How to relate internal pressure and weight?

[lpfaustini]

Dear fellows,

Please someone correct me if I'm wrong. In appendix F "internal pressure cannot exceed the weight of the roof".

So:
Pi (kN) < Wr (kN)

-> Wr is a known value (ton);
-> Internal pressure is limited to 3kPa;
-> Di is the inside diameter of the tank (m);

Dp < Wr
pi*Di^2/4*Dp < Wr*9,81

Then, "internal pressure cannot exceed the weight of the roof plus the weight of the shell".

So:
pi*Di^2/4*Dp < (Wr+Ws)*9,81


Thanks in advance

 

[IFRs]

Not sure what revision you are looking at but the general idea is if the internal pressure does not exceed the weight of the roof plate then you are not into Appendix F at all. If the internal pressure is more than the roof plates alone but does not exceed the weight of the shell and roof then use F.3 through F.6. If the internal pressure exceeds the weight of the shell and roof then use F.7. If the internal pressure exceeds 2 1/2 psi then you are out of the API 650 world.

 

[lpfaustini]

Dear IFRs,

I appreciate your comment, but I am aware of all of it. I simply wanted to know if my calculations were right. Please, correct me if I'm wrong. Thank you.

 

[JStephen]

In the first equation, I'd just normally make the comparison on a unit basis. The roof weight there does not include weight of rafters acting on shell. So just weight of plate/ square meter vs pressure.

In the second equation, wr would include the weight of rafters supported by the shell as well.

 

[lpfaustini]

JStephen,

I suppose "weight of plate/square meter", the "square meter" is pi*ID^2/4. Am I right?