Pre-mix Foam

[yellowjacket]

Having never seen or used this, I have a couple of questions.
Is it just foam concentrate poured into an appliance water tank at the appropriate ratio?
Does it stay in a homonogeous solution or does it require any measures to keep it ready for use?

[John Webb]

While I was working on foam testing at the Fire Research Station we used premixed solutions from 10 litres up to 1000 litres. The small quantities were easy to shake to ensure the solution was well mixed; when we made large quantities we would pump the solution round for a few minutes, keeping the outlet of the hose from the pump below the surface to avoid entraining air and to encourage the mixing.

I would think in an appliance tank the natural sloshing about due to the motion of the vehicle would keep things well mixed. We stopped work on foams in 1988, but the Research & Development Group at Moreton-in-Marsh were doing work on pre-mixed solution use for some while afterwards.

[AnthonyB]

Pre mix can happily stand around in Foam trolley & portable extinguishers for 5 years before replacement, both static or sloshing on a vehicle.

Scalling it up to an appliance doesn't produce any obvious flaws in my mind, other than the freeze issue as already discussed in another thread.

[Chunty]

Been using pre-mix based on concentrations of either Angus Tridol or Petroseal for many years without the slightest problem and without any special equipment or procedures.

[yellowjacket]

For exercises do you just pump away the pre-mix and refill?

The reason for my interest is that my club uses a Class B WrT as it's appliance, and the attractiveness of pre-mix is that it takes the inductor out of the question, increasing speed of deployment considerably. The drawback is that the hundred odd litres of FFFP gets expensive if we have to keep replacing it after regular training! Is is possible to decant the pre-mix into an IBC or whatever and then refill after training or will the foam be degraded by this?

[Chunty]

Hi Yellowjacket

Never having done it I can only estimate that by decanting a tank load of pre-mix in to another vessel and then transferring it back to the appliance later, this will create a certain amount of turbulence, the severity of this will depend on how carefully it is done, but this will cause some foaming to occur increasing the volume but essentially decreasing the liquid content. Instinctively I wouldn't recommend it although I have no scientific facts to base that on.

The matter of using up good foam for training is a major cost factor to smaller operators, what we try to do is combine many functions when we decide to take the plunge and empty the tank,i.e. in addition to carrying out an exercise, do some drills first, then standard test the hose and test the foam quality on a flammable liquid fire, in a nutshell get as much value as possible from the tank capacity. There is an option in purchasing training foam but its not that much cheaper and you would need to empty the tank to apply the training foam anyway so it isn't a practical option.

The best thing is to plan your training program, estimate foam usage from the modules that involve the need for it and budget for it. Unfortunately if your budget doesn't meet this estimated cost you may end up like a lot of smaller operators and have the training program dictated by cost rather than the other way around.

[John Webb]

If the pre-mix solution can be decanted by gravity into an IBC container, preferably filling it from the bottom upwards to minimise getting air into it (although as I recall AFFF, being synthetic, is not adversely affected by contact with air as protein-based foams are), and likewise the IBC container is raised (forklift?) to empty the pre-mix back into the appliance tank in a similar gentle fashion, I don't think there would be too much problem. I would avoid pumping the solution about - it's possible the mechanical stress of repeated pumping might affect the nature of the foam molecules in the water?

Any foam formed on the surface of the liquid will be a very small part of the bulk amount and will eventually drain back in in any case.

'Training foam' is a bit cheaper and may also be better for the environment?

[yellowjacket]

Thanks for all the input folks, it confirm my thoughts- that it's possible, but very awkward. On balance, I might be better off sticking with the inline inductor, with the flexibility it gives, traded off versus the increased training it'll require for users.

The off shoot is we'll be able to train a lot more inexpensively with the system -using training foam, which should help promote increased frequency.