Abstract: The present invention refers to three or two phase separators provided with an inlet centrifugal device (40, 70) for the preliminary separation of the gas phase from the fluid mixture; the centrifugal separation device includes a first stage (40′, 70′) having a circular section delimited by a wall (42, 63) and by the external surface of the second stage plate and a second stage (40″, 70″), internal and coaxial to the first stage, realized by a plate rolled as an ‘Archimedean’ spiral around the vertical axis common to the two stages of the centrifugal separation device, in order to operate the separation of the gas phase from the liquids, obliging the flowing fluid to follow a circular path that brings the liquid and its droplets to adhere to the wall surface (42, 63) and to the internal surface of the spiral (47), obtaining their separation from the mixture.