Hydrocyclone for the separation of fluids having more than one phase, comprising: - a substantially cylindrical fluid feed section, having at least one tangential fluid inlet pipe, the fluid feed section being closed at the upper circular surface thereof and having a light phase outlet orifice in the central region of the upper circular surface, the fluid feed section also being partly closed at its lower circular surface whereon, also in the central region, there is disposed a seat for connecting an acute conical section, - a feed head housed within the fluid feed section, having the form of a cylindrical ring of smaller dimensions than the feed section, such that an annular space is defined between the wall of feed section and an external surface of said feed head, the feed head having at least two equal channels, diametrically opposed and curved, extending from the external surface to an internal surface of said feed head and wherein the transverse cross sectional area of said channels gradually diminishes serving to accelerate the fluid stream in a moderate manner and to introduce it within the hydrocyclone; - a light phase outlet control device in the form of a hollow interchangeable part having a plurality of different diameters, having external diameter suitable for insertion into light phase outlet orifice permitting, by means of each diameter, alteration of the hydrodynamic characteristics of the hydrocyclone and adaptation of the band of use thereof in accordance with the fluid stream; - an acute conical section having a first end connected to the seat of the feed section, and a second end, having a smaller internal opening diameter than the first end, the acute conical section serving to initiate formation of the vortex following the stage of acceleration in feed head; - at least one moderate conical section having a third end connected to the second end of the acute conical section, and a fourth end, having a smaller internal opening diameter than the third end, the at least one moderate conical section having a length exceeding that of the acute conical section, serving to continue propagation of the vortex and to increase the separation of both the heavier phase and of the lighter phase; - a final cylindrical section having a fifth end connected to the fourth end of the moderate conical section, and a sixth end having the same internal opening diameter as the fifth end, the final cylindrical section serving to concentrate the heavier phase on removal thereof through lower outlet. - a substantially cylindrical fluid feed section, having at least one tangential fluid inlet pipe, the fluid feed section being closed at the upper circular surface thereof and having a light phase outlet orifice in the central region of the upper circular surface, the fluid feed section also being partly closed at its lower circular surface whereon, also in the central region, there is disposed a seat for connecting an acute conical section, - a feed head housed within the fluid feed section, having the form of a cylindrical ring of smaller dimensions than the feed section, such that an annular space is defined between the wall of feed section and an external surface of said feed head, the feed head having at least two equal channels, diametrically opposed and curved, extending from the external surface to an internal surface of said feed head and wherein the transverse cross sectional area of said channels gradually diminishes serving to accelerate the fluid stream in a moderate manner and to introduce it within the hydrocyclone; - a light phase outlet control device in the form of a hollow interchangeable part having a plurality of different diameters, having external diameter suitable for insertion into light phase outlet orifice permitting, by means of each diameter, alteration of the hydrodynamic characteristics of the hydrocyclone and adaptation of the band of use thereof in accordance with the fluid stream; - an acute conical section having a first end connected to the seat of the feed section, and a second end, having a smaller internal opening diameter than the first end, the acute conical section serving to initiate formation of the vortex following the stage of acceleration in feed head; - at least one moderate conical section having a third end connected to the second end of the acute conical section, and a fourth end, having a smaller internal opening diameter than the third end, the at least one moderate conical section having a length exceeding that of the acute conical section, serving to continue propagation of the vortex and to increase the separation of both the heavier phase and of the lighter phase; - a final cylindrical section having a fifth end connected to the fourth end of the moderate conical section, and a sixth end having the same internal opening diameter as the fifth end, the final cylindrical section serving to concentrate the heavier phase on removal thereof through lower outlet.