Patent ID: 8734577

Claim:
A separator tank for separating oil and gas from water, and comprising an essentially cylindrical vertical tank with at least two separator tank units, the separator tank unit having an upper part and a lower part, an inlet for fluid flowing tangentially into the separator tank unit, an inner annular wall for dividing a vortex flow outside the inner annular wall from a flow inside the inner annular wall during operation of the separator tank, at least one first outlet in the upper part of the separator tank unit, at least one second outlet in the lower part of the separator tank unit, and a central pipe extending from the first outlet to the second outlet, the central pipe being blocked with a flow barrier between the first outlet and the second outlet, wherein the central pipe has an upper extension extending out of the separator tank unit and a lower extension extending out of the separator tank unit; said inner annular wall having a first opening at an upper end of said inner annular wall allowing communication between the upper part and the lower part of the separator tank unit, wherein the two or more separator tank units are arranged on top of one another; the separator tank further comprising an inlet pipe connected with the inlet for fluid in a first of the at least two separator tank units, the second outlet in the first separator tank unit being connected with the inlet for fluid in a second of the at least two separator tank units, and at least one pressure control device controlling the pressure downstream of the first outlets for oil and gas to be lower than the pressure at the second outlets during operation of the separator tank.