Class D fire extinguisher

[Badabinski]

Hey folks!

Quick question about fire extinguishers. I once had an unfortunate incident where some cutting oil in the chip tray caught fire when I was turning hardened steel. I've learned a lot since then (like don't turn hardened steel with cutting oil), but fire safety has always been a concern for me.

I currently have an ABC extinguisher. That will cover most of my bases, but my girlfriend mention that it would probably be worthwhile to ask whether or not a class D extinguisher is necessary, since metal fires really suck!

I know that fire extinguisher selection depends on what you work with, so let me go into that. I primarily machine steel (usually 1114, 4140, A2, S7, D2, H13, and O1) and aluminum (7075 and 6061), with occasional stainless (mostly 15-5PH and 17-4PH, with a bit of 303). I never, ever want to machine magnesium, and it's unlikely I'll machine titanium any time soon.

Given the metals I'll be working with, is there a chance I'd get a fire that couldn't be put out with an ABC?

 

[Aaron_W]

Unlikely, and Class D extinguishers are material specific so you would need to ensure you bought the right kind of Class D for the material if you were to buy one.

Dry sand is quite effective on small quantities of most "common" machinable flammable metals.

Aluminum is theoretically combustible, but unlikely in a home shop setting. Steel is not a concern, the fire hazard being related to hot chips and cutting oil. ABC should be fine, I'd recommend at least one 5 lb ABC extinguisher.

 

[Flyinfool]

Another point to consider, most of the dry chemical powders are very abrasive and corrosive, not to mention make a heck of a mess to clean up. Do you really want to unleash that on your machines. Yes putting out the fire is of No 1 importance but after the fire is also important. The fire in the chip tray will not do much damage other than to wiring or some cosmetic plastic parts of a machine, it will not hurt the metal. Dry powder can do a lot of damage to the precision surfaces of a machine. A fire on a machine is almost always an oil fire, Very rarely a metal or electrical fire and unless you machine wood on your machines a wood fire is also very unlikely unless you cut a lot of wood to cover things in wood chips and wood dust and then sart into steel throwing hot chips into the pile, but then you are trying to make a fire.
I have a 10 lb CO2 and a 20 LB Halon that are both BC rated which will cover any oil or electrical fires on the machines and do no additional damage to anything. The A rating is for wood or paper fire. I also have a A rated extinguisher for the unlikely case of a wood or paper fire. There is also the garden hose in the shop for that purpose also.

I do have a couple of the powder ABC units around but they are always a last choice for an emergency. If I have to grab those I am also at the point of calling 911. It means that 30 lbs of BC or a garden hose could not put it out. And yes I have put out wood, grass and paper fires with a CO2. It aint the best but will do in a pinch.

 

[tq60]

We got a god deal on c02 and haylon replacement units and have them all over the place.

The gas type can be used multiple times without recharge due to gas.

Less mess as well.

Sent from my SAMSUNG-SM-G930A using Tapatalk

 

[Aaron_W]

The mess from Dry Chem extinguishers is real.

The C is ABC means it is non conductive below 600v, realistically other than the electrical hazard water would work on most machining fires since you rarely have deep pools of burning oil. Unfortunately the electrical hazard is there with water. The B in ABC is flammable liquids, but is really only needed when fuel is a few inches deep, not a thin puddle.

CO2 will extinguish an A fire, but it will rekindle if the heat is still there, such as with a pile of sawdust. It can buy you time to get water on it, and spreading it out to dispurse the heat may even put it out.

I am a fan of the old pressurized water can Class A extinguishers as well. They work well and you can recharge them yourself with a hose and air compressor. I keep one handy when I'm welding since most welding fire hazards are Class A materials, other than the welder itself catching firee. Garden hose with a good nozzle is quite handy, just less mobile.

CO2 works well, is pretty cheap, and mostly safe but they are heavy. I wouldn't bother with Halon unless you have sensitive and expensive electronics at risk. It is not cheap and creates toxic gasses when exposed to flame. CO2 won't hurt most electronics so is generally preferred.

For a fire in the drip pan baking soda (never baking powder) is an option, many BC extinguishers just use a fine grain baking soda as the agent. Dumping a box of baking soda makes a lot less mess.

 

[Badabinski]

Sounds like I need to switch out my ABC out there! Thanks for all the advice. I definitely didn't do enough research on this so I'm glad I asked and got so much info.

 

[Aaron_W]

I wouldn't get rid of the ABC, just add a CO2 if you want a cleaner option, ABC is going to be your most effective option for all around use.

Also be aware Halon and CO2 have an asphyxiation hazard in a small space, that is partly how they work on a fire.

 

[Uglydog]

Unlikely, and Class D extinguishers are material specific so you would need to ensure you bought the right kind of Class D for the material if you were to buy one.

Dry sand is quite effective on small quantities of most "common" machinable flammable metals.

Aluminum is theoretically combustible, but unlikely in a home shop setting. Steel is not a concern, the fire hazard being related to hot chips and cutting oil. ABC should be fine, I'd recommend at least one 5 lb ABC extinguisher.

One of the fires we were at was a welding/machine shop which specialized in car repair. My partner and I were tasked with getting the fire under the enclosed stairs. It was filled with 55gallon drums which were on fire. The owner was on scene and told command they were stuffed with old blueprints and misc papers. So... we worked our 2 1/2" hose into the tight space and bounced water off the bottom of the steps into the open 55gallon barrels. There may have been some paper in those barrels but there was also magnesium auto parts. Now we had added water to the burning magnesium barrels. Went up like chimmneys.... We bailed and the shop was evacuated. Burned for a long time until the front end loaders arrived with dry sand.

Years later there was some metal rounds on a pallet of misc I bought at auction. I was told to take it all. Ok.
I got fireworks when I attempted to turn it. Was nice metal, but didn't like the fireworks....
Ended up learning that the pallet had come from a manufacture of replacement hips (medical).

Stay away from metal fires.... Just don't go there.
Best plan is just don't do it. Make sure that you have a quick and safe escape route, close your eyes and hold your breath. If you can't get out you need a better plan (for this exercise turn all your machines off first). Emergency safety switches are good. Quick disconnects appropriate.
Extinguishers are for buying you enough time for getting out of a building and maybe small waste basket fires. FD often bring in "Water Cans" if no signs of active fire.

Daryl
MN