You respond to a trouble call with a batch mixer. A motor overload burned open, but insulation resistance testing shows no problems. As the mixing system is recipe-driven from the PLC, you suspect the ingredients are being added in a way that creates a thick slurry and overloads the motor.

You ask the operator if it's possible to change the recipe to avoid this problem. Unfortunately, that decision can't be made from the floor.

You leave, knowing this problem will recur. You make one more stop and then look for your supervisor to discuss the mixer problem. But she finds you first, informing you that the operator on that mixer you fixed just narrowly escaped injury and the E-stop didn't work.

No matter how diligent you are with the actual repair, the last person to work on a system is the first person suspected of leaving it in an unsafe condition. To avoid this, always test E-stops, light curtains, and similar devices on any system so equipped.