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What happens to crude oil before it enters a refinery fractionating column?

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Aerial view of an oil refinery complex near New Orleans, Louisiana, with storage tanks, industrial structures, and smoke rising from the facility, surrounded by open land. — petroleum refining Aerial view of an oil refinery near New Orleans.

Before crude oil enters a fractionating column, it undergoes a series of preparatory steps to ensure efficient processing and prevent equipment damage:

Heating and Desalting: Crude oil is pumped from storage tanks through heat exchangers to reach approximately 120 °C (250 °F). Fresh water is added, and the mixture enters a desalting drum. Here, an electric field is used to separate the saltwater phase; removing salt is critical to prevent it from depositing on furnace tubes and causing plugging.1
Final Heating: The desalted crude passes through additional heat exchangers before entering a furnace. It is heated through steel alloy tubes to temperatures between 315 and 400 °C (600 and 750 °F), depending on the specific crude oil and desired end products.1

Following this heating process, the resulting mixture of vapour and unvaporized oil is fed directly into the fractionating column for separation.1