UG-28 1

[Fizza453]

Intermediate semi ellipsoidal head also acts as a stiffener when making external pressure calculations as per UG-28, is it correct?


Nasir
Welding Engineer
DESCON ENGINEERING LIMITED
PAKISTAN

 

[gr2vessels]

Well, the circ weld is a line of support (UG-28(b)(1). Now, what do you mean 'intermediate'?
Cheers,
gr2vessels

 

[prex]

I don't see a specific treatment for intermediate heads in UG-28, but I also don't see why an intermediate head should not be considered as a line of support at h/3. However, as an intermediate head could be designed for differential pressure and be therefore thinner wrt the shell, I guess that the condition to be satisfied is that the intermediate head can withstand the design external pressure when applied to its convex side.

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[Fizza453]

Vessel has three semi ellipsoidal heads, the middle hedad is called intermediate head.
Now, again the same question when designing the shell against external pressure would intermediate head be considered as a stiffner? so that unstiffened length L may be reduced accordingly.
One more question, if the intermediate head is flat unstayed head (of UG-34), would this head be considered as stiffener?


Nasir
Welding Engineer
DESCON ENGINEERING LIMITED
PAKISTAN

 

[prex]

For the flat head, should not be difficult to prove conformance to UG-29 even by using only a small circumferential portion of it.

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[prex]

One further thinking: is the flat intermediate head subject to pressure when the shell is under the external pressure?
If yes, then there might be a problem, as a stiffener per UG-29 is not subject to any other stress than the one related to its stiffening function.

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[Fizza453]

Yes intermediate flat head is subjected to pressure too.


Nasir
Welding Engineer
DESCON ENGINEERING LIMITED
PAKISTAN

 

[prex]

Coming back on your problem to state that for sure the intermediate flat head is a line of support.
The fact that a flat head per UG-34 is a line of support, though this case is not explicitly treated by UG-28, is a matter of evidence: the flat head must of course resist the external pressure, thus it prevents the shell from buckling.
Now if the intermediate head is also subject to the external pressure, then it must be capable of withstanding it, and it is also preventing the shell from buckling: it is therefore a line of support.

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