Need for Halon or Fire Bouy System on Diesels

rslifkin said:

Dripping diesel is unlikely to cause a fire unless it's landing on something very hot. Even then it'll probably make a bunch of smoke before there's much fire. But a cracked injector line or other source of spraying diesel under pressure can be a big problem very quickly if it hits something hot enough.

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Agree. Diesel is very difficult to ignite when it is cool. But when it is hot it will ignite. We had to have boat crew candidates put out a live fire. The fire chief wanted to use diesel floating on water. We tried matches and finally a road flare and could not get it started. I suggested adding a bit of gas and then it went right up. One candidate extinguished the fire. Then with the diesel hot it would reignite with a match. So get some dripping or spraying on a hot manifold or turbo and it will ignite. Our turbo exhaust is around 700 degrees. Certainly hot enough to ignite diesel, fortunately there isn’t a diesel supply near the turbo.

psneeld said:

https://www.passagemaker.com/lifestyle/fire-suppression-systems


Fire in the engine room is an experience most owners would rather not have. It is a frighteningly dangerous proposition, and one that can prove expensive in so many ways.


Fortunately, it is not a common problem aboard diesel-powered vessels. Indeed, it is so infrequent that there is very little information about engine-room fires, and separating fires aboard diesel-powered boats from the more common gasoline-powered inboard boats is all but impossible, even for the USCG's Office of Boating Safety.


While it is a rare occurrence, it does happen. According to Tom Hale, chairman of the Technical Board of the American Boat & Yacht Council (ABYC), there are perhaps 50 fires aboard inboard diesel boats each year. Given the thousands of pleasure boats on the waterways, this is a very small number.


The general consensus is that with better reporting data, we would likely determine that fires are not related nearly so much to propulsion machinery and fuel systems, as they may be to other causes for which preventative measures can be tak en. That list could include the electrical system, in the galley, and accidents.

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This article was written a very long time ago, Tom Hale, who is quoted, hasn't worked for ABYC for 20 years, and Parlatore left PMM in 2016. It says it was originally printed in 2012, but that might not even be correct, I suspect it's older. The article is outdated, here's one example...

"If it is determined that the air change rate is greater (or more frequent) than once per minute, then there is an additional recommendation for an automatic fire-extinguishing system: the system, once triggered, should automatically discharge the suppressant agent, and also turn off engines, generators, and blowers. Just shut everything down, and keep the concentration level high enough to extinguish the fire."

The air turnover aspect of the standard was eliminated long ago, here's how it now reads...

4.8.5.3 Diesel Boats
4.8.5.3.1 The system shall be designed and installed so that:
4.8.5.3.1.1 the engine(s), generator(s), and blower(s) located in the protected space shut down automatically and after discharge the minimum required design concentration in accordance with A-4.8.11 must remain.

Diesel fuel is far safer than gasoline, however, it can and does burn (I use it to help start my fire pit fires), and it does not need to be compressed to do so. The flash point, the point at which it vaporizes enough to be flammable, is a minimum of 125F for #2 diesel (100F for #1). If it is heated to that temperature and an ignition source is present it can ignite. The auto-ignition temperature, the temp at which it will combust is between 950 and 1200F, which is lower than gasoline incidentally.

If diesel runs onto a hot engine, it will vaporize, and if an ignition source is present it can ignite. If it leaks onto a exhaust manifold, and the engine is running hard, it's possible it could auto-ignite, but the exterior of an uninsulated portion of diesel exhaust won't be that hot unless the engine is running at or close to WOT. If a high pressure fuel line springs a leak, and it fills a hot ER with vaporized fuel, it could ignite, the alternator could be an ignition source. All of these cases are rare.

Diesel powered vessels do catch fire and it often has nothing to do with fuel. Still, the USCG and CFR have a slew of regulations that apply to gasoline powered vessel fuel and electrical system that do not apply to recreational diesel vessels because statistically they don't catch fire or explode as often as gasoline powered vessels.

IMO, every diesel engine room should be equipped with a fixed fire suppression system, one that meets current ABYC Standards.

True Steve but the part I reprinted still hold true I believe.
I usually post stuff like that so some will think and research further.

Drummer48 said:

I own a Cruisers Yacht 3850 and it has two Caterpillar diesel engines. My question for the group is do I need a Halon or Fire Bouy fire suppressant system onboard??

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It might be nice to have, but there's no legal requirement to have one and the vast majority of diesel powered recreational boats do not have one.

Engine room fires on diesel powered recreational boats are pretty rare.

How can you say that the vast majority of diesel boats do not have a built in fire extinguishing system? Where did that data come from? I have done hundreds and hundreds of vessel safety checks and can’t remember one diesel boat that didn’t have a built in system. There may be some out there but I doubt that there is a vast majority that don’t have a system.

Comodave said:

How can you say that the vast majority of diesel boats do not have a built in fire extinguishing system? Where did that data come from? I have done hundreds and hundreds of vessel safety checks and can’t remember one diesel boat that didn’t have a built in system. There may be some out there but I doubt that there is a vast majority that don’t have a system.

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This is far from my experience in anything less than 40-plus feet.

My surveyor told me that I needed an automatic system that would also shut down the engine in order to keep my insurance company happy. Extinguisher needs to be inspected ever 7 years (I think) and when it was inspected the tech said that they're required to confirm that it was correctly sized for the cu/ft of the space. So they need to inspect them in place, you can't just take the cylinder to him

An interesting idea is "Fire Port" I think they are called. I have them aboard so long I forget. They are 2" diameter clear plastic ports which are installed over your engine space. You can then check your engine space for flames without lifting the hatch, block your intakes, then punch out one or more ports and inset your extinguisher/s.
I've never had to use them but they seemed like a great idea. Most below deck fires don't really go wild until a hatch is raised. Plugging my engine space intakes would take about 40 seconds for me.

psneeld said:

True Steve but the part I reprinted still hold true I believe.
I usually post stuff like that so some will think and research further.

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That 'further research' includes clicking on the article link you included, and the article is dated/inaccurate. However, I'm not blaming you, you have no way of knowing this, this is really on PMM, such legacy tech articles should include an accuracy disclaimer, "This is a reprint, to the best of our knowledge, this article was accurate when it was printed, however..."

sean9c said:

My surveyor told me that I needed an automatic system that would also shut down the engine in order to keep my insurance company happy. Extinguisher needs to be inspected ever 7 years (I think) and when it was inspected the tech said that they're required to confirm that it was correctly sized for the cu/ft of the space. So they need to inspect them in place, you can't just take the cylinder to him

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For ABYC compliance, an auto-shut down is required. The cu ft of the space should be confirmed, I do this routinely and periodically find under and over sized bottles. A proper inspection includes weighing the cylinder and testing the manual discharge cable (also an ABYC requirement) and demonstrating the auto shut down system.

The vast majority of recreational diesel vessels I inspect are equipped with fixed fire systems.

An interesting idea that is used in airplanes, but I've never seen in a boat is this: a second slow-release bottle to assist in maintaining adequate agent concentration. So if the system triggers, the first bottle dumps, then either right away or after a few minute delay, the second bottle starts to release and slowly dumps over the course of 10 - 15 minutes.



A system like that would ensure the extinguishing agent concentration stays high enough for longer (to allow things to cool and avoid re-ignition), especially on boats where you can't easily and automatically seal off all engine room vents.



Another thought is whether the typical single point of sensing systems are adequate. On my boat, the halon tank sits on the aft engine room bulkhead between the engines. So an engine fire would trip it pretty readily. But a fire caused by the generator, water heater, or something else at the other end of the engine room (12-ish feet away) would take much longer to get enough heat to the bottle to cause a discharge. By the time it goes off in that case, it might be too late to be useful.

Steve DAntonio said:

For ABYC compliance, an auto-shut down is required. The cu ft of the space should be confirmed, I do this routinely and periodically find under and over sized bottles. A proper inspection includes weighing the cylinder and testing the manual discharge cable (also an ABYC requirement) and demonstrating the auto shut down system.

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Is there a performance problem with oversized bottles?

Portage_Bay said:

Is there a performance problem with oversized bottles?

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No but there is a safety issue. If the agent is non-toxic, such as FM200, it is only non-toxic at the designed concentration, exceed that and it could become lethal.

Engine rooms are considered normally unoccupied spaces, so there is no mandate in the US for non-toxic agents, however, toxic agents cannot be used on CE compliant vessels.

I spec non-toxic clean agents for engine rooms, even if not mandated. I spend a lot of time in engine rooms, as do many of my clients, I want that protection in that space.