Foam fire extinguishers - AFFF

[[2574]]

A recent post discussed what extinguishers are best on board. I'm a little confused about foam extinguishant. Is there AFFF and other types of foam or is all foam AFFF?

AFFF seems to have been specified for burning liquid fires therefore perhaps not best for galley fires? Dry powder seems the best but makes a huge mess. Any guidance appreciated.

rob

 

[Talbot]

Old foam extinguishers were created using ox blood. The foam had to be floated over a surface to extinguish a blaze. Thus any elevated blaze needed a ton of foam. It was good at fuel fires but not very effective at much else.

The water extinguisher was used to cool an area below flash point, but provided little protection against re-ignition.

The AFFF (Aqueous Film Forming Foam) is a substance that can be added to normal water extinguishers to create a great multi-purpose system. The foam creates a film so can be sprayed over a surface like fuel, or onto levated structures , and the film cuts off the oxygen to the blaze, and the water cools the burning item. It works like magic on a fire and is much less messy than old fashioned foam.

If you know what you are doing with it, it can be used for most fires including galley. However, if the galley fire is hot oil, nothing is better initially than an asbestos blanket, cause that will minimise flare up risk.

 

[wanderlust]

It would be interesting to look in to the reliability of AFFF extinguishers on boats. A few years ago I used to race in the British off road championships. A vehicle caught fire and we were all using AFFF extinguishers as Halon had been banned. The first AFFF extinguisher did not work. Niether did the next 7. The extinguishers were all different makes. The fire was finally put out by a halon extinguisher. There was a theory that all the bouncing around in the vehicle caused the extinguishers to fail. I am not sure if this is the case but it would be the same for boats. Anybody got a view?

 

[ccscott49]

I wouldn't have AFFF on a boat, powder is as good if not better. Plus it can be used on electrical fires, not AFFF.

 

[sarabande]

This is very confusing to people who do not have access to professional or expert opinion. Methinks we need definitive advice here. Any firefighters on the forum ?

Penton Hook has its annual regatta on 16/17 June, and I have arranged for the local Fire Brigade (Surrey) to come along and give advice, do demos with hoses, extinguishers etc.

If we haven't resolved clear and concise info as to which extinguisher does what (again ?!) by then, I will get info and post it.

On a personal note, powder has no place on my boat. I use CO2, and AFF, fibreglass fire blankets, and the ubiquitous bucket and lanyard.

Having seen recent videos of boat fires in marinas, shortly I will have an electric Jabsco pump (off a separate battery) to use as a mobile bilge pump, wash down and fire pump.

 

[Amphitrite]

Why not choose a mobile engine driven pump? We had them on the traditional vessels I have sailed on and they provide a complete, independent back-up system.

 

[Vara]

Youre right it is a bit confusing, I've been out of the active fire fighting game for a little while .

However my 2ps worth,I like and have used in anger AFFF it has a very good knock down and cooling factor.I didn't find it particularly smelly or difficult to clear up.
Take cc's point about not suitable for electrical fires but on the sort of boats I sail and have sailed in thats not an issue.
I have dry powder at home cos they are cheap and the engine knackering and cleaning up isn't an issue.
Dont forget that most boats have access to tons of one of the best extinguishers as used by Fire services throughout the world........water.

I would rather have lots of small extinguishers(2Kg) than one big one.

The old man used to use the old type time expired foam as tomato fertiliser and very good it was too.

 

[[2574]]

Yes, agreed, very confusing, hence my attempt to get some clarity. I have talked with various organisations since the original thread about this (about a week ago?) and am more confused than when I started.

For example - engine room extinguishers - some say CO2 is the stuff, others say GTFE from Firemaster. Is GTFE CO2? Dunno, this is one example of what appears to be a confused subject. There's nothing on the Hampshire Fire Service website either which is a surprise - they must have the most boats of all fire services to look after and would have expected a section that advised boatowners as to what they consider most appropriate.

Hmmmm...........maybe there's a professional hereabout who can wrap this up.

rob

 

[Talbot]

Cant comment on those extinguishers. All they are is a water cannister which has some AFFF added, plus a pressure cartridge, normally something like CO2. If they failed, it would be because the pressure ctg was not working - either poor design, or poor safety checks.

I never had a problem with one in some 10 years plus experience of proper ones.

 

[peterb]

[ QUOTE ]
The AFFF (Aqueous Film Forming Foam) is a substance that can be added to normal water extinguishers to create a great multi-purpose system. The foam creates a film so can be sprayed over a surface like fuel, or onto levated structures , and the film cuts off the oxygen to the blaze, and the water cools the burning item. It works like magic on a fire and is much less messy than old fashioned foam.

If you know what you are doing with it, it can be used for most fires including galley. However, if the galley fire is hot oil, nothing is better initially than an asbestos blanket, cause that will minimise flare up risk.

[/ QUOTE ]

Two points.

First, none of the foams will deal with a flowing fire (such as a leaking tank). Foam works by blanketing the surface, thus separating the fuel from the oxygen. If the fuel is flowing then you can't complete the blanket and put out the fire. For this job you need a flame suppressant. Dry powder does the job, though halon is even better. (Halon interferes with the chain reaction in the flame; unfortunately that's the same property that causes it to suppress the ozone layer.)

Second, you certainly won't be able to buy an asbestos fire blanket nowadays. Most of the replacements are made from glass cloth. They work reasonably well, though not as well as asbestos!

 

[Anonymous]

[ QUOTE ]
First, none of the foams will deal with a flowing fire (such as a leaking tank).

[/ QUOTE ] You do surprise me. I used to work for a large well-known fire detection and protection company - also one of the largest UK manufacturers of portable extinguishers as well as fixed systems and major projects - but on the detection and automating extinguishing side, though I did get to work on the design of some large tank farms, LPG filling plant and petrochem refineries. We used AFFF fixed systems on the tanks, AFFF fixed and portable monitors wherever the budget would allow the cost. What else would you use on a flowing fire such as a leaking tank or bund?

As for the AFFF vs powder - there are pros and cons and I have used all sorts many many times in controlled training and demo areas. AFFF is a better fire fighting agent for boats, of that I am certain. It is messy but heck, so is powder! Furthermore, provided the pressure is OK AFFF will work whereas powder can cake - you ought to give them all a really good shake every so often.

 

[peterb]

I spent over 20 years doing research (primarily on detection, but some on foam testing) at the government's Fire Research Station. Yes, you are right, foam can be used on installations such as you describe, but primarily to control the fire rather than to extinguish it. It's difficult to blanket a moving stream of fuel, though if you put enough on you can blanket up to the leak.

I remember standing some 20 yards away from some rail tankers (16 tankers, each with 100 tonnes of 4-star petrol). The driver had delivered them to a tank farm, then coupled up the first four and started discharging through four 6" flexible pipes. Someone pointed out to the driver that he shouldn't be discharging while the engine was coupled to the train, so he drove off. Unfortunately he forgot to uncouple first so the four hoses all broke. Someone shouted, he put the brakes on, the sparks lit the petrol and a good time was enjoyed by all. I can't remember how many pumps attended, but it was at least fourteen. The heat affected the seals on the valves of the next tanker in the line, which gradually began to trickle burning petrol at an increasing rate. When that one was burning nicely it started to affect the next, and so on down the line. In the end the fire was stopped by applying sufficient water to keep the valves cool; the flow stopped and the fire was extinguished.

The point of the story was simply that while the fuel was flowing the brigade had great difficulty in extinguishing the fire, even though they had plenty of foam available. Stop the flow, then control and extinction were rapid.

On a slightly different topic, one of the major causes of extinguisher failure is lack of knowledge of the operation procedure. How many of you, faced by a fire at night, would know how to operate the extinguisher without re-reading the instructions?

 

[tcm]

powder does make a mess and can wreck gear (engines etc ) if sprayd liberally. I bought a 10 kilo C02 thing in addition to powder things for blasting at fire to help get people out, tho i know i also need to smother the fire as soon as co2 stops, but should cause less wrecked gear at sea. However, er, I would guess that for a galley fire an ordinary fire blanket shiould be first shot. and probly poweder would not make too much mess though once started they must be discarded and if yours are the type thatgo on and on, chuckem off the boat asap. I imagine the co2 will blast the buring food everywhere although the initial fire will be be "out" in might then be "in" the saloon...

 

[Anonymous]

I mostly dealt with the FOC - but occasionally went over to the FRS, in the mid 1980s.

 

[Graham_Wright]

[ QUOTE ]

Dont forget that most boats have access to tons of one of the best extinguishers as used by Fire services throughout the world........water.


[/ QUOTE ]

At an RNLI lecture I (naively?) asked what was wrong with using water on a boat engine fire. The answer was that you shouldn't use water on electrical equipment. Not having the courage to further make a fool of myself, I refrained from observing that 12v should not pose a risk to life!

However, an engine compartment is often almost perfectly sealed for reasons of sound-proofing. Does this not mean that, provided the air intake is shut, CO2 would be extremely effective?

Likewise, water, available in infinite quantities, could be admitted to the engine compartment until it immersed the fire. It is unlikely to affect buoyancy catastrophically in the quantity required.

 

[Anonymous]

[ QUOTE ]
I refrained from observing that 12v should not pose a risk to life!

[/ QUOTE ] Yes, that's right, there is no risk with 12V but remember that these days a high proportion of people keep inverters running so be careful as an inverter is every bit as dangerous as the public mains.

[ QUOTE ]
However, an engine compartment is often almost perfectly sealed for reasons of sound-proofing. Does this not mean that, provided the air intake is shut, CO2 would be extremely effective?

[/ QUOTE ] Yes, but you need very high concentrations of CO2 for total flood - 30% or so, ISTR - whereas you only need 5% of Halon. At 5% Halon is harmless to people whereas CO2 will asphyxiate you. So CO2 would be too bulky and expensive as well as dangerous.

[ QUOTE ]
Likewise, water, available in infinite quantities, could be admitted to the engine compartment until it immersed the fire. It is unlikely to affect buoyancy catastrophically in the quantity required.

[/ QUOTE ]Yes, water is the extinguishant of choice. Foam compound added to water makes it (the water) go further, makes it cling to the items on fire and helps keep air out while the water reduces the temperature by boiling. It would be mad to have a water extinguiser on a boat when you could as easily add the AFFF concentrate, which makes it 20 times as effective kg for kg and cc for cc.

 

[peterb]

[ QUOTE ]
[ QUOTE ]
However, an engine compartment is often almost perfectly sealed for reasons of sound-proofing. Does this not mean that, provided the air intake is shut, CO2 would be extremely effective?

[/ QUOTE ] Yes, but you need very high concentrations of CO2 for total flood - 30% or so, ISTR - whereas you only need 5% of Halon. At 5% Halon is harmless to people whereas CO2 will asphyxiate you. So CO2 would be too bulky and expensive as well as dangerous.[ QUOTE ]


Yes, you are right. In fact, we used to reckon that the fire would continue to burn until you had reduced the oxygen content of the atmosphere to about 10%, as against the normal 21%. The effect wasn't so much the reduction in the oxygen, more the increase in the non-oxygen content relative to the oxygen. The heat released by the oxygen had more gas to heat up, thus reducing the flame temperature to the point where the fire stopped spreading.

 

[curious]

I have read all this with great interest. I need to review my own fire fighting ability on board so this has been illuminating.BUT first its AFFF then no, then something else. If 12v fires are very unlikely then it is fuel (diesel/cooking oil/food) that has to be dealt with (until the GRP/wood etc catches light). So is there an all round type that can be used without killing the crew given that the fuel source can be cut off/limited.