ANyone have dust collector (metal) fire?

I have no idea what Shot Peening is. However, there are "terrible" fires happening, and that's a bad situation. Is it possible to put some distance between the shot peener (or whatever it is) and the dust collector? Maybe you can lay an additional three or more feet of pipe in between with a p-trap, similar to the p-trap you see under most any sink. That might give the bigger embers a place to drop out before they hit the filters, and (hopefully) the smaller embers will burn out and turn into dust along the way.

You have to keep those hot embers out of the dust collector somehow. Adding some distance and giving the larger pieces somewhere to fall before they hit the filters sounds like a good way to go.

It would not be a bad idea, either, to call others in the same business. You don't have to call anybody local if you don't want. Call somebody across the country, and maybe they'll be a little more open about the practices in their shop.

Is there anything else, at all, that can be causing this problem? Is the equipment kept clean? Are there any wires anywhere? Where, exactly, do the fires start?

A lot of times with something that has caught on fire, you can put that thing on a bench, take it apart, and do a little detective work.

I'm willing to bet that just about any science teacher at any local college would be interested in helping you dissect your system to look for a cause.

If you don't find the problem, and/or you don't get any decent suggestions here, try to at least post some pictures and give a better description of the problem you're having.

Good Luck!

Daven

snipped-for-privacy@hotmail.com (Don) wrote in news: snipped-for-privacy@posting.google.com:

Is your dust collector piping properly grounded? Most fires and explosions in dust collectors are due to static electrical discharge. As the air moves through the pipe a charge builds up until, zap. Most wood type dust collectors have a bare copper wire inside the pipe secured through the length of the run to help bleed off the charge. If you collector is all metal it could still have sections of pipe isolated by poor grounding and or rusted connectors.

A thorough inspection of the complete system is in order. If a spark is the ignition source, then a ash can type filter at each entry point might be a possible solution.

My 2 cents

Jim Vrzal Holiday,Fl.

In the asphalt industry Nomex bags are available to help with dust collector fires although if the material you are catching burns fireproof bags don't help much. Steve

..and keep that P-trap full of water Texas Parts Guy

At work, while going through our welding safety course, our instructor told us about a plant he visited (either as a welder or a paramedic, as he is both). This company stored explosive chemicals in a room within the plant. Every so often, the room would explode without a trigger because of the nature of the chemicals. My instructor was astounded, but the workers seemed to have gotten used to the random explosions.

Your situation sounds similar in that people have, perhaps, gotten used to these "terrible fires". I don't have a specific solution for you, but I'm sure you could find a company who knows what to do about your situation in the yellow pages ("industrial ventilation" or some such). It's scary that this problem wasn't rectified after the first fire...

There are enough ways to get killed at work...

Regards,

Robin

Nomex bags are great, but IIRC they are only good for about 400-500'F, at least that's what my supplier said. I know they WILL melt! We have a DC in our thermal sand reclaimer that has 144 bags, 12 bags in a row, 12 deep. We use 3 rows of Nomex at the input side, then the rest are polyester. Of course Nomex is about 4X the cost of poly bags.

I think there are some even higher temp DC bags available, called Vulcan, or something like that. C&W Technical Sales in central WI might be able to help.

Since nobody else mentioned it, there are automatic extinguishers used with dust collectors. A fire detector of some sort (optical emission from the flame, or smoke out of the exhaust) shuts off the blower, drops steel accordion dampers over the inlet and outlet, and fires off a CO2 extinguisher in the bag house.

Jon

We never had dust collector fires during operation, but if a grinding spark hit the dust box under the machine, that stuff would burn merrily. A Class D extinguisher is the only way to stop it, I am told. We used to just haul the burning box outside and let it go. I finally put the collector outside, with a long pipe, and perhaps that prevented any possibility of fire. The pipe was 6 inch metal truck exhaust pipe; is yours a plastic pipe, with the problem of static? I considered building a device whereby the pipe would have a very fine water nozzle in it, driven by a small high-pressure pump, allowing the dust and water to mix during its journey through that 40 feet or so of pipe, and a centrifugal separator outside the building to catch the slurry and let the cleaned air go. The slurry would collect in the bottom of the separator and drain off when the vacuum was shut off. Never got around to it. It would be a lot more efficient than the dust filters/bags, no back pressure, no fire risk, and none of the filth associated with the dust.

Dan

I'm not exactly certain on what's burning, but it sounds like metal. Is CO2 considered Class D? I think it's usually just a cylinder of compressed gas (as a power source) and sand....

Also, why not try to prevent the fires instead of just dealing with them?

Regards,

Robin

No they're not. This is an old canard and it's (in almost all circumstances) untrue.

The only way to have a dust collector fire is to mix a flammable material with an ignition source of sufficient energy to ignite it. There are two ways to get this two happen in practice; suck up some solvent vapours, or suck up a spark / glowing ember.

A static discharge has inadequate energy to cause a fire or dust explosion in woodworking workshop dust collectors. There are _NO_ recorded instances of such an explosion or fire.

There are many burnt out woodworking dust collectors. Almost all of these were caused by the "burning ember" route. Sparks, cigarettes, spontaneous combustion of finishing supplies. There are some real risks here and they should be guarded against.

In non-woodworking industries, the usual cause of dust collector fires, and of almost all dust collector explosions, is from sucking up flammable solvent vapours. These _are_ capable of being ignited by a static discharge. The usual culprit is toluene, particularly when a non-toluene process with a safe dust extractor has switched to using toluene.

In this case, it seems impractical to stop sparks from shot peening. The approach should instead look at removing the fuel source. I don't know of any shot peening process that's likely to produce flammable dust (maybe some paint stripping), so I'm wondering if there's a shared dust extraction system here where a fuel-rich dust stream is getting mixed with the spark-rich stream from shot peening. Such systems should be segregated, not mixed - similarly for mixing collectors for solvent vapours.

Yup, you're right, these were for dust collectors in woodworking shops, where the burning material would be a lot more effectively extinguished by CO2. I wasn't thinking straight!

Jon

"Robin S." wrote

My feet came out from under me once and I fell/slid down a flight of stairs and ended up at the bottom laying on my back. The fall knocked the wind out of me and I couldn't breath. My thought was that I broke my back and because of where it was broken, the signal to breath wasn't getting from my brain to my lungs, and I figured I was going to die. Then, the thought came into my head, "What a bummer to die at this sucky job." -- dt

CO2 can be a fire _accelerant_ in woodworking workshops !

A pile of sawdust (the usual culprit) has enough interstitial air and enough of a tendency to smoulder that squirting it with a "blanket" of either CO2, dry powder or even foam won't extinguish it. Even worse, the blast of gas from a CO2 extinguisher will distribute burning embers all over the place, giving a much worse problem to deal with. To extinguish wood dust collectors, the only thing that works is gallons of water and waiting a few hours to check it really as coolied down and doesn't re-light.

Woodworking is one of those environments where you really do need multile extinguishers, and to use the right one. There are electrics, solvents and bulk finely-chopped timber -- all need their own extinguishers.

Look up "spark arrestor" systems for your DC.

Just a thought, are you treating a mix of aluminium and steel parts? If so you may accidentally be making thermit - burns at 3000 degrees+, this is a mix of iron oxide(rust) and aluminium and will ignite explosively if finely divided and fluidised in air. Thermit is used for welding heavy steel parts, railway lines etc and rocket fuels. Mark

We used to blast a mix of aluminum, zinc, steel and cast iron parts. The aluminums and zincs were alloys, with the zinc containing aluminum, and the aluminum containing magnesium. Knowing, of course, that magnesium burns readily, and that aluminum seems to have similar but less spectacular combustive properties, the dust would burn rather well. I used to wonder if the heat of the burning non-ferrous metals would release oxygen from the other oxidized metals and feed the fire, hence the need for the class D extinguisher. Burning rubber also requires Class D. I think. I am no firefighter but someone lurking here would know these things.

Dan

One *never* sees the following words on tombstones:

"Damn I Wish I Had Spent More Time at Work"

:^)

Jim