We have fabricated a Pressure vessels as per ASME SEC VIII DIV 1,in which Ovality exceeds the tolerance given in UG 80.Fabrication of vessel is completed . We tried to reduce the ovality by External stiffeners, but we are not able get the ovality with in tolerance. Please advice how to solve this


Prasanna

We have fabricated a Pressure vessels as per ASME SEC VIII DIV 1,in which Ovality exceeds the tolerance given in UG 80.Fabrication of vessel is completed . We tried to reduce the ovality by External stiffeners, but we are not able get the ovality with in tolerance. Please advice how to solve this

Prasanna,

Make a design change as non-Code vessel and then call your client if they will accept the vessel as is, otherwise cut your loses and scrap the vessel. ASME Code Section VIII-1 will not provide you a solution and your AI will not allow this. Next time consider using stiffeners to control ovality and adhere to 1% limit of UG-80.

leem817

What is the diameter and thickness ?
and
How are you checking Ovality ?

Prasanna,
The vessel section doesn't have to be circular. It can be obround, rectangular, or any shape you can imagine. Thus, nothing prevents you from making a "not truly round" shell. It only needs to be designed the proper way. You can't use UG-27, and other rules as they are. Perhaps you will have to go to U-2(g), develop some way of dealing with local bending stresses etc. And of course, talk your client and your AI into it. As you can see, it's just a matter of your attitude: it can be a scrapping problem (as leem817 suggests) or an engineering (a paper) problem. As a design engineer, I would suggest redesigning rather than scrapping. A quick cost calculation should help with choosing the right way.

_________________
Konrad Anikiel

Outside diameter=2500 mm,thickness=10 mm

I think you may not use roller to form you shell, hehe

otherwise, 1%*2500=25mm. it is much big enough for forming/

maybe you use two half or some other method to fabricate the course?

_________________
Paul Wei

Inside dia measured are 2457 & 2490 mm.1% of Individual Dia are with in tolerence but the difference of Dmax and Dmin is more than 1%