Fluorine Free Foam for Tank Protection

There is not much to say about F3 foams and tank protection. The properties of fluorinated surfactant based foams are very important for a number of tank fire fighting methods. This has often been attributed to ‘fuel shedding’ proprieties of AFFF’s, however, there doesn’t appear to be any real confirmation of why AFFF works as it does. None of the major design standards (NFPA 11) allow the use of F3 foams for these applications, so it is difficult to see how a fire protection engineer can design such systems. In Late 2017 the Australian Standard for foam systems, AS 1940, was updated and wording for allowed foam types was generalised to allow the use of F3 foams (or any foam), however, the design application rates are almost certainly inadequate.

Sub-surface injection relied (more than anything else) on the fuel shedding properties provided by the fluorinated surfactants. So sub-surface injection should not be considered with F3 foams unless realistic, large scale testing is done to prove it. My guess is you would be wasting your money to test the products currently available.
Top application. The evidence is that even existing foams don’t work very well for larger tank fires, the design application rate needs to be higher for them, so F3 foams will have a problem too. New systems that very gently apply the foam might help, but getting the F3 foams to flow long distances might also be a challenge.
Monitor application. Non-aspirated application is probably not going to work at present, see more here…. Using aspirated nozzles might work if the F3 foam can pass forceful small scale fire testing but large scale testing is almost certainly needed as well.

I should note that low viscosity AR-AFFF’s would not seem to be as good as the high viscosity versions in terms of burn back resistance. From our fire testing, the burn back resistance of high viscosity foams on hydrocarbons fuels is much higher than for the low viscosity AR-AFFF variants. In most applications, we do not believe the low viscosity variants offer any real advantage (low temperature use is the main exception). Proportioning systems can be engineered to use the high viscosity versions.

The major oil companies have carried out extensive large scale fire testing of fluorinated foams for tank applications. No such test data exists at this time for F3 foams that we are aware of. The SP Fire Research report on Tank Fires (See reference below) lists 42 additional references for tank fire testing.

Industry experience and a number of research projects suggest that the present approval standards, such as UL 162 & EN1568, for foams do not adequately simulate tank fire conditions, this is particularly true for polar solvent tank fires and for larger hydrocarbon tank fires. This applies to both fluorinated foams and F3 foams.

If any foam concentrate manufacturer has witnessed test data for this application we would be pleased to be able to publish it here along with their recommendations for application rates.

References.

Fighting fires in oil storage tanks using base injection of foam — part II, Nash, P. & Whittle, J. Fire Technology (1978) 14: 147. doi:10.1007/BF02308909

Tomakomai Large Scale Crude Oil Fire Experiments
Fire Technology, ViX. 36 No. I 2000 Hiroshi Koseki, Yusaku Iwata, et al.

FOAMSPEX. Large Scale Foam Application – Modelling of Foam Spread and Extinguishment. SP Fire Research, Sweden.

Tank Fires. Review of fire incidents 1951–2003. SP Fire Research here…

ETANKFIRE. Ethanol Tank Fire Fighting. SP Fire Research here…