Dangers of capacitors blowing up

Question

I was wondering what kind of damage a 350V, 6000uF (link to capacitor) electrolytic capacitor could do. will this kill me if it blew up next to me? I have never blown capacitors before, but I definitely would not want to blow this one. Has anyone reading this blown a capacitor this large before? If so, what could I expect to happen, and how could I take precaution against it?

Answer 1

Exploding this capacitor deliberately will not be so exciting. As other answers describe, the precut vents will open up to release the pressure harmlessly.

But you can make it spectacular if you charge it with 350V DC (in the correct polarity of course) and short out its terminals with an iron screw driver. The full energy can be held by this capacitor is 367 Joules and this is pretty nasty. If you short the terminals in a fraction of a second, hundreds of ampere will flow causing metal melt down with huge pop and spectacular arcing....

That will be far dangerous than exploding the capacitor itself. Having said all these, I don't recommend you to try this out unless you know the dangers associated with it.

Answer 2

If properly abused, that capacitor would make quite a bang and mess. It is unlikely that the bang would kill you even if you were a couple of feet away, but you can't rely on that, and it could certainly hurt you pretty severly. A serious injury like loosing one or both eyes isn't far fetched at all.

The secondary effect could be quite serious too. The whole room will be filled with stuff you really shouldn't breath. It could immediately damage your lungs, possibly killing you from oxygen starvation before any medical help could reach you. Even if you can still breath, you may end up at a greatly elevated risk of cancer.

Depending on what is nearby, there may be additional dangers. Anything flammable could get ignited, which comes with its own dangers and likelyhood of property loss.

Deliberately exploding it for fun or to see what happens is irresponsible and a waste of resource. But if you do that for whatever reason, do it in a open field with you at least 20 meters and upwind.

Answer 3

Large capacitors are less spectacular than small ones, because they always have some kind of vent. Often these days, it's in the form of scores in the aluminum can which weaken it so it will fail in a fairly predictable fashion in case of internal overpressure. Top vent:

Typical manufacturer's caution on vent clearance:

Another caution note here

Old-school computer capacitor with bottom vent (the grey rubber circle)

Dangerously hot chemicals can be ejected, as well as bits of aluminum, particularly if stupidly high power dissipation is involved. You should not deliberately induce such failures, and getting too close to any kind of unhoused power electronics should involve at least eye protection and perhaps a full face shield where higher power is involved. The chemicals are not particularly toxic, but they won't do you any good if inhaled.

Answer 4

There are too many factors to consider to say "yes it will kill you" or "no it will not kill you". It might just pop a seam and vent smoke for a while, or the entire thing might explode violently, showering the entire room with boiling electrolyte and send shrapnel everywhere.

Your best bet at prevention is to just not be stupid. Don't over-volt it and don't connect it backwards. If you're still concerned about it exploding, set up a blast shield between you and the capacitor (but don't enclose it! That could act like a secondary bomb!)

If you keep it within its specified operating conditions, it won't explode. Just be smart and be safe.

Answer 5

In my experience large electrolytic capacitors all have pressure vents built into them, especially those with screw terminal connections. An overload or reverse voltage will cause the capacitor to heat up until the vent (usually hard rubber) pops and vents out smelly gases, maybe leaving a puddle of electrolyte by the vent. At this point the capacitor is already destroyed and not usable.

The capacitors that go "BANG" and send their metal cans flying along with a cloud of stinky wax paper are the smaller 'can' type electrolytics found on pc boards. I have seen tantalum capacitors go "POP" but with much less violence-though they are prone to catching fire and burning the PCB. Disc capacitors tend to crack open if overloaded-the polarity does not matter. Unless you overvoltage them or reverse voltage them or have a high current ripple in the DC power line beyond the capacitors rating they are safe to use.

I have had them (electrolytic can capacitors) explode in my face due to being installed in reverse. When building circuits pay attention to DerStom8's answer and do not install one in reverse!

Answer 6

Based solely on a video of a 1 Farad, which is 200 times greater capacity than a 0.006 farad capacitor you link, it's unlikely to do anything other than take your eye out or leave a welt. It's not big enough to spew much liquid electrolytic, and not big enough to fill a room or even a small cabinet with smoke. It may just vent instead of explode. Think of a small firecracker.

https://youtu.be/6OaR58pLmlQ

A 6 milli farad cap is pretty small. It will however stink the room up something fierce.

Unless you are holding it in your fist or something when it explodes. That could take a finger off.

Answer 7

With a 3-phase Variac supplying voltage through a rectifier with nothing limiting the charging current, I once blew up several 350 V, 2500 uF capacitors by turning up the voltage too quickly. At least one capacitor blew out the top and the Variac was damaged. The rectifiers and capacitors were inside a perforated metal enclosure. That was about 45 years ago and it taught me some lessons that I still remember.

Over the years, I occasionally heard reports from people I worked with describing similar capacitor explosions due to various types of faults. We never used capacitors like that without some kind of protective enclosure.

Answer 8

Small capacitors without precut vents are the dangerous ones. I had the can of one dent it's self on the ceiling at work. Germanium low power transistors in a metal TO1 can are even more dangerous. They have heatsink compound inside that can vaporize & blow the can off like a bullet. In a chart recorder pre-amp I repaired, where an insulation breakdown had applied mains voltage across it, it had dented the aluminium lid, while the bottom came down so hard, the edge sheared through one of the steel wire leads & cracked the PC board. If you are likely to blow one of them up, WEAR SAFETY GLASSES!, & a face mask if it's a germanium transistor.

Answer 9

Likely to KILL you? Not unless you put your head right next to it or something. Likely to spatter you with hot gunk from its internals? Oh HELL yes! It’s unlikely to do more than scare you senseless, and give you some nifty burns.... like what you get from accidentally dropping molten solder on yourself while soldering. Hurts like hell but won’t kill you. Of course if any of those acidic chemicals or the safety plug hit you in the EYE, it’ll be a whole different story. Seriously, if you must blow up that capacitor, treat it like a big ass firework, stay at least 30 feet away, and do it outside. Source: I’ve worked as an electrician for over ten years.

Answer 10

Stored energy = 0.5CV^2 =~ 367 Joule.
That's a serious amount of energy - slightly below
the muzzle energy of a '38 special'.

IF you directed all that energy unidirectionally and drove something solid with it then it could kill.
IF you could couple all that energy into a 6mm steel ball bearing it would have an exit velocity of about 1 kilometre/second [!!!].

BUT in almost all cases worst case is being shot in the face with an energetic wad of caustic goo. Losing an eye could happen, but more likely is just having a story to tell to your friends.
(Ask me how I know :-) - but not THAT energetic).

So, as has been noted in various ways by various people.

• Check polarity

• Be aware if you stand above it that you are facing a loaded gooey-shelled 38 special equivalent.

• Do not place such a capacitor in an enclosure such that the energy could be focused and channelled.