System and method for separating a fluid stream

A system for separating a fluid stream comprising gas, a light liquid and a heavy liquid, the system comprising a separation vessel that is arranged to define a downwardly extending separation space and comprises a downwardly sloping tube, the separation space having an inlet for the fluid stream at a first height, an outlet for heavy liquid at a second height below the first height, an outlet for light liquid at a third height between the first and second heights, an outlet for gas above all outlets for liquid, wherein a further outlet for light liquid is provided at a fourth height between the first and third heights, and wherein at least the outlet at the third height is provided with a control valve that is operative to open and close in dependence of the type of liquid in the pipes at that level, and a method of separating a fluid stream comprising gas, a light liquid and a heavy liquid in such a system, wherein an indication of height of an interface between heavy and light liquid in the separation vessel is obtained and the control valve at the third outlet is operated in dependence on the height of the interface.