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Exploding vacuums?

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  • rklopp
    replied
    One thing I notice is that I can get a wicked static shock after vacuuming while milling canvas phenolic. We're talking major lightning strike - yeowww! Makes a normal carpet and cat-related doorknob shock seem like nothing. I can avoid it by making sure I am always touching some part of the grounded machine while vacuuming.

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  • J Tiers
    replied
    Originally posted by bhowden View Post
    I wonder if there is any issue with the contents of the vacuum spontaneously combusting long after you left the shop. If you were sucking up cotton waste or sawdust as well as the oil and then not emptying it right away it might cause issues later. I have never seen it even get close but there are videos out there of shop rag containers catching fire in the middle of the night.

    Brian
    Probably, if you slurp up material containing "drying" oils, like linseed oil.

    "mineral" oils do not do that, but certain vegetable oils will. Ones where the carbon chain has "double bonds", oils that will "dry" in a fairly short time to form a paint like coating.

    Cooking oils typically take many days or weeks to harden, and generally do not spontaneously combust because they do not polymerize fast enough to reach ignition temperature.
    Last edited by J Tiers; 03-28-2020, 04:32 PM.

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  • bhowden
    replied
    I wonder if there is any issue with the contents of the vacuum spontaneously combusting long after you left the shop. If you were sucking up cotton waste or sawdust as well as the oil and then not emptying it right away it might cause issues later. I have never seen it even get close but there are videos out there of shop rag containers catching fire in the middle of the night.

    Brian

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  • JoeLee
    replied
    Originally posted by nickel-city-fab View Post
    I think the newer shop vacs blow up easier because they're have so much HP already ... but you notice the ads never say how much TQ.

    Nah. It's really hard to light WD40 in my experience.
    Remember when all the air compressor companies would brag about the HP of their motors calling them for example 5HP when in fact they were not even close. Had big stickers all over them saying "5HP". Then in fine print somewhere in the specs it would say "develops 5 HP at XXX number of RPM's . I used to call them "Fake 5's" You could hold it back by placing your hand on the flywheel and turning it on. No starting torque. Especially a problem if the unloader valve didn't unload ! Try starting the compressor with tank pressure against one of the pistons.

    JL......................

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  • kitno455
    replied
    The corvair owners club used to do exactly this at their club meets- suck gas from a bucket and time how long the vacuum would run with flames shooting out of its exhaust. Then the insurance company found out

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  • dian
    replied
    vaccums are weird. once mine exploded for no obvious reason (at least i never found out why). it didnt destroy itself but i was several meters away and got pretty frightened. at that moment i was vacuuming up the grinder but i had used it for chips before.

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  • The Metal Butcher
    replied
    Originally posted by Corbettprime View Post

    As I have said before, the home vac mfgs are a bunch of b s artists. That SIX hp shop vac? They got that figure by jamming a screwdriver into th e fan, and recording the highest amp draw the millisecond before it went up in flames. You will never see a true six hp motor run on a 120 volt 30 amp circuit.
    It's worse than that. It's calculating "brake" hp counting the inertia of the motor/impeller if a brake was applied over X period of time. So I guess my lathe has 40HP, at least. Put a bigger chuck on it, that's more horsepower.

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  • J Tiers
    replied
    Originally posted by nickel-city-fab View Post
    .......

    Nah. It's really hard to light WD40 in my experience.
    At least with the chips, any volatile solvent in the WD40 is likely long gone by the time they get vacuumed up, and the oil is not volatile enough to be lit by a spark, unless it were to be broken up into a mist, and even then it would likely take a flame.

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  • nickel-city-fab
    replied
    Originally posted by Corbettprime View Post

    As I have said before, the home vac mfgs are a bunch of b s artists. That SIX hp shop vac? They got that figure by jamming a screwdriver into th e fan, and recording the highest amp draw the millisecond before it went up in flames. You will never see a true six hp motor run on a 120 volt 30 amp circuit.
    I know, It just drives me nuts when I see BS advertising like that.... ditto for lawn mowers, notice how Briggs don't always give the HP any more, just some "TQ" bs? Back of the envelope quick calcs shows that 6 HP would need 40 amps, not gonna happen on a 110 circuit. (I wonder if I should have used "sarcasm" tags in my earlier post)
    Last edited by nickel-city-fab; 03-27-2020, 11:06 PM.

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  • Corbettprime
    replied
    Originally posted by nickel-city-fab View Post
    I think the newer shop vacs blow up easier because they're have so much HP already ... but you notice the ads never say how much TQ.

    Nah. It's really hard to light WD40 in my experience.
    As I have said before, the home vac mfgs are a bunch of b s artists. That SIX hp shop vac? They got that figure by jamming a screwdriver into th e fan, and recording the highest amp draw the millisecond before it went up in flames. You will never see a true six hp motor run on a 120 volt 30 amp circuit.

    Leave a comment:


  • nickel-city-fab
    replied
    I think the newer shop vacs blow up easier because they're have so much HP already ... but you notice the ads never say how much TQ.

    Nah. It's really hard to light WD40 in my experience.

    Leave a comment:


  • JoeLee
    replied
    I've sucked up metal chips with my shop vac for the last 20 years. I've used WD and other various cutting oils and never had a problem. I have given it a thought at one time but after going this long I don't worry about it. I also vacuum the shop floor, saw dust wood chips and everything else. I use a filter bag in the canister and a filter on the motor.
    I have a rubber hose on the vac, it doesn't give static bites like the corrugated plastic hoses that come with these vacs does. Now you have me thinking.
    My rubber hose is about shot and has gotten pretty short from having to cut the end when the rubber splits.
    It may be dangerous to use the plastic hose.

    JL................

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  • Glug
    replied
    I recall a mythbusters where they explored vacuuming gasoline with a shop vac. Totally weird that it did not explode. And yet, not exactly confidence inspiring.

    A quick search turned up this video with a former cast member. Similar result. Really kinda odd. They cheat at the end, and it is satisfying.

    https://www.youtube.com/watch?v=C-0-PH-ZU_0

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  • J Tiers
    replied
    Well, oil burns if finely divided and mixed with air, even heavy oil, so I guess that proves WD40 does not contain oil.... !

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  • Yondering
    replied
    Originally posted by wierdscience View Post
    WD-40 doesn't ignite very well, you can barely get it to flash after it's been boiled off as vapor. I don't think you have anything to worry about unless some random confluence of events happens and some interaction with a static discharge occurs.
    This. Seems like a lot of discussion about how to prevent it with very little consideration to how dangerous (or not) it really is. You'd be hard pressed to cause any sort of explosion with WD40, even spraying it directly into the vacuum.

    Many years ago spray cans of WD40 were much more volatile because of the propellant (some say propane) but it hasn't been that way for a long time now. Those fun experiments we used to do with using WD40 to power a cannon just don't work any more with modern WD40.

    Easy test - spray some WD40 on your mill table, concrete floor, or whatever, and try to light it with a propane torch. Not much happens. Even lighting it directly aerosolized from a spray can, it makes a small flame but nothing like spray paint, hair spray, or many other products, and even then, most of the WD40 fails to ignite.

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