Distillation is also used at other points in the refining process to remove impurities. Since the boiling points of the various crude cuts are constant, the distillation curve shows the percentage of each compound in a given grade or batch of crude. Also used to remove impurities added during the refining process. The shorter the drum cycle, the more economical the coke manufacturing process. In one kind of exchanger, process hydrocarbons are circulated through tubes surrounded by cooling air or water, very much like in an automobile radiator.
Crude oil is primarily a mixture of hydrocarbon compounds.
Compare lubes . Preventive maintenance is facilitated by failure analysis to devise design improvements, and the use of diagnostic instrumentation to anticipate potential problems. Compare turnaround . A refinery's MTBF is one indicator of the effectiveness of its maintenance program. They are often manufactured as part of the refining process.