Jacket Space Width (ASME SECTION VIII DIVISION 1)

[brs766]

In 'Mandatory Appendix 9 - Jacketed Vessels' there is an equation to determine the maximum jacket width based on your jacket type. This value is the maximum distance between the outer radius of the shell and the inner radius of the jacket. What is the mechanical significance of this constraint? Is there a derivation of the equation j = (2*(St^(2))/(P*Rj))-((.5)*(ts+tj)). Thank you in advance for any help in describing this concept to me.

 

[gr2vessels]

I'm not sure of the question, but I'll give you my interpretation;- for a given material, the limit of jacket space is function of the stress developed in the weld at the junction of closure and inner vessel and the stress at the weld of closure to the jacket wall. Obviously, increasing the jacket pressure, the jacket space will get smaller due to the need of proportional reduction of closure size, in order to keep constant the maximum allowable stress in the welds.
I hope my wording is not too confusing.
Cheers,
gr2vessels

 

[brs766]

Thank you, I understand it much more now. Is the weld stress a function of the inner surface area of the jacket and the outer surface area of the shell?

 

[gr2vessels]

It is the junction of the inner shell and the closure which could be overstressed due to pressure increase or junction space increase beyond the maximum calculated.
Cheers,
gr2vessels