A separator tank comprises an essentially cylindrical vertical tank (1) having an upper part (6) and a lower part (7), a tangentially arranged inlet (2) for fluid in the upper part of the tank, at least one first outlet (4) in the upper part of the tank, at least one second outlet (3) in the lower part of the tank, and means (12) for calming a stream around the second outlet. An inner annular wall (5) has a first opening (8) at an upper end of said inner annular wall to allow communication between the upper part and the lower part of the tank. The separator tank comprises a rod-shaped vortex eye breaker (11) extending vertically at the center of the tank in order to improve the capacity of the tank.