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pogen
04-18-2016, 10:58 AM
In going through the last few items on my RRS checklist, I saw that in addition to conventional fire extinguishers (Class B/C , I guess) , it is recommended that racers have a fireblanket and also Class D extinguisher if they are using Lithium house batteries.

I looked on Landfall, they have fireblankets that are 3'x3' (really only good for galley) and 6'x6' , and they are not cheap and since they are fiberglass are not good for anything else.

I found one on Amazon here: http://www.amazon.com/MFASCO-Emergency-Fire-Blanket-Kit/dp/B001B9RNMC

which is wool/poly with retardant, it may not be quite as good for fires, but it can double as an extra layer if you are getting hypothermic.

I also looked for a compact Class D extinguisher without success -- they all seem to be big 30lb beasts. But maybe I don't know where to look. Ideas? It seems like a good thing to have, but 30lbs is big and heavy, and as I understand it B/C extinguishers are useless against D (metal) fires, and also vice versa.

For general fire info, please see Steve's presentation from last year here: http://sfbaysss.org/resource/doc/Yacht_Fire_Safety_Steve_Hodges_20150603.pdf

He is an industrial fire safety pro, and I think his info is valuable.

hodgmo
04-18-2016, 02:09 PM
Bottom line up-front: Having any rated fire blanket aboard and at hand in your bunk or chart table is a great idea; they’re cheap, effective and clean. A combination of ABC and BC dry chemical extinguishers, mounted in intelligent locations is recommended – and don’t be shy about having more than the minimum USCG requirements. A fire port on an inboard engine enclosure is also recommended. Be aware of the unique hazards presented by Li-based batteries (large and small) and have a plan to match. Make sure your installation includes a tested, high-quality battery management system. Class-D extinguishers are not needed with LiFePO4 batteries.

Discussion

The large (~6X6 ft for ~$45) fire blanket referred to above is essentially the same as the one I showed in my ‘Yacht Fire Safety’ presentation (slide 27/35), and what I have on Frolic. Another smaller (3X3 ft for ~$15) option, less $ and space claim, is this:

http://www.amazon.com/Hot-Headz-Fire-Blanket-36-Inch/dp/B00IYCE7IC/ref=sr_1_1?ie=UTF8&qid=1461002996&sr=8-1&keywords=fire+blanket

The smaller fire blanket is certainly better than nothing, and should be suitable for a galley fire, and either is much more convenient than dumping a pound or more of dry chemical (fine powder) in the cabin (what a mess!). I’m tempted to switch to it, and move the bigger blanket to my garage. Note that the larger blanket can be wrapped around a person with clothes afire, while the smaller blanket is probably too small for that. But wool blankets will fill that function. If you have a galley fire involving propane, don’t forget to stop the gas flow as quickly as practical.

After the galley, the next most likely fire sources are the engine or an electrical fault. Engine fires are likely to involve fuel (or on some boats hydraulic fluid) and best attacked via a fire port with a good B-rated handheld extinguisher. The fire port is a small hole in the engine enclosure that allows you to attack an inboard engine fire without opening the enclosure and feeding the fire with clean air. Electrical fires may involve burning solids, like plastic and wood, and if so an A-rated extinguisher is recommended. For these reasons, it is recommended to have at least one good ABC extinguisher on hand. But be aware that ABC agents are ammonium phosphate based powder which are somewhat corrosive to metals, and irritating to breathe. If the amount of solid involved in the fire is ‘small’ then most BC dry chemical extinguishers (sodium or potassium bicarbonate) should be adequate, and they are less corrosive and irritating than ABC dry chemical. Note that while both sodium- and potassium-bicarbonates are rated BC, potassium-bicarbonate is roughly twice as effective by weight. A big boat could consider the bulkier and heavier CO2 (BC) extinguisher, but beware of using CO2 in a confined space (suffocation risk). So-called clean BC agents are available ($$$) and their advantage is that they become gaseous when discharged so no cleanup is necessary, and in normal use they aren’t an asphyxiation hazard. But beware of fluorinated agents (most clean agents and all Halons) as firefighting byproducts include seriously toxic gases. There are no toxic byproducts or other inhalation issues associated with the dry chemicals, they are just messy. Finally, keep in mind that in a pinch, BC agents can be augmented with the vastly available A-rated agent available to a floating yacht: sea water (another use for the scared sailor with a bucket). But be very careful if you have an inverter on – while fairly harmless with exposed 12 VDC circuits, salt water and 120 VAC can be shocking. In fact, for any electrical fire it’s generally a good first step to disconnect the batteries and make sure that the electrical system is down.

One of the most important things about extinguishers is how they are installed. Rather than mounting an extinguisher in the galley so that you may be compelled to reach thru fire to get it, mount the extinguisher near where you sleep and/or in the cockpit. Mount them with metal brackets (throw away the cheap plastic ones) so they are available when you need them. Don’t be shy about having more firefighting equipment aboard than the minimum USCG requirements! Think through the most likely scenarios and be prepared for those and similar.

Regarding Li-ion battery fires… Recommended protection depends on the type of Li-based battery and its size and support system (ie, battery management system). A class-D (rated for metal fires) extinguisher is really only needed for Li-based batteries that include a significant amount of Li metal in their construction, and only if the first recommended action – tossing the burning battery overboard – isn’t an option (got tongs and a metal bucket?). Most house batteries installed on yachts these days are LiFePO4 and these are currently the safest Li-based batteries for this application, especially if installed correctly with a high-quality battery management system. But, like any battery, they can fail, and unlike lead-acid, the electrolyte is flammable. However burning metal isn’t a primary fire source so a class D extinguisher isn’t needed for LiFePO4. And, unlike more energy-dense Li-based batteries, a LiFePO4 is very unlikely to produce enough heat to create an open flame or to melt through the boat bottom. But if a LiFePO4 (or any Li-based) battery does have a thermal event (and like any high-density electrical storage device, they can), then be prepared to deal with a lot of toxic smoke that may render the cabin uninhabitable for a while. The discharged gas, while not at flame temperature, is hot enough to ignite nearby solids, for example thin plastic or wood, paper, etc. Such a secondary fire would call for an ABC extinguisher, or a good douse of water. As with any big battery, mount the LiFePO4 in an enclosure that isolates it from such easily combustible materials. Other higher energy density Li-based batteries may warrant a stainless steel enclosure.

pogen
04-18-2016, 02:17 PM
Thanks Steve,

Well that is good to know , I think most of us with Li batteries have the LiFePO4 variety, which have the safest reputation.

D.

pbryant
04-19-2016, 01:14 PM
I considered upgrading my lead/acid batteries to LiFePO4 lithiums. The electrical characteristics are nearly ideal: four times the energy density, light weight, high cycle life, high efficiency of charge/discharge ratios, and deeper discharge tolerance (you can only get 50% of the charge capacity out of lead/acids without drastically reducing their cycle life).

But the fire hazard is so great, especially from insidious causes like the formation of internal dendrites that can short a cell and trigger thermal runaway, that I'd only carry them in a barge towed behind the boat. Once ignited, the fire is very difficult to extinguish, produces copious amounts of toxic gasses, and without containment and heat dissipation will likely burn a hole right through your hull. It's unlikely that you will put the fire out with an extinguisher (studies have shown they are ineffective with lithium fires since the burning battery produces its own oxidizer), and throwing water on it produces hydrogen gas. Throwing the battery overboard (somehow) is the only sure way to stop the fire. All you'll need is a self-contained breathing apparatus suit (you have one on board, right?) to survive the fumes, and once it hits the water, stand back for the hydrogen reaction!

Boeing is highly committed to these batteries in their 787 design. And they've had fires in production airplanes. One battery caught fire in a Boeing contractor's lab, and despite the best efforts of the fire department, it burned the building to the ground. http://www.seattletimes.com/business/787-battery-blew-up-in-rsquo06-lab-test-burned-down-building/. If a cell shorts internally, the heat will conduct from one cell to the next triggering a thermal runaway chain reaction. Consequently, if you have 4 cells in close proximity, expect to have to extinguish 4 fires. You probably won't survive the toxic gasses long enough to do that.

Boeing's "risk mitigation" is to enclose the batteries in a steel case (negating some of the weight savings), and provide an overboard vent for the toxic fumes.

JohnS
04-19-2016, 08:52 PM
LiFePO4 batteries are chemically different with different characteristics where safety is concerned than the Lithium ion batteries used in Boeing's Dreamliner. A good place to start understanding the characteristics of LiFePO4 batteries can be found at: https://en.wikipedia.org/wiki/Lithium_iron_phosphate_battery#Safety Personally, I would not be concerned about carrying LiFePO4 batteries on board if the bank is well built with a good battery management system. And you could always put them in a steel fire box like Boeing and place them near the companionway for a quick eject should the worst happen. Did someone say "fire blanket"?

pbryant
04-20-2016, 08:37 AM
As with most fires, it's the toxic fumes that'll get you.

https://www.youtube.com/watch?v=FvkiyVTvhMI