An “engineer” I worked with has made a few classics.
#1: January start up in the factory, the juice making department were not getting a steam supply, he offered “the steam might be frozen in the pipe”
#2: We had service contractors in to analyse our compressed air supply. We make PET drinks bottles, we use 40bar of compressed air to “blow” the plastic preform onto a bottle. They rig their monitoring box to various sample points on the air ring main, their box of tricks then takes readings. After each one they take the contaminated glass vial off the machine for disposal, fresh one on for the next point. He asks “do you take the air sample back to the lab and look at it under the microscope?”
I’m sure I’m as guilty, although I must have blanked them from my memory.