Rotary kinetic fluid motors or pumps – Working fluid bypass
Reexamination Certificate
1999-06-09
2001-03-20
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
Working fluid bypass
C415S169200, C415S169400
Reexamination Certificate
active
06203271
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a high-pressure or intermediate-pressure turbine as an individual machine or a combined high-pressure/intermediate-pressure turbine, having an inner casing, consisting of bottom part and top part, and an outer casing, and in particular to a connection between these parts of the inner casing by means of shrink rings as well as to bleeding for diverting steam from the turbine into a pipeline to an apparatus disposed outside the turbine.
BACKGROUND OF THE INVENTION
Turbines whose bottom part and top part of the inner casing are held together by means of the shrink-ring technique are known. This technique has proved successful in turbines having higher pressures and is in particular considered to be cost-effective. The shrink rings are used in those turbines whose taper angles (of the blading duct) are small, namely in high-pressure turbines, intermediate-pressure turbines or combined high-pressure/intermediate-pressure turbines accommodated in a common casing. (In contrast to turbines having higher pressures, flanged or screwed connections are more likely to be used in low-pressure turbines.)
A plurality of such shrink rings are typically arranged at regular intervals. The invention described here, then, relates in particular to the shrink-ring technique in the region of a bleed point of the turbine.
To assist the operation of apparatuses such as feed heaters or a boiler, steam is bled from the turbine and is directed via a pipeline out of the turbine casing to the apparatuses mentioned. To this end, a bleed slot, which leads through the inner casing into the space between inner and outer casings, is arranged at the outer contour of the blade duct of the turbine. The steam flows from the blade duct of the turbine through the bleed slot and is collected in a sealed-off annular space, which is formed above the bleed slot by a cast bleed ring in the form of a collar on the outer surface of the inner casing. This bleed ring is fastened to the inner casing in a sealing manner. Arranged on the ring is a pipe connection which leads through the outer casing to the outside and is connected to a pipeline, which leads to a feed heater, boiler or other thermal apparatus.
The shrink rings and the bleed ring are each fixed to the inner casing by a plurality of bolts and screws, so that the rings cannot be displaced relative to the casing.
A disadvantage with this prior art is that a plurality of components and small parts, which are individually produced and fitted, are required for the bleeding and for holding together the inner casing by means of shrink rings in the region of the bleed point. In particular, the manufacture of a cast bleed ring requires several production steps. Finally, for the many components and small parts required, this means a long fabrication and assembly time and resulting high costs.
SUMMARY OF THE INVENTION
Accordingly, one object of the invention, in view of these disadvantages, is to provide a novel device in the region of the bleed point of a high-pressure or intermediate-pressure turbine for holding together the top part and bottom part of the inner casing of the turbine and for collecting the bleed steam. The inner, as well as the outer, casing of a steam turbine is typically divided along a horizontal plane at the level of the rotor axis into a top and bottom part whereas the top part refers to a top half-shell encompassing the upper 180° and the bottom or lower part refers to a lower half-shell encompassing the lower 180° of the respective casing. The top and bottom parts or half-shells of the casings cooperate with one another by means of the separating plane which lies horizontally and passes through the rotor axis. This device requiring a reduced number of components and its production and fitting being as simple as possible and thus cost-effective.
This object is achieved by a steam turbine according to the preamble of claim
1
, which steam turbine, in the region of the bleed point, has a shrink ring, which is arranged above the bleed slot of the turbine and has at the location of the bleed slot a half-open cavity facing the inner casing, the cavity together with the outer surface of the inner casing forming an annular space, in which bleed steam flowing through the bleed slot collects. On both sides of the cavity, the shrink ring is designed to be flat, so that its contours are adapted to those of the inner casing. The shrink ring therefore combines the function of both the shrink ring and the bleed ring in a single part and is designated here as combined shrink ring/bleed ring. Furthermore, the shrink ring has an opening for an extraction connection, which leads out in a sealing manner through the outer casing to a pipeline.
The advantage of the combined shrink ring according to the invention lies in the fact that it consists of a single component, which contains both functions, that of holding together the casing parts of the turbine and that of forming a collecting space for bleed steam from the turbine. Instead of a plurality of parts as in the prior art described at the beginning, only a single part is to be produced and fitted here for these two functions.
The combined shrink ring/bleed ring according to the invention is turned in one operation by means of a forging bush. Since only one large part has to be produced instead of a plurality of parts, the production time is significantly reduced. In particular, cast parts, which require a plurality of cost-intensive working steps, are no longer necessary. The assembly time is likewise reduced, since only one part has to be fitted instead of a plurality of parts. Finally, the number of small parts such as axial fixings is considerably reduced, which saves further time during fitting.
REFERENCES:
patent: 2323904 (1977-04-01), None
patent: 600025 (1946-04-01), None
Graf Peter
Stojkovic′ Tihomir
Asea Brown Boveri AG
Burns Doane Swecker & Mathis L.L.P.
Look Edward K.
McAleenan James M
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