Abstract: An oil-and-water mixture is supplied to a tank which is closed at the bottom and open at the top, generally midway between top and bottom. A closed vessel envelops the upper portion of the tank. A vacuum is drawn at the top of the tank and vessel. An oil coalescer is placed between the mixture supply and the open tank top and a water coalescer between the supply and the closed tank bottom. Separated oil spills over the open tank top into the vessel, and is discharged from there. Separated water is discharged from the closed tank bottom.

Abstract: A generally vertical tube communicates at its lower end with a reservoir containing the heavier of two liquids to be separated (water in the case of oil and water separation). A vacuum system is used to create at the top of this tube a lower pressure than at the bottom. The mixture of the liquids to be separated is injected into the tube at an intermediate location between top and bottom with relatively low velocity and turbulence, and close to, but below the level of the interface between the two liquids, which becomes established as they separate. The interface level location is maintained by controlling the top-to-bottom pressure difference and the evacuation rate of the lighter liquid.