How does transformer oil dehydration remove moisture from oil?

Dehydration removes moisture by exposing oil to vacuum, heat, and large surface area contact so dissolved water and trapped gases can evaporate. A typical dehydration unit warms the oil, passes it through filters to remove particles, then routes it through a vacuum chamber where pressure is reduced and moisture flashes off. Some systems use coalescers or molecular sieves to improve water removal. Dry oil reduces the risk of dielectric breakdown and slows paper insulation aging, since moisture accelerates cellulose depolymerization and reduces electrical strength in the paper oil insulation system.