Spontaneous Combustion

[BigBoy1]

I have been doing a lot of work with aluminum and vaccuming up the chips. My concern is Spontaneous Combustion. Is there any chance that the cutting fluid and the aluminum chips can cause a fire on their own? Aluminum is an excellent oxidizer and the cutting fluid (Tapmagic) is organic based. An oxidier and a fuel equal fire.

In the past there has been a problem with oily rags and they were to be stored in metal can because of the chance of Spontaneous Combustion. Do I need to worry or should I make it a habit to empty the vaccum every night?

Appreciate thoughts. Thanks.

Bill

[Bruce Griffing]

Aluminum is a reducer, not an oxidizer. Aluminum will burn (oxidize). An oxidizer is something that will provide oxygen for an oxidation reaction.

[jacampb2]

I would be more concerned with aluminum chips mixing with any caustics that may have been vacuumed at some time. Strong caustics are part of many cleaning solutions, things like oven cleaner, toilet bowl cleaner, and some commercial degreasers to name a few. I use several of the above when I am cleaning and degreasing old machines. Most strong caustic solutions will react with the aluminum, oxidizing the aluminum and releasing Hydrogen gas. In a shop vac that is not running, it would be possible for enough gas to accumulate that the next time you switch it on it makes a big bang!

Later,
Jason

[Rich Carlstedt]

I would think your concern would be valid with the "old"
Tap Magic..for ferrous materials.. they would caution you
to use the Aluminum only version..as The Ferrous stuff, desolved Aluminum
(Boy I wish had some ..when you got a stuck tap, you poured
it around the tap, and it ate up the chips in a hurry)
Then in 1980 or so then deadened the Ferrous stuff and it no longer
attacked AL, but they still want you to use AL only fluid.
I have never heard of a problem as you mentioned !
However I have heard that mixing iron dust and Aluminum
is a concern ??
Rich

[lane]

I suck up every thing in mine . It has never blown up are caught fire. . Alum cutting oil tap majic wood chips what ever, never gave it a thought. O heck tomorrow my shop is going to burn down. And I got 2 gallons of that old good tap majic both kinds ,for steel and the alum . stuff

[J.Ramsey]

The only combustion I've seen recently is when IOWOLF , and D.Thomas get together

[Fasttrack]

I would think your concern would be valid with the "old"
Tap Magic..for ferrous materials.. they would caution you
to use the Aluminum only version..as The Ferrous stuff, desolved Aluminum
(Boy I wish had some ..when you got a stuck tap, you poured
it around the tap, and it ate up the chips in a hurry)
Then in 1980 or so then deadened the Ferrous stuff and it no longer
attacked AL, but they still want you to use AL only fluid.
I have never heard of a problem as you mentioned !
However I have heard that mixing iron dust and Aluminum
is a concern ??
Rich

Iron dust and aluminum can potentially cause a thermite reaction which is very powerful. The real danger is with iron oxide and aluminum. If it were pure aluminum and pure iron it wouldn't do jack. Mix in some rusty iron, though, and you *could* (unlikely) cause the oxidation of aluminum and reduction of iron (thus the aluminum acts as the reducer in this case, not an oxidizer as Bruce Griffing pointed out) and a bunch of heat.

They use it for welding ship propellors and rails and whatnot. Or at least thats what i've heard ... i've got not expierence in the ship building area!!

[Forrest Addy]

Short Answer: No.

[oldtiffie]

Sensible and consistent good shop hygiene is the "way to go" as it not only reduces the risk of fire but of fumes!!.

I never put oilly rags together tightly or in a container - especially sealed.

One "old rag" in particular regulalry gets tossed out of the house here by my wife - ME!!

I keep any oilly rags "spread out to dry" - and I have a few of them - but when they are real oilly - out they go every collection day into the garbage.

Fire or combustion needs all three of heat, oxygen and fuel simultaneously for combustion to not only occur but be sustained. Remove any of the three - end of fire. Usually achieved by water (cooling) or "smothering" (foam?) for removal of oxygen.

In a shop I worked in we were milling rocket/missile wings which the were made on magnesium which like aluminium required kerosene as coolant/lubricant and sharp cutter at high speed - 4" spiral slab milling cutters at 2,000 + RPM (max) and "full on" rapid traverse" table feed. Result - excellent cutting and parabolic stream of cuttings (and kero) into a bin about 6 feet away. And then the inevitable happened - the magnesium and kero combusted with a blinding white light that lit up the whole shop and blinded everyone using a machine for several minutes. Maybe self-combustion or some "smart**se dropped a lighted paper or rag into the small pile in the bin.

Never was allowed to happen again. "Management" were "not happy/pleased" - at all.

But I've never forgotten that lesson - hence the fussiness about oilly rags even now.

[Forrest Addy]

Education time:

We need to distinguish between oily rags and oily rags.

Oily rags that contain mileral oil and solvent residues present no spontaneous combustion hazard. Only the flamibility hazard presented by a flammible liquid wicked into a flammible absorbant, that is, high enough to warrant a closed used rag can for fire safety but not a spontaneous combustion hazard.

Mileral oils and solvents are not in the same class of hazard as vegetable oils treated to become "drying oils" such as those used in finishes. These draw oxygen from the air and polymerize to form a tough paint film. This is a form of oxidation, an exothermic reaction that generates heat and heat accellerates the oxidation. Rags used in paint cleanup pose a spontaneous combistion hazard. Loosely wad a rag damp with oil based paint or varnish, leave in a quiet environment, and it soons generates heat, maybe enough to start smoking sometime enough to burst into flame.

It's worth the time to perform a little experiment to drive the lesson home. Dampen a couple of shop towels with oil based clear finish and drop them in a coffee can and loosely cover. Set the coffee can on the barbecue grill. Do tthis in the morning. Check the can every hour or so. Within a few hour the can will be warm and not too long after it will start smoking. If you disturb the rags and let fresh air into the folds you may get suddent vilent combustion.

Animal fats do not seem to subject to spontaneous combustion, only drying oils and vegetable oils once used for frying. Some raw oils pose a problem under certain conditions.

Metal chips can pose problems too especially active metals like magnesium. Aluminim alloy chips are relatively inert. Dust from aluminum sanding combined with dust from steel grinding (contains a high percentage of iron oxide) will support a thermite compustion. Once started these can be difficult to extinguish. Cast iron by itself is no problem but since it rusts quickly in water, under confinement a small amount of hydrogen released by the rusting process can accumulate.

All these hazards have to be separately researched. But coarse aluminum in a container with oily coolant is no more of a fire hazard than the coolant itself.

Forgot to add. Good shop fire safety means spreading out into a single layer any rags containing drying oil products. That way the oil can cure normally until the rags can be safey disposed of. I use the rungs of a handy ladder, bushes, cyclone or wire fence, clothes line or any other suport that permits free air to circulate. Allow a couple of days for them to fully cure before it's safe to put them in the garbage.

Or, if you want a roaring structural fire in your wood frame shop, stuff them in a cardboard box and leave them by the plastic lawnmower gas container next to the big pile of wood rippings. It'll take about the time for you to haul your work crew for a burger and a beer and a short romp through the big box store.