Fire is one of the biggest dangers to the power voyager. However, not all fires are the same. There are different types of fire in different parts of the boat. And because fires can differ, not all fire-fighting techniques work well for all fires. What kind of fires are we talking about and where do they start?
Engine room: Most boat fires start in the engine compartment, which is not surprising when you consider all the flammable materials normally found in engine rooms. Gasoline or diesel fuel, hydraulic fluids, oils and greases, oil-soaked rags, solvents, insulating materials, even laundry – you name it; if we don’t know where else to put it, it goes in the engine room. A broken, leaky or corroded high-pressure fuel or hydraulic line can result in a fine spray of combustible fluids on a hot manifold and then ignition of the fuel. Once you’ve got ignition of a primary source, all the secondary sources are only too ready to make their contributions, increasing the speed, intensity and spread of the fire. Polyurethane foam is a major secondary contributor; it burns with great intensity and gives off toxic fumes, making it extremely difficult to fight the fire with handheld extinguishers.
Such fires are referred to as Class B fires, that is, fires involving flammable liquids – gasoline, diesel and hydraulic fluids, oils and greases, paint, tar and flammable gases like liquefied petroleum gas (LPG, propane or butane).
Galley: The second most common place for fires to start is in the galley. Here again, most of these fires are associated with cracked fuel lines, loose connections or just faulty installations.
Galley fires are particularly critical because often the galley and the wheelhouse are in close proximity, and there are lots of secondary sources such as cooking oils and greases, paper, wood and other organic materials, and again, insulation. Since all the vessel’s communications and navigation equipment, the engine and steering controls are located in the wheelhouse, the ability to control the vessel or to send distress messages can be quickly lost. Fires involving organic materials such as wood, paper, cloth, trash, etc., are classified as Class A fires, so a fire like the one described above would be a Class AB fire.
Electrical Systems: Batteries, battery boxes, and electrical wiring and devices are other frequent sources of fires. Loose or corroded wiring connections, short circuits or wiring that is too small for the current load could all cause the wires to overheat and ignite oil- and dirt-impregnated wiring insulation. The insulation ignites, the fire travels along the wire run, ignites bulkhead insulation and the fire is off and running. Or overcharged batteries may release excessive amounts of explosive hydrogen gas trapped in the battery box, and a starting motor or just static electricity could ignite the hydrogen. Electrical fires are classified as Class C fires and they are particularly treacherous because they are seldom detected until the fire is well underway.
Fire
fighting
chemicals
Halon:
For
many
years,
Halon
was
recognized
as
the
best
choice
for
protecting
boats
from
fires.
Halon
is
a
colorless,
nearly
odorless,
low
toxicity,
electrically
non-conductive
gas
that
is
extremely
effective
for
extinguishing
fires
and
leaves
no
residue.
In
the
1301
version,
it
was
used
as
a
flooding
agent
for
enclosed
spaces.
In
the
1211
version,
it
was
used
mainly
in
handheld
or
portable
extinguishers.
Halon
was
not
recommended
for
paper,
wood
or
cloth
(Class
A)
fires
because
these
materials
require
thorough
soaking. It was, however, excellent on liquid fuel fires (Class B) because these are surface fires. Halon also effectively smothered the flames on electrical (Class C) fires because there was no residue to clean up or corrode electrical or electronic equipment.
Unfortunately, Halon contains carbon, fluorine, chlorine and bromine. Because of their bromine content they are even more destructive to the ozone than CFCs and because of this, worldwide production of Halon was halted in 1996, although it was still possible for a period of time to obtain recycled Halon for refilling extinguishers in critical applications. As of Jan. 1, 2004, though, it was no longer available.
Dry chemical powders: Dry powder chemical extinguishers may contain a number of different extinguishing agents, typically sodium, potassium and bicarbonate compounds. Ordinary dry chemical extinguishers are not recommended for use on Class A fires but are effective on Class B and C fires. However, there are multipurpose dry chemicals that use ammonium phosphate and are effective on all classes of fires.
The problem with dry chemical agents is that they leave a residue that can make quite a mess and be difficult to clean up. Worse yet, this residue can be seriously damaging to electronic equipment.
Carbon dioxide: Carbon dioxide (CO2) extinguishers are effective on both Class B and C fires, and they do not leave a residue. The problem with CO2 is toxicity. It works by depriving the fire of oxygen, but a sufficient concentration of CO2 used to extinguish a fire will not support life, so it could be a threat to crewmembers. Since it is most effective when applied from within two to three feet of the base of the fire, it can make fire fighting hazardous in enclosed spaces like engine compartments. For this reason it is most often used as a flooding agent for these spaces.
Halogens: With the withdrawal of Halon from the market, extinguishing agent manufacturers turned to other, less ozone-damaging halogens in their efforts to develop acceptable alternatives. Chief among these alternatives are DuPont’s FE-241, also called HCFC-124; FE-227ea, also called HFC-227ea; and Great Lakes Chemical’s FM-200. Like Halon, these are colorless, nearly odorless, electrically non-conductive gases that leave no residue and are safe for people.
FE-227ea and FM-200 are replacements for Halon 1301 for flooding applications in unoccupied spaces and both are approved by the Underwriters Laboratories (UL) and Factory Mutual (FM Global), a global commercial and industrial property insurer.
FE-241 functions both as a flooding agent, replacing Halon 1301 for unoccupied spaces, and as a streaming agent replacing Halon 1211 in handheld units.
Fire extinguishing systems
Handheld extinguishers: Training in the proper use of the different types of portable extinguishers is strongly advised. A fixed, automatically-activated extinguishing system should be considered for boats with an unattended engine room.
Fixed Extinguishing systems: In unattended spaces, fires may go undetected until it’s too late to deal with them effectively. Also, fighting fires in enclosed spaces can be particularly difficult and hazardous to crewmembers. Opening and attempting to enter an enclosed space engulfed in flames is not a good idea. The sudden inrush of a fresh supply of oxygen can create a huge fireball, which may cause injury and will only make matters worse. A fixed system can respond faster and more effectively than you can. But how big should it be?
The basic idea is that you’ve got a closed compartment of a specific volume, i.e., the volume of the space less the volume of the space occupied by the engine(s), generators, tankage and other large objects. If a fire starts and temperatures reach approximately 185� F the extinguishing system will activate and discharge its extinguishant, filling the enclosed space with the extinguishant gas, displacing the oxygen and making the fire go out. A gasoline engine or generator, deprived of oxygen, will shut down, but the bilge ventilation system will continue to ventilate the space, pumping out the extinguishant gas. That’s not good. Diesel engines and generators will also keep running, ingesting the extinguishant and pumping it out the exhaust so there will not be enough to suppress the fire. Automatic engine shutdown on diesel engines is required.
So,
the
system
must
be
large
enough
to
completely
fill
the
space
with
extinguishant
and
automatically
shut
down
the
engine(s),
generators
and
blowers.
Such
systems,
called
“pre-engineered
systems,”
are
available
on
the
market.
The
problem
here
is
that
it’s
not
always
convenient
to
have
your
engines
shut
down
–
especially
in
heavy
weather
and
rough
seas.
So,
assuming
your
system
has
a
recommended
alarm
with
an
audio
and/or
visual
display
at
the
helm
position,
it
should
also
have
a)
an
override
that
will
delay
activation of the extinguishing system, thus buying you some time to position the boat safely, and b) a manual pull cable to activate the now-disabled extinguishing system.
Automatic systems range from the smaller, single-bottle units with release valves set to open at 175° F to engineered systems designed for a particular installation. Some of the major suppliers to the power voyaging yacht market are Kidde, Fireboy/Xintex, Sea-Fire Marine and Nautical Fire Suppression. Sea-Fire Marine has both automatic and engineered systems. Fireboy/Xintex has a line of automatic (CG2 Series) and automatic/manual (MA2 Series) systems. And Kidde Marine recently released a new system for yachts called the SBS series. Designed for pleasure craft and smaller commercial vessels, the SBS Series comes in the Sentinel for smaller vessels and the Sentinel Pro for larger vessels.
So, bottom line, if you decide to go with a pre-engineered, fixed system, be prepared to take the time and trouble to accurately calculate the volume of the space to be protected, and make sure the system you select has the features described above.
