Large Rectangle Openings in Vessel. 4

[curlyjackme]

I am trying to verify the replacement area for a 17' 2" x 22' rectangle opening in a 40' diameter vessel with .635" wall thickness. Is ASME VIII Div 1 section 1-10 allowable to calculate the replacement area for this large of an opening?
Is replacement area the same regardless of shape? I could not find anything in Section VIII that specifically deals with this size of opening in a vessel. Did I overlook it?

 

[Unotec]

I am assuming this is a steel tank, right? API 650?

Just a question.

Why would you replace such a large piece of the tank? Corrosion?


<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying ” Damn that was fun!” - Unknown>>

 

[curlyjackme]

No the vessel is to be built to ASME section VIII. However it will not be required to be stamped.

 

[saplanti]

I guess the manufacturing is in accordance with ASME VIII not the design. In that case you need to use the fundamental structural calculation to overcome the reduction of strenght on the vessel due to opening. You may use reinforcements around the opening area to compensate.

The other restriction might be differantial deflections around the opening in case a flange connection involved.

Regards,

Ibrahim Demir

 

[TomBarsh]

Sounds like a very large "breech opening". Browse through your reference books for breech openings in exhaust stacks. The book "Tubular Steel Structure" by Troitksy, from Lincoln Welding Institute, has a detailed chapter on design of breech openings. So does the steel plate engineering manual published by the Steel Plate Institute.

By the way, what is the design pressure?

 

[curlyjackme]

The design pressure is 30 psi internal with full vacuum external. There are some large internals to the vessel that have to be replaced periodically that is the reason for the large opening. Thanks for the information about the books.

 

[BUTCHCWIQAM]

this may be a stupid question but can someone help me out a little , when can you have a vessel that is 30 psi with full vacuum and get away with not haveing the vessel stamped, is this a state regulation or am I missing something here, I was under the belief that if you cut ,grind or weld on a vessel you had to recertify said vessel...I sorry guys maybe the grey matter isnt working today. thanks for helping me out

 

[JohnGP]

Butchcwiqam,
I don't think the vessel is built, so no need for recertification. Section VIII has a number of exclusions to its scope and if this vessel fits into any of the relevant categories, the stamping would not be required. Maybe it's not in the US - I have seen vessels designed and built to ASME VIII, but subject to the European PED, so CE stamped in lieu of ASME U stamp. Just my 2 cents worth.

John

 

[BUTCHCWIQAM]

I have seen these types of vessles and That I completely understand but the way I read the 1st post was as if the vessle had been built and wroking and now they are going to make some changes to the shell and lets assume that the vessle is in the states... would the owner still have to have the vessel certified Stamped to be able to carry insurance on this vessle. this one has me by the tale and will not let go
I am sorry guys for wasting your time

 

[curlyjackme]

BUTCHCWIQAM, This is a new vessel that has not been fabricated as of yet. It is still in the engineering phase.

 

[Unotec]

curlyjackme

The design pressure is 30 psi internal with full vacuum external

Does this mean that the vessel will be inside another vessel that is at vacuum?

BUTCHCWIQAM I also thought it was an existing vessel

<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying ” Damn that was fun!” - Unknown>>

 

[curlyjackme]

It is not inside another vessel. Let me try to clarify the design pressure. It is +30 psi and -15 psi (Full Vacuum) on the internal. I ususally treat the vacuum pressure as an external load on the shell of the vessel that is the reason I stated that way. Thanks for all the comments. After doing a lot of reading I think I have this figured out.

 

[saplanti]

The attachment might give you an idea about how the opening supported. Unfortunately, I do not have previous pages of the document.

Regards,

Ibrahim Demir

 

[racookpe1978]

So you have atmosphere (15 psia) - the 40' pressure vessel with a 17' x 22' rectangular opening in its .635" side wall - then a "full vacuum" (0 psia) internal pressure ?

What it really seems like is that you're (unbolting and removing periodically) a section just about 1/4 of the around the tank wall.

Why not consider it like a pressure vessel of 20'-0" radious, then put a 2" thick x 3" wide reinforcement (for the (hundreds!) of tapped bolt holes around your 17 x 22 opening, then add the "cover plate" calculated as a tank wall of radius 20' 2"?

You won't want to use a "flat" cover plate.