Techie's one ring brought darkness by shorting a server Monday brings the shock of a return to work, a transition The Register always tries to ease by bringing you a new instalment of Who, Me?, the reader-contributed column in which your fellow readers admit to errors and disclose how they dodged the consequences. This week, meet a reader we'll Regomize as "Steven," who once got …
Wearing rings, watches, bracelets or any other metal items while anywhere close to electricity is a mistake many people only make once, regardless of their ability to learn.
Even the non-fatal cases can do things like permanently weld your wedding ring to your flesh and leave a painful injury to remind you for the rest of your life.
I can't remember right what I was going but I was working on my car and something tickled my wedding ring. Nothing bad because as soon as I felt it I moved it well away.
As you say, you only make the mistake once. Sometimes you can be lucky to tell other people about it. Doesn't always work out that way though.
yep, I had my ring get caught on a bracket in a rack, and on another occasion, I had my watch hang up in a rack and broke the pin holding the strap, I wear neither a wrist watch or wedding ring any longer. I still have them both, perhaps when retirement comes(sooner than later it appears) I'll get the battery and the strap for the watch replaced? The ring can stay in the box where it lives.
I once caught a signet ring on an overhead sign when I was showing off my ability jump 6 inches high. I ended up with a deep cut on my right ring finger which I treated by wrapping it in bathroom paper towel. And this was on the way to the drinking spot so you may imagine the stupid things I, and others in the party, got up to on the way home.
https://www.theknot.com/content/silicone-wedding-bands
No more accidents, and they can be chucked in the nearest bin should an emergency emerge. You just have to keep a secret stash of identical ones to avoid trouble back at home the next day. Mine is the one with the secret rubber-filled pocket, thanks.
But less flexible in the event of being widowed! I have been widowed twice and now wear both wedding rings on my right hand as a memorial rather than on my left hand. And of course, if a wedding breaks down for other reasons, a permanent wedding ring might not be so good!
I once saw someone who nearly had a serious injury from handling heavy oil drums; his wedding ring caught, and he very nearly had a degloving accident - as it was, it tore the flesh but came unstuck before he lost a finger. I would be cautious about rings and heavy lifting as well as the electrical accident mentioned by most!
I posted this here last year in a thread titled Field support chap got married – which took down a mainframe
I can still remember, in the early 80's DEC VAX field service engineers removing their wedding ring before working anywhere near the computer's backplane. Apparently the current available from the power supply could heat the ring to red heat in only a short contact.
Indeed. I've done a lot of work with car batteries - lead acid - which will red-heat a wedding ring, or indeed a carelessly placed spanner. A couple of weeks ago I was building a 15kWh 50v battery... my ring stayed firmly off my finger, and my watch off my wrist. I hate to thing what the short circuit current might be - but the system is fused at 500A.
Which is why firemen are trained to feel their way round burning buildings using the back of their hand with fingers bent, so that if the back of the finger touches an exposed live cable the reflex will pull the hand away from danger rather than grabbing hold of it.
Anon comment.
I was once in an air force military maintenance shop (country and date unspecified) that worked on radar systems and other funky electronics. As I was being shown a radar head, I reached out to point and ask a question. My wedding ring passed over a contact. The ***KRAK*** noise was accompanied by a blue lightning flash and stumbled back a half dozen feet into a nearby wall.
Luckily, the head had not been energized for some time and a lot of resident electricity had bled off. At full charge, the head would hold several hundred thousand volts (Being deliberately vague here). There was a grounding tool with thick copper lashing to drain the stored energy for maintenance, but whoever did it last didn't hold it on for the prescribed time and there was just enough electric left to make an impression.
I woke up in the hospital with a mild concussion. Ring was fine save for some carbon scoring that rubbed off. Lesson learned. I never wore it to work ever again.
Ref battery, 500A short circuit current? 500A would be a very conservative estimate. One of the standard ratings for car batteries is CCA, Cold Cranking Amps, being as you'd expect the measure of the current that a cold battery can sustain into a load like a starter motor attempting to start a cold engine, short circuit would therefore surely be a lot higher?
some vaguely pertinent anecdotes:
(partial repost)
From a previous life as a Saab tech, I have in my toolbox a 10mm combination spanner with a right-angle bend in it as a reminder never to rush a battery installation. In a moment of inattention I allowed it to touch both battery terminals of a brand new battery (on a 900 so at least 550A CCA) momentarily, & it immediately tack-welded itself in place. In the couple of seconds it took to grab an adjacent screwdriver & lever one end of the spanner off the lead post (thank chosen deity that lead is soft) the spanner was already glowing cherry red & it just bent round as if it were made of hot toffee.
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My late brother managed to bridge the battery connection & casing on a starter motor with the stainless strap of his Seiko Belmatic. Fortunately there was a chunky screwdriver within reach with which he was able to prize them apart. When he pulled the strap off his wrist the skin had melted & flowed in between the links of the strap, & "resembled hot cheese on a pizza" in the way it extruded. He had a very impressive scar to the end of his days.
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Tangentially related:
I have a nice little mark on my left wrist from welding the clutch pedal on a Mk1 Saab 900 back together in situ (a common job on high mileage RHD versions). That involved lying upside down in the footwell & welding above your face. Safety glasses etc obviously, & trying not to be directly underneath didn't stop a big blob of weld from falling off & dropping into the space betwixt wrist & watch strap. It took me lot less time to exit the footwell than it had to wriggle in there.
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A mate has an impressive "sign of Zorro" on his chest from when he was learning to TIG weld about 40 years ago. A big blob of white hot metal spat out of the weld & managed to find a small opening at his throat between face mask & leather welding apron. It made it's way down his front, changing direction each time he patted it (whilst correctly yelling "Ooh! Ow! Feck! Yer Bastard! etc) until it settled in the waistband of his underpants. Cue half-naked chap running around the workshop to the cheers from his puzzled but entirely" supportive" (ie pointing & laughing) workmates, of whom I'm not ashamed to admit, I was one.
Oh, welding blobs.
I still have a dimple in one foot. Welding overhead at the farm, blog of white hot steel dropped off and went down ... the top of my welly. Obviously, it went as far as where it gets tighter around the ankle area. There I was, hopping around, uttering phrases that could translate to "gosh, that's hurting somewhat" - and trying to decide if pulling the welly off will be worse as it means pulling the tight bit past where the blog is sizzling away into the top of my foot and pressing it harder in.
And when I was an apprentice, apparently one of the other lads had packed up when he realised he'd missed a small bit of weld. He couldn't be bothered setting up again, so just shut his eyes and did it blind. Next day his face looked like a beetroot, not helped by being an albino and hence sunburning very easily.
A friend of mine reached behind a large bank of relay racks and managed to get his Rolex watchband across the large 48V supply ... The resulting loud "CRACK!" and fans spinning down, coupled with the smell of roasting/burning pork, were rather disturbing. To say nothing of the screaming. I managed to calm him down & get him to the ER ... the X-ray machine showed little balls of gold melted into his wrist behind the 3rd degree charring. The surgeons later told him he was lucky to still have full use of his hand. Today, over half a century later, the scarring is still impressive, despite skin grafts. He got a new band for the watch, and now wears it on his other wrist. It still works.
And people wonder why I always take off my wedding ring when working on electrical stuff. Yes, that includes cars, trucks, bikes, boats, etc.
For the record, the power supply was no worse for the wear, and the equipment in the relay racks automatically powered back up as if nothing had happened ... Thank you, Lorain.
Note that the Levis 501 "watch pocket" is the perfect place to park a ring for the duration ... I don't wear any other jewelry, so you're on your own for anything else.
I once designed and soldered together an experimental PC board with PC/AT bus with a load of LS-TTL electronics to control the exposure time of a CCD video camera and microscope illumination. Inserting this into one of the lab's image processing stations and switching it on caused a distinct feeling of apprehension. I was half expecting some "KZZEERRT" type noises, some smoke, and the distinct smell of burnt silicon. However, nothing happened, which was a huge relief. I started up the controller program to detect the presence of the new board, and nothing continued to happen, which was less encouraging. I then poured over the design, and checked the documentation of the PC/AT bus. It turned out I had missed a thin line over the ACK pin, i.e. it was logically NOT ACK. Luckily I had a spare NAND gate on one of the 74LS00 chips on the board, and could use that to invert the ACK signal. The board worked flawlessly after that. I soldered together some 6 of them, and each time inserting them into a PC and switching it on made me nervous, but happily no fireworks ensued.
I used to work at a board manufacturer and almost every time someone started up a new board, someone would time their walking behind and clapping their hands to induce the maximum panic reaction.
A remember Dr. B (if you are reading, Hi) turning on a 6U board and it showing no activity on the front of the board. I asked him what the orange LED at the back of the board signified - It was VME backplane power pins shorting and glowing!
I used to work at a board manufacturer and almost every time someone started up a new board, someone would time their walking behind and clapping their hands to induce the maximum panic reaction
Always a good spectator sport. I recall when I was a teenager going to electronics nightschool. The instructor had a massive (and I mean desk drawer pedestal massive) 'scope - it was a long time ago. So there I was, feeding the signal generator into the X chanenl, and the same signal into the Y channel - via me, and playing with contact pressure to vary the shape of the Lissajous curve. Someone suggested "try licking your fingers", which I did, then hesitated before touching the terminal again, and then when I did ... BANG came from behind me and I nearly lost control of my bowels.
Mind you, some years later when I was an apprentice, we had a signal generator and a variac - so I planned to drive X with the variac (to get a low enough voltage) and Y with the signal generator. When I hooked up something (I forget the precise orer now), there was a bit of a pop and the magic smoke came out of the signal generator. You know what they say about "assume" ? Well I'd assumed the variac would put out a low voltage when turned down - which it did ... by varying the neutral rather than live. So instead of something like 10V out, I had 220-230V out. Luckily, when we opened it up, it was just some caps between output and chassis as the sig gen was floating internally.
"Well I'd assumed the variac would put out a low voltage when turned down - which it did ... by varying the neutral rather than live. So instead of something like 10V out, I had 220-230V out."
Variacs are normally autotransformers, so there is no galvanic separation between input and output - unlike with from normal transformers. Not everyone knows that, and they may not be labelled to indicate that :( - as you discovered.
See https://en.wikipedia.org/wiki/Autotransformer for a pretty picture which is clearer than my explanation above.
Indeed, but (I thought) it's a reasonable assumption that it would be wired with neutral as the common, and vary the output between 0=neutral and 100%=live. Not wire it with live as common and 0%=both neutral and live of output at input live. But you know what they say about learning by experience - I never assumed that again !
And how many here have had that jumper ping across a system after a long day? Damn, it's right under the system board. How the bloody hell did it get there? It _shouldn't_ short, but ya can't leave it.
(No interesting story here, I just wanted to use the subject title :D )
There will almost certainly be a seatbelt tensioner, which is an explosive charge that pulls the seatbelt receiver down to tighten it in an accident.
There may also be airbag wiring - a lot of cars have side airbags in the seatbacks, but I haven't heard of any airbags in the seat bases.
When user generated content started to become a thing there were quite a few videos on there of scrapyard employees launching themselves several feet into the air by placing an undeployed steering wheel airbag on the floor facing upwards & sitting on it (on a cushion or some similar load-spreader) whilst their mate detonated it from a safe distance with a 12v battery. What larks. A few of those clips looked to me to be a shoe-in for a spinal compression injury.
(Reminded now that, when airbags became standard fit for Saabs in the UK (1994?) there was a spate of "kids" twocking our customer's cars to drive them into things just to experience airbag deployment. That was always fatal for the cars as Saab, in a bid to prevent damaged cars from being repaired, wired the cars so as to blow every ecu if the airbags deployed to put them beyond economic repair.)
Upthread someone was querying the safety of rooting around under car seats with regard to pre-tensioning seat belts. I've only ever met two basic types, the ones in early Volvo's were triggered by a kind of pendulum in the seat belt reel housing striking a percussion cap, & the early Saab ones were triggered electronically from the same system that fired the main airbags. I never encountered anything under a seat that could cause unintentional deployment without using extreme stupidity. The Volvo ones did need to be made safe before removing or tipping the seat, by means of inserting a small plastic clip that was provided in each car, not a dealership special tool. If you have one it's under a clip-on plastic trim on the side of the seat.
NB! My knowledge is 25 years out of date, do your own research before using extreme stupidity!
This post has been deleted by its author
Many moons ago I worked in hardware maintenance. We had contracts for a county council (no names, no pack drill), and they had a problem with a monitor attached to an old Amstrad PC (the first ones they did). These particular PCs had the PSU for the whole thing buried in the monitor rather than a separate ones for display, CPU etc. One power cable means less mess, right?. Amstrad had obviously learned a lot from their CPC range of home computers.
I turned the monitor on, saw that nothing happened, and went for it. I did the usual of re-solder the joints on the tube neck PCB, checked for dry joints elsewhere, checked a few capacitors, and made sure that the distinctive smell of magic smoke was not present. With the case of the monitor still sat on the floor, I reached to the back of the monitor and pushed the power button.
After a fleeting, well known tingle, all the lights went out in the room I was in. And the un-occupied room next door. The wall sockets weren't working either. It turns out that the tingle was due to my little finger resting across the two solder points of the main fuse in the monitor and throwing the RCD. It turns out that little fingers are amazingly good conductors of 240v AC electricity.
I found my site contact, made my excuses, said I needed to take the monitor to the workshop for repair, and left quickly.
As a follow-up to little fingers being good conductors, I once discharged a different CRT monitor through me by having said small phalange touching the screwdriver I was using to short the tube to earth before dismantling it. That was in the workshop though so no real damage done.
> little fingers are amazingly good conductors of 240v AC electricity.
And 350V DC. 50 years ago I worked on audio. Tube audio. Several times I was caught between live parts and chassis return (I eventually wised-up). The little finger in tape recorder is numb but getting better. The other little finger exposed to 600V will never get better.
That was before GFI/RCD. The first GFI that I bought tripped-out VERY easy. I did not feel the shock when the lights went out, but it musta been me and my rubber sneakers on a concrete floor. Since then I've been militant about GFI near water, dirt, or concrete.
I started in a new job, and to say the server room needed a bit of TLC was an understatement.
I thought a good thing to get started on was to see what was plugged into what UPS and how much current were they drawing.
Most had the nice nice networked management, but one just had the serial port, labelled as a serial port, with the instructions giving the baud flow control etc, you know serial port stuff.
So I plugged in a serial cable, read out the details and disconnected it.
What I didn't know that unless you use the specific APC serial cable, the act of plugging in a serial cable tells the UPS to shut down the outputs, cue a big chunk of servers / switches going off line (yes some had both power plugged into the same UPS I *DID* say it needed some TLC)
Once I found this out I quickly restarted and confessed, fearing the the worst, bringing down servers a few days into my new job.
The outcome? I was taken for a beer after work, the general consensus was that it was F_ing stupid design and there is no way that plugging a standard serial cable into what appears to be and has every indication of being a standard serial connection should do anything except give a serial connection.
That was when I knew I was working with really great guys.
I've learned to never discard any cable, plug, gender changer or adapter that has a DB-9 or DB-25 in at least one end. Some 20+ years ago getting onto the console port of a stray Cisco CSS 11500 load balancer (previously known as Arrowpoint; now known as Obsolete) in our data center to zeroize and dismantle it took me five separate plugs and cables (since our sometimes too diligent DC manager had already kindly removed all cables from the box, including that one super secret pinout console cable we kept for that one remaining unit in the network segment everyone hated), but I got there in the end. The Adapter Cluster(tm) extended at least 10 cm out from the faceplate and required careful balancing on top of my laptop screen not to come apart.
Icon: Mine's the one with the light blue DB-9 to RJ45 cable in the pocket.
I did the same thing! We had APC and Eaton in the same Equipment room, I used the serial cable that was left by a previous tech on the APC, and I brought down two racks, the silence of those fans spinning down is deafening! You got that right APC and the cable is a tale for more beers!
Everyone who's read the very fine manuals they don't provide these days knows that it's a non standard pinout - and one of the lines a standard serial cable will drive (to the wrong state) is the "power off NOW" signal. Alongside the data in and out lines, there are outputs to signal "on battery" and "low battery" and an input for "shutdown" - these are the basic signalling and can be driven from the control lines fo a serial port with some level changing circuitry (which is built into the APC cables).
You will only forget this once - even if that once is after many years of working with them and knowing about the non standard connections and special cables. Guess how I figured that out.
I was always fairly careful of rings and wrist watches (especially with metal bands) for this particular reason but had never encountered anyone who had suffered an unfortunate outcome from their jewelery. Even working in the vicinity of cryogenic magnets I always wary of any ferrous material and wondered about relatively non-magnetic stainless steel watch straps and watch cases.
Screwdriver bits falling out of the driver into the electronics caused grief on more than one occasion. Epoxying a proper rare earth magnet into the driver fixed that but then I needed a pair of pliers to change bits.
Tungsten carbide rings were a fad a couple of years ago (may still be) and at the time given the relatively low electrical conductivity of WC (~0.2 μΩ·m) I wondered whether they would be a better bet. At the time they were popular with tradies. I use to joke if they fell into a pool of molten metal their ring would survive. (Aqua regia or HF - possibly not.) At the time the WC rings were all pitch black perhaps with some gold inlay; too close to Vetinari's stygium signet ring. ;)
Those are their own special flavor of idiocy... gold/platinum/silver/etc are fairly soft and can be cut off your finger by EMTs/hospital if needed. Guess how well a ring cutter works on tungsten carbide?
Also a good way to crack your windshield.
P.S: Properly annealed austenitic stainless is non-magnetic. Cold-worked portions of a part often have some magnetism to them, you can sometimes find this around the edges of stainless steel canteens that weren't annealed after they were formed.
I was strongly-impressed by the hazard posed by various clothing items and jewelry when as a young child I met a friend of my father's.
This friend worked in a rare-metals refinery. One day an accident flung molten metal about the area. Some of it ran down inside this fellow's glove, and capillary action held it between his wedding ring and his finger.
He lost the finger.
Edna Mode in The Incredibles elaborates:
https://m.youtube.com/watch?v=1z_GF0KAAkg&pp=ygUYdGhlIGluY3JlZGlibGVzIG5vIGNhcGVz
A guy I know had the city-slicker habit of tucking his jeans into his cowboy boots. He managed to spill about three quarters of a cup (~240ml) of liquid nitrogen right into the top of his left boot. Being the typical macho city-slicker cowboy boot wearer, he neglected to tell us of his mistake for over half an hour. The eventual skin grafts ran from the inside of his shin, wrapping around the top of his foot and down to the middle third of his sole. The doctor commented that it was the first time he had dealt with second and third degree frostbite of the foot that didn't involve the toes ...
Ouch. IIRC from my brief time spent working with liquid nitrogen many moons ago, it's fine to get on your skin so long as it isn't allowed to pool there - i.e. a thin layer that can immediately boil off before it has a chance to freeze anything it's come into contact with is OK, a more significant quantity that remains trapped in contact with your skin in its liquid form, not so good. It seemed counterintuitive at first to be told to not wear safety gloves when handling it, and then they explained why...
A friend told me of a friend of his who (among other things) made regular deliveries of liquid oxygen to the local shipyard where they use a LOT of oxygen - mostly for welding. Such was the quantity, it was delivered by tanker and pumped into a big tank. A very large rack of pipes acted as the heat exchanger to provide the heat to turn it into a gas for distribution around the site - by the end of a working day, these pipes disappeared into a house sized block of ice, and overnight it would melt away.
Apparently, the first time this guy had a spillage onto his glove, he went off the A&E and they insisted on letting his finger thaw out before they'd do anything (i.e. amputate it) - and apparently it was exceedingly painful during that wait. The next time, he grabbed a hammer and just snapped the finger off before going to A&E.
I seem to be posting rather often under this TFA, sorry.
An ageing friend's now deceased best mate was an armourer on Britain's V Bombers & had several entertaining stories of small amounts of the really antisocial propellants they used getting onto boots & spontaneously combusting later in the mess, to the amusement of all concerned.
He had a good one about getting something nasty on his hands & finding out when he went for a pee...
"He had a good one about getting something nasty on his hands & finding out when he went for a pee..."
Which is why safety instructions at some plants used to tell you to wash your hands _before_ you went to the loo.
See also: Strap On (fnarr fnarr) and Strap Off, referring to the anti-static wristbands which must be worn at all times except when working on live equipment.
Repairing machines, had several shocks from touching iMac power supplies which were helpfully installed board side out with no insulation, so you couldn't easily see where the mains connection was.
I was 10 or 11, and messing about with old mains radios, usually getting them working too!
I wanted to swap one for another that was on a long extended cable that snaked round the skirting board to a wall socket - one of the old big three pin round types. with a festoon of adapters and several identical 2 pin plugs. I dutifully unplugged the cable, then not wanting bother to unwrap all the insulating tape on the cable joint chopped through it with wire cutters. There was a near deafening bang and the cutters were now welded shut and had two neat holes through the blade edges.
Dad came racing in from the lounge. I think he was more shocked than I was. Remember I mentioned the identical plugs... well they also had identical cloth covered cables, and I'd unplugged the wrong one. Oh, and that socket had been on a 30A rewirable fuse down in the cellar.
There was an electrical engineer in the year above me at Uni. He was super smart but a mechanical klutz. He was part of a joint electrical-mechanical engineering project developing an electric vehicle. During one session, he managed to drop a spanner directly across the battery terminals, shorting everything and melting the spanner! He really put the 'spark' into 'sparky'! Once in industry, the rumour was that he was chaperoned on-site by an electrician, to make sure he didn't electrocute himself or bring down the whole plant.
I know someone who used to work on railway power systems.
One of their guys was working on the top floor of a substation, where everything was isolated and locked off. He dropped a large torque wrench, which managed to fall between some gaps in the lattice flooring and land across a set of bus bars for the lower, live section.
The guy did not survive the resulting arc flash.
Take care out there people.
I used to volunteer at a Trolley museum, which used 600V DC in the overheard wire to provide power. How many amps you ask? Enough to move a 20 Ton trolley filled with people... anyway, we were working on a big old railway crane and tracing cables through the slip ring at the center of the crane turntable. All the power came via the back of the crane, which has a long line with stick and hook on the end. You would shutdown the overhead line above the crane, but power it by hooking into a live segment nearby on the overhead.
Anyway, we were working on the crane in the shop and it was amazed to see 50v of leakage we would see when the switches were off on the power controller. But 50v when you need 600v to spin a motor is just nothing to think about.
Fun times playing there...
A few years ago we had an argument with someone from the canal world who was adamant that 12v electricity was entirely safe and couldn't possibly cause you any harm, obviously based on the fact that it won't normally directly stop you heart. Apart from making sure we stayed well out of the way if he was working on his boat electrics I did explain that not long previously someone had managed to short their battery with careless use of a spanner, jumped back and very nearly landed in the water - with plenty of metal around to hit a head on (and some of it quite sharp) that could have been a fatality; he still required treatment for burns. There were plenty of tales of watches and the like causing problems as a lot of boat electric systems had pretty dodgy wiring*.
*Like instead of using proper ring terminals a previous owner of one of my boats had soldered the wires onto small squares of copper sheet with holes drilled in them as we discovered shortly after buying the boat and fixing the alternator. I won't say the replacement control panel was a thing of beauty but at least it was reasonably safe!
One of the engineers at a place I used to work at was testing a new power board for an 80v, 650A motor controller.
He was having trouble getting some thermocouples to stay where he wanted them, so he found a large, heavy object to weigh them down.
He put it on top of the board, where upon it started jumping up and down and throwing blobs of glowing metal in all directions.
Lessons learnt:
1) Brass is conductive;
2) Turn the power off first (the power supply was rated at 1000A continuous, with a much might peak capability from the huge capacitor bank).
I'm reminded of an incident during a machines lab on my ill-fated & brief college career, (an HND course at NSP, North Staffs Poly as was, or Not a Serious Polytechnic as it was universally known. Hello to all fellow alumni / victims. It was ill-fated as, at the beginning of the summer term in year one, the course tutor walked into our first lecture & announced "sorry, there's been a mistake & we've been teaching you the wrong stuff all year, we're going to have to do the whole year this term." As I hadn't understood much of what they'd been trying to teach me up to that point it was the last straw & it was soon suggested that both mine & the poly's prospects would be enhanced if I continued my "academic career anywhere else but here." We had been told that we 29 lads & one girl were the guinea-pigs for the first ever BTec course in the country, hopefully they got better subsequently.)
Every engineering course has at least one class clown, & we were no exception. He always turned up loud & late, & usually inappropriately dressed, so when he burst into the machines session wearing shorts & a tiki shirt no-one was surprised. When he sat down extravagantly on a tall stool & swung round such that his knee shorted two terminals on a three-phase variac, he was thrown back against the door quite violently. He just sat there in a heap making odd whimpering noises, & someone remarked loudly & sympathetically that it was the quietest he'd ever been. Might not have been me...
I've never managed to do that, I've seen the scars on my friend's wrist from accidentally shorting a car battery with a gold bracelet
So I don't wear anything around my neck, wrists or on my fingers which could accidentally contact a high current bus bar in the back of a DC powered rack or a server (I almost never get to play with AC power)
Back in my days in that business (as an engineer) I had observed the linemen removing watches and rings before donning protective insulated gloves. Although the gloves provided adequate insulation to do "hands on" work up to 2400V when new, the friction of any jewlery risked wearing a thin spot into the inner rubber liner.
It was also humorous to watch them at the beginning of each shift. Taking the rubber inner gloves and blowing them up like balloons. Looking for pinhole leaks.
An appropriate and chilling comment from a lineman to BigClive's video about how screwing around with microwave oven transformers is likely to kill you:
"My high voltage gloves got partially pierced by a metal splinter on a ground transformer and allowed a path to ground on a 13.8KV line.
It was only 20-30 seconds of time slowing down to where a second feels like a minute. You feel fear and a great sense of dread as your heart goes into afib because of confused messages from the vagal nerve trying to override your SA node. About three second in all your muscles start to cramp and burn(literally) along the path to ground. You cant make yourself let go and you cant think of why, but you definitely know you are being electrocuted. About ten second in you start to smell burning pork and your vision starts to close in around the edges because your heart cant pump blood. You feel as dizzy and high as you have ever felt as the color starts to leave your vision. About fifteen seconds in you start to miss your wife and kids because as your vision fades slowly out you understand you are dying. As your world fades from view, and a blackness so deep it envelops all of your being smothers you, you are left with a great sense of sorrow and pain that stretches to eternity, or in my case, when I woke up in the ICU a month later missing the small parts of me that made up the ground path. There was only sorrow and fear and pain the entire time from my grounding to my waking. It felt like I was gone for twenty years, like when you visit your childhood home after your parents are gone. Without perception of time, time has no meaning. The lack of perception is eternity. "
As an undergraduate Engineering Physics student in the 80s, I worked in the Physics department's electronics lab repairing stuff. Where I was gently but very effectively trained, by a supervisor I greatly liked and respected, that rings or wristwatches on the job were a danger to my life, and prolonging said vital asset required pocketing these items when working on equipment.
It wasn't a complicated lesson, nor a difficult message to take on board.
I read somewhere of someone dropping a spanner on the terminals of a car battery. When everything had cooled down, he was able to pick up the battery by the spanner.
I had to bale out of car once when it caught fire. The molten carburettor dropped onto the starter motor and shorted out the solenoid. As the car was still in gear, I had to watch it, now a mass of flames, making its last (20 yardsl journey. Luckily on a country road with no parked cars.
That sounds like a typical day's work for a Holley carb.
The Americans seem to love them but in my quite extensive experience of dyno & rolling-road testing fast road & race engines they were good only for two things compared to the Weber or Dellorto alternatives, turning a lot of fuel into a relatively small amount of power, & setting fire to the engine bay.
In my younger days (almost 50 years ago now) I was employed at a prestigious university in sillycon valley I witnessed a real BZZERT story. Back then graphical interfaces were pen plotters, specifically a Calcomp 565. It made nice graphs on roll paper by moving a carriage and a drum. The roll paper was kept tensioned by using a small 120VAC motor that was allowed to stall then the action was motionless. All fine and good, but these motors (capacitor run as I remember) did wear out. My boss had taken the cover off and was in the process of soldering the wires back, when I mentioned that he should turn the power off before doing that. He mentioned that he had soldered live wires before and it would be no problem. Then he touched the line soldering post with the GROUNDED soldering iron which did three things: 1) Evaporated the top of the soldering post, 2) blew the fuse. and 3) Destroyed the soldering iron tip. I then walked out to the storeroom and mentioned "I'll get a new fuse and tip" on the way out. His comment: When did they ground the tips of soldering irons? When they started having sensitive MOS integrated circuits (and insulated gate mosfets).
The body parts adventure: Back in those days, we used hard copy Selectric typewriter based terminals. One of my co-workers was of the long hair female persuasion. She leaned over the terminal and her hair gor wrapped around the shaft that was internal to the mechanism/ Thankfully she was able to get to the power switch before her hair was completely wound up in the terminal. When the IBM field guy came out he said some like "cut the hair". Which didn't set well. Being engineers her fellow compatriots didn't like that "solution" and seing tht there were two identical terminals next to each other, used one as a model on how to tear down the offending example. In the end, the hair was released, and two terminals were in pieces. All ended up good since they were leased fixtures anyway.
As mentioned in a TV show "Let's be careful out there".
About two billion years ago (in Internet time) ... and not to far away from Herby's story, above ... in the age of TIPs and IMPs, I had long hair. Very long hair. Long enough to sit on. I got it caught in an IBM 1403. Ripped a small chunk of scalp out. Had no time to think about it, just a quick tug and it was done. Much bleeding and swearing, but surprisingly little pain. Used an entire box of kleenex on the way to the ER, across campus (Stanford). I still have the scar, visible if you part my hair in the right place. The ER nurse who stitched me up commented that I should probably donate my hair to the cancer kids if I was going to insist on working on dangerous equipment. It was a throw-away comment on her part, but the next weekend I did just that. Because of this, I'm known as Baldy in certain quarters to this day. I've also grown it out and donated it three more times. Recommended, but sans the traumatic bit. I know how lucky I was ... Could have been much, much worse.
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