Vessel shell / dome mismatch
Vessel shell / dome mismatch
(OP)
Recently we came across a big problem.Fabricated dome and shell dia got mismatched.
Fabricated Ellipsoidal dome id 3476 mm
Fabricated Shell id 3400 mm
Kindly help me with possible solution.
Fabricated Ellipsoidal dome id 3476 mm
Fabricated Shell id 3400 mm
Kindly help me with possible solution.





RE: Vessel shell / dome mismatch
RE: Vessel shell / dome mismatch
How about slit the shell lengthwise & add a 238mm[9-3/8"] strip & re-roll?
RE: Vessel shell / dome mismatch
Head ID: 3476 mm = 136.85"
Shell ID: 3400 mm = 133.85"
You are only 3" off. Seems like a conical reducer at the intersection would be about as simple a fix as any.
Good luck...measure twice and cut once!
Brian
Pressure Vessels and Autoclave Systems
www.mcabeeconstruction.com
The above comments/opinions are solely my own and not those of McAbee Construction.
RE: Vessel shell / dome mismatch
The conical reducer sounds like an obvious option. But whatever you do, you're either going to have to do some re-engineering to make everything fit (and possibly reduce allowable pressure as well) or else bite the bullet and buy/fabricate the right item. If you put that conical reducer in, everyone that sees the thing for the next 50 years will wonder why it was built that way.
In the event that the thickness was considerably larger than the the offset, you might have other options. If the design pressure were actually very low, you'd have some other options.
RE: Vessel shell / dome mismatch
RE: Vessel shell / dome mismatch
In addition to his request you might add whether the vessel was PWHT'ed and the length.
PS:
I would get someone to fab the reducer if you go that way. The insulation guys are going to love you.
RE: Vessel shell / dome mismatch
To reduce the amount of welding you may have only 3 petals and a small central crown. A good fabricator can easily maintain the shape with in limits.
RE: Vessel shell / dome mismatch
Without the material/thickness/etc. information requested by weldtek, I would have to guess that in general, a new formed head may be less than or equal to the cost of the intensive cutting and welding required to resize the existing head.
RE: Vessel shell / dome mismatch
Steve Braune
Tank Industry Consultants
www.tankindustry.com
RE: Vessel shell / dome mismatch
Thank you all for your valuable suggestions.
Shell / dome Mateial of construction as under
Dome : Thickness 25 mm 516 GR-70
: Ellipsoidal ratio 2:1
Shell : Thickness 14 mm 516 GR-70
Dear WELDTEK, could you suggest little more?
RE: Vessel shell / dome mismatch
If you need the smaller diameter, the first thing I would do is contact the head fabricator to discuss the possibility of having him reshape the head(s). If you feel that none of these ideas will work, let us know, because there's obviously lot of talented people participating in this forum.
RE: Vessel shell / dome mismatch
Have you spoken with your AI? The Jusrisdiction?
I would require a NCR,new calcs.,NDE and maybe PWHT. It would be painful,but doable.
RE: Vessel shell / dome mismatch
I can't see any customer accepting anything other than a "normal" shell correctly sized and attached to a correctly sized "normal" head, i.e. you fix the mistake so the vessel won't look like a "Frankenstein". While some of the suggestions are certainly "viable" options and structurally/code acceptable, I just can't seem to see some of them as anything other than "booty fab"...and I feel a customer would see them as the same, i.e. a cheap attempt to remedy a major mistake.
Best of luck.
Brian
Pressure Vessels and Autoclave Systems
www.mcabeeconstruction.com
The above comments/opinions are solely my own and not those of McAbee Construction.
RE: Vessel shell / dome mismatch
RE: Vessel shell / dome mismatch
What are the design conditions which are causing disned end of 25mm thickness and shell of 14mm?
RE: Vessel shell / dome mismatch
you have to accept and eat the mistake.
If you have a machine to expand the shell ends, disregard the above and calc for the thinning and enlarged OD
ER