Method for comparison of different fire extinguishing technologies – Part 2.
Introducing the Foam Application Efficiency: proposal for the industry for comparison method of fire fighting technologies for Storage Tank Fires.
The R&d Department of FoamFatale International Inc. suggests to use the
FOAM APPLICATION EFFICIENCY (η)
as the numerical expression how effective the examined fire fighting technology is.
Requirements against the method:
- It has to provide the qualification of the examined technologies in figures, instead of subjective opinions.
- The results shall be based on correct measurements even in real situations and laboratory conditions.
- It has to be applicable for all kinds of Tank Fire Extinguishing Technologies.
- It has to be applicable for all kinds of Storage Tank Types.
- It has to be able to be carried out easily, without complicated instruments, precise equipment, etc.
- The method shall be able to open ways for further calculations, improvements, giving orientation on the direction of improvement of new fire extinguishing technologies.
FoamFatale Intl. worked out the next model to demonstrate the methodology.
F means the respected fire surface, in cylindrical tanks it is F=D2*π/4 [m2]
h means the measured foam blanket thickness in the moment of the successful extinguishment.
How can we collect these simple data after successfully finished real tank fire extinguishment?
If we accept that the foam based fire fighting is similar to a military battle, where the Commander has its Army (all of the foam volume that was available and used during the “Foam Attack”), and the foam volume we can measure on the hydrocarbon surface is the mass of the lucky “Survivals”, we can announce that the best war strategy, (Fire Fighting Technology) is where the Survivals / Warriors rate is the highest, in other words we have the less victims.
1. The WINNERS (Survivals)
The tank diameter is known, we can calculate the figure of F.
We can measure the existing foam blanket thickness h in the tank after extinguishing. It takes some courage to climb up to the top of the tank, especially because the metal parts (the stairway, the shell and the walkway around the tank upper edge maybe hot, and then we must measure what is the foam blanket thickness over the rest of the hydrocarbon.
Anyhow it can be carried out since it is usual to look around in the tank after the “Fight” to see whether the extinguishment was really complete, there is no source or danger for later reignition of the foam covered fuel.
It is easier to measure such value of foam blanket thickness if we are running tests in laboratory circumstances, e.g. in standard test trays.
The mass of “WINNERS” is Vremaining = F * h [m3]
2. The “WARRIORS” (“The Army”)
There are further data what we can measure during the fire fighting.
Let us suppose that we were operating several Fire Trucks in a manner of Over the Top application, by foam snorkels.
The produced foam by one truck is: V1 = Iv1 * t1 * er [m3]
V1 = the foam volume produced by the equipment #1, that has a Foam Solution Flow Rate of Iv1,
t1 is the operation time of equipment #1,
er is the expansion ratio of the branchpipe, foam monitor, aspirating foam generator, foam pourer that was used at equipment #1 for making foam of the foam solution,
V2 = the foam volume produced by equipment #2,
V3 = et cetera.
Vtotal = the foam volume that was produced by all of the equipment during the “FoamAttack”
Vtotal = V1 + V2 + V3 +….
Iv = the average foam application rate.
The mass of the “WARRIORS” is = Iv average * textinguishing time [m3]
Iv average = the average foam flow rate of the used equipment,
textinguishing = the duration of the “Foam Attack”.
What are these figures used to?
3. The end of the WAR (the fire is put out)
Using these figures we can calculate the number of the stars what the Combatting General will get from the President as a Good-conduct Medal.
In fire fighting we can talk about the
FOAM APPLICATION EFFICIENCY
η = THE FOAM APPLICATION EFFICIENCY 
Its value varies between 0 and 100%, depending on effective the fire fighting technology is. Hooray!
The next question is: what are our chances on influencing this figure? How can we improve the success rate of the fire fighting?