Tandem dual element intershaft carbon seal

1. A sealing system for use with two rotating shafts, comprising:

a first tandem seal arrangement contacting a first surface of a first one of said shafts, said first tandem seal arrangement comprising a first pair of segmented ring assembles for contacting said first surface;

each of said segmented ring assemblies forming said first pair having a contact surface in contact with said first surface;

a second tandem seal arrangement contacting a second surface of a second one of said shafts, said second tandem seal arrangement comprising a second pair of segmented ring assemblies for contacting said second surface;

each of said segmented ring assemblies forming said second pair having a contact surface in contact with said second surface;

said first tandem seal arrangement being housed in a first housing and said second tandem seal arrangement being housed in a second housing and a main housing forming a wall portion of said first housing and a wall portion of said second housing;

said first housing having a first cavity for receiving a fluid, said first cavity bounded by a surface of said first tandem seal arrangement opposed to said contact surfaces of said segmented ring assemblies on a first side and a first surface of said wall portion of said main housing on a second opposed side and said second housing having a second cavity for receiving said fluid, said second cavity being bounded by a surface of said second tandem seal arrangement opposed to said contact surface of said segmented ring assemblies on a first side and a second surface of said wall portion of said main housing on a second opposed side;

each of said first housing and said second housing having a seal plate which is integrally formed with said main housing and which extends inwardly from said main housing towards one of said shafts;

said seal plates forming two opposed sides of a central cavity; and

said fluid in said first cavity having a pressure greater than a pressure in said central cavity.

2. The sealing system according to claim 1 , wherein each said seal plate provides a first sealing surface against which a first one of said segmented ring assemblies abuts.

3. The sealing system according to claim 2 , wherein each said housing further comprises a cover plate for providing a second sealing surface against which a second one of said segmented ring assemblies abuts.

4. The sealing system according to claim 3 , wherein each said housing has a groove and wherein a retaining ring is positioned within said groove, said retaining ring securing said respective tandem seal arrangement within said respective housing.

5. The sealing system according to claim 3 , further comprising means for preventing rotation of said segmented ring assemblies in each said housing.

6. The sealing system according to claim 3 , wherein said first cavity is bordered by said first surface of said wall portion of said main housing portion, said first tandem seal arrangement, said first sealing surface, and said cover plate.

7. The sealing system according to claim 6 , further comprising means for supplying a pressurized fluid to said first cavity.

8. The sealing system according to claim 1 , wherein each said tandem seal arrangement further comprises a spring plate positioned between said segmented ring assemblies.

9. The sealing system according to claim 1 , wherein each of said segmented ring assemblies is formed from a plurality of arch shaped carbon elements.

10. The sealing system according to claim 9 , wherein each of said segmented ring assemblies is formed from at least three of said arch shaped carbon elements.

11. The sealing system according to claim 9 , wherein each of said shaped carbon elements has a groove and tongue arrangement at each end.

12. A sealing system for use with two rotating shafts, comprising:

a first tandem sealing arrangement for contacting a first surface of a first one of said shafts;

a second tandem sealing arrangement for contacting a second surface of a second one of said shafts;

each of said tandem sealing arrangements comprising a pair of segmented ring assemblies for contacting a respective one of said first and second surfaces;

each of said pair of segmented ring assemblies being positioned within a respective housing and having a pair of contact surfaces in contact with said respective one of said first and second surfaces;

each said respective housing having a first wall formed by a portion of a main housing portion with an integrally formed seal plate for providing a first sealing surface against which a first one of said segmented ring assemblies abuts, and said first wall being opposed to a contact surfaces;

each said seal plate extending inwardly from said main housing towards one of said shafts;

said seal plates forming two opposed sides of a central cavity; and

each said respective housing further having a cover plate, a groove within said first wall, and a retaining ring abutting said cover plate for securing said pair of segmented ring assemblies being positioned within said groove;

each said respective housing having a cavity for receiving a fluid, said cavity being bounded by a surface of said first wall on a first side and surfaces of said pair of segmented ring assemblies opposed to said contact surfaces on a second side opposed to said first side;

said fluid in said first cavity having a pressure greater than a pressure in said central cavity; and

each said tandem sealing arrangement including means for preventing rotation of said segmented ring assemblies, said rotation preventing means being positioned between said cover plate and a second one of said segmented ring assemblies and engaging a groove in said cover plate and a groove in said cover plate and groove in a second one of said segmented ring assemblies.

13. The sealing system of claim 12 , wherein said means for preventing rotation comprises a member selected from the group consisting of a pin, a tab, and a keyway.

14. The sealing system of claim 12 , further comprising means for supplying a pressurized fluid to each said cavity.

15. The sealing system of claim 12 , wherein each said tandem seal arrangement further comprises a spring plate intermediate said first one of said segmented ring assemblies and said second one of said segmented ring assemblies and a garter spring element associated with each of said segmented ring assemblies for holding each of said segmented ring assemblies in contact with a respective one of said shafts.