set in" nozzles versus "Set on" nozzles - pros &cons?
(OP)
Hello all
I have recently been asked to update a standard drawing design which includes a 1" nozzle projecting from a larger diameter elbow. But the problem in terms of structural strength, welding practicality etc is whether to make it a 'set on' or 'set in' nozzle. Has anybody else out there looked into the pros and cons of each possibility?
Any advice, links, references etc would be really appreciated.
Cheers.
I have recently been asked to update a standard drawing design which includes a 1" nozzle projecting from a larger diameter elbow. But the problem in terms of structural strength, welding practicality etc is whether to make it a 'set on' or 'set in' nozzle. Has anybody else out there looked into the pros and cons of each possibility?
Any advice, links, references etc would be really appreciated.
Cheers.





RE: "Set in" nozzles versus "Set on" nozzles - pros &cons?
However, when vessel wall thickness becomes large (over 3/4"?) and is much larger than that of the nozzle, a sit on nozzle may become more practicable. Weld thickness becomes smaller and this occasionally may allow to avoid a PWHT.
prex
http://www.xcalcs.com
Online tools for structural design
RE: "Set in" nozzles versus "Set on" nozzles - pros &cons?
My preference is the "set on" (a.k.a. saddle on) method - because it's self-supporting during fit-up. You don't have to worry about the nozzle or branch dropping through the hole before the welder gets a tack in place.
Also, the "o-let" family of branch connection fittings are intended to be "set on" the pipe.
Regards,
Donf
RE: "Set in" nozzles versus "Set on" nozzles - pros &cons?
The weld-in (contour)type of fitting has many theortical advantages. The weld-in includes a generous "forged-in crotch radius" that results in enhanced structural advantages. It can be seen in B31.3, Appendix "D" that the SIF is significantly less for the weld-in fitting and that bodes well for fatigue life. Also note that "the o-let" family of fittings includes both the weld-on (wled-o-let) and the weld-in (sweep-o-let).
BUT, it is easier to fabricate branch connections that employ the weld-on type fittings.
Regards, John.
RE: "Set in" nozzles versus "Set on" nozzles - pros &cons?
Never understood why process engineers always want a thermoweld in the worst case elbow.
Which ever type you decide to use put it in right and treat it right. Watch the chainfalls.
RE: "Set in" nozzles versus "Set on" nozzles - pros &cons?
Always thought that both set-in and set-on nozzles were technically acceptable the decision to use one or the other being a question of which is the cheapest weld to make.
athomas236
RE: "Set in" nozzles versus "Set on" nozzles - pros &cons?
Not being critical I think I would have used the words "most economical for this situation" instead of cheapest. This word scares me when it comes to welding. I've seen too many cheap welds, in fact yesterday. The ones I saw yesterday, Ray Charles could have done better.
The word cheapest is usually picked up by upper management and the battle is on. Over the years, when forced to accept welding contractors our group deemed marginal in qualifications the cost of rework was squared not doubled.
RE: "Set in" nozzles versus "Set on" nozzles - pros &cons?
Thanks very much for all the various perspectives.
It thus appears that while both methods of nozzle attachment are technically sound, the criteria for choosing between the two options thus becomes a practicality and cost issue.
Thanks again
RE: "Set in" nozzles versus "Set on" nozzles - pros &cons?
Glad the answers were useful, didn't realise we had to be so careful with the use of words rather than concepts.
athomas236
RE: "Set in" nozzles versus "Set on" nozzles - pros &cons?
Having attended many conceptual pre-project meetings where you have everyone present and ready to pounce,I learned that a word sometimes carried more weight than 1" bolt. Though most of these meetings are as exciting as watching a Lava Lamp there is always a pickup and play on words.
I had a magazine article that had 100 words to never use and 100 words to use. I remember that “cheap” was one to never use because you had no out. Where as if you use the something like “most economical” you have some hedge room. There might have been some accountants from "MBOT’s" company watching.
I didn’t take my own advice “don’t lead with your lips”
RE: "Set in" nozzles versus "Set on" nozzles - pros &cons?
No probs mate - when it comes to simply requesting a few ideas (like i did), i'll check out the words, concepts, comments, philosophies, anything!
RE: "Set in" nozzles versus "Set on" nozzles - pros &cons?
2) hope you weld the branch on the neutral axes and not on the extra or intrados of the elbow;
3)for a pressure vessel use "set in " nozzles;strength wise the minimum nozzle size should be 2".
RE: "Set in" nozzles versus "Set on" nozzles - pros &cons?
Just one question though - where did you find this information...are they general engineering rules of thumb or is this info hidden away in some spec?