Oil refineries are a 24 hours a day, 7 days a week operation. An important step in the process of refining is Fluid Catalytic Cracking. This is done with a machine referred to commonly as the CAT cracker. During this process, crude oil is converted into more valuable derivaties, ranging from heavier oils like diesel, to lighter ones like gasoline, kerosine, and gasses.
This is a companion discussion topic for the original entry at https://peerlearning.is/shell-connects-its-engineers-and-then-gets-out-of-the-way/