Calculation of Shell Thickness from Seismic Calculation in API 650

[TheEverest]

In a Pressure Vessel Handbook by Megyesy, I found a formula to calculate the thickness of the shell by using a Maximum seismic moment at the base of the tower. But in API 650, I could not find the exact formula to calculate the minimum thickness of the shell by using seismic calculation (or seismic moment).
Can anyone please help me?
Thank you!

 

[HTURKAK]

The shell thickness as per API 650 is determined acc. to section (5.6 SHELL DESIGN ) using the hydrostatic test loading , design liquid loading or other minimum requirements.

The determined shell thicknesses are checked for seismic loading and if necessary, the thickness of the relevant shell course increased but in general , the thickness will be satisfactory unless high seismic zone or H/D ratio is high.

 

[JStephen]

Refer to Annex E.
There is one section relating to seismic hoop stresses, which is one check.
There is a different section relating to seismic uplift and overturn, which is based on shell compression, which is a different check.
In those equations, you assume a thickness and calculate stresses to confirm adequate thickness, rather than calculating thicknesses directly.

 

[TheEverest]

Thank you HTURKAK for the reply.

Yes, JStephen, I was referring to Seismic Hoop Stresses in Annex E, and I was wondering if the shell thickness is directly calculated because I found an example problem where thickness due to Seismic calculations was written separately. Since the example problem was downloaded from google, it might not be an authentic one.

Anyways, now my doubts are cleared with your replies.

PS: Can anyone of you please provide me any calculation report from one of the software you use for API 650 tank calculation? I am having lots of difficulties because I am not using any software. I would truly thankful for your help and support.
KIND REGARDS

 

[HTURKAK]

I am retired engineer and in past , I developed my excell spreadsheets and suggest you to develop your own spread sheets. There is a worked example at APPENDIX EC .EXAMPLE PROBLEM #6.

 

[TheEverest]

Thank you HTURKAK. I am trying to build up my own spreadsheet for the overall API 650 calculation. And I come across several confusions, so I was hoping to get some genuine example problems so that I could clear my doubts as well as verify my work.