Shell thickness check for Hydrotest of Half-Pipe Jacket Coil

[ashaykadam]

We are designing a vessel on which Half-Pipe spiral coil jacket is provided on shell from BTL upto half of shell length.

Hydrotest pressure for Half-Pipe spiral coil jacket is considerably high.

We wish to know how to check shell thickness adequacy during Hydrotest of Half-Pipe spiral coil jacket.

I guess, we need to design shell for external pressure as Hydrotest pressure of Half-Pipe spiral coil jacket. But I am not sure what unsupported span shall be considered?
Will it be "complete shell + 1/3rd part of both dished end" as we consider during vacuum condition?
Or it will be "upto half of shell length where coil is placed"?
Or it will be equal to "coil pitch"?

Also tell me whether we can consider Half-Pipe spiral coil jacket as stiffner in such case?

 

[brkmech1234]

FEA is correct way analysing this. But, I suggest a short cut. You assume this to be a long flat plate with width equal to id of half pipe jacket. You may use roarks or UG 34 to calculate the stress induced during hydro.

 

[jamesl]

Take a look at nonmandatary appendix EE in the Code. Apparently shell thickness calc does not consider pressure in half pipe jacket.