Rotary kinetic fluid motors or pumps – Including heat insulation or exchange means – Working fluid on at least one side of heat exchange wall
Reexamination Certificate
1999-10-28
2001-01-09
Ryznic, John E. (Department: 3745)
Rotary kinetic fluid motors or pumps
Including heat insulation or exchange means
Working fluid on at least one side of heat exchange wall
C415S110000, C415S219100
Reexamination Certificate
active
06171053
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a device for thermally insulating casing parts of a steam turbine, in particular between an inner casing and an outer casing of a steam turbine having a spiral inflow.
Published, Non-Prosecuted German Patent Application DE 36 17 537 A1, for example, discloses an inflow casing of a steam turbine having a spiral inflow. In this case, between two casing parts of the steam turbine, which are supported against one another or rest on one another, in particular in the region of a torque support or a supporting bearing of an inner casing in the outer casing, large forces of, for example, about 1000 to 2000 kN and large temperature differences between the outer casing and the inner casing normally occur. Thus a high torque is produced on the respective support or bearing lug on account of the high pressure of, for example, 60 bar of the steam flowing into the steam turbine. The force which is thus produced on the respective support may be about 150 tons at this steam pressure.
Specified in Published, Prosecuted German Patent Application No. 1 055 549 is a shim which is disposed in a region of a dividing flange of a turbine outer casing between the turbine outer casing and a supporting lug of the turbine inner casing, the supporting lug resting on the turbine outer casing. In this case, the shim is a pressure plate that has holes that limit supporting cross sections. The intended purpose of the pressure plate is to expressly prevent inadmissible stresses from occurring in the flange of the outer casing if play present in the cold state between the supporting lug of the inner casing and the flange of the outer casing is bridged as a result of pronounced thermal expansions.
This is achieved by holes in the pressure plate which ensure plastic deformation of the pressure plate and thus a reduction in the input of stress into the flange of the outer casing.
A steam turbine having a spiral inflow is specified in each case in Swiss Patents CH 665 450 A5 and CH 666 937 A5. In the region of the respective flanges of the outer casing, unspecified components are disposed between the outer casing and the inner casing.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a device for thermally insulating a steam turbine casing which overcomes the above-mentioned disadvantages of the prior art devices of this general type, in which casing parts of the steam turbine are thermally insulated from each other including spiral inflow casing parts.
With the foregoing and other objects in view there is provided, in accordance with the invention, a device for thermally insulating casing parts of a steam turbine, the casing parts have supporting bearings facing one another and defining a bearing region there-between, the device includes a shim element to be inserted into the bearing region of the supporting bearings of the casing parts, the shim element has bearing surfaces facing the supporting bearings and has a reduced cross section between the bearing surfaces, the shim element serving to transmit forces between the casing parts when steam is admitted in the steam turbine.
Provided in this case is a shim element or an intermediate element of reduced cross section, which can be inserted into a bearing region between two supporting bearings or supporting surfaces, facing one another, of the casing parts.
The shim element serves to transmit force between the casing parts of the steam turbine, at least if steam is admitted to the steam turbine. It is likewise possible for the shim element to be additionally or alternatively made of a material that has a higher strength relative to the respective material of the casing parts at a temperature that is increased relative to room temperature. This is especially important in particular in steam turbines which are subjected to high pressures and temperatures above 500° C., in particular above 550 to 650° C.
The invention in this case is based on the idea that, on the one hand, a material reduction of the shim element down to the value of the admissible compressive stress or surface tension is possible within a shim element also serving to orient casing parts relative to one another, since the admissible compressive stress within the shim element is several times higher than the admissible surface pressure from the shim element to the casing parts. On the other hand, such a deliberate material reduction of the shim element appropriately configured with regard to the dimensions and the material brings about a reduction in the heat quantity flowing through the shim element, since this heat quantity is determined by the remaining cross section within the shim element. Thus insulation is produced as it were, in which case no novel materials have to be used for the casing parts of the steam turbine. At a high temperature of the steam flowing into the steam turbine, for example, 580° C., a large heat quantity could be transferred from the inner casing via the respective support into the outer casing. If the inner casing is made of a heat resistant cast steel and the outer casing is made of a ductile iron having a comparatively low admissible thermal strength of a maximum of 350° C., an inadmissibly high heat transfer from the inner casing to the outer casing is prevented by the shim element. The temperature differences between the inner casing and the outer casing may be about 200 to 300° K.
To reduce the cross section between the two bearing surfaces, the shim element preferably has cross-section-reducing apertures and/or cavities. Such cross-section-reducing apertures may be made in the shim element subsequently, for example by drilling, milling, laser-beam treatment and further suitable processes. In this case, the shim element may be of one-piece or multi-piece construction. In a multi-piece construction, the apertures or cavities may be formed by recesses, slots, hollows or the like in parts of the shim element to be joined to one another. In such a shim element consisting of a plurality of parts, each part preferably has recesses, in particular grooves, which, when the parts are joined together, form passages separated from one another by webs. Steam or a similar cooling medium for cooling the shim element may flow through such passages.
In an advantageous refinement, the shim element, which is expediently parallelepiped-shaped, has a number of through-holes disposed next to one another. These through-holes advantageously run parallel to the opposite bearing surfaces of the shim element and preferably transversely to its longitudinal direction. Flow may therefore occur through the through-holes in order to cool the shim element, e.g. by use of an additional cooling medium or solely by convection. This is also ensured when the through-holes run in the longitudinal direction of the shim element. This is expedient, for example, when flow through the shim element in the longitudinal direction is desired or necessary on account of the position or fitting position of the shim element.
The shim element, in particular a drilled shim element, is especially suitable for use in a spiral casing having two torque supports which are disposed opposite one another and are expediently formed from supporting lugs, facing one another, of the outer casing and the inner casing. In this case, the supporting lugs are integrally formed on the inside of the outer casing and respectively on the outside of the inner casing. The shim element may also be advantageously used as a feather key or as a shim for orienting the casing parts relative to one another.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a device for thermally insulating a steam turbine casing, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within
Greenberg Laurence A.
Lerner Herbert L.
Ryznic John E.
Siemens Aktiengesellschaft
Stemer Werner H.
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