What is the correct way to pressurize the interstice of a double-walled tank during a pre-installation air test?

Pressurizing the interstice of a double-walled tank with air from the inner tank is the correct method to ensure integrity during a pre-installation air test. This approach allows for the detection of leaks by creating a controlled environment where any drop in pressure can indicate potential breaches in either the primary or secondary containment layers.

By using air from the inner tank, it allows operators to effectively monitor pressure changes and ascertain if there are issues that need to be addressed before installation. This method ensures both the inner and outer walls are structurally sound and that the interstitial space remains sealed and intact, which is critical in preventing environmental contamination from stored products.

Utilizing gas from the outer tank could lead to inaccurate pressure readings if the outer tank is not properly evaluated for structural integrity beforehand. Filling the interstice with water could also complicate the testing process and obscures leaks in this space. Choosing not to pressurize at all would neglect this critical detection step, increasing the risk of undetected leaks and possible regulatory violations post-installation.