Mistakes that taught you the most?

Just burnt up an output card because I forgot to include a relay between the output and a contactor, so the inrush shorted the output to always being on.

What are the mistakes in the field that have taught you the most?

VERY early in my career I burnt the logic supply overvoltage protection MOVs out of 10 Allen-Bradley 1391 servo drives all in one fell swoop.

The logic supply was derived from a 230/460VAC primary transformer and produced a 36VAC centertap secondary. I had powered up about 10 of these drives individually before and had never had a logic supply issue so I rather cavalierly tossed the juice to the bank of 10 without checking the logic supply voltage first. Turns out that someone had connected the transformer primary in the 230VAC configuration and we were on a 460V system. I can still remember the fire coming out of the tops of all the drives as they received 72V at the logic supply terminals.

Check everything, every time, even if it has been OK the 1000 times before that. One I'll never forget.

Keith

Just a couple for now...

- Read the VFD manual regarding how long to wait after power down to re-power. Blew up the caps on a 40HP drive (It was very loud) because we turned it off and on repeatedly in a short time period.

- Unplug a right angle drill before changing the bit (good plan for any drill really). My hand accidentally hit the on switch which was a big plate, the chuck key swung around pushing my hand into the on switch keeping it on and basically locking the drill to my hand. Finally used the other hand to pull the plug and got free. Got about 10 stitches for that one.

My wife went into labor with our 3rd when I was at work. On the way out of the door, a tech grabbed me and asked me to look at a load cell that wasn't working. I knew I had time, she was with her mom on the way to the hospital, but she was many hours away from delivery. So I said, UGH FINE. The load cell was on a press that had a hot stamp on it to stamp an foil emblem onto a part. I asked if the stamp was hot and he said no, it has been off all day. So
I pushed up on the stamp to watch the load cell readout. Should I have checked? Yes. Was the stamp hot? ALSO YES. Burned a Home Alone style emblem into my palm. Made my way through the ER and still made the delivery. NEVER TRUST ANYONE. AND the damn load cell worked just fine.

Early on in my career, was working near a team building a conveyor moving big *** metal pallets. My project was in the same area that was safety taped off from the rest of the shop. I never really got a safety rundown of anything, and my team didn't talk to the other one.

As is tradition, there was stuff randomly laying everywhere, and it was a bit of a maze to get to our work zone inside the taped off area. One day we took a slightly different path from usual. The conveyor hadn't moved in days, so we went through a gap. One guy lunged at the estop. I thought he was psyching us out, trying to trick us into being scared. NOPE!

Turns out they were TRYING to get the conveyor to move, and just had no idea why it wasn't....

Two big lessons from this:

1) Force the safety conversation, keep your head on a swivel, and communicate with those around you. "What are possible hazards in the area?", etc. Don't expect others to care as much about their lives as you care about yours.

2) Don't walk through a gap in a conveyor

Hit a momentary E-Stop on what should have been a three-wire control circuit. The starter was wired wrong by the factory (at no extra charge), and when released I got full voltage to a motor spinning at nearly full 3550 rpm speed. Lessons learned:

1) Check the wiring - factories screw up a lot

2) Always use latching twist-to-release E-Stops

3) A 4" coupling shearing sounds a lot like a bomb going off

travispedley said:

My wife went into labor with our 3rd when I was at work. On the way out of the door, a tech grabbed me and asked me to look at a load cell that wasn't working. I knew I had time, she was with her mom on the way to the hospital, but she was many hours away from delivery. So I said, UGH FINE. The load cell was on a press that had a hot stamp on it to stamp an foil emblem onto a part. I asked if the stamp was hot and he said no, it has been off all day. So
I pushed up on the stamp to watch the load cell readout. Should I have checked? Yes. Was the stamp hot? ALSO YES. Burned a Home Alone style emblem into my palm. Made my way through the ER and still made the delivery. NEVER TRUST ANYONE. AND the damn load cell worked just fine.

Click to expand...

Yeap. "Trust but verify." Is an important lesson for everyone.

This story also reminds me of a couple of rules. Don't work when distracted and slow down and take your time to do things right. Most of my expensive lessons have come from being in a hurry and/or being distracted (either with other work-related tasks or something external).

Although mine isnt as costly as some of the above.

I had to pull a program off a PVP that was connected RS232 to a ML1500. I restored the program in FTVS, modified what needed to be modified and loaded the program back into the PV. All of a sudden, diagnostic error messages pop up. so i kinda freak out and say 'ok just reload the program that DID work just fine thats still on the PV', so i do that, and im getting the same diagnostic errors. so at this point im sh*tting bricks because 'well i didnt touch the old .mer that worked'. low and behold when i loaded the 'new' .mer i had picked the wrong COM port in FTVS for the PVP to talk to the ML1500, and i 'replaced communications setup' when i loaded the new .mer. I chose COM 3 because that was the COM that the ML1500 showed UP on in RSLinx with my USB-Serial adapter. well after a call to ABtech line because i was so worried that i had just bricked a machine and didnt want to waste my time possibly screwing it up more, the very nice man on the phone went over the COM port stuff with me a few minutes into the phone call, i made a new .mer, loaded it up and was so happy i wouldntve cared if those bricks i thought i was gonna sh*t earlier actually did make it into my undies.

moral of the story, taught me to always double check even when i think ive got it right.

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.

Intrinsically safe load cells on a winder application. The main control board failed and needed replacing. 120VAC power had a small whisker sticking out to the next terminal. I powered up. BOOM the cell controller let the magic smoke out. I was just starting out and every dollar really counted. $5,000.00 was the price for the loadcell and new controller, expediting, machine shop to make the new mounts for the long obsolete load cell. That almost cost me my business.

100hp VFD had been setting on the shelf for several years. We powered up and the drive exploded. No one including myself read where the drive needed to be powered up and set for xx hrs before trying to use it.

Went to a start-up 80 miles away through Los Angeles rush hour traffic and when I got there realized I forgot to bring the floppies (late 1990's) for the HMI (Advisor PC). That was a long drive of shame that day.



So I created a startup checklist after that.

Dont do stuff you dont know

Was on a work trip commissioning plants. A colleague ask me to download a very small change to a existing plant nearby. Unfortunately it was a Siemens PLC. I told him i'm not experienced with Siemens. Not a problem, just make a backup and download the new program. So, i made a backup of the current "program" and downloaded the new one completely ("program" and "hardware configuration" :nodi. Unfortunately his version had a very old "hardware configuration" which didnt include the BMS system
So, next call the BMS supplier. But we couldnt reach them for hours. So after several hours of trying different "hardware configurations" i went home without beeing able to connect to the BMS. The next week my colleague went to fix the issue.

I was starting as a Field Engineer commissioning a very large winch which has a drilling machine attached to it.

The project got seriously delayed and my back-to-back decided to skip a couple of steps in the test procedure to move on towards putting the line in said winch. When I arrive to take over from him he said that these functions to be tested are unchanged since at least 5 years ago and have been thoroughly tested so not to worry and test it later on.

Well, the day arrives, I read the test procedure and didn't understand why we would do it that way. Stopped, mulled over it during coffee break, came back looked at the code for another thirty minutes and still could not understand why test the system that way... but I assumed that people that wrote the damn thing knew what they were doing and since this is a standard machine installed all over the place, it will be fine.

I was lucky... about 5 million USD damage but no one got hurt. Turns out, the function interface had changed and the testing procedure was never updated.

Always trust your gut feeling and stop if something looks out of place.

Also, never trust people when it comes to isolations... either when you're the one in the line of fire or when you're the one holding the trigger.

Doing some online edits to a brick stacking machine I saved the program before I began.
I saved all the values in the data registers too.

After much messing about under the managements orders (They were trying to speed up the operations to get more bricks out per shift) They asked me to put it back as it was originally.

I downloaded the saved project to be sure we were back as we were.
Except.... I also downloaded the data values.
Some of these values were for keeping tabs on where the cycle was.

The giant hydraulic mast that lifted a row of bricks to stack them now thought it was putting the second row in, where in fact it was on row 10.

It crashed into the stacked bricks demolishing them and bending the mast.
2 days downtime to repair the mast... oops

I could probably come up with a few, but this one is from the beginning of my career and partially because of that took all mistakes more heavily than necessary. Luckily the only cost in this case was the money my employer had to put on my wages that couldn't be billed from the client.

So, back then my work laptop had some faulty hardware, but as I was just a trainee at that time, no one bothered to spend the extra money to buy me a new laptop, or send this one for fixing. Weird enough, it would work normally for days at the office, but when I left the office it would start giving me BSOD couple of times a day.

I was commissioning one of my very first solo projects, which included small PLC program and application done with VB6, which would save data from the PLC to CSV file. I had initial version on the company's server, but the commissioning was at customer's site. For few days I was making tweaks and adjustments to the program and fixing problems I found and making it more stable. Then, when I had done all I could come up with and was satisfied with the outcome, I compiled the code and made the .exe-file out of it. As soon as it had finished, my computer crashed. 'No biggie', I thought and tried to run the file after reboot and it worked just fine. I copied the application to the client's computer, tested that it works, packed my stuff and left the site, mentally patting myself on the back for a job well done.

The next day I arrived to the office and was supposed to upload the project files to the server, but decided to admire the VB6 code just once more. To my horror I noticed that no matter what I tried, I was not able to open the source code! I spent some time trying to figure what to do, but neither me nor my coworker was able to recover it, so in the end I had to spend a day or two rewriting it. What I learned from this? Since then, I make sure to take sufficient amounts of back ups and keep at least one in external storage.

Hietsu said:

So, back then my work laptop had some faulty hardware, but as I was just a trainee at that time, no one bothered to spend the extra money to buy me a new laptop, or send this one for fixing.

Click to expand...

I've seen the same on a billion dollar company with the guy I was mentoring... At the end of a very frustrating trip because of his laptop I asked him to back everything he had on it at the end of the day.
The next morning I "accidentally" spilled an entire coffee mug (with plenty of sugar just to be on the safe side) on it. He wasn't happy... until he realised he was going to get a proper one the next day.