SEAL RING ASSEMBLY FOR A DYNAMOELECTRIC MACHINE

Abstract

A seal ring assembly for a rotor shaft includes a seal casing defining a radially inwardly directed channel. The seal ring is disposed in the radially inwardly directed channel of the seal casing. The seal ring is resiliently joined about the shaft to form a seal, and the seal ring comprises an electrically insulating or dissipative material or a non-metallic material.

Claims

1. A seal ring assembly for a rotor shaft comprising: a seal casing defining a radially inwardly directed channel; a seal ring disposed in the radially inwardly directed channel of the seal casing, the seal ring being resiliently joined about the shaft to form a seal; and the seal ring comprising an electrically insulating or dissipative material or a non-metallic material.

2. The seal ring assembly of claim 1, the electrically insulating material or the non-metallic material is comprised of an organic thermoplastic polymer.

3. The seal ring assembly of claim 1, the electrically insulating material or the non-metallic material is comprised of polyether ether ketone.

4. The seal ring assembly of claim 1, the electrically insulating material or the non-metallic material is located on the seal ring in a location that is directly opposed to the rotor shaft.

5. The seal ring assembly of claim 1, the electrically insulating material or the non-metallic material is located on a radially inwardly facing surface of the seal ring.

6. The seal ring assembly of claim 1, the electrically insulating material or the non-metallic material is located on substantially all exterior surfaces of the seal ring.

7. The seal ring assembly of claim 1, the seal ring comprised substantially or entirely of the electrically insulating material or the non-metallic material.

8. The seal ring assembly of claim 1, the seal ring biased radially inwardly by one or more springs, the seal ring having a tapered surface, the one or more springs configured to be seated against the tapered surface.

9. A seal ring assembly for a rotor shaft comprising: an upper seal casing defining a first radially inwardly directed channel; a lower seal casing defining a second radially inwardly directed channel; a first seal ring and a second seal ring, each respectively disposed in the first and second radially inwardly directed channels of the upper and lower seal casings, the first seal ring and the second seal ring being resiliently joined about the shaft to form a substantially 360° seal, the first seal ring and the second seal ring biased radially inwardly by one or more springs, each of the first and second seal rings having adjacent tapered surfaces, the one or more springs configured to be seated against the adjacent tapered surfaces; and each of the first seal ring and the second seal ring comprising an electrically insulating material or a non-metallic material.

10. The seal ring assembly of claim 9, the electrically insulating material or the non-metallic material is comprised of an organic thermoplastic polymer.

11. The seal ring assembly of claim 9, the electrically insulating material or the non-metallic material is comprised of polyether ether ketone.

12. The seal ring assembly of claim 10, the electrically insulating material or the non-metallic material is located on each of the first seal ring and the second seal ring, in locations that are directly opposed to the rotor shaft.

13. The seal ring assembly of claim 10, the electrically insulating material or the non-metallic material is located on a radially inwardly facing surface of each of the first seal ring and the second seal ring.

14. The seal ring assembly of claim 10, the electrically insulating material or the non-metallic material is located on substantially all exterior surfaces of the first seal ring and the second seal ring.

15. The seal ring assembly of claim 10, each of the first seal ring and the second seal ring comprised substantially or entirely of the electrically insulating material or the non-metallic material.

16. A seal ring assembly for a rotor shaft comprising: an upper seal casing defining a first radially inwardly directed channel; a lower seal casing defining a second radially inwardly directed channel; a first seal ring and a second seal ring, each respectively disposed in the first and second radially inwardly directed channels of the upper and lower seal casings, the first seal ring and the second seal ring being resiliently joined about the shaft to form a substantially 360° seal, the first seal ring and the second seal ring biased radially inwardly by one or more springs, each of the first and second seal rings having adjacent tapered surfaces, the one or more springs configured to be seated against the adjacent tapered surfaces; and each of the first seal ring and the second seal ring comprising an electrically insulating material that is polyether ether ketone.

17. The seal ring assembly of claim 16, the electrically insulating material located on each of the first seal ring and the second seal ring, in locations that are directly opposed to the rotor shaft.

18. The seal ring assembly of claim 16, the electrically insulating material located on a radially inwardly facing surface of each of the first seal ring and the second seal ring.

19. The seal ring assembly of claim 16, the electrically insulating material located on substantially all exterior surfaces of the first seal ring and the second seal ring.

20. The seal ring assembly of claim 16, each of the first seal ring and the second seal ring comprised substantially or entirely of polyether ether ketone.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 illustrates a perspective view showing upper and lower seal rings.

[0012] FIG. 2 illustrates a schematic cross-sectional view of a seal system for a dynamoelectric machine.

[0013] FIG. 3 illustrates a schematic and partial cross-sectional view of a seal ring assembly for a dynamoelectric machine, according to an aspect of the present invention.

[0014] FIG. 4 illustrates an enlarged cross-sectional view of one seal ring, according to an aspect of the present invention.

[0015] FIG. 5 illustrates a schematic and partial cross-sectional view of a seal ring assembly for a dynamoelectric machine, according to an aspect of the present invention.

[0016] FIG. 6 illustrates a schematic and partial cross-sectional view of a seal ring assembly for a dynamoelectric machine, according to an aspect of the present invention.

[0017] FIG. 7 illustrates a schematic and partial cross-sectional view of a seal ring assembly and electrical insulation system for a dynamoelectric machine, according to an aspect of the present invention.

[0018] FIG. 8 illustrates a schematic and partial cross-sectional view of a seal ring assembly and electrical insulation system for a dynamoelectric machine, according to an aspect of the present invention.

[0019] FIG. 9 illustrates a schematic and partial cross-sectional view of a seal ring assembly and electrical insulation system for a dynamoelectric machine, according to an aspect of the present invention.

[0020] FIG. 10 illustrates a schematic and cross-sectional view of a seal ring assembly for a generator, according to an aspect of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0021] One or more specific aspects/embodiments of the present invention will be described below. In an effort to provide a concise description of these aspects/embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with machine-related, system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

[0022] When introducing elements of various embodiments of the present invention, the articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Any examples of operating parameters and/or environmental conditions are not exclusive of other parameters/conditions of the disclosed embodiments. Additionally, it should be understood that references to “one embodiment”, “one aspect” or “an embodiment” or “an aspect” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments or aspects that also incorporate the recited features.

[0023] FIG. 3 illustrates a schematic and partial cross-sectional view of a seal ring assembly 300 for a dynamoelectric machine. The dynamoelectric machine may be a motor, generator, a hydrogen cooled generator or any other machine in need of the disclosed seal assembly. The seal ring assembly 300 is located circumferentially around the rotor shaft 16. The seal casing 326 defines a radially inwardly directed channel 324. The seal rings 312 are disposed in the radially inwardly directed channel 324 of the seal casing 326, and each seal ring 312 is resiliently joined about the rotor shaft 16 to form a seal. An upper seal casing and a lower seal casing (not shown) are disposed on both sides of the rotor shaft 16 and combine to form a substantially 360 degree seal. The seal rings 312 are biased radially inwardly by the one or more springs 340. The seal rings 312 include an electrically insulating material 360 or a non-metallic material 360. Electrically insulating materials are broadly defined to include insulating, dissipative and anti-static materials. The material 360 is located on a radially inward facing surface of the seal ring, and in a location that is directly opposed to the rotor shaft 16. For example, the material 360 may be a layer that is about 1 mm to about 4 mm thick, have a dielectric strength of about 15 kV/mm to about 40 kV/mm and a volume resistivity of about 1×10.sup.7 Ohms-inch to about 1×10.sup.15 Ohms-inch. The resistivity can span the range from dissipative to insulating, depending on the properties required. However, suitable values above or below these ranges, and any suitable non-metallic and/or electrically insulating or dissipative material may be used as desired in the specific application.

[0024] FIG. 4 illustrates an enlarged cross-sectional view of one seal ring 312. The seal ring 312 may be comprised of steel, or some other suitable metal, and includes a tapered surface 313. The spring 340 is configured to seat against the tapered surface 313 and bias the seal ring 312 in a radially inward and axial direction. With specific reference to FIG. 4, the spring 340 would push the seal ring 312 down and to the left. A neighboring seal ring (as shown in FIG. 3) also includes an adjacent tapered surface, and this seal ring would be pushed down and to the right.

[0025] The electrically insulating and/or non-metallic material 360 may be an organic thermoplastic polymer, polyether ether ketone, or any other suitable material. Polyether ether ketone is both substantially electrically insulating and non-metallic, so it is a suitable material for use in the present invention. Preferably, the material 360 is a layer of electrically insulating material sufficient to reduce or stop rotor shaft currents from passing through the seal rings 312 and the seal casing 326. As mentioned above, rotor shaft currents passing through the seal rings and seal casings may cause electrical pitting of the seal rings, seal casing or both. Excessive electrical pitting can reduce machine efficiency or even machine shut down in extreme cases. An advantage to polyether ether ketone (and other suitable organic thermoplastic polymers) is that it can operate at high temperatures while retaining dimensional stability. These features allow the seal rings to withstand elevated hydrogen seal oil temperature excursions as well as high seal ring temperatures due to a variety of causes. Polyether ether ketone also has excellent hydrolysis and chemical resistance, which allows for greater ability to withstand surface corrosion while the seal rings are in a hydrogen environment. Steel seal rings typically have a tin-copper-antimony containing alloy (babbitt) located at a radially inner portion of the seal rings. Non-metallic materials at the seal ring/rotor interface would eliminate the effects of hot corrosion, which is a weakening of the babbitt material where high oil temperatures cause the copper constituent to react with chemicals in the oil leaving the babbitt copper depleted. Loss of copper lowers the strength and melting point of the babbitt.

[0026] FIG. 5 illustrates a schematic and partial cross-sectional view of a seal ring assembly 300 for a dynamoelectric machine. The electrically insulating and/or non-metallic material 560 is located on substantially all exterior surfaces of the seal ring 312. The full coating of material 560 further enhances the insulation effect of the seal rings. The material 560 may be coated or deposited on the seal rings 312 by any suitable process. Alternatively, material 560 may be attached to seal rings 312 by the use of adhesive or mechanical fasteners.

[0027] FIG. 6 illustrates a schematic and partial cross-sectional view of a seal ring assembly 300 for a dynamoelectric machine. The seal rings 612 are comprised substantially or entirely of the electrically insulating and/or non-metallic material. As mentioned above the material may be an organic thermoplastic polymer, such as polyether ether ketone. Even greater insulation effects may be obtained with seal rings 612 made entirely of the electrically insulating and/or non-metallic material, as no part of the seal ring 612 is electrically conductive.

[0028] The organic thermoplastic polymer and polyether ether ketone materials provide several benefits over known steel babbitted seal rings. Suitable organic thermoplastic polymer materials and polyether ether ketone are electrically insulating, exhibit high temperature performance (e.g., continuous use at temperatures up to about 500° F.), exhibit excellent hydrolysis, low friction and are self-lubricating. These latter features reduce wear on rotor shaft 16. Dimensional stability is improved over steel rings and the non-metallic materials exhibit excellent long term creep and fatigue capability. A further advantage of organic thermoplastic polymer and polyether ether ketone materials over steel is that the non-metallic materials provide a weight reduction in the seal rings fabricated entirely of organic thermoplastic polymer or polyether ether ketone materials. The lighter seal rings permit the use of weaker springs 340 and this facilitates assembly and disassembly.

[0029] FIG. 7 illustrates a schematic and partial cross-sectional view of a seal ring assembly and electrical insulation system for a dynamoelectric machine. In an uninsulated arrangement the seal ring assembly 300 is electrically connected to ground 780 through the end shield 770. The direct metal-to-metal conductive contact between the casing and the end shield 770 is typically used on the turbine end side of the generator. In contrast the collector end of the generator is usually insulated. However, by locating the electrically insulating and/or non-metallic material 360, at least on the radial inner surface of the seal rings 312, the seal ring assembly provides a single insulated arrangement on the turbine end side of the generator.

[0030] FIG. 8 illustrates a schematic and partial cross-sectional view of a seal ring assembly and electrical insulation system for a dynamoelectric machine. In a single insulated arrangement the seal ring assembly 300 is electrically insulated from end shield 770 by insulating mounting ring 890. The non-metallic mounting ring is placed between the seal casing and the end shield 770 to act as an electrically insulating barrier. However, this arrangement does not allow for online insulation resistance measurements unless the shaft 16 is insulated from the bearing/end shield 770. However, by locating the electrically insulating and/or non-metallic material 360, at least on the radial inner surface of the seal rings 312, the seal ring assembly now provides a double insulated arrangement.

[0031] FIG. 9 illustrates a schematic and partial cross-sectional view of a seal ring assembly and electrical insulation system for a dynamoelectric machine. In a double insulated arrangement the seal ring assembly 300 is electrically insulated from end shield 770 by two insulating mounting rings 890 that are sandwiched over a metallic mounting ring 995. This arrangement does allow for online insulation resistance measurements without insulating the rotor shaft 16 from the bearing/end shield 770. However, the various metallic and non-metallic rings add a significant amount of cost and complexity. The addition of the electrically insulating and/or non-metallic material 360, at least on the radial inner surface of the seal rings 312, creates a triple insulated arrangement. An advantage to this configuration is that the complex insulated mounting ring 890—metallic mounting ring 995—insulated mounting ring 890 sandwich can be simplified to that as shown in FIG. 8, as triple insulation redundancy is typically not required or desired. It is to be understood that the substantially fully coated seal rings or completely non-metallic seal rings of FIGS. 5 and 6 could be used in any or all of the systems shown in FIGS. 7, 8 and 9.

[0032] FIG. 10 illustrates a schematic and cross-sectional view of a seal ring assembly 300 for a generator. The seal ring assembly 300 is located circumferentially around the rotor shaft 16. An upper seal casing 326 and a lower seal casing 327 are disposed on both sides of the rotor shaft 16 and combine to form a substantially 360 degree seal. The seal casings 326, 327 define radially inwardly directed channels 324, 325. The seal rings 312a, 312b and 314a, 314b are disposed in the radially inwardly directed channels of the seal casings, and each seal ring is resiliently joined about the rotor shaft 16 to form a seal. The seal rings 312a, 312b and 314a, 314b are biased radially inwardly by the one or more springs 340. The spring 340 is seated against adjacent tapered surfaces 313 (see FIG. 4) on the opposing seal rings (e.g., 312a and 312b, or 314a and 314b). The seal rings include an electrically insulating material 360 and/or a non-metallic material 360. The material 360 is located on a radially inward facing surface of the seal ring, and in a location that is directly opposed to the rotor shaft 16.

[0033] In summary, adding a non-metallic provision to the hydrogen sealing rings 312 in hydrogen cooled generators effectively introduces another layer of electrical insulation to the system. This allows a standard uninsulated configuration to become single insulated without the need for any mounting ring. It also allows a standard single insulated system to become double insulated without the need for the complex multiple mounting ring arrangement. As stated, triple redundancy in the electrical insulation is not required. Therefore, the standard method of double insulating becomes obsolete with the introduction of non-metallic sealing ring provisions.

[0034] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.