FIELD OF THE INVENTION
This disclosure relates generally to a steam turbine plant, and more particularly to a main steam governing valve used for the steam turbine plant.
BACKGROUND OF THE INVENTION
During various outage & maintenance activities on 300 MW Cross-fleet unit, the existing HPGV (high-pressure governor valve) had shown significant deterioration across various plants. Few noticeable observations are: 1) increased dimensional clearances between spindle and bush; 2) deep scoring marks on the bush bore and spindle.
In the current design, the valve bush is a single casting block which needs to be replaced whenever any damage or increased clearances are observed. There are various challenges associated with the replacement of the bush: 1) availability of the spare bush within an outage; 2) forced increase in outage duration due to non-availability of spare bush; 3) machining challenges in removing the bush from the casting block 4) Assembly Challenges of new bush in the casting block; 5) lead time for manufacturing new bush.
BRIEF DESCRIPTION OF THE INVENTION
In one embodiment, the present disclosure provides a valve comprising a frame; a main bush mounted inside of the frame; a spindle assembled inside the main bush for opening and closing the valve; and an inner bush assembly comprising at least one bush between the main bush and the spindle.
In another embodiment, the present disclosure provides a valve comprising a frame, a main bush mounted inside the frame, a spindle assembled inside the main bush for opening and closing the valve and an inner bush assembly between the main bush and

the spindle, wherein the inner bush assembly comprises a first bush assembled inside the main bush on an upper part thereof, a second bush is assembled under the first bush, and at least one seal ring disposed between the first bush and the second bush, a third bush assembled on a bottom part of the main bush, and a plate assembled above the first bush and a top of the main bush.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
Fig. 1 is a sectional view of a steam valve, in accordance with an embodiment of the present disclosure;
Fig. 2 is a sectional view of a steam valve, in accordance with another embodiment of the present disclosure;
Fig. 3 is a part of sectional view of a steam valve, in accordance with an embodiment of the present disclosure;
Fig. 4 is an enlarged sectional view of seal rings, in accordance with an embodiment of the present disclosure;
Fig. 5 is a perspective view of an inner ring, in accordance with an embodiment of the present disclosure;
Fig. 6 is a perspective view of an outer ring, in accordance with an embodiment of the present disclosure;
Fig. 7 is an exploded sectional view of a seal ring, in accordance with an embodiment of the present disclosure; and

Fig. 8 is a top view of a steam valve, in accordance with an embodiment of the present disclosure.
DETAILED DESCRIPTION
Embodiments of the present disclosure will be described herein below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the disclosure in unnecessary detail.
Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terms "first," "second," and the like, as used herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Also, the terms "a" and "an" do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced items. The terms such as "front," "back," "bottom," and/or "top," unless otherwise noted, are merely used for convenience of description, and are not limited to any one position or spatial orientation. The term "or" is meant to be inclusive and mean either or all of the listed items. The use of "including," "comprising," or "having" and variations thereof herein are meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The terms "connected" and "coupled" are not restricted to physical or mechanical connections or couplings, and can include electrical connections or couplings, whether direct or indirect.
Referring to FIG. 1 of the drawings, a steam valve 10 is illustrated. The steam valve 10 comprises a main bush 13, a frame 12 (or bonnet) mounted on an outside of the main bush 13, a spindle 11 assembled inside the main bush 13 for being moved up and down to open and close the steam valve 10, an inner bush assembly 20 assembled between the main bush 13 and the spindle 11. In one embodiment, the steam valve 10 is used for HPGV (high-pressure governor valve). In one embodiment, the inner bush

assembly 20 comprises at least one bush 21. The steam valve can avoid steam leakages and provide maintenance flexibility.
Referring to Fig. 2 of the drawings, the frame 12 is mounted outside an upper part
132 and middle part 133 of the main bush 13. The main bush 13 forms a space 15 at a
tail part 134 thereof. In one embodiment, the steam valve 10 comprises a valve casing
30 defining an inlet from the sides of the steam valve 10. The steam valve 10
comprises a valve head 14 assembled with the spindle 11 adapted to contact with a
valve seat 40. The valve seat 40 guides an outlet where the steam is discharged.
When the spindle 11 moves the valve head 14 up, the steam comes inside the steam
valve from the inlet, and gets out through the outlet. When the spindle 11 moves the
valve member 14 down to contact to a valve seat 40, the steam valve 10 is closed. In
one embodiment, the valve seat 40 may or may not belong to the steam valve 10.
Referring to FIG. 3 of the drawings, the inner bush assembly 20 comprises a first bush 21 mounted inside the main bush 13 on an upper part 132 thereof. The inner bush assembly 20 comprises a plate 24 mounted on top of the main bush 13 and the top of the first bush 21 by screw to retain the first bush 21 under the plate 24. The first bush 21 has a first end portion 211 under the plate 24, a second end portion 213 on a distal end from the plate 24, and a middle portion 212 between the first end portion and the second end portion of the first bush 21. The middle portion 212 of the first bush 21 is narrower compared to the first end portion 211 and the second end portion 213 of the first bush 21, so that there is a clearance between the middle portion 212 of the first bush 21 and the main bush 13, and there is also a clearance between the middle portion 212 of the first bush 21 and the spindle 11. The main bush is a single casting block. The proposed material for the main bush 13 is stainless steel. The proposed material for the first bush 21 is steel material.
The inner bush assembly 20 comprises a second bush 22 mounted on a middle part
133 of the main bush 13 under the first bush 21. The second bush 22 has a first end
portion 221, a second end portion 223, and a middle portion 222 between the first end

portion 221 and the second end portion 223 of the second bush 22. The middle portion 222 of the second bush 22 is narrower compared to the first end portion 221 and the second end portion 223 of the second bush 22, so that there is a clearance between the middle portion 222 of the second bush 22 and the main bush 13, and there is also a clearance between the middle portion 222 of the second bush 22 and the spindle 11. The proposed material for the second bush 22 is stainless steel.
Referring to Fig. 4 through Fig. 6 of the drawings, the inner bush assembly 20 comprises at least one seal ring 25 disposed between the first bush 21 and the second bush 22. The seal ring 25 comprises an outer ring 251 having a step 252 extending inwardly inside the outer ring 251, and an inner ring 253 disposed inside the outer ring 251 on the step 252 forming a cylindrical ring. As shown in Fig. 7, a sectional view of the seal ring 25 shown that inner ring 253 has an outer surface with fillets 254 on top side and bottom side thereof. The inner ring 253 create a smaller clearance between the inner ring 253 and the spindle 11, which means the clearance between the inner ring 253 and the spindle 11 is smaller compared to the clearance between the first bush or second bush and the spindle 11. The proposed material for the outer ring and inner ring is stainless steel.
Returning to Fig. 3 of the drawings, the main bush 13 extents outwardly forming a block 131 at a lower part 135 under the second bush, a third bush 23 is assembled on a bottom part of the main bush between the block 131 and the space 15. Between the block 131 and the second bush 22, at least one seal ring 25 is provided. The seal ring 25 is same with the seal ring 25 as explained above. The proposed material for the third bush 23 is stainless steel.
Referring to Fig. 8 of the drawings, a top view of the steam valve 10 is shown. The spindle 11 is in center of the circle. Outside the spindle 11, there is the plate 24 assembled above the inner bush assembly 20 and the main bush 13. Outside the plate 24 is the frame 12.

The present disclosure also provides a method of maintaining a steam valve comprising a main bush 13, a frame 12 mounted on an outside of the main bush 13, a spindle 11 mounted inside the main bush 13 for being moved up and down to open and close the steam valve 10. The main bush 13 is a single casting block. When the main bush 13 damages or increase clearance is observed between the main bush 13 and the spindle 11, the method of maintaining a steam valve described below can be adopted, wherein the main bush can be re-used.
The method comprises when a damage of the main bush or increased clearance between the main bush and the spindle is found, inserting an inner bush assembly 20 between the main bush 13 and the spindle 11, wherein the inner bush assembly comprises at least one bush. Inserting an inner bush assembly 20 between the main bush 13 and the spindle 11 comprises inserting a third bush inside a bottom of the main bush 13 below a block 131. Inserting an inner bush assembly 20 between the main bush and the spindle comprises inserting a second bush and a first bush inside the main bush from a top of the main bush. Inserting an inner bush assembly 20 between the main bush and the spindle comprises inserting at least one seal ring under the second bush and between the first bush and the second bush. Inserting an inner bush assembly 20 between the main bush 13 and the spindle 11 comprises mounting a plate above the main bush 13 and the first bush 21 for retaining the first bush 21 under the plate. Inserting at least one seal ring comprises inserting an outer ring with a step extends inwardly and inserting an inner ring above the step.
This modernization method gives the flexibility to restore the operational functionality of the main bush 13 without replacing it whenever there is a damage on the main bush or increase clearance is observed between the main bush and the spindle. Assembling three individual bushes and seal rings of this method is easy and reliable to restore the design clearance between the main bush and the spindle. Comparing with the main bush replacement solution, this method can greatly save

cost. A design integrity validation of the steam valve of the present disclosure are within allowable limits. The first bush will not hit with the plate.
While the disclosure has been illustrated and described in typical embodiments, it is not intended to be limited to the details shown, since various modifications and substitutions can be made without departing in any way from the spirit of the present disclosure. As such, further modifications and equivalents of the disclosure herein disclosed may occur to persons skilled in the art using no more than routine experimentation, and all such modifications and equivalents are believed to be within the spirit and scope of the disclosure as defined by the following claims.

WE CLAIM:
1. A valve, comprising:
a frame;
a main bush mounted inside of the frame;
a spindle assembled inside the main bush for opening and closing the valve; and
an inner bush assembly comprising at least one bush mounted between the main bush and the spindle.
2. The valve as claimed in claim 1, wherein the inner bush assembly comprises a first bush assembled inside the main bush on an upper part thereof.
3. The valve as claimed in claim 2, wherein the inner bush assembly comprises a plate assembled above the first bush and a top of the main bush.
4. The valve as claimed in claim 2, wherein the first bush has a narrower middle portion compared to an end portion thereof.
5. The valve as claimed in claim 2, wherein the inner bush assembly comprises a second bush assembled under the first bush.
6. The valve as claimed in claim 5, wherein the second bush has a narrower middle portion compared to an end portion thereof.
7. The valve as claimed in claim 5, wherein the inner bush assembly comprises at least one seal ring disposed between the first bush and the second bush.
8. The valve as claimed in claim 5, wherein the inner bush assembly comprises at least one seal ring disposed under the second bush.
9. The valve as claimed in claim 7, wherein the at least one seal ring comprises an outer seal ring with a step extending inwardly, and an inner seal ring disposed above the step of the outer seal ring.

10. The valve as claimed in claim 9, wherein the inner seal ring has an outer surface with a fillet.
11. The valve as claimed in claim 5, wherein a clearance between the at least one seal ring and the spindle is smaller compared to a clearance between the first bush and the spindle.
12. The valve as claimed in claim 1, wherein the inner bush assembly comprises a third bush assembled on a bottom part of the main bush.
13. A valve, comprising:
a frame;
a main bush mounted inside of the frame;
a spindle mounted inside the main bush for opening and closing the valve; and
an inner bush assembly mounted between the main bush and the spindle,
wherein the inner bush assembly comprises a first bush assembled inside the main bush on an upper part thereof, a second bush is assembled under the first bush, and at least one seal ring disposed between the first bush and the second bush, a third bush assembled on a bottom part of the main bush, and a plate assembled above the first bush and a top of the main bush.
14. The valve as claimed in claim 13, wherein the at least one seal ring comprises an outer seal ring with a step extending inwardly, and an inner seal ring disposed above the step of the outer seal ring.
15. The valve as claimed in claim 14, wherein a clearance between the at least one seal ring and the spindle is smaller compared to a clearance between the first bush and the spindle.
16. The valve as claimed in claim 13, wherein the first bush has a narrower middle portion compared to an end portion thereof.

17. The valve as claimed in claim 13, wherein the second bush has a narrower middle portion compared to an end portion thereof.
18. The valve as claimed in claim 13, wherein the inner bush assembly further comprises the at least one seal ring disposed under the second bush.
19. The valve as claimed in claim 18, wherein the at least one seal ring comprises an outer seal ring with a step extending inwardly, and an inner seal ring disposed above the step of the outer seal ring.
20. The valve as claimed in claim 19, wherein the inner seal ring has an outer surface with a fillet.