JPS61234203A - Repair of impeller - Google Patents

Abstract

PURPOSE:To improve workability by cutting down blades, in a condition where they are joined with a shroud, at their effective parts and subsequently welding their tip blocks shaped as initially designed. CONSTITUTION:In a condition where a shroud 15 is joined to the plural number of blades 1 by means of tenons 14, blades 1 are cut down at their effective parts 1a. Subsequently, welding tip blocks 25 shaped as initially designed are joined to the cut down parts through welding. This reduces quantity of welding and improves welding points, therefore, workability of repair can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention 1] The present invention relates to a method for repairing blades of a steam turbine.

[Technical Background of the Invention] Generally, in a low-pressure rotor of a large steam turbine for power generation, etc., blades having a large average diameter and a long length are used in order to flow a large amount of steam. In such a huge rotor, in order to solve manufacturing technology and economic problems, the wheel in which each stage of blades is implanted is manufactured separately from the shaft, and then the wheel is heated and then 1N-
A so-called fired wheel is used.

FIG. 10 is a schematic sectional view showing a steam turbine rotor having such a fired wheel.
) is embedded in wheel 2. The wheel 2 of each paragraph is attached to the shaft 3 by firing,
An axial key 4 is mounted between the wheel 2 and the shaft 3. Note that a coupling 5 for connection to an adjacent rotor (not shown) is fitted to the end of the shaft 3.

In a steam turbine rotor having a fired wheel with such a structure (hereinafter referred to as fired rotor), the 11th
A crack as shown by the symbol C in the figure and FIG. 12 may occur in the inner diameter portion of the wheel 2. This is because the temperature change rate between the steam temperature and the metal temperature in the turbine differs during the process of increasing or decreasing the load on the turbine, resulting in the area around the keyway becoming repeatedly dry and wet, and due to centrifugal force and shrink-fitting. Circumferential stress acts on the inner diameter of the wheel due to blood pressure, which causes a stress concentration phenomenon near the keyway.
Stress corrosion cracking (SC) occurs due to the action of corrosive factors such as chlorine ions and oxygen contained in trace amounts in steam.
C). 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 wheel before such a serious accident occurs.

Conventionally, the method of repairing a rotor when such a crack occurs is to remove the cracked wheel from the shaft,
The plan was to replace it with a newly manufactured wheel.

Even if the wheel is replaced in this way, it is not a complete solution, and there is still a possibility that SCC will reoccur after reuse for a period of time. However, in recent years, numerous technological advances have made it possible to manufacture extremely large materials, so it is possible to eliminate the root cause of this problem by replacing the wheel and shaft with a rotor that is manufactured as one unit (hereinafter referred to as a single weight shaft). It's now possible.

When replacing the shaft 3 and wheel 2 of a shrink-fitted rotor with an integrated axle, it is common to make new blades 1 as well, but S
It is clear that it is uneconomical to replace even the first blade for CC.

By the way, the relationship between the wheel and the blades is as follows.

Generally, in a turbine impeller for a steam turbine, etc., the roots of the blades (hereinafter referred to as implants) are connected to circumferential grooves formed in a single or multiple stages in the radial direction on the outer periphery of the rotor disk. In addition, a device is used that restricts movement in the radial direction.

FIG. 13 is an exploded partial view of the turbine impeller. On the outer periphery of the rotor disk 1, a plurality of stages extending on both front and rear surfaces are formed. On the outer periphery of the rotor disk 1, blades 3
The implanted part 3' is fitted in a hollow shape, and the implanted part 3'
The protrusion 4 formed on the opposing inner surface of the rotor disk 1
is engaged with the groove 2 of.

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'. After inserting the implanted part 3' of the blade 3 in the radial direction from the notch 5, move it in the circumferential direction m to remove the rotor disk 1.
By coupling to the outer periphery of the blade 3, movement of the blade 3 in the radial direction is restricted.

In this way, a predetermined number of blades 3 are pressed against each other in the circumferential direction and assembled into an annular body. In the final stage, the notch 5 has the following features as shown in FIG.
A stopper blade 7 having a grooved portion 6 that matches the shape of the notch.
is engaged.

The engagement between the groove 6 of the stopper blade 7 and the notch 5 of the turbine disk 1 is a simple fit, unlike the case of the blade 3, and the movement of the rotor disk 1 in the radial direction is not restricted. As shown in FIG. 15 or 16, the stopper blade 7 has a rotor circle 5181 on the joint surface of the implanted part of the stopper blade 7 and the adjacent blades 3a, 3b, or the adjacent blades 3c, 3d. A bottle hole 8 in the thickness direction is provided, and a pin 9 is press-fitted into it, and a bottle 11 is press-fitted into the stopper blade 7 and the notch 5 that fits into the stopper blade 7 by forming a bottle hole 10 that passes through them. It is done by this method.

When the stopper blade 9 is assembled in this way, movement of the blade in the circumferential and radial directions is restricted.

On the other hand, on the blade tip side, as shown in FIG. 15 (hereinafter referred to as shroud) is pressed into contact with the blade group assembled in the annular body.
As shown in the figure, several sheets are made into one group and are divided and fixed into several groups in the circumferential direction.

FIG. 17 is an enlarged view showing the joining parts of the blades 1 of the shroud 15, and shows the tenon 14 connected to the flat caulked part 1.
The shroud 15 is fixed to the blade 1 by caulking until it reaches 4'. The steam force acting on the shroud 15 due to the tenon 14 and the caulking portion 14'
It resists centrifugal force and various other excitation forces.

Since the steam turbine rotor has such a structure, when once used blades are removed from the rotor and reused, the following procedure may be required.

In other words, in order to handle the blades, it is sufficient to reverse the assembly procedure for the turbine impeller described above, but since all the blades are arranged in groups as shown in Figure 15, first It is necessary to separate all the blades to be sampled into individual blades. For this purpose, the shroud 15 is usually cut using a grinder or the like as shown by the two-dot chain line in FIG. The blades separated in this way are first
Stopping blade 9 in Fig. 5 is treated, but for this purpose bottle 1
Just type 1.13 and do f&.

Once the stop blade 9 is handled, the remaining blades 1a1
1b, 1c, . . . can be slid in the circumferential direction along 2' in FIG. 13, and can be easily handled from the notch 7.

The individual blades handled in this way are first cut into the tenon crimped portion using an appropriate tool as shown in Figure 19.
4' is removed, the shroud 15 is extracted, and then, as shown in FIG. 20, by grinding or machining,
A new 1-non 16 will be molded using a part of the effective part of the blade.

This is because, as mentioned above, since the tenon 14' is shaved off, a caulking allowance corresponding to the tenon caulking portion 14' is secured when the shroud 15 is fitted and fixed to the rotor disk 2 again. As a result, the height of the effective part of the new blade 17 becomes shorter than the original height 1 by 12, that is, Δ, so it is called a normal layer sagging, and ΔP is called a shoulder sagging.

On the other hand, if the damage ranges over the entire circumference, it is necessary to lower the shoulders of all blades belonging to the turbine impeller. In this case, the method of separating the shroud and tenon may be used as described above, but it is better to remove the shroud and tenon by lathing all around them on a lathe. There are many.

That is, as shown in FIG. 21, first, the shroud 13 is cut off from both sides along the cutting line 1a11b, leaving a tenon width. At this point, it is also possible to cut the blade 3 deeply by an amount corresponding to the shoulder cutting edge Δβ in FIG. Next, by removing the Tenon caulked portion 12' along the cutting line (2), the remaining shroud 16 can be removed by a simple blow from the inner surface of the sea urchin shown in FIGS. 22 and 23.

In this state, if the tops of the tenon 14 and blades 15 are finished using a grinder or the like as shown in FIG. 20, preparations for reassembly will be completed.

In this way, it is possible to repair only the top portion of the blade 3 without removing it. Of course, if manual work is done using a grinder or the like, the latter method of all-around repair can be applied to the former partial repair, and conversely, if it takes time and effort, the former method of separating into individual blades as described above can be applied. can also be applied to the latter all-around repair.

This technique of lowering the shoulders is extremely effective for local repairs or temporary measures in emergencies, but as shown in Figure 20, the originally required effective blade length ℃1 is removed by the shoulder lowering interval Δβ. Therefore, it is unavoidable that the efficiency of the blades decreases.In particular, when this technique is applied to the entire circumference of the rotor impeller, the effect cannot be ignored, and the If applied to multiple stages, the performance of the steam turbine itself will be considerably degraded. For example, it is necessary to avoid downgrading of a 265 MW class thermal power turbine, that is, to compensate for Tenon's scraping FIL1 2' by some other method. For example, as shown in Fig. 24, Tenon's overlay welding A method of reshaping is also partially used.

The reason why this method is not generally carried out is that even if a proper welding rod is used and proper welding and heat treatment are performed, the remaining tenon 017 and the built-up part 18 will be removed as shown in FIG. During this period, a heat affected zone 19 due to welding and a macroscopic welding defect (referred to as an undercut) occur at the welding start point 20a.
Tenon 12, which must withstand long-term high loads containing vibration components, is likely to occur at the end point 20b.
This is because the reliability is not sufficient.-0 Figure 25 shows the position of the blade in relation to the nozzle when the blade is reused. Generally, in order to ensure fluid performance in a steam turbine, the lower surface diameter r6 of the shroud 18 is smaller than the inner diameter of the nozzle outer ring 23', as shown by the two-dot chain line.
It is set to be slightly larger than 7, and the lamp stone is shown as ugly. However, if the blade shoulder sliding transmission Δk is larger than the above-mentioned wrap @m (m < Δβ)
In this case, the positional relationship r 7 < r 6 is reversed, and the positional relationship between the new shroud lower surface diameter r8 and the nozzle outer ring inner diameter 7 becomes r , < r 7, and the shroud 18 is moved by n from the nozzle outer ring inner diameter r7. It will be directly exposed to the i-speed vapor flow flowing through 23.

When reusing blades that have been shoulder-slipped in this way, either replace the nozzle 23 at the same time, or use some method to change r7 roughly larger than n to make the shroud lower surface diameter "8". Unless it is made smaller, a decrease in efficiency will inevitably occur.

This phenomenon cannot be avoided even if the radial spill strip 24, which is provided to minimize leakage steam passing through the upper surface of the shroud 15, is replaced with one of an appropriate height.

Not only that, but Shroud 15 and the new Tenon 16
is now directly exposed to the high-velocity steam flow mentioned above.
It is clear that condensate or solid particles in the steam can easily erode it.

The method for reusing blades when replacing a fired rotor with an integral axle has been described above as an example. However, for example, when repairing damage to the top of a blade (tenon, shroud), the same method as described above can be used to reuse the blade. Needless to say, it is necessary to either reshape the Tenon by lowering the shoulder or reshape the Tenon by welding.

[Purpose of the invention] The present invention aims to improve the disassembly and assembly techniques of blades, which are disadvantages of repair methods based on the prior art, such as shoulder-sliding or Tenon welding. By welding a prefabricated blade tip block to the effective part of the existing blade, workability is improved and the old wire method can be maintained, so performance is not compromised, and in terms of strength, it is more reliable. The purpose of the present invention is to provide a method for repairing blades that can regenerate blades with high levels of corrosion.

[Summary of the Invention 1 In other words, the present invention provides a tenon that is formed to protrude from the top of a plurality of blades that are implanted in an annular row on a rotor disk, and a tenon that is inserted into a fitting hole to connect the plurality of blades. In a method for repairing an impeller having a flat shroud that interconnects the blades, each of the plurality of blades is cut off at the effective blade part with the shroud connected, and then a cut is made in the cut-off part of the blade. This is an impeller repair method characterized by welding a blade tip block having the originally designed shape of the fallen blade portion.

[Embodiments of the invention] Hereinafter, details of the method of the present invention will be explained using the drawings.

2 and 3 are examples of the method of the present invention,
In this embodiment, instead of disassembling the blade 1 after cutting the shroud 15, the shroud 15 is caulked to the blade 1, and the blade 1 is cut at an arbitrary radius r9 of the effective part of the blade 1.
The effective part of the blade is cut by appropriate machining, and removed from the blade 1 as a blade tip block 25 including the shroud 15, tenon 14, and blade tip effective part 1a shown in FIG.

As a result, the blades 1 assembled in the rotor disk 2 cut at an arbitrary diameter r, have no shroud 15 and are no longer configured as a group, so they can be treated as individual blades, and the rotor disk It can be easily handled from the notch 7 of No. 2.

Figure 4a shows the blade 1 removed from the rotor disk as a single blade, and the 20th blade was prepared separately in advance to fit exactly the joint surface cut at an arbitrary radius r9.
The blade tip block 1a shown in Figure b is aligned with the joint surface and joined along the welding line 26 by, for example, EBW as shown in Figure 26.

In addition, when using normal welding means instead of EBW, for example, as shown in FIG. 7, chamfering X is performed on the joint surface of the blade tip block 1a along the welding line 26 and using the material as a welding groove. Good. Further, although not particularly shown in the drawings, it goes without saying that this welding groove may be provided on the blade 1 side.

FIG. 8 shows another embodiment. In this embodiment, a blade tip block 1a and a shroud 15, which were separately manufactured in advance, are crimped together with a tenon 14 to form a blade tip block 25. It is connected to the blade 1 incorporated in the rotor disk.

That is, in the prior art, the weld line 26 is connected to the remaining tenon 19.
6 and 8, the weld line 26 occurs entirely within the vane effective area, as opposed to the upper surface and therefore within the reshaped tenon 14. become. Further, as is clear from, for example, FIG. 26C, a welding start point 22a and a welding end point 22b also occur in the effective blade part.

Welding at the blade effective portion in this manner is easy to automate, and is extremely convenient for completing uniform parts made of agricultural products.

In other words, according to the method of the present invention, the weld line 26 or the heat-affected zone caused by it is moved from the tenon part, which is subject to high centrifugal force and is extremely stressed, to a part with a large cross section that is easy to deal with stress, thereby reducing the strength margin. It becomes possible to take a larger value.

In addition, even if welding defects such as undercuts that tend to occur at the welding start point 22a or the welding end point 22b occur, they will occur on the side surface of the effective part of the blade, which is easier in terms of stress, so cleaning with a grinder etc. is extremely easy. Be able to do it.

Furthermore, unlike Tenon overlay welding using conventional technology, the blade tip block prepared in advance is welded, so the amount of welding is small, and therefore the heat input due to welding is also small. Thermal effects due to heat input can also be kept to an extremely small level.Also, since the Tenon 14 part, which is most severe in terms of strength, is made from sound parts in advance, it will not be affected by repair welding and will remain as it was originally. The strength and reliability as designed can be ensured.

In addition, the blade tip block 25 cut in FIG.
remains organized in groups, but if this part maintains its integrity, it can be used as is as the blade tip block 25 in FIG. 8.

FIG. 9 shows an embodiment in which a rectangular parallelepiped 27 larger than the cut blade tip block 1 is welded to the joint surface shown in FIG. 4 above. For such methods, Tenon 1
Although a step of processing the blade to return it to its original shape, such as cutting out the blade in step 4, is required, the manufacturing of the rectangular parallelepiped 27 is extremely easy compared to welding the blade tip block 1a as shown in FIG. 25b. An additional advantage is that you do not have to worry about positioning for welding.

Additionally, since the welds are machined, extremely precise finished shapes can be created. In this case,
If a welding groove is required, the blade 1 (not shown)
It is preferable to put the number on the side.

In addition, since the shaping of the blade effective part and Tenon can be carried out directly from the middle of the original blade manufacturing procedure, there are no particular difficulties in carrying out the process.

[Effect of the invention 1 As described above, according to the present invention, when cutting the effective part of the blade and reusing a part of the existing blade, it is possible to reduce the gap between welds and improve the position. Therefore, work efficiency can be greatly improved, and it is also possible to supply recycled blades with extremely high reliability. Furthermore, since this regenerated blade can be made to have exactly the same dimensions as the original design, it is possible to provide an extremely superior blade repair method without degrading turbine performance.

This greatly contributes to improving the operating rate of the steam turbine and maintaining economic efficiency.

[Brief explanation of the drawing]

FIG. 1 is an external view showing cutting at the effective blade part in an embodiment of the method of the present invention, FIG. 2 is a side view showing cutting at the effective blade part in FIG. Figures 4 to 7 are external views showing the case where the blade is regenerated as a single blade. Figure 8 is an external view of the blade tip block configured. Fig. 9 is an external view showing another embodiment of the method of the present invention, Fig. 10 is a longitudinal sectional view of a steam turbine rotor having a fired wheel, and Fig. 11 is A of Fig. 10.
12 is a cross-sectional view taken along the line ■-■ in FIG. 11, FIG. 13 is an exploded partial view of the turbine impeller, FIG. 14 is an external view of the stop blade, and FIG. The figure is an assembled side view of the blade, Figure 16 is a cross-sectional view along c-cwA in Figure 15, Figure 17 is an enlarged view showing the joint between the shroud and the blade, and Figure 18 is a cut of the shroud. Plan, 1st
Figure 9 is a longitudinal cross-sectional view showing the removal of the tenon, Figure 20 is a cross-sectional view showing the blade being lowered, Figure 21 is a vertical cross-sectional view showing the cutting of the tenon and shroud, and Figure 22 is a cross-sectional view of the tenon and shroud. The figure after cutting, Figure 23, shows the Tenon and shroud VJi! FIG. 24 is a side view showing the conventional Tenon weld build-up, and FIG. 25 is an explanatory view showing the relationship between the nozzle, the blade, and the shroud after the shoulder has been lowered. 1...Blade 2......〇-ta disc 7...Notch 14...Tenon 15. ......Shroud 19...Remaining tenon 21...Heat shadow part 22a...Welding start point 22t)... ...Welding end point 26...Welding line 1a...Blade tip effective part 25...
...Blade tip block 17...Cubic block Applicant Toshiba Corporation Patent attorney Noriyuki Chika (and one other person) Figure 2 Figure 3 Figure 4 Figure 5 Figure 6Figure 8Figure 9Figure 10Figure 11Figure 12Figure 13Figure 14Figure 15Figure 16Figure 17Figure 18Figure 19Figure 20Figure 21Figure 22Figure 23 Figure 24

Claims (1)

[Claims] (1) Tenons formed to protrude from the tops of a plurality of blades implanted in an annular row on the rotor disk;
In this method of repairing an impeller having a flat shroud which inserts the tenon into a fitting hole and connects the plurality of blades to each other, each of the plurality of blades is cut off at the effective part of the blade with the shroud connected. . A method for repairing an impeller, comprising: thereafter welding a blade tip block having an originally designed shape of the cut-off blade portion to the cut-off portion of the blade.