Misalignment Fit up Head to Shell in a boiler
Misalignment Fit up Head to Shell in a boiler
(OP)
Hi All,
I have an issue on a fit up of a flat head (tubesheet) with the shell.
head & shell th 45mm
ID 2000mm
in order to keep final lenght due to an error on nozzle fit up the head have been reduced in hight (smaller diameter) and i have now a misalignment of about 15 mm all around.
What will be the maximum misalignment allowed according to ASME VIII div 1,
Yhank in advance





RE: Misalignment Fit up Head to Shell in a boiler
I'm having trouble understanding your expression "misalignment". The ASME VIII Div 1, UG-34 would give you all the "fit-up" requirements for the flat head (tubesheet). Please note that misalignment means offset of two centerlines, which cannot be measured in terms of 15 mm all around. Also remember, a picture tells more than 1000 words, try post/send a sketch of your misalignment as an attachment and we'll try to help you.
Cheers,
gr2vessels
RE: Misalignment Fit up Head to Shell in a boiler
thank for this quick answer, you are right I mixed up with alignment it is mmore an offset.
I attached a sketch of it.
RE: Misalignment Fit up Head to Shell in a boiler
RE: Misalignment Fit up Head to Shell in a boiler
RE: Misalignment Fit up Head to Shell in a boiler
Is the weld prep as drawn?
Has the weld prep been completed?
RE: Misalignment Fit up Head to Shell in a boiler
The welding will take place next week with a "transition weld" on the inside and then outside part by SAW.
For shell part
the design pressure about 800psi and Temperature 550F.
thanks
RE: Misalignment Fit up Head to Shell in a boiler
Joe Tank
RE: Misalignment Fit up Head to Shell in a boiler
I agree with Joe. Keep us informed of the outcome.
RE: Misalignment Fit up Head to Shell in a boiler
It looks a bit dodgy for a cookbook type of vessel design, but it's not hopeless. The code is recommending a few "standard shapes" for those dished ends, but does not preclude the use of other shapes, if you can produce a calculation (or even a FEA) to show the head is OK. Try to create the shape of a semi or tory head using the available thickness of material, then run the calcs for the given maximum thickness you can squize out of the fit-up sketch. It could herald some bad news, like de-rating of your vessel, but you may also be lucky to salvage the vessel rating, who knows. At least you know where you are, when the AI will tell you to scrap the dished end.
cheers,
gr2vessels
RE: Misalignment Fit up Head to Shell in a boiler
RE: Misalignment Fit up Head to Shell in a boiler
For your info
A transition weld will be done by SAW on the inside and outside.
regards
RE: Misalignment Fit up Head to Shell in a boiler
cheers,
gr2vessels
RE: Misalignment Fit up Head to Shell in a boiler
Could you psot pictures or cross-sectional sketches of the repair for us that are "pictorally challenged" ?
Thanks...
-MJC