Containment for Sodium Hydroxide - Tight-Wrap Double Walled Tank

[OneManWolfpack]

I'm looking for guidance on containment for a 15,000 gallon steel tank to store 25% sodium hydroxide. I have specified a double-wall tank in lieu of a containment bund. I received an inquiry from the tank supplier asking if a "tight-wrapped double walled containment" is acceptable in lieu of 115% containment capacity. I did not specify 115%, only that the tank must be double-wall construction.

What does tight-wrapped construction entail, and how is this different from a standard double-walled tank? Any double-walled tank would provide >100% containment, correct? What is the significance of 115%?

Thanks for your help.

 

[bimr]

Tight-wrapped means there is intimate contact of the inner and outer tanks.

Tight-wrapped would mean that there is no way to check the integrity or paint the tank walls. I believe that tight-wrapping is mostly used on smaller tank designs. It would also be difficult to monitor the leakage.

There is nothing magical about the 115%. I believe the standard is 100% plus the 24-hour rainfall.

 

[chicopee]

It is best to have an air gap between the primary and secondary containment so that it can be slightly pressurized. If the primary containment failed the interstitial pressure would drop to atmospheric pressure. A pressure gauge would be the means of detecting failure of the primary containment.