Engineers: Have You Ever Burned Off Your Fingertip?

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Exploding meter
ttemple   7/18/2012 10:05:32 AM
Many years back, I was using an inexpensive digital meter to check for the presence of 480 volts.  It turned out that I had the meter leads in the current measurement positions.  The meter was giving me funny results, and I was getting rather annoyed.  I kept trying to get a reading, and suddenly the meter exploded in my hand.  The front half of the case split from the rear half, and was hanging by some wires.  I had a charred spot on my shirt, and the lead sockets were basically vaporized.

There was photographic evidence taken, and I wish I could find it.  Since I wasn't actually injured, it was a pretty funny picture.  I was holding the exploded meter, with the leads hanging down, with the charred spot square in the middle of my shirt, and a big smile on my face.

Jennifer Campbell
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Re: Exploding meter
Jennifer Campbell   7/18/2012 10:18:01 AM
Thanks for sharing your story, ttemple. Given your level of annoyance/frustration over the uncooperative meter,  it must have been a little satisying when it vaporized itself! Glad you weren't hurt.


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Filament input resistor fire
gsmith120   7/18/2012 12:15:07 PM
Fresh out of college I was given a filament circuit to design, prototype and test.  One day in the lab my mentor was helping me with something in the lab and for some reason wanted me to apply more input voltage than required.  I remember telling him the input resistor isn't rated for this kind of power.  He said no problem keep going... I kept going... then I said that resistor is getting hot...he said no problem keep going...as the resistor glowed..smoked and then fire... The fire scared him and for some reason seemed to surprise him.  I was thinking I kept telling you that resistor wasn't going to make it.   But to his defense people would be a little jumpy in our lab since we designed high voltage circuits. 

Not really a funny story on paper, it was much funnier to me back then.

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Burned fingers? Sure!
warren@fourward.com   7/18/2012 12:29:51 PM
I was a marine service engineer while completing my college studies, and I got a call to work on the Mal de Testa, the ship the original Goodbye Mr. Roberts was filmed on.  They had a radar problem.  I reached under the console to feel where the 24VDC power wires were going and my wedding ring shorted out the reverse-biased protection diode was mounted and blew a chunk out of my wedding ring and burned my finger nearly down to the bone.  Yes it hurt.

Now I am careful.  Very careful.  I get to show off my scar from time to time, so it wasn't a total disaster...

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Prairie Dogging
tekochip   7/18/2012 12:46:57 PM
Too many to list, but here's the biggest.
I was working on an electric oven control.  This one was for Europe and ran off of 50Hz.  We didn't have 50Hz supplied to the building, but we did have a rotary converter (a motor with a generator attached) by the docks to provide 50A/230V 50Hz in the labs.  My technician had made a slight wiring error on the control I was working on and I had a dead short across the mains.  I plugged the control into the wall socket and instantly the walls of the building began to vibrate at 50Hz because the wiring inside was vibrating from the dead short.  With a 50A breaker and hefty wiring to handle oven currents, nothing was going to open the circuit.  I tried to pull the plug from the wall, but it only moved a couple of millimeters before becoming welded inside the socket.  Everybody in the building was now "prairie dogging" to see what the source of all the noise was.  I waited a second for the plug to melt a little and then pulled it out another couple of millimeters until it welded again.  I had to do this a couple more times before the plug was clear of the socket showering me with a little splash of molten copper.
Since then I always test the controls with a small load and a tiny fuse before stepping up to the real world.

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Exploding Switchboard
akili   7/18/2012 1:16:37 PM
I had a problem with the 100A three-phase feed to the earth station servo system. I traced the problem right back to the main station distribution switchboard, well beyond my pay-grade at the time.  With the chief electrician in charge reading out the maker's instructions I followed his every word to remove and inspect the contact carriage. According to the book by means of a "special feature" it was supposedly safe to do this operation off-load but with the rest of the switchboard on-line.  We had never used that brand of switchboard before and we took the instructions at face value.  "Remove locking screw A" - OK.  "Raise latch lever B" - OK.  "Grasp carrier firmly, lift and pull out" - BANG!  When our eyes and ears returned to normal I was unhurt and had not received an electric shock but my hand was covered with that lovely bronze sheen from vaporised copper.  The switchboard was wrecked and we never used that brand again.  Surprisingly they are still in business.  No names, no pack drill...

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Where to begin?
NadineJ   7/18/2012 2:02:37 PM
The fact that I have all ten fingers is remarkable.  I'm always amazed when my fingerprints reappear.

I've defintely burned and sliced off my finger tips several times.  I think it all started when, at the age of 12, I put a sewing machine needle through my right index finger.  All of the adults panicked but the nail eventually grew out.

Charles Murray
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Re: Exploding meter
Charles Murray   7/18/2012 5:25:49 PM
ttemple: "...holding the meter, with the leads hanging down, with the charred spot square in the middle of my shirt..." Sounds like a classic Wile E. Coyote picture. The only part missing was the burn marks on your face.

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Lessen in heat transfer
Tim   7/18/2012 9:58:36 PM
As an engineer, i have had my fair share of experiences with errant voltages and shocks from contact with incorrect wires, but my only real injury was due to inexperience when I started my first job out of high school.  At the company, rookie engineer projects were usually completed through the build process with the engineer working with the necessary support personnel to physically complete the project.  My design called for a bracket of steel bent into a certain angle and then drilled and tapped.  The technician that I was working with explained that they usually complete brackets like this by heating the bend point cherry red and attaching a clamp and bending the bracket into place.  I said no problem and the tech left for break.  I attached the clamp, began heating the steel and when it was cherry red, i grabbed the clamp and immediately learned that heat transfers through steel quickly.  I missed the step that stated to attach the clamp after the metal was hot.  I still have the burn scars to remind me of the heat transfer capabilities of steel.

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Re: Lessen in heat transfer
MaruaderMan   7/19/2012 9:38:48 AM
Sorry to be a nit-picker, but you also need a "lessen" in spelling.

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