My father works in similar industrial installations and he's supplied with what I can only describe as a swiss cheese padlock. It's a hoop with two plates full of holes to close it, which you then thread a padlock through, locking the isolator in the safe/off position.
If someone else was working on another part of the installation that used the same isolator they'd thread a second padlock in to the plate so that the first person couldn't inadvertently re-start the unit
Biting the hand that feeds IT
