| T O P I C R E V I E W |
| kevinloh |
Posted - Nov 14 2003 : 7:28:53 PM
Capacitors can blow up and explode loudy when heated in fire for a few minutes. I don't recommend it to anyone. I tried it yesterday a use a very small capacitor but it explode in a tremendous force. I wonder what would happen if a large capacitor explodes. Anyone knows how temperature cause it to explode. Reversing polarity and and applying twice the rated voltage can also cause it to explode.
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| 11 L A T E S T R E P L I E S (Newest First) |
| Junkman |
Posted - Nov 29 2003 : 01:03:03 AM
Quite simply, caps 'POP' for exactly the same reason popcorn does, when heated. (Either externally applied, as in a fire, or internally, as in reversed polarity, the end result will be the same.) Popcorn has a small aount of moisture which gets turned to steam, and eventually, the pressure builds up to overcome the hard outer skin, or shell. A Electo cap is no different... the 'moisture' might be of a different composition, but the mechanics are still the same. I've inadvertantly 'poped' a rather large electro cap, and the bang scared the Hell out of me. Sounded like a shotgun shell going off. Believe it or not, once I 're-formed' that cap, it still worked! (Though it died sooner than it should have had it not been poped) It vented, in proper terms, which it was designed to do, and in the process, lost some of the electrolite. This was a comon problem with early electrolitics, they tended to vent rather easily, and dry out as a result. This is why one should NEVER apply full voltage to a vintage tube type radio that has been sitting for a long time. The caps can dry out even without excessive heat. "Re-forming' can save some of them, though most people will just replace them all as a matter of course. The problem I find with this is that new, modern caps with the 'same' ratings, often are more efficent, not always a good thing, and can cause failure of a component 'downstream'. Ditto for rectifiers... The older ones were often selenium, NOT silicon. The voltage drop in the selenium was taken into account by the designers of orginial circuit, swapping them out for modern silicon diodes can be too 'efficent', applying too much voltage downstream. And popping the almost dryed out caps in the process. I saw a stop motion photo once of a large cap being explosively detonated on purpose, a stop-the-bullet-in flight type of photo... And it illistrated very well why you do NOT want to be too close to one if it blows. The paste inside is caustic, and would not feel too good in your eyes, not to mention the shrapnel flying around.
Junkman
Junkman |
| kenmce |
Posted - Nov 23 2003 : 9:51:19 PM
quote:
I wonder what would happen if a large capacitor explodes. Anyone knows how temperature cause it to explode.
The air and whatever else is in it tries to expand. Because it is trapped in a metal case it can't expand, but the pressure it applies to the case increases as it gets hotter. Eventually the case fails catastrophically. You are reinventing the grenade here. You might want to stand back while you test your grena^H^H^H capacitors...
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| Kale |
Posted - Nov 18 2003 : 1:35:43 PM
Electrolytic capacitors are filled with a paste. When you reverse the capacitor and apply voltage, or just apply too much voltage in the forward direction, the paste starts to heat up. Eventually (or rapidly depending on how much power you're using!) the paste boils. This produces the expanding gas which raises the internal pressure of the capacitor until it bursts.
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| n/a |
Posted - Nov 18 2003 : 12:24:01 PM
The excess heat (from being in a fire) causes gas to form inside the capacitor under high pressure until the case cannot tolerate it anymore...BaNG!!! If the case is weaker or has more weak spots as in the bigger electrolytics, it won't allow as much pressure to build up resulting in less of a bang.
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| kevinloh |
Posted - Nov 18 2003 : 06:52:47 AM
Anybody here knows what causes it to explode?
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| n/a |
Posted - Nov 17 2003 : 6:03:46 PM
i didnt think it was fun when the capacitor in my network switch popped 
Yesterday USA, Jetzt Deutschland... RYE |
| Epsilon! |
Posted - Nov 17 2003 : 3:33:01 PM
yeah, tantalums are dipped and sealed pretty good, do the small size cannot hold a lot of pressure, so they pop better
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| YS |
Posted - Nov 16 2003 : 9:41:05 PM
Electrolytics, especially large ones, are made with certain protection against explosion. Even small aluminums have a "cross" on the top - specially designed weak place, so it opens relatively easily to prevent large pressure. I did not see anything like that on tantalums.
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| cirvin |
Posted - Nov 16 2003 : 5:15:04 PM
i would expect the big electrolytics to be less spectacular, because they are soo largem the cases have more weak points and plases for the gasses to excape, less violently.
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| Kale |
Posted - Nov 16 2003 : 4:01:18 PM
Some guys who built a railgun housed their capacitors in a cinderblock box in case they exploded. These were kV-range capacitors and apparently they explode quite well.
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| Epsilon! |
Posted - Nov 14 2003 : 10:03:46 PM
i find that tantalum caps pop better than small electrolytics. Must be cause tant caps are all enclosed and there is more pressure when its heated. I never tried any big electrolytics.
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