Ken,
Thanks for the kudos but it's NOT "my" document. As it notes up front I
merely compiled and organized information that may people submitted.
Regards,
Rob M.
The Pedantic Mechanic
USAussie - Downunder
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
USA '77 Kingsley - TZE 267V100808
-----Original Message-----
From: Gmclist [mailto:gmclist-bounces] On Behalf Of Ken
Burton
Sent: Thursday, February 16, 2017 8:10 PM
To: gmclist
Subject: Re: [GMCnet] Have you checked your Fire Extingwisher lately? YOU
SHOULD if you love your spouse and yourself
Rob Mueller's excellent document from 2013 accurately covers the pluses and
minuses of most common fire extinguishers types. Almost any type of
extinguisher will work when used under conditions that they are designed
for. That is where we come into a problem. What conditions are we most
likely to find in a motorhome.
I suggest that these are the most common areas listed in order of
probability:
1. A gasoline (fuel) fed fire in the engine area.
2. A lubricant (oil or trans fluid) fed fire in the engine or transmission
area.
3. A propane fed fire in the refrigerator, or furnace area.
4. A gasoline fed fire in the generator area.
5. A propane or grease started fie in the kitchen area.
6. An electrical started fire anywhere in the coach.
After I had a coach fire and fought it successfully about 10 years ago, I
decided to learn about the various fire possibilities and way to protect or
fight them in the future.
When I say "successfully" I am saying that I luckily put the fire out after
several attempts with what I had at hand. I did not have the best
extinguisher types available.
After the fire I still had State Farm pay me just under $10,000 to fix all
of the damage. I had more damage from using dry chemical extinguishers
that I did from the actual fire.
I, and several other GMCers, decided to learn as much as possible and to
spread what we learned to the GMC community. One of the participating
GMCers
was a full time fire fighter. Another major resource was our local airport
manager who is also a lieutenant with the fire department. He also
organized and ran a 2 week hands on fire fighter school for various fire
departments in a 150 mile radius of our airport. One other resource we had
is the owner of a local company of about 440 employees that makes fire
fighting equipment. He also is building a fire training tower for all
interested departments to use.
In summary here is what we learned by extinguisher type.
1. Halon and it's more modern substitutes gas types.
This type works well in closed environments (specifically rooms) and does
little if any damage to equipment in the treated areas. To it's detriment
the area treated (usually rooms) needs to be completely evacuated prior to
its deployment. When used in open areas, because it is heavier than air,
it quickly falls to bottom and away from the fire. So in areas around an
engine (where the bottom open) it needs to be applied from the top and needs
to be over applied so as to keep the top area flooded as it extinguishes the
lower areas an falls away. This is difficult to accomplish when an
engine is moving down the road or stopped running with the radiator fan
blowing in fresh air from the outside.
Note: In a past life I use to design and sell halon systems for large
computer, telephone, and industrial motor rooms.
2. CO2 is another gas extinguisher like Halon, but is also cools very
rapidly. While it also settles down like Halon, it also can damage whatever
it
touches if it is not applied judiciously. At one time I worked as an
electrician in a very large steel mill.
The company ran their own rebuild facility for motors and generators. So if
we had a motor or generator burn up it would be sent to the motor shop
for rebuild. Some of these motors were large enough that we would climb
inside them to clean insulators and check brushes etc. on a weekly basis.
We
were expressly FORBIDDEN to use CO2 on any motor or generator because it
could, and usually did, crystallize the metal components and frame so as to
make it no longer rebuildable. All of that said, I did use CO2 on my coach
when it caught fire and I still have one in my coach.
3. Dry Chemical fire extinguishers work well but the clean up and damage
can be extensive. Most dry chem extinguishers (except sodium bicarb) are
very caustic. I had problems removing the dry chemical after my fire. I
tried compress air first. Then pressure washing it with soap and water.
After that did not work well, I tried neutralizing it and cleaning it again.
In the end it corroded everything copper and brass and pitted steel
items like my headers. I had to replace every wire in the engine area and
in the front of radiator all the way to the head lights. I replaced ALL of
the engine accessories except the AC compressor and later had to replace the
compressor clutch. I spent more money on fixing dry chem damage than I
spent on actual fire damage. On top of that when I tried dry chem it would
put out the fire for 5 or 10 seconds and then reignite. I finally used
CO2 to extinguish the fire.
4. The last one I'll cover is AFFF. AFFF is my extinguisher of choice. In
its most common type it is 97% water and 3% concentrate. That is what
you will most commonly find. AFFF is my preferred extinguisher for all
around use in a GMC motorhome. It does an excellent job and does not leave
any residual damage.
AFFF has two negatives.
A. In it's normal mixture (3%) it does not like ethanol (polar solvents)
and will not sustain the foam when applied to a fire. It is approved for
the E-10 gasoline that a lot of us get today but it is right on the edge of
where it works. We have tried it with straight gasoline and with E-10.
When sprayed on an E-10 fire the foam dissipates much more quickly requiring
more AFFF to be applied. There is another product called AR-AFFF
(Alcohol Resistant-AFFF) that will work much better. The AFFF concentrate
that I use here comes from Ansul and is specified for use at both 3% and 6%
mixture. The 6% mix is AR-AFFF compliant while a 3% mix of the same stuff
is AFFF. So if you can find a vendor that will supply you with 6% mix you
will be way outside of the alcohol tolerance problem.
As a side note, the fire trucks at our airport mix the water and AFFF on the
fly. If it is a grass or structure fire that they are fighting, they use
straight water. If it is an aircraft fire they use 3% AFFF as specified by
the FAA. (Aircraft NEVER use alcohol diluted fuel.) If it is a vehicle
fire because of the possibility of E-10 being present they use the 6%
AR-AFFF mix.
The second problem with AFFF or AR-AFFF is the possibility of freezing.
Since the primary component of AFFF is water, it freezes quickly at just
below 32 F. While it usually does not damage the extinguisher, it does
cause the AFFF concentrate to separate from the water. (BTW, salt water
also
does this) When it thaws again you no longer get the expected 3% or 6%
consistently through mixture.
Ansul states that a frozen extinguisher must be drained and the mixture must
be "mechanically stirred" prior reloading again. They say just shaking
it up again is not acceptable. We do have a local fire extinguisher company
that has a paint shaker type device that they will put a loaded
previously frozen AFFF type extinguisher in to mix it up again. I do not
know as I have never had frozen one.
There are ways to get around the freezing problem. It turns out that AFFF
concentrate can be mixed with ethylene glycol antifreeze and water.
BUT......there is a limit. If the antifreeze is too concentrated then the
foam becomes flammable. The maximum mixture only takes the freezing point
down to +17 F. It turns out, and I did not realize it when we bought them
years ago, that Kidde used this +17 degree mixture in the 80 or so
extinguishers that we GMCers bought years ago. Unfortunately these were not
marketed properly and Kidde dropped these in their small extinguisher
line.
There is also a solution that will take the freezing point below 0 F. There
are several companies offering a non-ethylene glycol low freezing point
mixture. A steel mill near me with their own fire department uses this
mixture for their outdoor extinguishers all over the mill. They reload
their
own AFFF extinguishers with this stuff. I know of no vendors offering
extinguishers loaded with this stuff but it would be perfect for a parked
outside RV in the northern US and Canada during the winter.
Now you know everything I know about this topic. I hope this helps you
decide what to choose. Whatever you choose, it will probably be a
compromise
between what is available and what you think you really need.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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