Anti-freeze

[Chunty]

This is going to sound so stupid I almost embarrassed to offer it up for opinion; I had a call from one of the airfield RFFS' units I do work for asking me a technical question to which I can't be sure of a definitive answer.

Apparently one of the crew independently (!) decided to mix anti-freeze solution in the pre-mix (water and Tridol S6 AFFF) tank on their TACR2a. I was asked by a concerned member of the crew did this sound okay?

My initial reasoning was that if the individual that decided to mix anti-freeze with the pre-mix had no evidence or professional advice to suggest that this wasn't a problem then he should have not have done it, but I have no actual evidence myself to suggest that it could be a problem. However on a risk based appraisal surely the sensible thing would have been to not take a chance on it being okay and not do it until proven.

Any thoughts or technical advice?

[stevfire2]

chunty,
          i seem to remember that an almost unbelievably high percentage of water can be replaced by anti-freeze, (50%?) springs to mind, but what a cost! my concern would be how much did he put  into an ALREADY  pre-mixed solution. did he put enough in to alter the 6%ratio?
 weve been having issues with freezing on our 2nd truck that has to stay outside, the tanks ok, but the pneumatic valves in the deliveries has been freezing. been leaving it in engineering during this weather.
                                                                                                              steve

[AnthonyB]

I've checked with Angus Fire seems & bog standard Tridol S 6 is not meant to be used below the 0-2C range and must not have any type of antifreeze added.

If you have low temperature issues you need to use Tridol S6 LT which is formulated to work at -18 C or S6 XLT which can function down to - 30 C

[stevfire2]

judging by the lt and xlt titles, it sounds to me that theyre adding an antifreeze to the  concentrate at the factory, whereas a previous cap 168 did detail freeze protection measures. the only sure way is to consult your foam supplier. couldnt you get the vehicle into shelter if necessary?
                                                                                                     steve

[Chunty]

Thank you both for your assistance.

As I said this is an airport where I train the guys but I'm not their full-time or part of the operational crew so why the appliance wasn't housed or the precise details behind it I can't be sure of yet, I'm there tomorrow, the only facts I know are those in my original post and again thanks for your comments.

[AnthonyB]

Looking at the hazard data sheets the LT & XLT variety's seem to be just with ethylene glycol added, but no doubt they will say it is specially blended at the factory and may include something else 'special' so as not to degrade the foam.

The main thing about adding your own antifreeze against Angus's instructions is that if something goes wrong and the foam doesn't perform correctly at an incident they will drop you like a hot brick and ensure that they are no way liable for the failure.

[yellowjacket]

It sounds a lot  like they just got a batch of foam for training use.

[FC1]

OK slightly off thread but IF a vehicle is not on the run over the winter and cannot be garaged or protected can a pre-mix solution of whatever quantity be decanted into a protected storage receptacle and then decanted back onto the vehicle at a later date?  Would decanting degrade the quality of the foam if it was done slowly so as not to produce excessive amounts of bubbling?

FC1

[AnthonyB]

I don't see why not - to correctly inspect a cartridge type pre mix foam extinguisher you have to empty out the contents into a bucket to inspect the interior of the cylinder & then replace the contents making up small losses with water (if you spill a lot new charge is required to be made up). The same should apply on a larger scale. The only problem is it's very fiddly with the bubbling that can occur.

The only caveat is that you don't exceed the shelf life of the pre mix solution, which used to be 4 years for pre mix AFFF in extinguishers, but is now usually 5.

[JC100]

OK slightly off thread but IF a vehicle is not on the run over the winter and cannot be garaged or protected can a pre-mix solution of whatever quantity be decanted into a protected storage receptacle and then decanted back onto the vehicle at a later date?  Would decanting degrade the quality of the foam if it was done slowly so as not to produce excessive amounts of bubbling?

FC1

Everytime a new vehicle is bought back 'on the run' after any time away, be it from the winter, major servicing etc, then a complete fuctional test should be carried prior to emergency use to check for any problems. Surely the answers to issues you mention would be resolved. If in doubt the normal annual foam test could be done again to check. 

[FC1]

I wonder how many low cat aerodromes carry out annual foam tests!

[JC100]

If small airfields dont have to stick to the same standards as larger ones, what is the point of larger airfields doing these tests either? Are they not important?
If they are important, maybe low cat airfields should just not use foam trucks at all and just use a landrover with a 90ltr AFFF on a trailer. Much easier to service and maintain.

[FC1]

I didn't say that they don't have to comply I said I wonder how many do comply.  In my experience - not many.

[JC100]

You're probably right! Using foam is a pain in the a**, and with all the environmental issues with where you can use it for testing / training must have made things even more difficult.

[stevfire2]

problem is, with pre-mix units, its all down to the accuracy of who-ever fills it.theres no proportioning kit or inductors to fail or go out of limits. you cant really partially discharge pre-mix to sample it as its nigh on impossible to top up accurately. after 3 months its discharged and thus replaced anyway. we have never had to produce certification for our pre-mix truck(s) just certificates of conformity. now we have a truck with seperate tanks though, we will have to have the inductors checked.
id go with FC1s, method, as long as very little is lost.