Difference in Head and Shell Thickness 2

[10815L]

Hi All,
I'm supervising pressure vessel Manufacturing Project(Three phase Separators) and noted difference in Head and Shell thickness and on enquring from vendor he replied, "The head thickness given is Minimum, after considering thinning allowance for forming. the nominal thickness for both shell and head at joint would be the same"
can any one explain me this further on thining allowance forming, thining allowance from what?
Thanks
10815L

 

[Latexman]

Heads are formed (cold worked) from blanks (shaped like a blind flange). The thickness of the formed head will be less than the original blank; i.e. it thins. Vessel fabricators do this so often, they know how much the thinning should be (thinning allowance).

Good luck,
Latexman

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[bimr]

The head manufacturer adds a thinning allowance to the heads to ensure that the finished heads meet the minimum thickness in all areas. During the head forming process, the metal does not disappear but may flow to the areas that are most worked. On a spun head, the flange may get thicker and the knuckle will get thinner due to cold working.

 

[MJCronin]

This is a question that should be asked in the "Boiler and Pressure Vessel forum"....better answers there

 

[Latexman]

Making a Head

Good luck,
Latexman

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[Compositepro]

I'm not an expert in this area, but I would assume that the metal is made as thick as it needs to be for the service. The stress in the cylindrical shell due to pressure (hoop stress) is twice the stress in a hemispherical head. So less metal can be used in the head.

 

[10815L]

Hi,
Thanks a lot for good explannation, particularly Latexman for sharing good video.
10815L