Worst thing to ever happen!!

dbh6

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Jan 2013
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Hello all,

We are all human, and based on that fact are pron to make mistakes, please share some of the things you unintentionally did, that say blew something, stopped a production line, etc, the purpose of this is so that others and myself can learn from others mistakes.

Mines happen recently when i was wiring up a Wago IO terminal block, with power on, so when i was unwiring and wiring a freaking loose wire touch a metal part of a terminal then created a short and poof, their goes my wago RTD module thats $461 a pop. Lesson, always and i mean always work with power off!!! unless under special conditions
 
Oooooh... let's see... I'll include things I've seen as well.


  • I have downloaded an incorrect program to a SLC 5/05-- resulted in an IP conflict that brought two lines to their knees.

  • Had an apprentice that built one of my panels. This thing was beautiful-- almost a work of art. The downside was that he didn't strip a single wire...

  • I think most of us have had the loose wire experience that you had.

  • A coworker replaced a hydraulic hose with one rated at 250psi.

  • Just today, I was setting up test limits on a line and didn't use the correct sign (+ or -). Failed a bunch of parts before I figured out what I did.
 
The worst thing???
Well the guy I was working with said "Hey, can you figure out how to make this PLC work??". I said "Sure!"
That was almost 50 years ago and I'm still suffering from it!!
 
I was moving a 5HP motor with a 6 ton trolley crane during a shutdown. I was holding on to the motor to keep it steady with one hand and working the controls with the other. I went to stop it and hit the wrong button on the crane. For some reason, whenever you are being dragged across the floor by a large crane, it never occurs to you to let go of the motor you are holding on to.

Luckily it was during shutdown so there was only maintenance guys there to laugh at me and i was able to pretend it didn't hurt too bad.
 
Explain these to someone less enlightened please.

Oooooh... let's see... I'll include things I've seen as well.

  • Had an apprentice that built one of my panels. This thing was beautiful-- almost a work of art. The downside was that he didn't strip a single wire...

  • A coworker replaced a hydraulic hose with one rated at 250psi.
 
  • Had an apprentice that built one of my panels. This thing was beautiful-- almost a work of art. The downside was that he didn't strip a single wire...
I knew someone who would strip just a little bit of insulation off the end, so the terminal block would clamp on the insulation. He thought this would hold better. The wires only made connection because they 'happened to' touch the inside of the terminal... :rolleyes:

Here's a few of my mistakes I can think of off the top of my head...

  • Was off by one terminal when wiring the L1, L2, L3, Ground on a brand new servo drive. L1 ended up on the DC Bus terminal, which instantly let every last drop of magic smoke out of the drive... 🙃

  • Forgot that there were SSRs controlling the heaters on a 480V heat tunnel, and accidentally touched one of the heater connections. A hard lesson in leakage current.. :eek:

  • Had to replace a capacitor on a VFD. I remembered to discharge the capacitors, but was too lazy to use a resistor. A scrap of wire will do... BANG!... I couldn't hear anything for the rest of the day... 🙃

  • Spent most of a day trying to figure out why part of my program wasn't working before realizing the subroutine wasn't being called. This mistake you learn never to repeat... :oops:
We all make mistakes... The trick is to learn from them.

🍻

-Eric
 
"The downside was that he didn't strip a single wire..."

if you don't strip the wire, the screw clamp terminal just squashes the PVC insulation a bit....


"..rated at 250psi."

many, most, all, (take your pick), hydraulic systems work at pressures way higher than 250 psi (17 bar)
 
Explain these to someone less enlightened please.

Not stripping the insulation off the end of the wire means that the terminal block makes contact with the insulation, not the wire underneath.

Hydraulics, as has been stated are generally rated for much higher-- in this instance, a 2500psi system. The hose was replaced at the top of a machine, so after putting it on, he went back down to turn the machine on, than back up to check for leaks. After about 15 seconds, the hose split apart, and approximately 40 gallons of oil were evacuated from the tank-- in less than a minute...
 
Meh $461 is an inconvenience, certainly not the worst thing to ever happen.

My worst programming mistake occured a few years ago, we were upgrading an existing facility. PLC-5 - ControlLogix conversations and such. Things were going well until part 5 of 6 of the project. At some point the plant had requested their raw material ID system be changed, overall this was a minimal risk change and did not impact much except for their existing batch system. Due to the recipe system and such, converting the batch system to the new material ID's was not an easy chore (hard coded string references in the PLC...) nor part of the scope of the project.

As a result I created a routine to translate the new ID to the Old for the batch system. All seemed to be working well until I came to the plant the next day. Plant management confronted me as soon as I sat down, ultimately the wrong ingredients got into multiple batches causing scrap product, the raw material was completely used and they had to truck in an emergency supply. Never got a final cost on that mistake but alot...

I looked in the code, and found a typo. Code I had tediously went through multiple times to ensure it was correct, however I was a victim of tunnel vision. I should have had another set of eyes look at it.

The lesson I learned beyond checking my code was to maintain my integrity. The plant management was taken back by the fact that I admitted it was my mistake. Apparently previous integrators did not come so clean when mistakes were made. I think they were even skeptical of the truth! Almost felt like they were ready for battle, but completley surprised they didn't have to fire a round.

At the end of the day, the Plant manager shook my hand and thanked me for my integrity, proceeded to compliment us on the job done so far and said: "This is why I have a risk budget for all projects." Life moved on.
 
Last edited:
In my beginning days...
Wired a 3 phase 480 motor as:
L1=T1, T2, T3
L2=T4, T5, T6
L3=T7, T8, T9

Power on and a very quick "poof".

..
 
Accidently brought a 415Volt mains supply together with a 415V UPS supply through an MCCB. The MCCB did not survive. First and last blow up I ever initiated and that was at age 61.
 
Mine happened yesterday!
Pulled the wrong relay in an ammonia detection system which opened the shunt trip on a fully loaded 4000A ACB which killed the refrigeration plant. Very lucky we got it fired back up in a few minutes.
 
Several I remember:

Working on a 1771-DB module and faulted the rack running the conveyors carrying Econoline vans from the body shop through the tunnel into paint for 5 minutes. Never saw so many scooters rushing to the panel thinking the world had come to an end (blocked the entire body shop).

Killed a bank of a dozen LVDTs when I brushed their 24V power with 110vac. Had to rush in the replacements from England.

Have crashed a few robot end-of-arm effectors causing delays and cost repairing them.

I'm sure there are a few more that I don't recall. There is truth in the old saying that if you haven't screwed something up or not in trouble, you're probably not working.
 
Started a robot cell up. I was in the cell doing some plc code. Set my laptop down and exited the cell. Started the robot. I heard a crunch. It was my laptop under the counter weight of the robot. That start-up didn't start up on time. But the llant manager laughed and laughed at me. He said to extra days was not a problem.
 
I knew someone who would strip just a little bit of insulation off the end, so the terminal block would clamp on the insulation. He thought this would hold better. The wires only made connection because they 'happened to' touch the inside of the terminal... :rolleyes:

Here's a few of my mistakes I can think of off the top of my head...

  • Was off by one terminal when wiring the L1, L2, L3, Ground on a brand new servo drive. L1 ended up on the DC Bus terminal, which instantly let every last drop of magic smoke out of the drive... 🙃

  • Forgot that there were SSRs controlling the heaters on a 480V heat tunnel, and accidentally touched one of the heater connections. A hard lesson in leakage current.. :eek:

  • Had to replace a capacitor on a VFD. I remembered to discharge the capacitors, but was too lazy to use a resistor. A scrap of wire will do... BANG!... I couldn't hear anything for the rest of the day... 🙃

  • Spent most of a day trying to figure out why part of my program wasn't working before realizing the subroutine wasn't being called. This mistake you learn never to repeat... :oops:
We all make mistakes... The trick is to learn from them.

🍻

-Eric

Someone else who knows the smoke theory!
 

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