STEAM TURBINE INNER CASING COMPONENT AND REPAIR METHOD THEREFOR

Abstract

Embodiments of the present invention relate to an inner casing component configured to form part of a steam flow path of a last stage of an axial flow steam turbine, the steam turbine inner casing component having a base made of nodular cast iron and a coating, on the base, in a region exposed to the steam flow path, consisting of manganese austenitic steel.

Claims

1. An inner casing component configured to form part of a steam flow path of a last stage of an axial flow steam turbine, the steam turbine inner casing component comprising: a base made of nodular cast iron; and a coating, on the base, in a region exposed to the steam flow path, comprising manganese austenitic steel.

2. The inner casing component of claim 1, wherein the coating is comprised of a material defined by the code EN 1.4370.

3. The casing component of claim 1, wherein the last stage comprises a stationary vane row and a downstream rotating blade row, and wherein the coating is located in a region radially between the rotating blade row and the base.

4. A method for manufacturing an inner casing component having a base configured to form part of a steam flow path of a last stage of an axial flow low pressure steam turbine, the method comprising the step of: applying a coating of manganese austenitic steel to the base in a region exposed to the steam flow path.

5. The method of claim 4, wherein the last stage comprises a stationary vane row and a downstream rotating blade row, further comprising the step of applying the coating to the inner casing component in a location radially between the rotating blade row and the base.

6. The method of claim 4, wherein the coating is applied by welding.

7. A method for repairing erosion damage of an inner casing component configured to form part of a steam flow path of a last stage of an axial flow low pressure steam turbine, the method comprising the step of: applying a coating of manganese austenitic steel to the base in a region exposed to the steam flow path during operation of the steam turbine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] By way of example, embodiments of the present disclosure are described more fully hereinafter with reference to the accompanying drawing, in which:

[0017] FIG. 1 is a sectional view of a portion of a steam turbine to which an exemplary embodiment of the disclosure may be applied; and

[0018] FIG. 2 is an expanded view of a section of FIG. 1 showing a coating of an exemplary embodiment.

DETAILED DESCRIPTION

[0019] Exemplary embodiments of the present disclosure are now described with references to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth to provide a thorough understanding of the disclosure. However, the present disclosure may be practiced without these specific details, and is not limited to the exemplary embodiments disclosed herein.

[0020] FIG. 1 shows a section of an axial flow steam turbine to which exemplary embodiments may be applied. Shown is an inner casing component 10, a steam flow path 22 and a last stage 20 comprising a stationary vane row 16 and a downstream rotating blade row 18.

[0021] The inner casing component 10 forms a radial outer limit of the axial steam flow path 22, thereby in part defining the axial steam flow path 22. The inner casing component 10 may additionally provide a carrier means for carrying one or more stationary vane rows 16. As shown in FIG. 1, the inner casing component 10 may form only a portion of the inner casing of the steam turbine. That is, the inner casing component 10 is one component of several components. Alternatively, the inner casing component 10 may define the inner casing of the steam turbine.

[0022] As shown in FIG. 1, contained within the axial steam flow path 22 are stationary vane rows 16 that are each followed downstream, that is an axial direction corresponding to the nominal flow direction or working fluid through the flow path 22, by rotating blade rows 18. The last vane row 16/blade row 18 combination contained within the flow path 22 defines the last stage 20 of the turbine.

[0023] In an exemplary embodiment shown in FIG. 2, the inner casing component comprises a base 12 made of nodular cast iron and a coating 14 that is located the base 12 in a region exposed to the steam flow path 22. The coating 14 consists of manganese austenitic steel, which, in an exemplary embodiment, is defined by the code EN 1.4370.

[0024] In an exemplary embodiment the coating 14 is located in a region radially between the rotating blade row 18 and the base 12, wherein the radial direction is defined at the direction perpendicular to the rotational axis of the rotating blade row 18.

[0025] Another exemplary embodiment relates to a method for manufacturing a steam turbine inner casing component 10 as shown in FIG. 2. The exemplary method involves applying a coating 14 of manganese austenitic steel to the base 12 in a region exposed to the steam flow path 22 In an embodiment, the region is a location radially between the rotating blade row 18 and the base 12.

[0026] In an exemplary embodiment, the application is by my means of welding.

[0027] In further exemplary embodiment, the method is a method for repairing erosion damage of the base 12.

[0028] Although the disclosure has been herein shown and described in what is conceived to be the most practical exemplary embodiments, it will be appreciated that the present disclosure can be embodied in other specific.

[0029] For example, although one work hardening manganese austenitic steel has been described, the exemplary manganese austenitic steel may be substituted for other cold work hardening stainless steels adapted for the steam turbine application.

[0030] The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restricted. The scope of the disclosure is indicated by the appended claims rather that the foregoing description and all changes that come within the meaning and range and equivalences thereof are intended to be embraced therein.