Which principle does a separator primarily rely on to separate phases?

• A. Centrifugal separation using rotation
• B. Gravity separation with adequate residence time
• C. Chemical demulsification at high temperature
• D. Mechanical filtration through fine screens

Answer: (B)

The principle being tested is gravity-based separation driven by density differences between the phases. In a separator, the heavier water settles to the bottom while the lighter oil rises to the top. With adequate residence time, droplets have time to coalesce and form larger bits that settle more readily, creating distinct, layered phases.

This is different from centrifugal separation, which uses rotation to amplify effective gravity and accelerate separation; such devices are used when gravity alone isn’t sufficient. It’s also not about chemical demulsification, which is a treatment to break emulsions rather than the fundamental separation mechanism. And it isn’t about filtration through screens, which removes solids rather than separating immiscible liquids.