Magnetic Drum Separator Working Principle Magnetic Drum Separator Working Principle. Working principle of magnetic separator in coal handling plant. magnetic s.Magnetic separation is a versatile technique used in sample preparation for diagnostic purpose. For such application, an external magnetic field is applied to drive the separation of target entity (e.g. bacteria, viruses, parasites and cancer cells) from a complex raw sample in order to ease the subsequent task(s) for disease diagnosis.