Distillation

When you are called out of your bed at 3 in the morning because the plant has gone off spec and the rain is coming down and the wind is almost blowing you off your feet then you need to know what is happening quickly.
I always looked at the facilities as if they were made of glass and I could understand what was happening in terms of fluid dynamics.
Consultants yes. They will undertake a study, and the outcome is that you need another study. Usually, they blame the operators.