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Old 05-06-2020, 18:38   #1
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Fire Suppression For Fun & Profit

Over in the 'The loss of Kokopelli' thread there is speculation regarding the proximal cause of the disaster and a fire appears to be the favorite culprit.

A number of posts discuss fires aboard fibre glass boats with a fair bit of emphasis on the alacrity with which these propagate, their severe intensity and the apparent toxicity of the fumes produced.

I contributed with observations made during a small electrical fire recently and speculated that a water misting system might be an effective solution. One of the things we do have good access to on a boat is generally water, either fresh from out water tanks or salt for those of with access to the sea.

What I would like to initiate with this thread is a discussion on the up and down sides of installing mist systems, in for example the engine enclosure but not limited to this area, and how one would best go about it.
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Old 05-06-2020, 18:52   #2
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Re: Fire Suppression For Fun & Profit

First you find a real expert in the design of such systems. I am sure there are dozens of them here.

Now you need a high volume, high pressure pump, with special nozzles in each compartment on the boat, and run the high pressure hoses everywhere.

Now you figure out how you activate the system. Is it manual? Or automatic? How do you handle electricity in the compartment with water mist activated?

A salt water mist will be a whole lot of fun on a boat with 110V or 220V power. Even 12 or 24 volt power shorted out with salt water just might make things worse. Maybe you have a cut off that kills the power to the boat before the pump starts... oh wait it’s an electric pump....

There are automatic and manual fire suppression systems for marine engine rooms that have none of these complexities. Most insurance companies will require them. Certainly common sense suggests they are important for any offshore boat. Just buy one and install it as it should be installed.
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Old 06-06-2020, 03:00   #3
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Re: Fire Suppression For Fun & Profit

+1 for Harmonie

With particular attention to:

Quote:
Originally Posted by SVHarmonie View Post
First - salt water mist will be a whole lot of fun on a boat with 110V or 220V power. Even 12 or 24 volt power shorted out with salt water just might make things worse. Maybe you have a cut off that kills the power to the boat before the pump starts...

Oh wait it’s an electric pump....
Nobody seems to get the exigencies of a saltwater environment.
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Old 06-06-2020, 15:34   #4
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Re: Fire Suppression For Fun & Profit

Just what I was hoping for. Two posts and already a number of issues have been identified:

Whether or not fire suppression is strictly the preserve of the experts.

The flow volume of water which might be required to implement a effective system.

The pressure required to form an effective body of water mist.

What sort of pump would be required to provide the required pressure and volume of
water.

Where in the boat the spray system would need to be installed in order to be effective.

The requirement for piping, pressure and size.

Activation of the system, manual ir automatic.

The need for a kill system for high voltage facilities such as generators or inverters.

Etc. Etc.

One of the methods I used in my professional design work was to search for analogies in other engineering disciplines. For example I notice that my motor car has a big hole in the front where water can come in, find it's way through the radiator, be smashed into mist by the radiator fan then be sucked through the alternator. The engine compartment is full of electrics but somehow the cat keeps functioning and without damage being done. Would emulating this in my engine compartment on my boat suppress a fire without excessive water damage?
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Old 06-06-2020, 17:12   #5
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Re: Fire Suppression For Fun & Profit

What is the purpose of what you trying to do, and how would you test it?
Water is in my opinion a very important part of firefighting, it’s likely one of the better agents if it’s a Class A fire, which I believe it will be even quickly if it started from fuel or electrical, so you would have at least a class A and a Class B fire together, and water is very good with a Class B fire.
I have quite a bit of fresh water available and keep a hose connected to it, but not a mist system, with the easy availability of very good effective, tested agents there is no need to try to invent or build something that you can’t really test.

But in my foolishness I can see where a pressure washer just might be a decent fire extinguisher from simple removal of heat, but I’m sticking with Halon and Halotron, and I guess those dry chemical things too.
I doubt much if any water gets through a radiator, especially a hot one, I’ve yet to open the hood and see a wet engine compartment from heavy rain myself.
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Old 06-06-2020, 19:35   #6
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Re: Fire Suppression For Fun & Profit

My electrical fire involved two areas in the boat, the enclosure which houses the solar regulator and mains battery charger and the battery box.

The dry powder extinguisher stored beside the companionway quiet readily handled the fire in the enclosure however at that time I was not aware of the secondary fire in the battery box.

I was able to handle the first fire on a single breath and get back into the cockpit however gaining access to the battery box consumed more time and I did breath in some fumes.

Part of the reason I was below so long was that the dry powder extinguisher refused to work even though it still contained pressure and was not empty of powder. I extinguished the fire with a pot of water from the galley.

This bought me to pondering on the nature of fires in boats and the fumes that modern materials generate when they burn. I was coughing for a day after the incident even though I had a fairly minimal inhalation of fumes. I had to enter a fume filled enclosed area in order to get to the fires and like most of us was not equipped with suitable breathing apparatus.

As a former commander of offshore drilling rigs I am familiar with fire fighting apparatus and it's use on including the massive Halon systems used in engine rooms but having had the recent experience now tend to the opinion that the relatively small portable fire extinguishers we have to comply with regulations are not adequate for the nature of fires we may encounter and that the fixed installations used on large vessels are not practicable for small pleasure vessels for their cost, complexity and space requirements.

There must be a middle ground.
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Old 17-06-2020, 15:30   #7
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Re: Fire Suppression For Fun & Profit

Water mist systems have been around for some time now, the majority of new build ships, platforms, rigs, fpso's and even shoreside power generation plants, office buildings and hospitals are fitted with them, the ship i work on now has them fitted in the engine room and generator room as well as the hydraulic room and over the shaft generators, and no you do not have to shut off the power.....

Eg: what do you think happened to all these guys in the machinery spaces of this Maersk Triple E-Class........they got damp, not zapped



you can even buy portable Extinguishers (Type S) that do the same...

https://www.amerex-fire.com/products/water-mist/

Quote:
Water mist is the ultimate extinguisher for Class A fires and where a potential Class C (electrical) hazard exists. The fine spray from the unique misting nozzle provides safety from electrical shock, greatly enhances the cooling and soaking characteristics of the agent and reduces scattering of burning materials. The Amerex Water Mist extinguishers contain de-ionized water (sold separately) making them the best extinguishers for protection of hospital environments, valuable books and documents, telecommunication facilities and “clean room” manufacturing facilities. The Amerex WaterMist extinguishers are easy to use, maintain, and service.
It's all in the application for small vessels, the tech is already known.
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Old 18-06-2020, 05:27   #8
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Re: Fire Suppression For Fun & Profit

The electrical fire rating of water mist systems is dependent on using distilled or DI water for the fill. This keeps the conductivity very low.


If you use seawater, or even tap water, that is a different animal.
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Old 19-06-2020, 11:55   #9
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Re: Fire Suppression For Fun & Profit

Having used a dry powder extinguisher on a small electrical fire I am now finding problems with some of the electronics installed in the cabinet where the fire occurred and now need to disassemble and clean off the circuit boards. Consequently I am tending to the opinion that provided they are not turned on at the time a dousing with fresh water, which would evaporate off, would have been less damaging than the dry powder.

Interesting to see the mist systems being used on ships. I worked on Maersk drilling rigs for a number of years and they all had halon suppression systems in the engine room. They were large complex systems with interconnections to the ventilation systems and even auto closing access doors. After the alarm went off you had a short time to vacate before the halon was introduced. If these are being replaced by water mist systems and these are just as effective at suppression the mist systems would appear to be a far superior solution.

So it looks like a low cost, DIY, mist system in the engine compartment and battery box using a chemical spray pump, nylon tubing and spray nozzles might be a viable option.
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