UL 58 TANK DISTINGUISHING

[Jay_]

Dear All,

UL 58 mentions the below,

"3.1 For the purpose of this standard, the following definitions apply.
3.2 TYPE I TANK – A primary tank wrapped by an exterior steel shell that is in direct contact with the primary
tank; where, the exterior shell is wrapped from 300 to 360 degrees of the primary tank circumference.
3.3 TYPE II TANK – An outer tank physically separated from the inner primary containment tank by standoffs;
where, the inner tank is completely contained within the outer tank."

Now, for tank type, means there should be no interstitial space?

 

[HTURKAK]

I have old copy of 1990 Edition and the following figure explains the Type II secondary containment tank.





Type I secondary containment tank, similar but there is no annular space btw two tanks. The interior is wrapped by an exterior tank and is in direct contact with the primary tank and the exterior shell ht covers around 80 % of the inner tank that makes from 300 to 360 degrees .

 

[Jay_]

Thanks @HTURKAK , i am curious about the construction of the type 1 tank, what does a "direct contact" actually mean,
Usually we fabricate the tank per EN 12285-1 and we enclose 300 degrees of primary tank shell with a secondary tank shell.
The way we do that is by installing the external shell on the internal shell and we create a small interstitial space by welding flat bars on the primary tank.
we tension the external shell against the flat bar and weld it in place against the tank shell top. So i am just curious about the term "direct contact". seems little confusing no?

 

[HTURKAK]

Usually we fabricate the tank per EN 12285-1 and we enclose 300 degrees of primary tank shell with a secondary tank shell.
The way we do that is by installing the external shell on the internal shell and we create a small interstitial space by welding flat bars on the primary tank

UL addresses for TYPE I TANK that there will be no annular / interstitial space. The exterior tank will have direct contact with primary tank. If you are using EN 12285 , IMO UL 58 should be best practice rather than mandatory requirement.

 

[Jay_]

Thanks @HTURKAK again The only thing that is making me kind of use UL instead of EN is diameter. EN allows for maximum of 3m. unless new versions came up with broader intervals.