Patent Application
20150198058
The subject matter disclosed herein relates to the art of steam turbomachines and, more particularly, to a steam turbomachine valve having a floating seal assembly.
Steam turbomachine systems generally include multiple turbine sections each of which extracts work from a flow of steam. The multiple turbine sections may include a high pressure (HP) steam turbine portion, an intermediate pressure (IP) steam turbine portion, and a low pressure (LP) steam turbine portion. One or more valves control the flow of steam passing from one of the turbine sections to others of the turbine sections and, in some cases, to a heat recovery steam generator (HRSG). Each of the one or more valves includes a valve body that supports a valve member. The position of the valve member is selectively controlled to block passage of the steam flow or allow the steam flow to pass. The valve may include a seal between the valve member and an inner wall of the valve body. The seal prevents steam leakage through a gap that exists between the valve member and the valve body.
According to one aspect of an exemplary embodiment, a steam turbomachine valve includes a valve body having an inlet portion, an outlet portion, and an interior portion. The interior portion includes an inner wall. A valve member is moveably disposed within the interior portion of the valve body. The valve member includes an outer surface that is spaced from the inner wall by a gap. A floating seal is mounted to the inner wall. The floating seal spans the gap and contacts the outer surface of the valve member.
According to another aspect of an exemplary embodiment, a steam turbomachine includes a high pressure (HP) turbine portion, an intermediate pressure (IP) turbine portion operatively connected to the HP turbine portion, a low pressure (LP) turbine portion operatively connected to at least one of the HP turbine portion and the IP turbine portion, and a steam valve fluidically connected to at least one of the HP turbine portion, IP turbine portion, and LP turbine portion. The steam valve includes a valve body having an inlet portion fluidically connected to the one of the HP turbine portion, IP turbine portion, and LP turbine portion, an outlet portion, and an interior portion. The interior portion includes an inner wall. A valve member is moveably disposed within the interior portion of the valve body. The valve member includes an outer surface that is spaced from the inner wall by a gap. A floating seal is mounted to the inner wall. The floating seal spans the gap and contacts the outer surface of the valve member.
According to yet another aspect of an exemplary embodiment, a steam turbomachine system includes a high pressure (HP) turbine portion, an intermediate pressure (IP) turbine portion operatively connected to the HP turbine portion, a low pressure (LP) turbine portion operatively connected to at least one of the HP turbine portion and the IP turbine portion, and one of a heat recovery steam generator (HRSG) and a boiler operatively connected to each of the HP turbine portion, IP turbine portion, and LP turbine portion, and a steam valve fluidically connected to at least one of the HP turbine portion, IP turbine portion, and LP turbine portion. The steam valve includes a valve body having an inlet portion fluidically connected to the one of the HRSG and the boiler, an outlet portion fluidically connected to the one of the HP turbine portion, IP turbine portion, and LP turbine portion, and an interior portion. The interior portion includes an inner wall. A valve member is moveably disposed within the interior portion of the valve body. The valve member includes an outer surface that is spaced from the inner wall by a gap. A floating seal is mounted to the inner wall. The floating seal spans the gap and contacts the outer surface of the valve member.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
A steam turbomachine system, in accordance with an exemplary embodiment, is indicated generally at 2, in
HP turbine portion 4 receives steam through a HP inlet 14 and passes steam to a HP portion (not separately labeled) of HRSG 10 through a HP outlet 16. IP turbine portion 6 is fluidically connected to an IP portion (also not separately labeled) of HRSG 10 through an IP inlet 17 and an IP outlet 18. LP turbine portion 8 is fluidically connected to a LP portion (not separately labeled) of HRSG 10 through a LP inlet 20 and a LP outlet 22. LP turbine portion 8 is also shown mechanically linked to a mechanical load 24 such as a generator, a pump or the like.
In accordance with an exemplary embodiment, a steam valve 30 is fluidically connected to IP inlet 17. Of course, it should be understood that additional valves (not shown) may be connected between steam turbomachine system 2 and HRSG 10. Also, a valve may be provided on HP inlet 14. As shown in
A first valve member 58 is moveably arranged within balance chamber 50. First valve member 58 may take the form of a control valve disk or an intercept valve disk and is operatively connected to a first valve stem 60. First valve stem 60 is connected to an actuator (not shown) which may be arranged on an upper portion (not separately labeled) of steam valve 30. The actuator controls the opening and closing of the first valve member 58 through the first valve stem 60 to control an amount of steam flow through steam valve 30.
First valve member 58 includes a first inner surface section 62, an opposing, second inner surface section 63 and an outer surface 65. First valve member 58 is formed from a nickel-chromium based superalloy such as Inoco® and is shiftable between a first or closed position and a second or open position. In the closed position, first valve member 58 rests upon a valve seat 68 formed in first interior portion 46 at inlet portion 42. In the open position, steam may freely flow from inlet portion 42 to outlet portion 44.
A second valve member 74, shown in the form of a stop valve, is arranged within an area (not separately labeled) bounded by second inner surface section 63 at valve seat 68. Second valve member 74 is operatively connected to a second valve stem 76 and is selectively closed to stop all steam flow through steam valve 30 in the event first valve member 58 fails to operate. Steam valve 30 is also shown to include a strainer 78 disposed about balance chamber 50. Steam inside balance chamber 50 is selectively evacuated to achieve a lower pressure differential between upstream valve member 58 and 74 and downstream outlet portion 44. The evacuation of steam enables first and second valve members 58 and 74 to be shifted to the open position with lower hydraulic actuator forces on respective ones of first and second valve stems 60 and 76. To further facilitate opening and closing of steam valve 30, a clearance or gap 84 (
Gap 84 is sized to facilitate operation of first valve member 58 while at the same time limiting steam leakage that might replace the evacuated steam. It is desirable to maintain gap 84 at a predetermined dimension over an operational life of steam valve 30. Accordingly, it is desirable, as will be detailed below, to limit oxidation growth on interfacing components to ensure an uncompromised operation of steam valve 30.
In further accordance with an exemplary embodiment illustrated in
In the exemplary embodiment shown, seal members 106 are arranged between a first seal support 116 and a second seal support 118. First seal support 116 is constrained within a first recess 120 formed in second inner wall 54. Likewise, second seal support 118 is constrained within a second recess 122 formed in second inner wall 54. Seal members 106 are arranged within a third recess 125 arranged between first and second recesses 120 and 122. Constraining first and second seal supports 116 and 118 within recesses 120 and 122 reduces clearance problems associated with oxidation growth. That is, recesses 120 and 122 constrain seal support displacement that might otherwise occur as a result of oxidation growth. More specifically, by locating first and second seal supports 116 and 118 within recesses 120 and 122, oxidation growth, which may occur on surfaces formed from 12 Chrome during operation, would have little effect on clearances between first and second seal supports 116 and 118 and seal members 106. In this manner, gap 84 is maintained at a desired dimension to, facilitate the “floating” nature of seal members 106 which is further described below.
First seal support 116 is secured to second inner wall 54 by a first plurality of mechanical fasteners 128. Similarly, second seal support 118 is secured to second inner wall 54 by a second plurality of mechanical fasteners 130. First and second seal supports 116 and 118 take the form of first and second split rings 134 and 136. A gap 140 exists between first split ring 134 and seal members 106. Gap 140 accommodates thermal and/or oxidation growth effects to enable seal assembly 100 to “float” or move within recess 125. In accordance with an aspect of the exemplary embodiment, first and second split rings 134 and 136 are formed from nickel-chromium based superalloy such as Inoco®. The use of nickel-chromium based superalloys enables seal assembly 100 to accommodate differential thermal expansions of balance chamber 50 and first valve member 58, while maintaining a radial clearance between seal assembly 100 and first valve member 58 through the operating cycle. Further, by mounting seal assembly 100 on second inner wall 54, balance chamber 50 may be formed by a material other than a nickel-chromium superalloy, such as a high alloy stainless steel including a chromium content of between about 10% and 16% such as Type 410 stainless Steel, Type 416 Stainless steel, Cost E, Cost B and/or 12 chrome. Forming balance chamber 50 from a material other than the nickel-based superalloy will greatly reduce production and maintenance costs of steam valve 30. Further, the use of the nickel-chromium based superalloy to form first valve member 58 and seal assembly 100 enables steam valve 30 to accommodate higher temperature steam flows. Specifically, nickel-chromium based superalloy to nickel-chromium based superalloy contact between seal assembly 100 and first valve member 58 ensures that clearances between outer surface 65 and second inner wall 54 remain substantially stable at all operational temperatures and pressures and further enables steam valve 30 to accommodate steam temperatures of 1150° F. (621.1° C.) or more.
First valve member 58, which is formed from a nickel-chromium based superalloy, expands at a higher rate than the balance chamber 50, which is formed from a high alloy stainless steel. The lower expansion rate of balance chamber 50 constrains the expansion of seal assembly 100, which might otherwise reduce gap 84. In accordance with an aspect of the exemplary embodiment, seal assembly 100 “floats” to account for the difference in rates of thermal expansion between first valve member 58 and balance chamber 50. The “floating” nature of seal assembly 100 maintains gap 84 at a desired dimension during an operational temperature range of steam valve 30. In addition, a gap 150 may exist between seal assembly 100 and balance chamber 50. Gap 150 may accommodate expansions of seal assembly 100.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
