Mistakes that taught you the most?

My three mistakes I learned from was 1) Never grab a moving sawzaw blade while it is still in motion. 2) Never put your forehead up against a 3 faze 480V block. 3) Always know where your thumbs are when using a table saw.

The best ones for me is when others do it....

1) Dont push a contactor in manually with a screwdriver when next to it you see the wires swapping the phase and its the reverse direction (small boom)

2) Dont purge a boiler with gas then let it try and start (very large boom)

3) When the heat exchanger leaks water into the hot oil side shut the system down asap (many med booms)

4) Never believe your boss when he says your raise is coming (no boom, just fire)

5) Never believe your friend when they say just take one hit you will like it....

My mistake was to use a multimeter without audible warning for falsely inserted leads.
Meter set to voltage, leads inserted for current - boom.

2 come to mind...one from early on in my career and one from recent

1) At a nuclear power station processing plant project in North of Scotland. Wired up a brand new GEC Minigem to the drawings. Powered up.....nothing was working...eventually discovered it could take dual voltage and we had wired the 240V to the 110V terminals due to a mistake in the drawing. Long wait for a new Minigem, and also next trip to head office, said burnt Minigem came back with me in the car to give to designer. Always check the drawings and supply voltage before power-up...

2) current job. First week. Finding out what tools I had been left by previous incumbent as no handover. Got his laptop, played around offline with what was on it to see what I needed. Went to go online to check RSLinx and PLC network - fine, went browsing some of the PLCs, until about an hour later, the electrical supervisor came up to the office, saying we appear to have a network problem, the line is down as our SCADA cannot see the main Computer running the Press...
Turns out previous incumbent had left a wee timebomb, by setting the laptop to a duplicate IP address of the main Press Computer..
so, never believe you can switch something on and plug it straight into a network..

my biggest mistake and hard one to avoid for me is that i believe to people from maintenance and to operators when they are describing the problem

A couple:
I had just started with a large water utility as an industrial electrician/PLC programmer. We were using PLC-5. I hardly knew anything about them and they sent me out with a guy who knew very little more that I did to look at a sequence in a program for a pump station (critical station). We got on line and did our check and then the work order also said to install and burn an EEPROM in the processor. I guess we disregarded the warnings that the processor would shut down if we burned the EEPROM. "EEPROM Successfully Burned!" it said on the screen. When 4 fifteen hundred HP 5KV motors all stop at once, let me tell ya it gets real quiet for the 8 or 10 seconds it takes for operations to come on the radio looking for you.
Before my major change to electrical, I had been a diesel mechanic and knew quite a bit about power generation, so I had been in the NW for a while and got a job as chief engineer on a crab boat. (Just like "Deadliest Catch") I didn't work on deck just took care of all the mechanical, engines, generators, etc.

We were out running the gear and although it was a pretty good sized boat one could hear the air compressor from the galley, and we were sitting in there for a break and I kept hearing it cycle on and off repeatedly. I asked one of the crew who had been engineer before what he thought was up and he just said they're using air in the forepeak. Well I did a head count and everyone was in the galley or the wheelhouse. So I ran down to the engine room to see what was up and the starboard gearbox shaft brake had just started to smoke. Turns out an air hose had failed and there was not enough air to keep the brake released. Called up to the wheelhouse and had the captain shut it down and fixed it. He told anyone that would listen that I saved their season. Maybe not that dramatic but it would have been a costly time consuming repair.

Conclusion: When you complete PLC edits/changes to a processor, you'd better know what happens when you click "OK". And, always go with your gut feelings about something amiss. Many people either don't know, don't care or are too lazy to go look.

JeffKiper said:

Several stupid things over the years.
Working for yourself, learn that there is a time NOT to answer your phone. They will be OK for another 5 minutes. Let your kids finish the story they are telling you.

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I love this. It can be hard to balance family life with the kind of jobs we do, but it's so important. A lot of the problems we are seeing with youth (and we repeatedly see with youth throughout the decades) arise from parents that don't give their kids the time of day. The financial security is important, but it rings hollow if your kids don't feel like they are important to you, and they don't think a big paycheck makes up for that lack of a relationship.

geniusintraining said:

5) Never believe your friend when they say just take one hit you will like it....

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We have the same friends

dont touch a braking resistor

Had my electricians install a braking resistors on some large-ish 200 HP Toshiba drives.

I commissioned the drive and off we went. We noticed that there was not much braking action to be had. I was on the phone with Toshiba support about it and the phone tech says , see if the breaking resistors are warm?

I reached under the resistors that were suppose to be in a protected cage to get closer to see if i could feel the heat. My electricians forgot to put the bottom of the cage on and guess what i reached up and touched.

The actual resistor which was the DC bus of the drive.

600V DC will really wake you up.

Lesson: Dont assume your electricians did his job correctly and look before you commit your hand to something. Was my first commissioning and last time i will ever do that. Happy to still be here with only a mild bruise on my hand from the incident but sure scared the hell out of me.

my biggest mistake and hard one to avoid for me is that i believe to people from maintenance and to operators when they are describing the problem

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The question that arises from this statement is why can't you believe what they're telling you?

Steve Bailey said:

The question that arises from this statement is why can't you believe what they're telling you?

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I've learned that maintenance and operators will give you some of the more important insights when troubleshooting a problem. You just have to understand that they are great at communicating symptoms and hit or miss when communicating causes.

To operator: did it just stop, or was there any unusual noises.
Operator: there has been a grinding noise getting louder every day for about a week. Today it was really loud, then it stopped.

Ronnie Sullivan said:

To operator: did it just stop, or was there any unusual noises.
Operator: there has been a grinding noise getting louder every day for about a week. Today it was really loud, then it stopped.

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This sounds like an obvious problem with the program.

mylespetro said:

This sounds like an obvious problem with the program.

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Yep... I saw him over there with that laptop thing, im sure its something he did (he who touches it last owns it)

rscott9399 said:

Had my electricians install a braking resistors on some large-ish 200 HP Toshiba drives.

I commissioned the drive and off we went. We noticed that there was not much braking action to be had. I was on the phone with Toshiba support about it and the phone tech says , see if the breaking resistors are warm?

I reached under the resistors that were suppose to be in a protected cage to get closer to see if i could feel the heat. My electricians forgot to put the bottom of the cage on and guess what i reached up and touched.

The actual resistor which was the DC bus of the drive.

600V DC will really wake you up.

Lesson: Dont assume your electricians did his job correctly and look before you commit your hand to something. Was my first commissioning and last time i will ever do that. Happy to still be here with only a mild bruise on my hand from the incident but sure scared the hell out of me.

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I put my hand near a large braking resistor with the cage removed. It reached out and got me. You are correct, 600VDC will definitely get your attention.
Just a few days before I had been trying to install a fuse in a solar inverter and got into 400VDC, so I had a good 2-fer that week.