The present invention relates to a seal arrangement for sealing an annular gap between a high-pressure steam space and an adjacent low-pressure steam space, which gap is defined between two turbine casings, with each casing split into two casing halves.
The seal arrangement has a seal element which is formed in a segmented and annular manner. In its intended state, the seal extends between the two turbine casings and engages in an annular receiving groove by means of at least one of its radial end regions. Furthermore, the invention relates to the use of such a seal arrangement for sealing an annular gap between a high-pressure steam space and an adjacent low-pressure steam space, to a turbine having at least two turbine casings, in each case split into two casing halves, which between them form a high-pressure steam space and a low-pressure steam space, wherein the steam spaces are separated from one another by an annular gap defined between the turbine casings, and to a method for repairing a worn seal arrangement of the abovementioned type.
In steam turbines, normally annular seal elements are used to seal annular gaps between two mutually adjacent steam spaces. The gaps are defined between two turbine casings in each case split into two casing halves. The seal elements normally have an I-shaped cross section and are split into two segments to enable them to be mounted. In the intended arranged state, the mutually opposite radial end regions of the annular seal elements engage in annular receiving grooves formed opposite one another on the turbine casings or on their respective casing halves. When the turbine is in operation, the seal elements and in particular the annular receiving grooves are subjected to wear phenomena due to steam erosion and due to mechanical loads. Repair of the seal elements is not economically possible. As a result, these elements have to be replaced. Reconditioning the annular receiving grooves involves considerable effort, with associated high costs. This effort is difficult to reduce since it is impossible to determine in advance, with any precision, the point at which repairs are going to be necessary. One known way of counteracting the wear due to erosion consists in selecting an appropriate material. However, this also involves very high costs.
Proceeding from this prior art, it is an object of the present invention to provide a seal arrangement of the type mentioned in the introduction, which has an alternative construction, is cost-effective to produce and offers problem-free maintenance.
In order to achieve this object, the present invention provides a seal arrangement of the type mentioned in the introduction, which is characterized in that the seal arrangement has at least one segmented ring whose first circumferential surface is, in the intended state, releasably attached to one of the turbine casings in the region of the annular gap, and whose opposite second circumferential surface is provided either with the annular receiving groove or, in a one-piece form, with the radially projecting annular seal element. The principal advantage of the seal arrangement according to the invention lies in the fact that, during a major overhaul, for example after 100,000 operating hours, it is possible to entirely replace not only the seal element but also the at least one segmented ring. Accordingly, it is possible to dispense with inspection, assessment of the wear and onerous reconditioning work. Moreover, a targeted, plannable and cost-effective replacement solution is possible also for the second overhaul interval, which is beneficial for planning reliability with respect to the expenditure to be incurred and also with respect to the downtime.
According to a first variant of the present invention, the seal arrangement comprises a first ring whose first circumferential surface is, in the intended state, releasably attached to one of the turbine casings in the region of the annular gap, and whose opposite second circumferential surface is provided with the annular receiving groove, and a second ring whose first circumferential surface is, in the intended state, releasably attached, opposite the first ring, to the other turbine casing in the region of the annular gap, and whose opposite second circumferential surface is provided with an annular receiving groove, wherein the seal element is formed as a separate component and, in the intended state, engages in the annular receiving grooves of both rings. In other words, in this variant the seal arrangement comprises a three-part construction with two segmented rings, which on one hand serve for attaching to the turbine casings and on the other hand define the annular receiving grooves, and a seal element formed as a separate component which, in the intended arranged state, engages in both receiving grooves.
According to a second variant of the present invention, the seal arrangement comprises a first ring whose first circumferential surface is, in the intended state, releasably attached to one of the turbine casings in the region of the annular gap, and whose opposite second circumferential surface is provided with an annular receiving groove, and a second ring whose first circumferential surface is, in the intended state, releasably attached, opposite the first ring, to the other turbine casing in the region of the annular gap, and whose opposite second circumferential surface is formed with the radially projecting annular seal element, wherein the seal element formed in one piece with the second ring engages, in the intended state, in the annular receiving groove of the first ring. In this second variant, the seal arrangement thus comprises only two respectively segmented components, to wit a first ring with a one-piece radially projecting seal element, and a second ring that defines the annular receiving groove in which the seal element engages in the intended state.
Preferably, the ring or rings is/are made of steel, as is the seal element. By virtue of the fact that, in the case of an overhaul, the respective components are simply replaced with new components, it is possible to use cost-effective materials such as P265GH or 16Mo3, resulting in a cost-effective construction of the seal arrangement according to the invention.
According to one embodiment of the present invention, the seal element has, in the region of its free end, a rounded and widened end section which, in the intended state, engages in the associated annular receiving groove. The rounding ensures a good fit of the seal element in the associated annular receiving groove. If the seal element is a separate component, correspondingly formed end sections may then of course be provided at both free ends of the seal element.
According to one embodiment of the present invention, the end section is of substantially oval cross section. Particularly good results have been achieved with this shape.
In order to achieve the object stated in the introduction, the present invention also relates to the use of a seal arrangement according to the invention for sealing an annular gap between a high-pressure steam space and an adjacent low-pressure steam space of a turbine, which gap is defined between two turbine casings of the turbine in each case split into two casing halves.
Furthermore, in order to achieve the object stated in the introduction, the present invention provides a turbine having at least two turbine casings, in each case split into two casing halves, and between, the casings form a high-pressure steam space and a low-pressure steam space, wherein the steam spaces are separated from one another by an annular gap defined between the turbine casings, which gap is sealed by a seal arrangement according to the invention. The possible dividing of each casing into upper and lower parts is for mounting reasons. For example, a rotor is inserted in the lower pants and then the upper pants are mounted.
According to one embodiment of the present invention, the turbine is a low-pressure turbine.
Furthermore, the present invention provides a method for repairing a worn seal arrangement of a turbine according to the invention, in which the worn seal arrangement is replaced in its entirety with a new seal arrangement, in particular within the framework of a major overhaul of the turbine.
Further features and advantages of the present invention will become apparent from the following description of embodiments of the present invention with reference to the appended drawing, in which:
In the following, identical reference numbers relate to identical or similar components.
All rings and sealing elements of the above-described four variants are preferably each split centrally into two segments and are made of steel. The releasable attachment of the respective rings to the associated inner casings can be brought about by means of press-fitting, attachment screws or the like.
Although,
An essential advantage associated with the seal arrangements 15, 26, 43 and 50 according to the invention consists in the fact that, within the framework of an overhaul, their individual components may, depending on the selected variant, be partially or entirely replaced with new components, whereby inspection, assessment and repair of the seal arrangements can be partially or entirely dispensed with. Costs may thus be reduced. Furthermore, replacing components, in contrast to testing and repair of the latter, is beneficial for planning reliability with respect to expenditure and downtime.
Although the invention has been illustrated and described in more detail by means of the preferred exemplary embodiment, the invention is not restricted by the disclosed examples and other variations may be derived herefrom by a person skilled in the art without departing from the scope of protection of the invention.
Number | Date | Country | Kind |
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13189280.4 | Oct 2013 | EP | regional |
The present application claims priority of European Patent Application No. EP 13189280, filed Oct. 18, 2013, the contents of which are incorporated by reference herein.