JPS61234207A - Method for extracting turbine blade - Google Patents

Abstract

PURPOSE:To remove a blade without damage by forming a notch groove inside a projecting portion of a rotor disc from both the sides in the axial direction and extracting the blade from the rotor. CONSTITUTION:A notch groove 17 is formed inside the projecting portion 2 of a rotor disc 1 from both sides of the rotor disc 1 in its axial direction. And engagement between a groove formed on the projecting portion 2 of the rotor disc 1 and a projecting portion 4 of the stud 3' of a blade is disengaged, and the blade 3 is extracted. Then rigidity of a remainder 18 of the disc remaining outside of the groove 17 is largely reduced and connecting condition can be released, so the blade can be removed without damage.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a method for handling turbine blades.

[Technical background of the invention and its problems] Generally, in a turbine impeller for a steam turbine or the like, a circumferential groove is formed in a single stage or in multiple stages in the radial direction on the outer periphery of a rotor disk. A device is used in which the root (hereinafter referred to as the implanted portion) is engaged to restrict movement in the radial direction.

That is, FIG. 3 is an exploded partial view of the turbine impeller, and the outer periphery of the rotor disk 1 has multiple stages rIi2 extending on both the front and rear surfaces.
The implanted portion 3' of the blade 3 is fitted into the outer circumference of the rotor disk 1 in a hollow shape, and the protruding portion 4 formed on the opposing inner surface of the implanted portion 3' is formed. It is engaged with the groove 2 of the rotor disk 1.

Incidentally, in the groove 2 forming portion of the rotor disk 1, one or more notches 5 are formed on the circumference, extending in the radial direction and having a width approximately equal to the thickness of the implanted portion 3'. , the blade 3 is moved in the radial direction by inserting the implanted part 3' of the blade 3 in the radial direction from the notch 5, and then sliding it in the circumferential direction and coupling it to the outer periphery of the rotor disk 1. This is so that it is regulated υ1.

In this way, a predetermined number of blades 3 are brought into pressure contact in the circumferential direction and attached to the annular body. In the final step, the notch 5 is engaged with a stopper blade 7 having a groove 6 that matches the shape of the notch as shown in FIG.

Unlike the case of the blade 3, the engagement between the groove 6 of the stop blade 7 and the notch 5 of the turbine disk 1 is a simple fit, and the movement of the rotor disk 1 in the radial direction is not restricted. As shown in FIG. 5 or 6, the stopper blade 7 has a thickness of the rotor disk 1 on the joint surface of the stopper blade 7 and the adjacent blades 3a, 3b, or the adjacent blades 3c, 3d. A method in which a transverse bottle hole 8 is provided, a bottle 9 is press-fitted into the bottle 9, and a pin 11 is press-fitted by providing a bottle hole 10 that passes through the stopper blade 7 and the notch 5 that fits into the stopper blade 7. is taking.

On the other hand, in FIG. 3, a protrusion (hereinafter referred to as a tenon) 12 is provided at the tip of the blade 3, which is integrally carved out from the blade 3, and a surrounding ring (hereinafter referred to as a shroud) 13 is pressed through the tenon 12. As shown in Fig. 5, several blades are assembled into a ring-shaped body as one group.
It is divided and fixed into several groups in the circumferential direction so that it can withstand various excitation sources including steam power.

FIG. 7 is an enlarged view showing the joint part of the shroud 13 with the blade 3, and shows the tenon 12 connected to the flat caulked part 12'.
Shroud 13 by caulking until
is fixed to the blade 3.

The tenon 12 and the tenon caulking portion 12' resist steam force and high centrifugal force acting on the shroud 13.

If damage occurs to the top of such a turbine impeller, more specifically to the shroud 13 or tenon 12.12', or if damage occurs to the shrink-fit disk in a steam turbine using a shrink-fit disk, etc. In the case of the former, the damaged parts are repaired; in the latter case, the parts damaged when removed are repaired and then reinstalled into the newly installed shrink-fit disc. use.

In particular, regarding the latter shrink-fitting disk structure, an explanation will be given here in advance to make it easier to understand the content of the invention described later. Generally, in low-pressure rotors and the like of large steam turbines for power generation, long blades with a large average diameter are used in order to flow a large amount of steam. In order to solve manufacturing technical and economic problems with such a huge rotor, the disk into which the blades of each stage are implanted is manufactured separately from the shaft, and then the wheel is heated before being fitted onto the shaft. A so-called fired disc is used.

FIG. 8 is a schematic sectional view showing a steam turbine rotor having such a fired disk, and the blades 3 in each paragraph are constructed using known technology (for example, the 4th revised Mechanical Engineering Handbook published by the Japan Society of Mechanical Engineers).
(Refer to Edition 13, 3.7.3), it is embedded in disk 1. The disc 1 of each stage is fitted onto the shaft 14 by shrink fitting, and an axial key 15 is installed between the disc 1 and the shaft 14. In addition, shaft 1
A coupling 16 for connection with an adjacent rotor (not shown) is fitted at the four ends.

In a steam turbine rotor with a shrink-fitted disk having such a structure (hereinafter referred to as a "sintered rotor"), a crack as shown by the symbol C in FIGS. This may occur.

This is because during the process of increasing or decreasing the load on the turbine, the temperature change rate of the steam temperature and the metal temperature in the turbine are different, so the area around the keyway is repeatedly dry and wet, and the centrifugal force and firing surface Circumferential stress acts on the inner diameter of the disk due to pressure, which causes stress concentration near the full key, and corrosive factors such as chlorine ions and element III contained in trace amounts in the steam act. This occurs as stress corrosion cracking (SCC).

If the turbine continues to operate with such cracks generated, the cracks will gradually develop and grow, and at a certain point a rapid destruction phenomenon will occur. Therefore, it is necessary to remove cracks from the inner diameter portion of the disk before such a serious accident occurs.

Conventionally, the method for repairing a rotor when such a crack occurs is to remove the cracked disk from the shaft and replace it with a newly manufactured disk. When replacing this disk with a new one, the blades attached to the disk are not damaged, so reusing the disk without having to make a new one has recently been actively considered. Since this greatly contributes to the effective use of resources and the shortening of periodic inspection periods, it has become one of the important issues to be considered, especially as the power source composition ratio of long-term plants increases.

What is important when repairing such composite structures is:
In addition to clearly classifying parts that have been damaged by am and those that are not, the undamaged parts must be disassembled, cleaned, and stored with sufficient protection so that they can be reused.

The same applies to the reuse of turbine blades.

As mentioned above, in a shrink-fitted rotor that uses shrink-fitted disks, if the disk is damaged due to SCC, etc., the blades incorporated in the disk may be removed from the assembled state for reuse. It is necessary to work with great care so as not to damage the blades, but one
Approximately 0.00 blades are assembled in a ring shape, and it has already been subjected to various loads under high centrifugal force and steam, and the fit between the disk and the blades is different from the state before use. The blades are so strong that they cannot be easily removed, and special considerations and techniques are required to remove them without damaging the blades.

FIG. 10 is a diagram showing the state of connection between the turbine disk and the blade after long-term use. Due to the use of the long vflll, the protrusion 4 formed on the opposing inner surface of the blade embedded part 3' and the groove 2 of the rotor circle 111 are in a state of complete contact, and the protrusion 4
Scale 16 and the like are attached between and 12, and the mutual sliding conditions are worsened. In other words, the surface condition of the groove 2 of the turbine disk and the surface condition of the protrusion 4 of the implanted part 3- of the blade 3, that is, the surface roughness, were poor at the time of manufacture, and although it could be easily incorporated during the turbine manufacture. It is in a state where it is difficult to disassemble it. It is very difficult to remove the blades in such a state, and conventional blades are often damaged, so there is a problem that there is no point in taking the blades out for reuse.

[Object of the Invention] The present invention has been made in response to the conventional situation, and when the blades attached to the disc are used as they are, they can be easily removed without damaging the blades to be reused. The purpose of the present invention is to provide a method for extracting a turbine blade.

[Summary of the Invention] That is, the present invention provides a rotor disk in which a blade implant is fitted into a protrusion formed along the outer periphery of a rotor disk, and these blades are arranged in an annular manner around the outer periphery of the rotor disk. In a turbine blade extraction method for extracting the blade from an impeller,
A method for handling turbine blades, characterized in that cutout grooves are formed from both sides of the rotor disk in the axial direction on the inner side of the ridges of the rotor disk, and then the blades are extracted from the rotor disk. .

[Embodiment 1 of the invention Examples of the method of the present invention will be described below with reference to the drawings.

In the method of the present invention, first, from the shaft 14 to the turbine disk 1.
Take it out. Next, as shown in FIG. 1, the connection state between the blade 3 and the disk 1 is measured in the turbine disk thickness direction on the turbine disk 1 near the lowest protrusion 4 of the implanted portion 3' of the blade 3. A groove 17 is provided for relaxation.

This groove 17 can be provided by machining or by a gas cutting device or the like. Groove 17
The machining position is as close as possible to the joint between the turbine circle 5J1 and the blade 3 in order to obtain the effect of relaxing the joint state between the blade 3 and the circle 1i11f1, and the position where the blade is not damaged by machining (as shown by the fat dimensions in the figure). ) is desirable. Furthermore, the depth of the groove 17 must be sufficient to promote stress relaxation.

The depth of the groove 17, indicated by the 0 dimension in FIG. 1, is five times or more the minimum width of the groove 17. This dimensional ratio is intended to achieve the effect of sufficiently releasing strain in the stress field generated in a strongly connected state.

This strain release effect is shown in FIG. In FIG. 2, the horizontal axis shows the ratio d/b of groove depth and groove width, and the amount of release strain for the nine wheels. It can be seen that when d/b approaches 5, most of the strain accumulated inside the disk is released.

By releasing this strain, the coupling state between the turbine disk 1 and the blade 3 is relaxed, and the rigidity of the remaining disk portion 18 remaining outside the groove 17 is greatly reduced, so that the coupling condition can also be relaxed. .

Due to such relaxation of the coupling state, the turbine blades 4113
When handling it, it can be easily removed because there is less resistance on the turbine circle W1 side.゛Furthermore, since there is less resistance on the turbine disk 1 side, the blade 3 will not be damaged.
A sufficiently reliable blade 3 can be obtained for subsequent reuse.

[Effect of the Invention il1] As described above, according to the method of the present invention, the turbine blade can be removed from the turbine disk without damaging the turbine blade, so that the blade has sufficient reliability to be reused. can be provided.

Therefore, not only can the blades that are still fully usable be effectively used, but there is no need to make new blades, so it is possible to shorten periodic turbine inspections, downtime for repairs, etc., and the steam turbine can continue to operate. It is possible to improve the ratio and maintain economic efficiency.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing an embodiment of the method of the present invention, Fig. 2 is a graph illustrating the magnitude of release strain depending on groove width and groove depth, and Fig. 3 is a graph showing the effect of the present invention. An exploded partial view of the turbine impeller, Fig. 4 is a detailed drawing of the stopper blade, Fig. 5 is an assembly drawing of the impeller, and Fig. 6 is the C-Cl1 of Fig. 5! 7 is an enlarged view showing the joint between the shroud and the blade,
Fig. 8 is a longitudinal cross-sectional view showing the fired rotor, Fig. 9 is a longitudinal cross-sectional view showing the location where SCC occurs in the fired rotor, Fig. 10
The figure is an explanatory view showing how the blade and disk are connected after long-term use. 1・・・・・・・・・Rotor disk 3・・・・・・
...Blade 5 ...Notch 12 ...... Tenon 13 ...... Shroud 14...
・・・・・・・・・Shaft 15・・・・・・・・・・・・
・Crack due to SCC 1 16...
・・・・・・Coupling 17・・・・・・・・・・・・
・Notch groove applicant Toshiba Corporation Patent attorney Nori Chika (and 1 other person) 'm I figure m sheet distortion figure 6 figure 7 figure 8 figure 9

Claims (2)

[Claims] (1) Fitting the implanted part of the blade into the protruding part formed along the outer periphery of the rotor disk, and extracting the blade from the impeller formed by arranging these blades in a ring shape around the outer periphery of the rotor disk. The method for extracting a turbine blade includes forming cutout grooves from both sides of the rotor disk in the axial direction inside the protrusion of the rotor disk, and then extracting the blade from the rotor disk. How to remove the feathers. (2) The method for extracting a turbine blade according to claim 1, wherein the notch groove has a depth that is five times or more the width of the groove.