free-water knockout

1. n. [Production Facilities]
A vertical or horizontal separator used mainly to remove any free water that can cause problems such as corrosion and formation of hydrates or tight emulsions, which are difficult to break. A free-water knockout is commonly called a three-phase separator because it can separate gas, oil and free water. The liquids that are discharged from the free-water knockout are further treated in vessels called treaters. Free-water knockout is abbreviated as FWKO.