JPS61200307A - Repairing method of impeller - Google Patents

Abstract

PURPOSE:To make removal of a shroud ever so easy, by cutting off the shroud and a tenon from the circumferential side of the shroud at least an impeller base material is formed, removing the shroud. CONSTITUTION:At the time of removal of an impeller in a damaged position, such a depth of cut IIIa as reaching to an impeller base material 3 is formed by a cutting-off tool or the like from the circumference of a rotor impeller or a slotted groove in depth as far as slightly adjoining the impeller base material 3 is formed otherwise. With this, a shroud 13 is bisected at both sides of the said groove IIIa, and afterward, width of this groove is mechanically expanded wider with a proper jig whereby the bisected shroud 13 is made so as to be extractable in a longitudinal direction. And, the remaining impeller 3 from which the shroud 13 is removed is set down to a single impeller which comes to be removed from the notch part installed in a part of the circumference of a rotor disc.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a method for repairing a steam turbine impeller.

[Technical background of the invention and its problems] Generally, in a turbine impeller used in a steam turbine, etc., 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. In this case, a blade is used in which the root of the blade (hereinafter referred to as the implanted part) is engaged to restrict movement in the radial direction.

FIG. 15 is an exploded partial view of the turbine impeller. On the outer periphery of the rotor disk 1, a plurality of grooves 2 extending on both front and rear surfaces are formed. The implanted portion 3' is fitted in a rectangular shape, and a protrusion 4 formed on the opposing inner surface of the implanted portion 3' engages with the groove 2 of the rotor disk 1.

By the way, in the forming part of the groove 2 of the mortar disk 1, there is one or more notches 5 on the circumference that extend in the radial direction and have a width approximately equal to the thickness of the implanted part 3'. After inserting the implanted part 3' of the blade 3 in the radial direction from the notch 5, slide it in the circumferential direction and connect it to the outer periphery of the 1]-ta circle 5181. 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. Then, in the final stage of C1a, the notch 5 is filled with the following as shown in Fig. 16.
A stopper blade 7 is engaged with the planar portion 6 that matches the shape of the notch.

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 movement in the radial direction with respect to the rotor circle W1 is not restricted. As shown in FIG. 17 or 18, the stopper blade 7 is attached to the rotor disk 1 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, into which a bottle 9 is press-fitted, and a bottle hole 10 passing through the stopper blade 7 and the notch 5 that fits therein is provided, and the bottle 11 is inserted into the bottle hole 8. This is done by press-fitting.

On the other hand, in FIG. 15, 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 (
13 (hereinafter referred to as shroud) is pressed into contact with the shroud,
As shown in Fig. 17, the group of blades assembled in an annular body is divided and fixed into several groups in the circumferential direction (in order to resist various excitation sources including steam power). It is being done.

FIG. 19 is an enlarged view showing the joint part of the shroud 13 with the blade 33, and the tenon 12 is connected to the flat caulked part 12.
The shroud 13 is fixed to the blade 3 by caulking until it reaches '. The tenon 12 and the tenon caulking portion 12' resist steam force and high centrifugal force acting on the shroud 13.

The top of such a turbine impeller, more specifically,
When damage occurs to the shroud 13 or the tenons 12, 12', if the damage is severe, the blades are usually replaced with new ones, but if the damage is mild, the blades are replaced. A technique called shoulder-sliding has been adopted to reuse damaged feathers for restoration.

In the latter case, standard procedures may be used depending on the extent of the damage. First, if the damaged area is narrow and located close to the stop blade 7, the damaged blade is removed from the group including the stop blade and the damaged part is repaired.

To remove the blades, you can simply reverse the above-mentioned turbine impeller assembly procedure, but since all the blades are arranged in groups as shown in Figure 17, first remove them. It is necessary to separate all the target blades into individual blades.

For this purpose, the shroud 13 is usually cut using a grinder or the like as shown by the dashed line in FIG. The blades separated in this way are first removed by the stopper blade 7 shown in FIG. 17, which can be done by handling the bin 9.11. Once the stopper blade 7 is removed, the remaining blades 3 (3a13b13c...) are slid circumferentially along the groove 2 in FIG.
can be easily extracted from.

As shown in FIG. 21, each blade extracted in this way is removed using a suitable tool.
Using a grinder or machining, a new tenon 14 is formed using a part of the effective blade part, as shown in FIG.

This is because the tenon 12' is shaved off as described above, so that there is enough caulking space for the tenon caulking part 12' when the shroud 13 is fitted and fixed to the rotor disk 1. . As a result, new feather 1
The height of the effective part of 5 is shortened by 8 (from 1 to p2), so the term ``layer down'' is usually used.

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, a method may be used to separate the blades into individual blades as described above, but rather, a method may be used to remove the shroud and tenon by lathing the entire circumference on a lathe. There are more people.

That is, as shown in FIG. 23, first, the cutting line 1a.

1b, cut the shroud 13 from both sides, leaving a non-width. At this time, the shoulder lifting Δ in Fig. 22
It is also possible to cut the blade 3 as deeply as the amount corresponding to °C.

Next, remove the tenon caulked part 12' along the cutting line H, and then remove the remaining part by a simple blow from the inner side, as shown in Figures 24 and 25. Sea 1 Loud 1
6 can be removed.

In this state, if you use a grinder or the like to grind the tenon 14 and the top fSll of the blade 15 by 41 degrees as shown in FIG. 22, you will be ready for reassembly.

By doing this, it becomes possible to repair only the top part of A without removing the blade 3. Of course, if you do manual work using a grinder or the like, you can apply the latter method of all-around repair to the former partial repair, or conversely, if you have the time and effort, you can divide the front fabric into individual blades as described above. Pretreatment methods can also be applied to the latter all-around repair.

This type of shoulder resting technique is extremely effective for local repairs or as a temporary measure in emergencies, but it is
As shown in the figure, since the originally required effective length λ1 of the blade is removed by the amount of scraping Δβ, it is unavoidable that the efficiency of the blade -C decreases.

In particular, when this technique is applied all around the rotor impeller, its influence cannot be ignored, and when applied to multiple stages of a steam turbine, it can seriously affect the steam turbine performance itself. This will result in a decrease in For example, when the technique described in "2" is applied to a 265 MV class medium-pressure turbine of a thermal power turbine, there is a case where the heat immersion wt ratio is reduced by 0.04%.

In order to avoid such performance deterioration, it is necessary to avoid the shoulder reduction described in -, that is, to reduce the amount of Tenon removal 12'.
It is necessary to compensate for this by some other method, for example, as shown in FIG. 26 (Reforming by Tenon overlay welding is also partially used).

The reason why this method is generally not covered by h"t' is that even if a proper welding rod is used and proper welding and heat treatment are performed, the remaining tenon 17 can be removed as shown in Figure 26. Overlay part 1
Welding defects (referred to as undercuts) between the welding heat-affected zone 19 and the Tenon 12 that must withstand the load
This is because the reliability is not sufficient.

In order to solve such problems, the present inventors first
In the blade tenon weld build-up method of forming a weld build-up portion on the residual tenon 12 remaining at the tip of the blade 3 as shown in FIG. A backing plate 25 having a slightly larger through hole is fitted onto the plate 25, and the front distribution plate 25 is fixed by keeping the gap between the outer periphery of the remaining tenon 12 and the inner periphery of the through hole at a predetermined value. Later, he invented a weld overlay method for a vane tenon, which is characterized by welding overlay on the remaining tenon 12 in a space formed by the upper surface of the remaining tenon 12 and the inner surface of the through hole, and filed an application for the same. .

18= According to the method of welding and overlaying a vane tenon according to the present invention, the workability can be greatly improved and a high quality rebuilt overlay tenon can be obtained. Therefore, repair by Tenon overlay welding can be used more widely.

On the other hand, in the conventional technology, as shown in FIG.
When re-caulking is performed from the finished shape 44 after Tenon build-up to regenerate the caulking part 12' at the top of the Tenon, whether the welding start point 20a or end point 20b and the heat-affected zone 19 are formed, the upper surface of the shroud 13 or its It will match the neighborhood.

FIG. 29 is a diagram showing a general stress distribution at the joint between the tenon 12, 12' and the shroud 13.
and 13b, and tenon 1 at the top of vane 3
At the root of 2, the root R12a is the alms. When such a part rotates at a high rotational speed, the chamfered portion 13b
A concentration of shear stress due to the centrifugal force of the shroud 13 occurs in the tenon 12' in contact with the shroud 12, and a concentration of tensile stress due to the centrifugal force applied to the shroud 13 and the tenon 12.12' occurs in the retracted portion 13a. . When we investigate the general failure modes of such a bonded body, we find that most of the cases are shear failure at the chamfered portion 13b or tensile failure at Tenon 12, and although this does not always occur, it is common In general, it can be said that the chamfered portion 13b is in a slightly more severe condition than the chamfered portion 13a.

[Object of the Invention] The present invention has been made in response to such conventional circumstances, and provides a 1q weld overlay tenon that allows easy removal of the shroud from the blade and has high strength and reliability. The purpose of this invention is to provide a method for repairing impellers that can be used to repair impellers.

['R, Akira Summary 1] According to the present invention, a shroud is arranged around the outer periphery of a blade having a tenon formed on its tip surface, and the tenon is placed in a through hole drilled in the thickness direction of this sealing shroud. In a method for repairing an impeller in which the shroud is fixed to the blade tip surface by inserting the shroud and caulking its tip, the shroud and the tenon are protruded from the outer peripheral side of the shroud in a cross section including the tenon. This method of repairing an impeller is characterized in that the shroud is removed from the blade after the shroud is cut to form a groove with a depth that reaches at least the blade base material.

[Embodiments of the invention] The details of the method of the present invention will be explained below with reference to the drawings.

In the method of the present invention, when disassembling a damaged blade, a cut groove is made around the entire circumference of the rotor impeller, for example, near the center of the tenon width in the axial direction, so that it reaches the blade base material from the outside in the radial direction. It is formed by

Fig. 1 or Fig. 2 shows an example in which the method of the present invention is applied when removing a damaged part by first separating a group of blades into individual blades and handling them from the rotor impeller. From the outer periphery of the rotor impeller, use a cut-off tool or the like to make a full cut [Ia] that just reaches the blade base material 3, or a cut groove mb that is just deep enough to touch the blade t43. C is carried out by forming.

When such a cut groove lea or mb is installed, as shown in FIG.
Alternatively, the shroud 13 is divided into both sides of the mb, and by mechanically expanding the width of this groove using a suitable jig, the divided shroud 13 can be easily pulled out in the front-rear direction.

After the shroud 13 is removed, the remaining blade 3 becomes a single blade as shown in Fig. 4 or 5, so it is
It can also be removed from the notch 81S5 in Figure 5.1. : It becomes easier.

The removed individual blade can be freely machined using an appropriate jig, and can be shaped into the blade 3 shown in Figure 4 or Figure 5.
There are no restrictions on the modification of the top design of C1.

On the other hand, FIGS. 6 and 7 show an example in which the method of the present invention is applied to a case where the blade 3 is corrected without being removed from the blade wheel. in this case,
First, along the cutting line IV, the tenon root portion 12 is cut to a depth corresponding to the tenon height required for performing tenon overlay.
The tenon caulking portion 12' is shaved off over the width of the tenon, and then a groove 1a or mb is cut approximately in the center of the tenon width. When such machining is performed m-d, as shown in FIG. 8, the shroud 13 is not only separated in the circumferential direction but also released from the Tenon caulked portion 12', so it can be removed extremely easily. , and the top shape as shown in FIG. 9 or 10 can be obtained.

It is obvious that the single blade shown in FIG. 4 or 5 above can also be shaped into such a shape.

Figures 11 and 12 are enlarged views of the remaining tenon 17 with such a top shape, which has been overlaid by overlay welding in accordance with the standard working method described above. The major difference between the two is that the build-up of the first WI is performed inside the groove 1 [a or mb.

J Narichi, groove in Figure 1 or Figure 2 ■a or mb
Figures 6 and 7 show how to divide a group of blades into individual blades using the simplest machining method, which is turning grooves ■v.
and by III a or Ill l for grooves,
This figure shows the simplest method of cutting all the blades of the rotor impeller into the shape shown in FIG. 9 or 10 at once. By adopting such a method, repair work can be completed in the shortest possible time.

However, in the prior art, the build-up shape as shown in FIG. 11 or 12 performed on the remaining tenon shape 17 is in the vicinity of the top surface line of the sea eraud 13 as shown in FIG. 26. There was a drawback that the heat affected zone 19 was located at the welding joint line 45, but in this embodiment, it is finished so that the heat affected zone 19 is located at the sea urchin blade material 3 side (not shown in FIGS. 11 and 12). 3 and the weld overlay 12'', and the weld joint line 45 is no longer flat. This has the effect of suppressing the progress of the steel, and the fracture resistance can be improved.

13 and 14 are examples in which the height of the remaining tenon 17 shown in FIG. 11 or 12 is approximately half the thickness S of the shroud 13. Formation of such a shape can be easily realized by cutting the depth of the cutting line IV to half the thickness of the shroud 13 in FIG. 6 or 7.

By doing this, it becomes possible to remove the welding start point 20a and end point 20b on the remaining tenon 17 from the maximum stress point 13b shown in FIG. 29, and further,
A highly reliable reproduction tenon can be obtained.

[Effects of the Invention] As described above, according to the method of the present invention, the shroud can be easily removed from the blade, and a high-quality welded overlay regenerated tenon with high strength can be obtained. In particular, the method of the present invention is extremely effective when it is necessary to repair the blades around the entire circumference of the rotor impeller.

Therefore, it becomes possible to apply repair by Tenon welding over a wider range of areas, and it is possible to provide an impeller repair method that does not reduce the performance of the blade Tenon portion. These things greatly contribute to improving the operating rate of the steam turbine and maintaining economic efficiency.

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams showing the processed shape of the impeller outer periphery by the method of the present invention, FIG. 3 is an explanatory diagram showing the processed shape of the impeller outer periphery as seen from the outside, and FIGS. 4 and 5 are explanatory diagrams showing the processed shape of the impeller outer periphery. Fig. 6 and Fig. 7 are explanatory drawings showing the processed shape of the impeller outer periphery by the method of the present invention, and Fig. 8 is an explanatory drawing showing the processed shape of the impeller outer periphery from the outside. 9 and 10 are explanatory views showing the shape of the blade top, FIGS. 11 and 12 are explanatory views showing Tenon weld overlay, and 13.
14 and 14 are explanatory diagrams showing Tenon weld overlay in another embodiment of the method of the present invention, FIG. 15 is an external view of a turbine impeller, FIG. 16 is an external view of a stop blade, and FIG. A front view showing the assembly of the blade, FIG. 18 is a longitudinal sectional view taken along the line C-C in FIG. 10, FIG. 19 is a longitudinal sectional view showing the joint between the shroud and the blade, and FIG. Fig. 21 is an explanatory drawing showing the tenon removed, Fig. 22 is an explanatory drawing showing the shoulder of the blade, Fig. 23 is an explanatory drawing showing the cutting of the tenon and shroud, Fig. 24 25 is an explanatory view showing the state of the tenon and shroud after cutting, FIG. 26 is an explanatory view showing the conventional tenon weld overlay, and FIG. 27 is the weld overlay of the vane tenon that the present inventor has already applied for. FIG. 28 is an explanatory diagram showing the method, FIG. 28 is an explanatory diagram showing a conventional residual Tenon, and FIG. 29 is an explanatory diagram showing the stress distribution of the Tenon. 1......Rotor disk 3.15...
Feather 5...... Notch 12.14... Tenon 13... Sikoroud 17...
・・・・・・Remaining Tenon 19・・・・・・・・・
...Heat affected zone 20a...Welding start point 20b...Welding end point 25...Welding plate 26...・・・・・・・・・Hore 30・・・・・・・・・・・・Cooling board fee instant patent attorney S; 11 S - TO) Figure 3 Figure 4 Figure 5 Figure 8 Figure 9 Figure 11 Figure 12 Figure 13 Figure 15 Figure 18 Figure 16 Figure 17 Figure 19 Figure 20 Figure 21 Figure 22 < Figure 23 Figure 24

Claims (1)

[Claims] (1) A shroud is placed around the outer periphery of a blade with a tenon formed on the tip surface, the tenon is inserted into a through hole drilled in the thickness direction of the shroud, and the tip of the shroud is swaged. In a method for repairing an impeller fixed to a blade tip surface, a groove having a depth that cuts through the shroud and the tenon and reaches at least the blade base material is formed in a cross section including the tenon from the outer peripheral side of the shroud. A method for repairing an impeller, comprising removing the shroud from the blade after forming the shroud. (2)
2. The impeller repair method according to claim 1, wherein the cross section including the tenon is a cross section approximately at the center of the tenon width.