API 650 paragraph F.7.5. 1

[Syahar1975]

Good morning Tank Builders,

API 650 - 2013 appendix F paragraph F.7.5 :

My understanding on this paragraph is we need to do the air test twice. First when the water reaching design liquid height. Second after the water completely disposed.

Appreciate if you can share me your opinion.

Syah

 

[JStephen]

I believe that is correct. The first test is loading the shell to design stresses, the second test is loading the anchorage to design stresses.

 

[Hardarie]

hi JStephen,i have different opinion

the first is also loading the anchorage, because bolt shall be tightening when tank is fully filled with water when test.
of course, that is prior to air pressure test. then when air pressure is applied, the anchorage is tested for design stress,

i'm still not getting any idea why second air pressure is needed when tank is empty

 

[JStephen]

You get a lot of uplift resistance from the water over the bottom plate. That isn't considered in the design in this case, but should reduce loading on the anchor bolts.