For the NFPA 30 tank tightness test (Section 21.5), it requires testing of the primary tank and the interstitial space. It does not tell us that the tests need to be conducted separately.
For the last two new aboveground horizontal storage tanks at our facility, they have pressurized the inner tank to 5 psi, and the interstitial space to 3 psi, simultaneously. This must be an industry standard, right or wrong.
This doesn't seem right to me. My intuition is that these should be two separate tests. Does anyone have any thoughts on this? It seems to me the pressure on the primary tank would be 2 psi in this configuration.