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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.

Most trawlers have a fixed Halon system in the engine room (or a system containing newer, more environmentally-friendly agents). These USCG-approved systems are designed to automatically discharge their contents in the engine room space when temperatures reach above approximately 185 degrees.

Chemically, fire can no longer burn when firesuppressant agents reach levels of concentration in an engine room. This fact has misled many owners to think of all Halon systems as "install and forget" equipment.

Unfortunately, many of us, as a result, have systems on our boats that will not put out a fire in the engine room.

Fire Safety Guidelines

Each major seafaring country has an organization to document and promote construction and safety guidelines for pleasure boats. ABYC is that organization in the U.S.

Its members are professionals in the industry who periodically review published standards to make sure all guidelines incorporate the latest concerns and issues, and address improvements in technology.

Chris Washburn, of Washburn's Boat Yard in Solomons, Maryland, knows a lot about boats. He even has had to occasionally repair fire damage on pleasure boats. Chris is the current president of ABBRA (American Boat Builders and Repairers Association).

He is also on the Technical Board of the ABYC. This board is responsible for Standard A4, which is the section in the ABYC Standards relating to fire fighting equipment.

Standard A4 was recently under review, a process which prompted Chris to later comment to me that many of us have been doing it wrong all this time.

I bet we can all learn something here.

Evaluating The Need

How big should a fire suppression system be? That is the first issue, sizing the system to fit the space.

According to Standard A4, a trawler (not specifically mentioned as such, but fitting the reference to an inboard boat with an engine compartment) must have either a fixed fireextinguishing system or provision for discharging a portable fire extinguisher directly into the engine room without having to open the primary access into that space.

Unless talking about a small boat, or very restricted engine-room space, the need for a fixed system is almost guaranteed for a trawler, as a properly-sized portable unit simply may be too big to handle during an emergency.

Chris Washburn explains the sizing formula: "According to A4, you take the volume of the room itself, and you subtract the tankage. That's your volume of the area.

"Now, that is a very conservative volume figure for sizing fire extinguishers. It does not consider the volume of the engines, or the boat's large water-heater tank, all the batteries, the two generators, and everything else that's in there.

"So you are going to put in a really big fire extinguisher."

This formula is used for determining both the size of a fixed fire-extinguishing system as well as a portable extinguisher.

The idea of using a portable extinguisher for an engine-room fire involves the installation of a small opening fire port, perhaps no wider than the nozzle of the extinguisher. It is essentially a porthole mounted on a bulkhead or cabin sole, capable of being opened from outside the engine room, and into which the entire contents of a portable extinguisher can be discharged. In some boats, a fire port mounted directly over the engine would be ideal.

Fixed System Is Best

A fixed system is better because it is preinstalled in the engine room, will automatically trigger should a fire occur, and does not require a person to operate it in the proximity of the fire.

"I don't like the fire-port idea," Chris told me, "because people are not professional fire fighters. To expect a typical owner to be able to maneuver a big manual fire extinguisher and hold the nozzle against a fire port and discharge the contents of a 1,000-cubic-foot extinguisher, and not have it go al l over the room he's in... That's asking a lot."

A fixed, automatic system is infinitely better. But there is a problem with the automatic system as well. Again, Chris paints the picture for us.

"In the case of Halon, specifically, if the engine is running, and the Halon system triggers, the engine will continue to run, ingest the Halon, and pump it right out the exhaust pipe, now as a deadly toxic gas.

"If the fire system had been sized to fit the space, having the engine ingest Halon now means you'll no longer have enough concentration of fire suppressant in the engine room to suppress the fire. You're now in trouble."

Because of the possibility of precisely this situation, ABYC's Standard A4 requires an additional calculation, the air change rate. Specifically, this is rate at which the air changes in the engine room space during normal operation, with engines, gensets, and blowers running.

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.

Sounds good, doesn't it? The automatic shut down feature involves electrical components wired into the discharge mechanism to control engines, generators, and bilge blowers. The best part is that they do not require any additional action by the crew in an emergency.

Automatic shut down is a much safer proposition should fire break out under way.

But, according to Chris, there may be a problem here...a classic two-edged sword.

Again, according to A4, one determines the volume of the engine room and then subtracts the tankage to get the volume of the area. That will result in a great volume for conservatively figuring the size of the fire extinguisher system. Big is better.

However, this same volume arithmetic is used to calculate the air change frequency, and, as we will see, can easily lead to a wrong conclusion.

"Let's say you've calculated an 800-cubic-foot engine room," Chris began, "and with your engines, gensets, and blowers running, the combined effort is evacuating 750 cubic feet per minute.

"Well, that's less than 800. So, according to A4, an automatically-triggered fire-suppression system would not need to also shut down the engines, gensets, and blowers.

"But the problem is this: The true volume of the engine room isn't 800, because the engine has volume, and the water heater and the two generators have volume. The actual true volume of the engine room may only be 690 cubic feet.

"In reality, then, you may be changing the air in the engine room every 48 seconds, far quicker than originally thought. But according to the A4 recommendation, you wouldn't need to have automatic shut down."

Once a fire system is triggered, with engines continuing to run, in just 20 seconds, there will not be enough Halon in the engine room (or FM- 200 or FE-241, today's more environmentallyfriendly suppression agents) to keep the fire out. Very practically, the suppressant can't reach its required concentration level, so your preinstalled, automatic fire-extinguisher system will not suppress the fire.

Therefore, it is vitally important to calculate the true net volume of your engine room when determining whether the automatic shut down feature is recommended for your vessel.

The Plot Thickens Even More...

And now we come to a real problem. In a trawler out cruising, it is easy to imagine situations where you would not want to have the main engines shut down automatically.

You're coming in an inlet," Chris theorized, "there are breaking seas all around, and you're trying desperately to stay on the back of the waves.

"If you have a fire in your engine room, you may decide, 'I'd really like these engines running for another 35 seconds to get to safety, and then I'll deal with the problem.'

"This is what can be done with the equipment on the market today: On a Krogen we just completed, there is an automatic firesuppression system, with automatic shut down on the engine, generator and blower.

"We also installed an override for the main engine. So if the owners are coming into that inlet, the fire-extinguisher system goes off as a result of a fire, shutting down the engine. They can turn a switch to manual and start the engine right back up again, and get to safety.

"Or, when they are coming in the inlet, they can turn the switch to manual, just in case of a fire, and the engine will not turn off no matter what. Everything else will shut down, but not the engine."

But owners with a manual override need to understand that if they engage that feature during the above-mentioned scenario, the only fire suppressant they've got to put the fire out will have evacuated.

So you really need to think about what you are doing. It may be that you get safely in through that inlet, and now you can't put the fire out because your approved automatic system has already gone off.

That is the crux of this dilemma.

A Case For Redundancy

All of the automatic fire extinguishers on the market today are the glass bulb variety. When the bulbs heat up to 185 degrees or so, they let go. Those units sold for boats are all USCG approved.

What Washburn proposes here is to have another large fire extinguisher that doesn't have the glass bulb's automatic feature, but rather a simple cable pull to manually trigger the system.

He would install this manual-only system right alongside an automatic fire system (with automatic shut down) in the engine room.

"So if a guy is coming in an inlet," Washburn speculates, "and the system goes off, and he just happens to be unlucky enough that it all happens together, he can get through the inlet under power. If the fire is still raging in his engine room, he then can trigger the manual system, and the fire will go out."

This would be a totally redundant system, but manually activated.

"We're not talking about a lot of money here, perhaps a thousand bucks."

No company is currently marketing such a system for marine use. They exist, of course, but only outside the marine market, as they would not be approved by the USCG.

SeaFire, one of the major suppliers to the pleasure boat marine industry, does make such a system, but it is not sold for marine use. It was originally developed for, and is now marketed to, racing car teams for use at the track.

Despite its non-approved status for use on boats, Washburn may look into it for use in conjunction with approved, automatic systems.

"When people are spending several hundred thousand dollars for a boat," Chris said, "to spend another thousand dollars for a manualpull- only system would be something that a lot of people would go ahead and do."

I agree. It makes sense.

Batteries, Boxes, Electricity

While we talked of fire-suppression systems, the conversation drifted into other, related topics, and Chris offered other comments that are absolutely worth sharing here...

"Now, there is another part of this topic," Chris began. "Let's take a great boat like a Hatteras 58 LRC. It's got a big engine room.

"Well, the most likely source of fire in that room is not the diesel fuel catching on fire. It is the batteries.

"I would like to see battery box lids not only be non-conductive, which is important, but also non-flammable.

"We had a boat here in the yard, a 70-foot Hatteras, where the starter motor hung up, unbeknownst to the owner.

"The starter circuits on these big diesel engines are not circuit-breaker protected. It's the only circuit on the boat that isn't circuitbreaker protected.

"So when a starter hangs up, and these giant battery banks, capable of turning over such huge diesel engines, keep cranking electricity to the starter, the electrical cable gets so hot that it ignites the battery box lid.

"That's precisely what happened on that boat, the fiberglass battery box lid caught on fire. Once fiberglass is on fire, you've now got a real hot fire/fuel system going."

The owner was fortunate. He had just docked the boat, and then noticed smoke coming out of the engine room. The fire extinguisher system did put out the fire, after it caused $35,000 worth of damage. It was a huge job.

Chris also pointed out that batteries are the most likely source of fire on inboard diesel boats. This is especially true today, as boats are getting more and more battery capacity to support 110VAC demands and 12VDC systems so the owners don't have to listen to the generator.

"There are some really hot high-output charging systems on the market today. We also have batteries on boats now that can take enormous absorption rates. When something goes wrong in a system like that, there is the potential for a lot of heat.

"Unfortunately, the master battery switches are almost always in the same room as these batteries. And that's stupid.

"If an electrical fire happens, the emergency fire extinguisher goes off, everything is shut what? The fire is out, but the room is not safe to enter. If the man goes running into the room to see what the problem was, he's just entered an environment where there is no oxygen, and possibly filled with toxic gas, and he can't see.

"Again, it's asking a lot of a guy to have the presence of mind to see that the fire is with the batteries, that it's an electrical fire, and then run over and turn off the battery switches."

So the main battery switches should never be in the same room as the batteries. Battery switches should be in another room. Somewhere else, so someone can cut off the source of the fire without having to enter the space where the fire is, or more importantly, where the fire suppressant is (and where there isn't any oxygen). If it won't support fire, it won't support life too well, either.

"It's not hard to imagine that he might trip, fall down, and knock himself unconscious. His wife can't get him out of there. He's dead, and if she goes in to try to get him out, she's dead.

"Even if it is not strictly life threatening, you also can't go in there because the environment burns your eyes and mucous membranes It is really horrible to enter to do anything.

"Unfortunately, if the owner evacuates the gas beforehand so that it is safe to enter, the fire may come back.

"So if I had a boat like a Hatteras 58 or a Krogen Whaleback, or some boat with a big engine room, I would invest in one of those little small pony bottles of breathing air. I would also make sure I had emergency lighting in the engine room that wasn't dependent on the batteries, or a really good, strong flashlight."

Still A Choice

Food for thought? You bet. ABYC is trying hard to make boating safer, and it is refreshing to see professionals candidly admit there remain things to learn. Standard A4 has not, so far, been changed.

A point of clarification: You really don't have to do any of this. The Coast Guard says pleasure boats don't have to have automatic firesuppression systems. Period. So to have one does not comply with a Coast Guard rule.

Yet as a result of the review, at least Chris Washburn is rethinking his yard's practices.

ABYC standards are, by and large, how all boat yards should be doing their work. And the recommendations represent a heck of a good model for the rest of us to follow. Approved or not, required or not.

It All Comes Down To...

People don't think much about fire on a boat. If they carry the minimum and correct number and type of extinguishers onboard, the crew is safe. Not true.

Had Chris Washburn not been on the Technical Board of ABYC, we'd still be in the dark. Thanks, Chris.

There are lots of boats out there. Fact is, if most of them had a fire in the engine room, their owners would lose the boats.

Many insurance policies require an automatic fire-suppression system in an engine room. But few companies require automatic shut down systems, just automatic triggering of the suppression systems.

So it remains a case of personal accountability and responsibility of trawler ownership. If it is to happen, it is up to you. If you are one of those people who needs to have it legislated for you, Coast Guard forced upon you, or boat builder taken care of for you//YOU LOSE!

Or you can get ahead of the curve and extinguish such concerns long before that first flicker of danger threatens to ruin your day.

Reprinted with permission. Copyright 2000 © Dominion Enterprises (888.487.2953)