A wondrous pump story:
I was dispatched to a automotive factory near Kassel to support a technician doing commissioning of a surface treatment plant with PLC knowledge beyond his abilities. The plant was a high capacity passivation and cataphoretic laquer (EPD) plant, so there are big basins, pumps, heat exchangers etc.
(something akin to THIS , but treating mig racks full of parts instead, wich were moved through those basins consecutively by two portal handlers)
The way to the control room lead trough the basement where about 40 pumps were working in two long rows, each on a little foundation of concrete and connected by large tubes to the basins above.
It was rather dark, hot and loud. Flow noise, the pumps and motors and the clanking of the parts, the squeal of the handling machinery from above added up to a veritable cacophony.
I had just arrived and was respectfully escorted to the control room by this way.
One pump stuck out. From some distance, it was sort of 'highlighted' for me. That was before I saw that it is not running. (The coupling between the motor and the pump was where you saw it immediately). And it was before I felt the heat radiated by it. I called the guy who had supervised the erection and comissioning of this plant to stop and told him that there is something wrong with that pump.
He told me that all is ok and that not all pumps are running at all times. Well, it was HIS plant, but it also was HIS ass, so after seeing my face, he inquired. One could not touch this pump. The motor had a surface temperature around 100°C. It turned out that a small piece of tubing, wich had somehow gotten into the larger tubing being connected to the pump, had wandered until arriving at the latter and was stuck in the rotor. This, combined with a motor protection relay set to around 210% of the motor's nominal current, caused the pump to be in this fully powered, stalled condition. As the motor was stationary, there was also no airflow.
I have no idea what made me notice this pump immediately under those conditions. It was like 'highlighted flashing red with the word FAULT' to me.