Summary
The boat will have fire detection and suppression systems installed in the engine room and the control room, also be a manually operated extinguisher built into the galley area. In addition there will be hand held units in the pilothouse and the forward cabin. The boat will be equipped with smoke detectors in the aft cabin, saloon and forward cabin. The boat will have a high pressure seawater pump stored in the cockpit locker. This pump serves multiple purposes. One purpose will be to fight any fire inside the boat. To that end there will be strategically place deck feed-throughs to which the pump will attach and spray water into the interior spaces of the boat. Particular attention will be made to preserving the carbon fiber mast..
The battery boxes will be positively vented when the batteries are being charged.
Fire detection/suppression devices are shown in the Internal Installation drawing in the Fire Safety Layer
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Discussion
This is an aluminum boat and aluminum will not readily burn unless exposed to very high temperature and/or if finely divided. For the purposes of this discussion we will consider it non flammable.
The things that will burn are, by definition, the fuels on the board, and much of the material making up the interior structures and furnishings of the vessel. The mast would also burn.
The sources of ignition are
1. any of the fuels on board e.g.
a. diesel
b. propane
c. gasoline
d. alcohol
e. kerosene
f. butane
g. hydrogen
2. plastic and wooden components of the boats interior
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This is quite a subjective survey. I suppose we could look at an array of flammability limits, flame speeds and ignition temperatures but I don’t think that would overcome my subjective feelings about these fuels.
I view gasoline and propane as the most hazardous. You can throw a lighted match into diesel and it probably would not ignite, gasoline definitely will. If there is a room temperature diesel leak I don’t think the diesel vapors in a closed space ( e.g. the engine room ) will ignite; with gasoline the vapor at room temperature can explode. Because of its hazardous nature gasoline is not allowed within the boat. It must be stored in a separate and drained compartment at the back of the boat. The only reason we have it on board at all is to power the outboard. We have not yet found a low power lightweight diesel outboard., and we are not prepared to go to an electric outboard because it might not have the necessary range.
After gasoline I think comes propane. This is on board for cooking. We can use it either at the back of the boat or in the galley inside the boat. Again, this stuff is sufficiently dangerous that the ABYC regulations specify that the containers must be on the outside of the hull. If this gas leaks it is heavier than air and can settle into the low parts of a space and explode upon ignition.
We are looking to see if electric cooking is feasible with the Fischer-Panda power source. I think at the moment it will be. Therefore we will not bring an active propane line into the boat at all. ( what this means is that we will install a line from the propane locker to the location of the galley stove. We will also make provision for installing a propane gas sensor/alarm in the cabin. However we will not attach the line at either end and we will not install the cabin propane sensor ).
We will still carry propane on board to power up the grill/barbecue at the back of the boat and in case the electric cooking fails. Even then, OVM has suggested using diesel cooking because the new diesel stoves have overcome the diesel smell issue. The other use for propane is with the Forespars minigrill. This takes the small screw-on DOT propane canister. These canisters we will keep outside the boat in the same locker as the larger propane bottles. We were planning to allow the use of this minigrill in the pilothouse but never inside the boat. We need to think about this some more. The kerosene and alcohol fuels are associated with the Mountain Sports camp stove and are only a liter or two.. These fuels as are not as inherently dangerous as propane but nevertheless they should be kept in the outside locker.
Hydrogen is produced from the batteries if they are overchanged and start hydrolyzing the battery acid. This should not happen with the Fischer-Panda battery charging system for the House battery nor for the engine powered alternator for the starter battery. However bad things can happen The good thing about hydrogen is that it will float upward and, unless the boat is closed up, should escape though the hatch or roof vents. The bad news is that it has the widest explosion limits of any gas. In principle the battery boxes should be vented over the side. Again this is something that needs more thought.
One danger is from a damaged or shorted component overheating and catching fire. This could cause a fire not, as in the case of gasoline and propane, an explosion. A sparking electrical system is, however, a classic ignition source for these other two fuels. The most likely scenario is for a semiconductor device to fail and some associated resistors to burn up. If this takes place on a commercial circuit board then the risk of fire is quite small. These boards are built to be flame retardant, our home-built circuit boards are the same way.
Seafire said that the engine was the most likely source of a fire and within the engine it was the electrical systems, e.g. the alternator and starter, that was most likely to start it.
Another danger is from shorted cables and damaged insulation. In an electrical system equipped with fuses, breakers and current monitors I rate this risk as small.
The materials used inside the boat for cabin furnishings are capable of supporting combustion. They are the most likely fuel for any fire outside the engine room. Inside the boat there is a lot of wood and a lot of epoxy composite materials and, perhaps, polyester composites. We have looked at the flammability of some of the common resins used in composite manufacture and have chosen Epoxical as our resin ( Flammability of plastic materials ) for any composite structures we might build.
In addition to the composite structure there will be fabrics for curtains, bedding, seat covers etc. Some of these can be treated with flame retardants but probably not all, and then there is all the “stuff” that is packed away in the lockers, cardboard, paper, etc.
The boat will be thermally insulated. At the present time the choice for hull insulation is foamed-in urethane of a flame retardant grade. The floor insulation is likely to be building grade polyurethane foam sheets. The insulation for the cabin roof is still also probably urethane faom
Fire Detection
Fire detection can start at the places where we are deliberately burning fuel. This means
1. Engine Room This would cover primarily diesel fuel fires. Fires in the engine room will be detected either by the melting of a fusible link, the emission of OH , or there was an article about a fire system that used a meltable hose (you must look that up ). I was told by SeaFire ( www.sea-fire.com) household smoke detectors would work in a boat.
2. Control Room. This space contains most of the high energy electrical wiring and also most of the computer systems and data acquisition. It will be protected by a similar system to the one in the control room.
3. Elsewhere in the boat we will have smoke detectors.
Fire Suppression
There will be basically three fire suppression systems on the boat.
The first will be a FM200-based system that handles fires in the control room and the engine room. This is automatic with a manual override. It will be triggered either the melting of a fusible link or the detection of uv flame emissions. If we can, we would use a Halon based system. It is cheaper, lighter and more effective than FM200. ( It is also not available in the EC.) SeaFire recommends two separate systems, one for the engine room and one for the control room. They recommend that the canister be located above the most probable site of a fire. Their fusible link goes at 71 deg C ( 160 Deg F ). Which canister to use depends on the volume within which you are trying to kill the fire. In our case I think it is about 8 cubic meters for both the engine room and the control room. That makes the system the FD275M and it weigh 12 kg. I still do not see why we cannot plumb one canister into both areas.
The second system will be a set of hand fire extinguishers. One in the pilothouse, and one in the forward cabin. They are designed to kill small grease fires or small plastic fires. We might consider a larger, built-in system for the area near the galley because of the relatively high probability of fires in that region. These systems will possibly be the Seafire F6240s.
If the internals of the boat become seriously alight then it will no longer be safe to fight the fire from inside the boat. The strategy then is to have two high pressure seawater pumps in the external locker aft of the cockpit, with the proper spray nozzle fittings, to be used to drench the flames. These pumps have multiple uses, e.g. salt water washdown, in addition to this fire fighting use. We can also vavle in the Rheinstom 6E pump ( if we can get to the valving ) to pump out seawater through the saltwater wash-down fitting. In order to avoid adding to the oxygen supply of the fire by opening hatches we will build in special nozzles that would allow the washdown pump hoses to be attached on the outside of the hull and spray water inside the boat. Some parts of the boat ought to receive particular attention, e.g. the diesel fuel tanks and the carbon fiber mast inside the hull.. You may want to have a deck fitting next to the mast that would allow you to flood the tube containing the mast from a deck hose.
Table of Fire Risk
|
Nature
of fire |
probablility of occurrence |
severity |
overall risk ( pob*s) |
overall risk ( poc*s^2) |
detection
methods |
suppression
methods |
comments |
|
|
|
|
|
|
|
|
|
|
propane
leakage in galley |
8 |
10 |
80 |
800 |
gas
detector in cabin |
none |
do not
use propane for cooking in cabin |
|
grease
fire in galley |
10 |
6 |
60 |
360 |
smoke
detector |
local fire
extringuisher and external water spray |
|
|
24 vdc
distribution box fire |
8 |
7 |
56 |
392 |
none |
none |
box is
aluminum skin, little fuel in box |
|
hot
diesel leak in engine room |
9 |
5 |
45 |
225 |
flame
sensor in engine room |
automatic
fire extinguisher |
the fire
suppression system must be easy to clean up and not harm electronics. |
|
control
room high current electronics |
9 |
5 |
45 |
225 |
flame
sensor in control room |
automatic
fire extinguisher |
the fire suppression
system must be easy to clean up and not harm electronics. |
|
fluorescent
ballast burnup. |
6 |
7 |
42 |
294 |
smoke
detector |
lfe and
ews |
|
|
overheated
pump/motor |
8 |
5 |
40 |
200 |
smoke
detectors |
lfe
&ews |
|
|
hydrogen battery
explosion |
4 |
10 |
40 |
400 |
none |
dilution |
keep
ignition sources away |
|
fire
inside commercial electronics |
10 |
3 |
30 |
90 |
device
functonality |
none |
commecial
box shuld be nonflammable. |
|
lightning |
5 |
5 |
25 |
125 |
loud bang |
lfe and
ews |
a lot of
stuff may be destroyed functionally |
|
control
room computer systems |
5 |
5 |
25 |
125 |
flame
sensor in control room |
automatic
fire extinguisher |
the fire
suppression system must be easy to clean up and not harm electronics. |
|
electrical
cable fires in cabin |
4 |
6 |
24 |
144 |
smoke
detector |
local
fire extringuisher and external water spray |
|
|
defective
110vac appliance. |
5 |
4 |
20 |
80 |
smoke
detector |
lfe
&ews |
|
|
|
|
|
|
|
|
|
|
Comments on Excel spreadsheet.
We ranked the diesel fire as more likely that a propane fire because the Fischer-Panda is running all the time.
It might seem presumptuous to say that there is more likelihood of a fire within the commercial electronics than within the ones I put together. However there is a lot more commercial stuff than my own stuff and some of that commercial stuff carries a lot of energy. My stuff is low power.
Notice that the ranking depends on how you model the overall risk. If you give equal weights to occurrence and to severity then the hydrogen risk in midway on the list. If you give more weight to the severity number then hydrogen moves up the list.