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Old 16 April 2012, 13:24   #1
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Engine firefighting - some possibly crazy thoughts

The VHF thread over in the electronics section brought this back to the front of my mind, so I thought I'd throw the high level idea to the masses and see what everyone thought.

There have been a few threads on engine fires in the past, and the one common conclusion is that once it's alight, the fire is in an enclosed space that to get any extinguishing medium in would involve squirting the extinguisher output through a relatively tiny hole at the back of the cowl, meaning you would need to lean over the fire and "out the back"to put it out!

This got me thinking - some form of remote release system piped into the cowl. Any powder system would potentially suffer settlement, so that leaves gas. Now CO2 as we all know is a common fire extinguisher agent. It then struck me. Remember the 80s? Soda streams were the thing to have in your kitchen. Fizzy drinks at your fingertips! (This lead onto a possibly more practical disposable canister for MIG welders with a 1/8 BSP connector instead of some weird propriatory fitting, but the theory still holds.)


I had a wee internet trawl. 60L Soda stream refill cartridge in argos - 9.99, Most Weklding shops punting the MIG CO2 can for 12-15. Now, the volume under the cowl of any engine is not anywhere near 60L. You could have the cyl mounted under your seat with a lifejacket type trigger (or a simple valve for the welding cyl) and pipe it back to the engine to fill the cowl with CO2 and extinguish the fire.

The two biggest problems I could see would be emptying 60L of pressurised CO2 in a hurry is likely to form a fair lump of ice round the discharge, instantly blocking the hose (probably not an issue if there;s a perol fire 3" away from it!) and if the cyls were mounted under the seat, how much air would be fanning the flames until the hose was fully purged and only moving CO2...... (an easy enough calulation to do, but what would the real world consequences be?)

It did strike me that the hose / air issue could be solved by "pre charging" the hose, and capping the end witha lid that would blow of as soon as the pressure built up. That way you might not need to dump quite so much CO2 into the hose in such a hurry, possibly reducing the freezing nozzle problem a bit. Problem I could see with that would be the CO2 leaching out in the same way helium ballons empty themselves, so how often would you need to re-charge the hose? - There are medical "CO2 proof" hoses out there......



So, Ribnet massive, your thoughts?
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Old 16 April 2012, 13:48   #2
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I think you need to get out more .

In all seriousness, if you maintain your engine properly the fire risk is surely pretty low. How many properly maintained cars catch fire these days? And they have more risk/heat sources from exhaust pipes near petrol lines etc.

If you were to rig up a system as described I really doubt the amount of O2 in the hose would be enough to worry about. It would soon be quenched by the CO2 that it wouldn't have time to make any real difference.
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Old 16 April 2012, 13:52   #3
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Use a smaller diameter hose to avoid blasting your fire with (much) air in the second before the CO2 arrives. CO2 is very dry you don't really need to worry about the tip freezing with ice. You might consider multiple tips though just in case one is blocked or not in the relevant area etc. You should really have a way to cut off the air intake )and the fuel supply) all your CO2 will be dumping out of it.

I have never heard of a fixed firefighting system for an outboard honestly. I am not entirely convinced its needed as all the fires I hear about over here are inboards of one form or another.
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Old 16 April 2012, 14:13   #4
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CO2 is very dry you don't really need to worry about the tip freezing with ice.
Not to mention the buildup would have to form so as to block the hundreds of psi pushing the CO2 out. Doubt ice clogging is an issue.

As an additional safety note, should you decide to install the system described, make sure to do regular inspections of the cylinder condition; most likely it was not meant for a corrosive environment (painted steel?), and rust-induced failure may become an issue.

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Old 16 April 2012, 16:15   #5
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Fixed extinguishing systems - my old specialty, marine and industrial. Trawling through my memory banks at the moment but very roughly 1kg CO2 required per metre cubed of volume. This does not factor into account leakage area as the gas really needs to be contained until sufficient heat has dissipated to prevent re-ignition. Your best option would be a 2kg CO2 extinguisher piped into the cowl via a flexible hose. The friend who bought my company would be able to supply you with an appropriate nozzle for less than a tenner I am sure. Let me know if you need assistance.
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Old 16 April 2012, 16:29   #6
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Fixed extinguishing systems - my old specialty, marine and industrial. Trawling through my memory banks at the moment but very roughly 1kg CO2 required per metre cubed of volume. This does not factor into account leakage area as the gas really needs to be contained until sufficient heat has dissipated to prevent re-ignition. Your best option would be a 2kg CO2 extinguisher piped into the cowl via a flexible hose. The friend who bought my company would be able to supply you with an appropriate nozzle for less than a tenner I am sure. Let me know if you need assistance.
I agree, the components needed are regularly available. You would need to make sure that all the components will survive in a marine environment, no point having a nozzle that corrodes and blocks.

These guys sell the components, probably worth shopping round as they are not the cheapest place.
Fire Extinguisher Plumbing & Nozzles | Fire Extinguishers & Accessories | Motorsport | Home | Demon Tweeks
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Old 17 April 2012, 05:06   #7
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At a simpler level, I had a vaguely similar idea a couple of years ago. I have an adaptor which goes onto the end of a Sodastream bottle to charge my beer barrels, basically you invert the bottle and push down and it opens the valve and that blows into a fitting on the top of the barrel and pressurises it.

My idea was to fit a "barrel fitting" on top of the engine cowl and carry a Sodastream bottle under the seat so in the event of a fire, you could grab the bottle, jam it in the fitting and fill the cowl up with CO2. As usual, I never bothered to get around to it, so it remains vapourware at the moment but it would only cost a few quid to do.
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Old 17 April 2012, 09:24   #8
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Quote:
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I think you need to get out more .
As soon as I win the lottery........

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Originally Posted by Erin View Post
In all seriousness, if you maintain your engine properly the fire risk is surely pretty low. How many properly maintained cars catch fire these days?
It is, and the salient point here is "these days". Remember my engine is older than some of the Ribnet members.... some bits of it are older than me!

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Originally Posted by BogMonster View Post
At a simpler level, I had a vaguely similar idea a couple of years ago. I have an adaptor which goes onto the end of a Sodastream bottle

<snip>

but it would only cost a few quid to do.
At least l'm not the only one thinking about this!

I had wondered about getting a gubbed soda stream & using the release valve. I kind of assumed these things were all plastic, but having not parktaken of that craze in the 80s it needs a bit more research....



The other thing about flooding the cowl with CO2 is that it will instantly kill the engine, so if it's an HT lead related ignition source, that also goes away.
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