I've finally read through this thread entirely on my phone, in between putting out fires. Feels like I started 3 days ago. Good to know I'm not the only one who has idiot moments. Considering how long it took me to read through it, I've had a lot of time to reflect back on all my idiot moments and I must admit there are an embarrassing lot of them. For that reason, I'll just make categories and list the worst in each category.
Most expensive mistake:
Turned off an extruder in the middle of a first-of-it's-kind experimental production run on a $500K oilfield downhole cable. This was when I worked Machine Maintenance in a wire & cable plant. I was on night shift, and the whole team of engineers was there babysitting their project which had been in the works for months. They had run several small lengths and dialed in their process and this was the first actual production run. It was (armoring left-hand lay)>(preheat)>(extrusion)>(armoring right-hand lay)>(reheat)>(extrusion again). I opened the disconnect for the portable extruder right in the middle. They were right in the middle, and neither end was long enough to sell, so they lost the whole thing. In my defense, there was a 480V 20A disconnect with a single plug beneath it on a pole. There was no sticker or other indication that there was another outlet connected to it on another pole, utilizing the same conduit that fed the disconnect. I can still see the lead engineer pacing back and forth, clutching his hair, looking toward the ceiling and moaning, periodically pointing his finger at me and trembling, saying nothing but "YOU....YOU....YOU...!" I didn't lose my job. The only outcome was a lot of meetings and short-lived policy that any desire to open any disconnect in the plant (except in emergency) had to be cleared by engineering first.
Bloodiest flub:
I tripped and fell into a cabinet disconnect; the type where the disconnect is mounted to the back of the panel and has a pointed spear sticking out of it at eye level which guides into the back of the handle when you close the door. I was leaning forward to retrieve prints from the bottom of the panel when I tripped, and the thing gored me in the top of the head. The impact was enough to knock me off balance: I bounced off and I waffled around for a few steps and fell down. When I got up, all I saw was blood, everywhere. It took the guys 3 of those cootie containment kits to clean it up and the trail I left on the way to the bathroom.
Closest brush with firey electrical death:
We had a tubular strander that had 9 gimbles with VFDs on each. There was a big 480V rectifier in the main cabinet, about the size of a 100HP VFD, which fed 600-700VDC through slip rings out to all the VFDs. Also going through the slip rings was Profibus, and we had a lot of comms issues because of the slip rings. We had to crawl into the machine at least once per week (sometimes once or more per day) to clean the slip rings. It had become such a routine occurrence that I became lax in my LOTO adherence. I would just tell the operator (because there's only one operator) "hey, I'm turning off the power, I'll be done in about 10 minutes, I'll let you know." So I told the operator this, went and cut power, climbed into the machine and removed the slip ring guards and went about my business. Next thing I know there some alien sounding blood curdling shriek and my head slammed against the inside of the machine. Took me a second after to realize that I was the one who made that noise. In between the time I cut power and got into the machine, the shift change had occurred with no more turnover than a high-five, and the new operator came in, saw the power was off, flipped it on, and the rest is history. I laid my sweaty arm on that HVDC slip ring and I don't know if it went through my heart or what, but i was out of breath, or out of something for a good while, like I got punched real hard in the stomach.
Second closest brush with firey electrical death:
During a long extrusion run, the hot water tank for the cooling bath stopped being hot. I found that the thermocouple wire from the tank to the main panel had an open in it, so me and another guy who was even more of a NOOB than I, were asked by the night shift production supervisor to pull a new thermocouple wire, quickly, while the machine continued to run. "sure" I thought, "it's just low voltage stuff, even the controller is just 24V." So we proceeded to pull new steel braid externally shielded wire through the panduits in the panel and out to the conduit. I had the thermo wire wrapped several times around both hands for a better, stronger pull - a strong pull that drug the uninsulated steel braided wire right across a 480V buss bar. There was an almost instant puff of smoke along the whole length of the wire, including around my hands. It didn't shock me at all, considering it was already a low-ohm path to ground, but it did burn what looked like tiny tractor tire tracks into my hands for a few weeks. Melted a bunch of panduit too.
Worst troubleshooting ever:
This happened just a couple of weeks ago and I'm actually really embarrassed and ashamed of it. I think telling you guys will be therapeutic.
I went out and installed a 25hp drive on a customer's industrial washing machine. It was supposed to be a 30 min in&out job. The drive was tested at the shop prior, was already programmed and tuned. Just bolt it to the wall and connect the wires, which I did, and when I turned it on, it was dead. I checked and it had DC bus voltage, so I knew the internal fuse was good, but no lights on. I figured it was the power board, so I brought that back to the shop and went back out with a new power board, control board, and digital operator. Replaced all 3, still nobody home. So I brought the whole drive back, and found in the shop that the precharge resistor was open. Replaced that, went back out to the field, and installed it, minus connecting the braking unit since I figured that was the only thing that could blow out the precharge resistor. Found it shorted on the input. brought it back to the shop, and another guy replaced the input components and said it was good. I took it back out and installed it, and it looked like it was working but the drive was tripping on overvoltage on decel. Braking unit still was not firing. Had to get a new braking unit, and install it. So several trips out there, and the logical conclusion is that on my first visit I connected the braking unit backwords at the drive. I'd like to think I'm not that stupid, but if my above stories haven't clued you in, I just might be that stupid. So the customer is unhappy with the week+ of downtime and all the field service visits and I'm unhappy about it too. Wish I could unlive that one.
