Dear Sirs,

I am designing a storage tank of diameter 10 m & 13 m height, in which design internal pressure is the full of water. (API 650, 11th edition, June 2007, Addendum 1, Nov 2008)

My concern is, does the "appendix F" is applicable? As per "Fig. F-1", it seems to be no!

I have calculated "maximum design pressure (P)" from F.4.1. Does this calculated pressure is applicable in F.5.1 & F.6?

If not, then what do mean by "Pi" in F.5.1 & "P" in F.6?

Please help me out with this queries.

If your internal pressure exceeds 18 kPa (2.5 psig) then you are outside the scope of API-650, and API-620 must be utilized.

The "P" computed in F.4.1 is the same "P" used in F.6.

The "Pi" used in F.5.1 is your specified input value of internal pressure. Note, "Pi" should not exceed "P" computed in F.4.1. Also note that the equations in F.4.1 and F.5.1 are the reciprocal of each other. One equation gives you allowed pressure in terms of area, the other gives you the required area in terms of pressure.

Dear Richard sir,

Thank you very much for your quick reply. I extremely appreciated your reply. Now, my philosophy about these pressures is very clear.