JPS59131703A - Repairing method for moving blade of steam turbine - Google Patents

Abstract

PURPOSE:To shorten the period of time needed to repair the moving blade of steam turbine, by first suspending the top ended shoulder portion of damaged tenon consistently to define a new tenon and then refitting a shroud. CONSTITUTION:A damaged moving blade 4 is removed from a shround and a shoulder portion A is suspended consistently as shown by a shade to define a new tenon 5. Then, the tenon 5 is engaged in the port of shroud and secured in position by tightening. In this manner, the damaged blade can be made reusable by taking a simple machining step, thereby eliminating the need to newly produce a moving blade for ensuring a short repairing period.

Description

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

[Technical background of the invention and its problems]

Conventionally, a steam turbine has a structure as shown in FIG. That is, in the figure, a plurality of rotor blades 4 are embedded in a rotor 2 inside a turbine caning 1 on the outer periphery of an impeller 3 (which may be shrink-fitted in some cases). Furthermore, the rotor 1!4 has a tenon 5 formed by cutting out the tip of the rotor blade 4 as shown in FIG. 2, and this tenon 5 has a hole in the shroud 6 shown in FIG. 7 and caulking the tip of the tenon 5 to fix the shroud 6' to form a rotor blade group. By configuring such a rotor blade group, the rigidity of the rotor blade 4 is improved, and the shroud is useful for improving performance by preventing leakage of power fluid in the radial direction.

During steam turbine operation, in addition to the centrifugal force that acts on the rotor blades 4, the rotor blades 4 are also subjected to high-cycle excitation force of several thousand times per second or more due to the jet flow from the upstream nozzle 8, and are also subjected to power generation due to the unevenness of the individual nozzle areas. Low-cycle excitation forces are also applied due to uneven distribution of fluid and changes in the direction of gravity due to fixed rotation. At the time of design, the excitation force applied to the rotor blade 4 and the characteristic number of worms of the rotor blade 4 do not match, but the area of each nozzle of the nozzle 8 changes over time due to erosion and other traps. Therefore, if the excitation frequency applied to the rotor blades 4 and the natural frequency of the rotor blades 4 match, large vibration stress will occur in the rotor blades 4 or shracto 6, and the stress will be particularly high among the group of blades. The tenon 5, which is a critical location, is damaged and cannot support and fix the shroud 6. In addition, the steam generated by boiling water contains impurities), which flow into the steam turbine together with the steam. These impurities are mainly composed of metal particles and corrode or wear out various parts within the steam turbine. Further, in the low pressure section of the steam turbine, steam condenses and becomes water droplets, and these water droplets also erode or wear out various parts within the steam turbine. In particular, after jetting from the nozzle 8, the rotor blade 4
If the steam passes through the outside of the shroud 6 without colliding with the rotor blade 4, the steam flow velocity will be higher at the tip of the rotor blade 4, so the degree of erosion or wear will tend to increase. Among them, Tenon 5 is the most susceptible to erosion and wear. If the tenon 5 becomes eroded or worn out, it will no longer be able to support and fix the shracto 6 and will need to be repaired. In this case, the repair method is to remove the rotor blades, which are connected by one shroud, from the impeller 3, as the tenon 5 has an integral structure with the rotor blades 4, and replace the damaged rotor blades with new ones. The method was to reassemble it and insert it into the impeller again.

Since the rotor blades must be newly manufactured in this way, there is a drawback that a large number of man-hours are required and the repair period becomes long.

[Purpose of the invention]

The present invention has been made in order to eliminate the drawbacks of the above-mentioned conventional methods, and it is a steam talpin that can shorten the repair period by reusing damaged rotor blades through simple processing without having to manufacture a new rotor blade. The purpose is to provide a method for repairing rotor blades.

[Summary of the invention]

In order to achieve the above object, the present invention removes a rotor blade with a damaged tenon part from a shroud, lowers its tip shoulder uniformly to form a new tenon, and then reinserts it into a hole in the shroud. , 4I is the enemy of fixing the nails by caulking.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. As shown in Figure 4, the rotor blade 4 that has been found to be damaged is removed from the shroud and lowered to make a new tenon 5 (to make the shoulder A shown with diagonal lines uniform). K the tenon 5 so that the caulking distance i is approximately 2.40.

Next, as in the prior art, as shown in FIG.
The hole 7 is fitted into the tenon 5, and the shroud is fixed by caulking to form a rotor blade group and restored.

According to this repair method, the height of the rotor blade 4 is somewhat lowered, so the radial gap between the tip fin 9 and the shroud 6 in FIG. 1 becomes larger, and the amount of steam leaking from the tip of the rotor blade increases. However, the performance of the steam turbine decreases, but the amount of decrease is generally 0.001. , S, which is extremely small) and poses no problem in terms of performance.

Furthermore, if the repair method according to the present invention is applied to the rotor blade 4 around the entire circumference, it is possible to keep the radial gap unchanged by manufacturing a new tip fin 9 that is longer by the amount that the rotor blade shoulder A is slid down. Therefore, the amount of steam leaking from the tip of the rotor blade does not increase, and there is no problem in terms of performance. [Effects of the Invention] As explained above, according to the present invention, the amount of steam leaking from the tip of the rotor blade does not increase. By carrying out a simple process such as uniformly sliding down the tip shoulder of the blade to form a new tenon, it is possible to perform the repair without having to manufacture a new rotor blade, which significantly shortens the repair period. This has the effect of shortening the time.

[Brief explanation of drawings]

Figure 1 is a sectional view showing the internal structure of a conventional steam turbine;
FIG. 2 is a perspective view of a steam turbine rotor blade, FIG. 3 is a front view showing a tenon and shroud at the tip of the rotor blade, and FIG. 4 is a front view showing an embodiment of the present invention. 4. Moving blade, 5. Tenon, 6. Shroud, 7. Shroud hole, A. Moving blade tip shoulder. Agent Patent Attorney Rules Kensuke Chika (and 1 other person) Figure 1 / Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] In a method for repairing steam turbine rotor blades, a tenon cut out integrally at the tip of the rotor blade is inserted into a hole in the shroud, and the shroud is fixed by caulking. After removing it from the shroud and lowering its tip shoulder evenly to form a new tenon,
A method for repairing a steam turbine rotor blade, comprising reinserting the shroud into the hole and fixing it by caulking.