NFPA 11, Bund Area & Application Rates

[Hotwheels1]

Hi Community!

We are in the process of designing the fire protection system for a gasoil and gasoline storage tank farm. The code followed is NFPA 11 and the system in question are "the Low-level foam discharge outlets for diked areas".

The tank farm will consist of 6 gasoil tanks and 6 gasoline tanks. See image below for simple sketch of arrangement.

Secondary spill containment will consist of external bund wall of 1.8m high (Black Line in Image), with 0.5m tall intermediate bund walls separating each tank (Red Line in Image).

When applying the application rate of 4.1 L/min/m2 for AFFF (NFPA 11, Table 5.7.3.2), we are debating whether to apply the foam to the smaller intermediate net bunded area per tank (E.g. Bund Area A), or do we apply it to the overall full tank farm net bund area for all 6 tanks (Bund Area A+B+C+D+E+F)?

Of course the water requirements for the smaller intermediate bund area is considerably more cost effective.

Further info:
Each tank will be fitted with fixed top foam pourers and shell cooling sprinkler systems, supplemented by foam and fire water hose streams.

 

[IFRs]

I thought the application rates were based on the area of the tank, not the area of the bund.

 

[Hotwheels1]

To be clear, this design is for the fixed bund foam pourer application.

 

[stookeyfpe]

An active fire suppression system for a containment structure (i.e., bund) is not required by NFPA 30. I have no experience with EU or Asian standards regarding this question.

 

[UFT12]

NFPA 11, 5.7.3.3.2. Since you are providing separation between tanks and since sprinkler cooling will be active for all neighboring tanks, why not take advantage of it by considering just one diked area? At the end, surely these will be insured somehow so what not checking with the insurance carrier?