Expansion turbine

1. An expansion turbine, comprising:

a case having an inlet and an outlet for a working fluid;

at least one stator ( 3 ) installed inside the case;

at least one rotor ( 2 ) installed inside the case and rotating around a respective revolution axis (X-X);

a short-pipe ( 4 ) constrained to the case;

a mechanical unit ( 5 ) installed inside the short-pipe ( 4 ); said mechanical unit ( 5 ) comprising a bushing ( 7 ) and a shaft ( 6 ) rotatably installed inside the bushing ( 7 ); said shaft ( 6 ) being rotated around the revolution axis (X-X) and connected to the rotor ( 2 ); wherein the shaft ( 6 ) is connected to the rotor ( 2 ) in removable manner and the whole mechanical unit ( 5 ) is extractable from the short-pipe ( 4 ) from the side opposite to said rotor ( 2 );

wherein the rotor ( 2 ) is movable along the axial direction (X-X) between a first configuration, in which the mechanical unit ( 5 ) is installed inside the short-pipe ( 4 ) and the rotor ( 2 ) is spaced from the short-pipe ( 4 ), so that the working fluid can revolve the rotor, and a second configuration, in which the mechanical unit ( 5 ) is extracted from the short-pipe ( 4 ) and the rotor ( 2 ) leans against the short-pipe ( 4 ) at a static seal ( 18 , 19 ).

2. A The turbine as claimed in claim 1 , comprising a self-centering joint ( 11 , 12 ) connecting the shaft ( 6 ) and the rotor ( 2 ).

3. A The turbine as claimed in claim 2 , wherein the self-centering joint ( 11 , 12 ) is tooth-coupled.

4. The turbine as claimed in claim 1 , comprising a tie-rod ( 14 ) inserted into an axial opening ( 13 ) of the shaft ( 6 ); said tie-rod ( 14 ) having an end ( 14 ′) connected to said rotor ( 2 ) and being integral with the rotor ( 2 ) along an extraction direction (A) of the mechanical unit ( 5 ) from the short-pipe ( 4 ).

5. The turbine as claimed in claim 4 , comprising a spherical coupling ( 15 , 16 ) connecting the tie-rod ( 14 ) and the rotor ( 2 ).

6. The turbine as claimed in claim 1 , wherein the rotor ( 2 ) is locked against the short-pipe ( 4 ) when said rotor ( 2 ) is in the second configuration.

7. The turbine as claimed in claim 1 , wherein the mechanical unit ( 5 ) further comprises a gland ( 9 ) placed between the bushing ( 7 ) and the shaft ( 6 ) at an end ( 6 ′) of said shaft ( 6 ) connected to the rotor ( 2 ), and an oil seal ( 10 ) placed between the bushing ( 7 ) and the shaft ( 6 ) at an end ( 6 ″) of said shaft ( 6 ) opposite to the rotor ( 2 ).

8. The turbine as claimed in claim 1 , wherein the mechanical unit ( 5 ) comprises rolling bearings ( 8 ) rotatably supporting the shaft ( 6 ) inside the bushing ( 7 ).

9. A method for disassembling an expansion turbine, comprising the following steps:

providing an expansion turbine according to claim 1 ;

moving back the mechanical unit ( 5 ) and the rotor ( 2 ) with respect to the short-pipe ( 4 ) until bringing said rotor ( 2 ) against said short-pipe ( 4 ) at a static seal ( 18 , 19 );

locking the rotor ( 2 ) against the short-pipe ( 4 ); and

extracting the mechanical unit ( 5 ) from the short-pipe ( 4 ) while the rotor ( 2 ) is being locked against said short-pipe ( 4 ).