What's the most dangerous failure's these days ? - Page 1
Forum section: electronics / beginners

author: lordvader88
author_rank: Frequent Contributor
timestamp: July 25, 2019, 10:51:26 pm
content: In terms of components failing and burning, even lighting fires, how often is it anymore , assuming the device is new and not full of dust, or made of something super flammable in the early days. For instance a lot of safety work has gone into computer PSU's so that they rarely catch fire anymore.Over the years, what parts failing do you think lit the most fires ? Caps, transformers, resistors ? ?

author: Nusa
author_rank: Super Contributor
timestamp: July 25, 2019, 11:08:42 pm
content: I don't know at the component level. Modern PC boards should be flame-retardant. They can burn, but should be self-extinguishing once the external heat sources consume themselves.However, when it comes to applying the word "dangerous", that really comes down to engineering, fuses and enclosures more than individual components. Power supplies in metal enclosures are probably not going to destroy much more than themselves. Plastic wall-warts on the other hand...

author: Brumby
author_rank: Unknown
timestamp: July 25, 2019, 11:10:52 pm
content: I was thinking along the lines of the EE equivalent of PEBKAC.

author: tggzzz
author_rank: Super Contributor
timestamp: July 26, 2019, 12:01:36 am
content: Speaking from a personal perspective, greengrocer's apostrophies such as "most dangerous failure's" or "consumer PSU's" are very dangerous. They raise my blood pressure so much I am likely to have an anueryism.https://en.wiktionary.org/wiki/greengrocer%27s_apostrophe

author: garethw
author_rank: Regular Contributor
timestamp: July 26, 2019, 07:12:32 am
content: Quote from: tggzzz on July 26, 2019, 12:01:36 amI get a similar feeling to licking a 9v when I see feral apostrophes. Sent from my iPhone using Tapatalk

author: Berni
author_rank: Super Contributor
timestamp: July 26, 2019, 10:49:33 am
content: Definitely things with lithium ion batteries.Its possible for a tiny spec of dust to end up between the layers of a lithium battery or some physical stress can harm it, causing a puncture in the very thin layers and starting off a rather existing chain reaction. The local failure can cause enough heat to damage the surrounding area, this damaged area releases even more heat, damaging more of the battery until the entire cell is going into failure, releasing all of that stored energy as heat in a matter of seconds. So much heat builds pressure inside causing the cell to burst and release flammable gas that catches fire and burns anything near by. If other cells are near such as in a battery pack the heat causes those cells to fail too in a cascading failure.So within a few seconds a harmless looking battery pack can turn into the equivalent of lighting a glass of gasoline on fire. Easily able to light anything flammable near by on fire and the protection electronics can do absolutely nothing about it. Tho bad electronics can help start this catastrophic runaway by allowing the battery to be overcharged, over discharged, unbalanced, overloaded...etc

author: ebastler
author_rank: Super Contributor
timestamp: July 26, 2019, 11:00:49 am
content: Quote from: tggzzz on July 26, 2019, 12:01:36 amI can relate to that. But "apostrophies" and "anueryism" do the same for me.

author: tggzzz
author_rank: Super Contributor
timestamp: July 26, 2019, 11:17:51 am
content: Quote from: ebastler on July 26, 2019, 11:00:49 amIt is a dangerous world out there; let's be careful.

author: EEVblog
author_rank: Unknown
timestamp: July 26, 2019, 12:17:57 pm
content: Multi layer ceramic caps can be dangerous with a grunty PSU behind it.I'm surprised they there aren't more issues than there are with things like motherboards with hundreds of them with people flexing the boards during install.But lithium ion batteries have to take the cake, they are exothermic if the get going, and they energy density of modern batteries is getting seriously high.

author: magic
author_rank: Super Contributor
timestamp: July 26, 2019, 12:37:45 pm
content: Quote from: garethw on July 26, 2019, 07:12:32 amI once licked a 19V laptop PSU output. Guess how it felt

author: ejeffrey
author_rank: Super Contributor
timestamp: July 26, 2019, 05:02:35 pm
content: Hmm. I know one person who burned down his garage with lithium ion batteries, but that was some DIY thing, not consumer electronics so it was likely his fault. I know one guy who had substantial heat damage to his kitchen cabinets and floor when the SSRs in his oven failed short-circuit while he was on vacation, probably due to lighting or other surge. My brother also had his oven spontaneously fail on but he was home and able to flip the shut off the breaker before it did any damage.Counterfit / knockoff / cheap power supplies are also likely a big factor. I used to work in a university that had a whole batch of computers with ATX power supplies with no fuse and under-rated rectifiers that tended to fail and throw breakers. DIdn't cause any damage other than turning out the lights.

author: Berni
author_rank: Super Contributor
timestamp: July 26, 2019, 07:16:20 pm
content: Wait ovens use solid state relays for all of the heating elements? I know id really prefer a clunking power switch there, at least on the heater selection knob.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 26, 2019, 07:46:52 pm
content: Mechanical relays fail short as well.Both types can be high quality & dimensioned properly so that the failure is very unlikely.The correct way to deal with the residual risk is thermal fusing.

author: Berni
author_rank: Super Contributor
timestamp: July 26, 2019, 10:35:10 pm
content: Well yeah i have seen relays fail short but its usually upon turning on under heavy load.But i have yet to see any of these big high power rotary switches fail short (That's what is commonly used to select between heating elements in ovens). Usually in those the contacts close under spring force and are pulled apart by the mechanical motion of the knob, so even if they lightly weld together there is a lot of force available to pull them apart upon the next switching operation.Tho i do agree that its a good idea to have a non resetable thermal fuse in there in case the temperature regulation fails. The old ovens have a bitmetal switch and those could certainly weld (Tho i never seen it happen luckily). But at least it wouldn't turn on by its own, only go out of control once turned on by the user.

author: Psi
author_rank: Super Contributor
timestamp: July 26, 2019, 11:02:07 pm
content: Main issue I encounter is pcb assemblers using non genuine parts in critical sections.Even when told that the part must be genuine

author: Siwastaja
author_rank: Super Contributor
timestamp: July 27, 2019, 08:59:50 am
content: Quote from: Psi on July 26, 2019, 11:02:07 pmSupply all critical parts for these Chinese assembly houses.Another reason I supply the parts by myself is the lead time and availability risk, which often applies to the very same critical, non-replaceable parts. Any part can be suddenly unavailable with 6 months of lead time. If you ask your assembler to source, that 6 months starts when you pay for your order. When you stock the parts yourself, you can order them as soon as your approximate schematic and proof-of-concept prototypes show you are going to use those particular parts.

author: ddavidebor
author_rank: Super Contributor
timestamp: July 27, 2019, 01:25:33 pm
content: Quote from: EEVblog on July 26, 2019, 12:17:57 pmWell motherboards are very thick and most of the MLCCs are very small (small = strong, counterintuitively)

author: aandrew
author_rank: Frequent Contributor
timestamp: July 27, 2019, 02:15:03 pm
content: Quote from: garethw on July 26, 2019, 07:12:32 amMy new favourite name for them. Brilliant!

author: Zero999
author_rank: Super Contributor
timestamp: July 28, 2019, 07:55:55 am
content: Quote from: ejeffrey on July 26, 2019, 05:02:35 pmThat sounds like very bad design. There should be a thermal fuse to cut the power to the element if the switch jammed on.

author: soldar
author_rank: Super Contributor
timestamp: July 28, 2019, 08:30:43 am
content: Quote from: tggzzz on July 26, 2019, 12:01:36 amPeople who do that kind of thing should be analyzed.And while we are at it, another thing I see more and more often is people who drop the final d or ed from verbs. Like writing "That is not what is being ask" instead of "that is not what is being asked". I see it more and more and it really gets to me. Is their brain so lazy or fuzzy they don't know the difference? People who do that should be analyzed. You know what I mean.

author: Psi
author_rank: Super Contributor
timestamp: July 28, 2019, 01:52:58 pm
content: Quote from: Siwastaja on July 27, 2019, 08:59:50 amThey'd probably just resell your good parts and still buy the cheap ones.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 28, 2019, 02:56:52 pm
content: Quote from: Psi on July 28, 2019, 01:52:58 pmNot happened to me. Yes it's possible, but requires a lot more resources from their part, making it less profitable. They need to identify the parts, change them, they need a market connection to sell the parts for profit, quickly...And it's much harder to explain to the customer, it's feels like a much more serious kind of fraud than just "accidentally" buying from a wrong source.

author: radiolistener
author_rank: Super Contributor
timestamp: July 28, 2019, 05:20:14 pm
content: Quote from: lordvader88 on July 25, 2019, 10:51:26 pmli-ion accumulators

author: Gyro
author_rank: Super Contributor
timestamp: July 28, 2019, 05:34:19 pm
content: Quote from: radiolistener on July 28, 2019, 05:20:14 pmAs in people who accumulate dodgy Li-ion cells?

author: radiolistener
author_rank: Super Contributor
timestamp: July 28, 2019, 07:35:16 pm
content: https://www.worldofbuzz.com/power-bank-plane-unexpectedly-catches-fire-passengers-forced-evacuate/http://www.forfyre.com/the-lithium-safe-battery-bag-for-the-fire-protection-of-lithium-ion-batteries-that-catches-fire-due-to-thermal-runaway/?lang=en

author: ebastler
author_rank: Super Contributor
timestamp: July 28, 2019, 08:06:07 pm
content: Quote from: radiolistener on July 28, 2019, 07:35:16 pmThat picture is rather misleading, I'm afraid. This severe FedEx accident had nothing to do with burning lithium batteries:Quotehttps://www.wikiwand.com/en/List_of_accidents_and_incidents_involving_commercial_aircraft

author: james_s
author_rank: Super Contributor
timestamp: July 28, 2019, 10:12:28 pm
content: Statistically speaking, heating appliances, especially space heaters are the most dangerous electrical devices in the home from a fire perspective. Both directly and also in fires caused by the relatively large load causing poor connections and low quality extension cords and wiring to heat up.

author: Gyro
author_rank: Super Contributor
timestamp: July 29, 2019, 12:57:02 pm
content: John Ward's YouTube channel is quite instructive on the danger of poor quality extension cords, power leads, cables, switches etc.https://www.youtube.com/user/jjward/videos

author: tooki
author_rank: Super Contributor
timestamp: July 29, 2019, 11:42:24 pm
content: Quote from: radiolistener on July 28, 2019, 07:35:16 pmHe was not-so-subtly telling you that in English, we call cells and batteries that can be recharged “rechargeable batteries”, and not “accumulators”. (The latter word fell out of common usage in English long ago, and the typical native speaker will have no clue what is meant by it.)

author: Illusionist
author_rank: Regular Contributor
timestamp: July 30, 2019, 01:35:22 am
content: Quote from: james_s on July 28, 2019, 10:12:28 pmExactly what happened to one of mine, and not a cheap one. a 2kW oil-filled radiator in our outbuilding stopped working one Winter. It looked like the fuse (I think, or maybe the contacts to the fuse) in the plug had overheated to the point that it burned out the entire inside of the plug. Even the wall socket got scorched and cracked down the middle. It had been in continual use several winters, running months at a time on full, but still a bad and potentially serious failure.Another failure I saw was from a mains socket where just a TV was plugged in, and had been for years in my parents house. That just started smoking one day when we were sat there. The cause: a sharply bent solid wire behind the plug. It must have been ever so slightly fractured at the bend, causing a slow heat build up at that spot, causing more damage from expansion... until it finally got thin enough to heat up from the TV load and melt the insulation.The worst one happened just a few weeks ago in our current house, again thanks to someone else's dodgy wiring: I was on the way to bed one evening and as I walked past the hallway cupboard where the (really ancient) consumer unit is, I smelled 'hot electrics', just slightly. I could feel the heat when I opened the cupboard and the metal CU was hot to the touch. Inside, the moron who had wired it had shoved two wires together into one terminal, instead of using the empty one next to it. I guess they didn't make good contact and one had gradually overheated and burned away the insulation for 6 inches down the live wire and damaged other wires near it. It probably wasn't far off being a fire.

author: Bud
author_rank: Super Contributor
timestamp: July 31, 2019, 03:00:39 am
content: Quote from: EEVblog on July 26, 2019, 12:17:57 pmThere you go: