What size extinguishers for engine compartment?

gordontytler

gordontytler

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I have found conflicting information on websites about the volume or floor area protected by automatic gas or powder fire extinguishers so thought I should ask here before buying.

My engine compartment (ignoring the bilge) is 3m x 2m x 1m and contains two BMW 636.

Should I get this 6kg powder extinguisher?

http://www.fireprotectiononline.co.uk/automatic-fire-extinguishers/

This 4kg FE36 http://www.fireprotectionshop.co.uk/Details.cfm?ProdID=275&category=&secondary=59 would be ideal but is the extra cost justified? Powder might wreak the engines (assuming this is true) but I will be insured anyway.
 
So you have 6 cubic metres of engine room... that is approx 6000 Litres of air....oh and by the way, you cannot ignore the bilge... it still is volume...

Two engines approx 6L = 12L of air sucked in at each second revolution (4 stroke at 2,000 RPM), which means that you will suck in 12,000 Litres of air each minute... which means that the air is fully exchanged every 30 seconds...

The six Kg powder is said to cover 20 cubic metres = 20,000 Litres, which therefore will be sucked fully into the engines within a very short time and possibly extracting agent away from fire ... so assuming this stops the engines (and presumably damage them ), you have limited (less) extinguishing agent left to fight the fire... nor engines to get you closer to shore...

Recommendation would be to go for full flood gas systems (or chemical agents), or to go for spot protection of the more vounerable areas such as firetrace....

Fire at sea is the worst scenario I can think of in respect to our chosen past time as the result usually means total loss of boat, and very short time from discovery of fire to being completely engulfed in flames with the obvious risk of hurting people directly or indirectly...
 
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Alf - I like your calculations. To check them someone would have to set fire to a real boat. I was hoping the RYA or MCA or someone had already done this and there would be a published standard but I couldn't find one. If the engine room air volume is sucked out in 30 seconds and the engines continue running how could the seller claim "fire extinguished before you know there was a fire"? Wouldn't the injectors be clogged in 1/2 second? Perhaps the engine will have some momentum and suck for another 1/2 second. If it were gas instead of powder then the injector won't get clogged and I was told a mechanism is needed to turn off the engines in this situation.

RUBBERDUCK - previously, when someone on this forum suggested using a professional, this is what I ended up doing in the end. However, my boat is exactly like thousands of others - wouldn't this be like asking a professional what boiler you need for a three bedroom house?
 
The guy suggested a/ Knows what he is doing & b/ Supplies many of the other plumbers with boilers hence being very reasonable. When I had the problem I approached many pro's in this field, all but one didn't have a clue but tried to sell a second rate solution.The one is the guy recommended. Ask Mapism of this forum. He helped in the great fire extinguisher hunt.:D
 
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gordontytler said:
...Powder might wreak the engines (assuming this is true) but I will be insured anyway...
Click to expand...

Having experienced a fire on a previous boat (twin diesels) and used dry powder extinguishers, I can tell you that you'll need to set aside a few days to clean up the powder. It really does get everywhere, and tends to 'set' in certain places, presumably where it combines with water.

I always worry that these auto-extinguishers might go off accidentally. Were that to happen, I'd be much happier if it were to be FE36 blatting around the engine bay.
 
I've never given much thought to engine bay fires but would guess the lions share of them have electrical fault origins. I don't see whether the (diesel) engines are still running or not during a fire as hugely significant, I'm thinking aloud here so don't shoot me down, so shutting it/them off might not be priority. Knowing the properties of diesel fuel, it could even have the power to douse a small electrical fire, but that would assume a fuel leak being in the correct vicinity of the flames, probably unlikely.

Of course a petrol engined boat will be a very different story.

Gordon, I don't see how your injectors will become clogged, or the relevance of it. Are/were you hoping this would stop your engines?

Carlton, what's in your extinguishers these days? I presume you now use FE36.

Hey MBM hacks, how about an article on this topic backed up with some MIAB and RNLI statistics?
 
My calcs are probably wrong (will remove the timings...)..., but my main concerns with any automatic system are;

1) How to place the sensors to the area(s) where fire is most likely to start (electrical system, fuel, exhaust etc.
2) When eventually discharged from the heat buildup, how much time have elapsed before the discharge happened?
3) How fast does the agent disperse and how does it interact with the fire ?
4) How are you notified of the discharge?

Did replace mine a while back and decided to go for a flexible, affordable system which would be traced across the most probable areas of fire and disperse the agent at the hot spot ... Good service and appears to be good system... and have just had the containter pressure tested and serviced for £75 ...

wrote about the installation here ...and I even covered the EL panel and dashboard in the process...

http://www.ybw.com/forums/showthread.php?t=198749
 
gravygraham said:
I've never given much thought to engine bay fires but would guess the lions share of them have electrical fault origins. I don't see whether the (diesel) engines are still running or not during a fire as hugely significant...
Click to expand...

In my case, it was indeed an electrical fire. The engines were shut down before extinguishing the flames.

gravygraham said:
...Carlton, what's in your extinguishers these days? I presume you now use FE36.
Click to expand...

Correct.

gravygraham said:
...Hey MBM hacks, how about an article on this topic backed up with some MIAB and RNLI statistics?
Click to expand...

Good idea.
 
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