I confirm that an aluminium refinery is not something you stop lightly. I remember something about taking two weeks to restart? Maybe more. Source, had family working at a large northern plant.
Being able to restart it at all makes it better than a lot of industries. Many of these liquid-metal affairs depend on convection and inertia to keep the metal molten, and if it solidifies inside a pipe—well, then you don't have a pipe anymore; you have a bimetal pole.
