A fluid sealing device for rotating machines having a rotor part including at least one disk carried by a rotating shaft rotating in and relatively to a stator part in the presence of a fluid is disclosed. The rotating shaft has a sealing system defining a first environment at a first pressure. The stator part has a wall in front of the disk of the stator part defining a second environment therewith containing a fluid at a second pressure. The device includes a movable ring placed between the wall of the stator part and the disk of the rotor part and has a front sealing gasket facing towards the disk. The movable ring is moved in the active position when the rotating machine is stopped to prevent the fluid passage from one environment to the other.