Hi,

For the section external pressure calculation, Elite estimates 3cases in different parts, such as chan_shell, shell etc, to chek if Pa < P.
Why it use those cases? It's mentioned by code?

Another question is how does Elite estimate external required thickness under external design pressure i.e. 0.18bars?

Thanks in advance

Please refer to ASME VIII Div. 1, Clause UG-28.

PV Elite computes the maximum external pressure the vessel can withstand per UG-28 as gr2vessels pointed out. These calculations are performed to help the user,

1. Use the given thickness and compute the maximum external pressure the vessel can withstand, Pa. This is also noted as EMAWP.

2. In the 2nd calculation, the thickness is varied till the Pa from UG-28 matches the external design pressure specified by the user. So, if you want to design for full vacuum and specify that in the input. Then, the program will keep on change the thickness until the Pa is equal to full vacuum pressure. This is helpful to the engineer to know the minimum required thickness for design, but also for future remaining life calculations.

3. In the 3rd calculation, maximum unsupported span is computed, using the thickness provided by the user, using the target pressure specified. So, the unsupported length of the element is changed till the Pa is equal to the desired external pressure. This is useful to find the optimum stiffener ring spacing.

So, in short this is a repetitive calculation process.

If you want to test it, take the required thickness computed by the program and put that in as the actual thickness then EMAWP will become equal to design external pressure specified.

Mandeep,

Thanks for more clear clarification about the calculation process.

It's helpful to me.