JP6239474B2 - Rotor gap inspection method and steam turbine manufacturing method - Google Patents

Description

  The present invention relates to a moving blade gap inspection method for inspecting a gap between moving blades of an all-round connection blade (or a low-pressure stage long blade), and a method for manufacturing a steam turbine.

  When the all-round connection blade using the untwisting action by centrifugal force is used for the low pressure stage of the steam turbine, it is important for safety to manage the shroud contact rotation speed at the time of the ascending or descending speed of the steam turbine. For example, in the long-term operation of the steam turbine, the expansion of the shroud gap may increase due to the influence of secular change such as a drain attack due to wet steam. Further, when the spread of the shroud gap increases, the shroud contact rotation speed increases, and the operation is performed up to a high rotation speed in the state of a single blade. For this reason, when the blade is operated up to a high rotational speed in the state of a single blade having no structure damping effect and the blade resonates, vibration generation stress becomes excessive and there is a risk of damage to the blade. In addition, since the shroud contact rotation speed is adjusted by the expansion of the shroud clearance at the top of the blade, it is necessary to periodically measure and confirm that the expansion of the shroud clearance is within the appropriate range in order to maintain reliability during long-term operation. is there.

  As an example of the technique relating to the management of the shroud gap as described above, there is a shroud gap measuring device disclosed in Patent Document 1. In this apparatus, light is transmitted through the shroud gap, captured as an image by the light receiving unit, and the image is analyzed to derive the gap value of the shroud gap. Next, as another example, there is a shroud gap determination device disclosed in Patent Document 2. In this apparatus, the gap between the shrouds is irradiated with laser light, and the reflected light is detected to determine whether or not the spread of the shroud gap is appropriate.

Japanese Patent Laid-Open No. 4-250304 (published September 7, 1992) Japanese Utility Model Publication No. 5-023014 (published March 26, 1993)

  By the way, in the conventional fixing method of the moving blades in the all-round connection blade, as a method of fixing the blade root to the blade groove of the steam turbine rotor (hereinafter simply referred to as “rotor”), in the case of a fork type blade root, The fixed method by pinning was adopted. On the other hand, in the case of the inverted Christmas tree type blade root, a fixing method by a caulking method using a taper pin has been adopted. In the fixing method by the caulking method using the taper pin, first, pinning is performed as shown in FIG. 4A, and the length of the pin is adjusted as shown in FIG. 4B. Thereafter, as shown in FIG. 4C, a caulking process is performed by the striking device, and unnecessary portions are removed with a lathe as shown in FIG. 4D. In the all-around connected blades to which the fixing method by pinning as described above or the fixing method by caulking method is applied, the blades are firmly fixed to the rotor even when the steam turbine is stopped. For this reason, in the above-described conventional all-around wing, it is possible to accurately measure the shroud gap one by one using, for example, a gap gauge or the techniques disclosed in Patent Documents 1 and 2 above. It was.

  However, when a reverse Christmas tree-type blade root is used for the blade root and only the movement in the axial direction is fixed using a key or pin (hereinafter referred to as the “blade root fixing loose method”), Are not completely fixed, there are various problems in accurately measuring the gaps for each. For example, when inspecting the gap between shrouds using a gap gauge with a set of gauges of multiple thicknesses, if a gauge with an inappropriate thickness is inserted into the gap between the shrouds, the blade moves in the direction perpendicular to the axis. The shroud gap widens and the shroud gap cannot be measured accurately. Further, in the techniques disclosed in Patent Documents 1 and 2, since optical inspection is performed, an appropriate cost for creating an inspection apparatus is required. For this reason, these conventional techniques have a problem that it is difficult to accurately measure the expansion of the shroud gap while suppressing the cost.

  The present invention has been made in view of the above problems, and its purpose is to reduce the cost by a simple method and to accurately measure the expansion of the gap between the moving blades. The purpose is to provide inspection methods.

  In order to solve the above-mentioned problem, a moving blade gap inspection method according to aspect 1 of the present invention is a moving blade gap inspection method for inspecting a gap between adjacent moving blades of a circumferentially connected blade. It is characterized by inspecting the spread of the gap between the moving blades by uniformly inserting a plurality of measurement members set to the same thickness based on an appropriate value regarding the gap between the moving blades. .

  In the above method, a plurality of measurement members set to the same thickness based on appropriate values for the gaps between the moving blades are uniformly inserted into the gaps between all the moving blades implanted in the stage to be measured. Therefore, a simple method of inspecting the spread of the gap between the moving blades is adopted. For this reason, by appropriately setting the thickness of the measurement member according to the gap between the moving blades, for example, a method of directly measuring the spread of the gap between the shrouds with a gap gauge, or using transmitted light or reflected light with respect to the gap Compared with the conventional method of measuring the gap value of the gap between the shrouds, it is possible to accurately measure the spread of the gap between the moving blades while suppressing the cost by a simple method.

  Further, in the moving blade clearance inspection method according to aspect 2 of the present invention, in the aspect 1, it is preferable to use a plurality of types of measuring members having different thicknesses as the measuring member.

  According to the above method, for example, the planned upper limit value of the shroud contact rotational speed is adopted as the thinner thickness, and the upper limit value on the strength accompanying the increase of the shroud contact rotational speed is adopted as the thickness of the thicker measurement member. By adopting it, it is possible to confirm that the gap between the rotor blades is not in a state that requires immediate replacement of all the circumferentially connected blades, but is in a delicate state that requires attention. For this reason, when it is confirmed that the above-mentioned subtle state is confirmed before it is determined that it is necessary to completely replace the all-round connection blades, the manufacture of the all-round connection blades to be replaced in advance is advanced. I can leave. Thereby, it becomes possible to minimize the stop period of the steam turbine.

  Further, in the moving blade gap inspection method according to aspect 3 of the present invention, in the above aspect 1 or 2, when the extending direction of the rotating shaft of the all-around connecting blade is along the horizontal direction, a plurality of the moving blades It is preferable to start inspection of the spread of the gap from the lowermost gap among the gaps.

  The gap between the moving blades of the all-circumferentially connected blades becomes smaller as it gets closer to the gap at the lowermost end due to the gravity acting on the moving blades. Conversely, the gap becomes larger as it gets closer to the gap at the uppermost end. For this reason, by starting the inspection of the clearance from the clearance at the lowermost end, it is possible to reduce the influence of the tension due to the weight of the moving blade as described above, and efficiently and appropriately check the expansion of the clearance between the moving blades. be able to.

  Further, in the moving blade gap inspection method according to aspect 4 of the present invention, in the above aspect 3, the gap between all the moving blades of the all-circumferentially connected blades is inspected at the position of the lowermost end of the allimetrically connected blades. Thus, it is preferable to inspect while rotating the all-round connecting blade.

  As described above, the gap between the moving blades of the all-circumferentially connected blades becomes smaller as it gets closer to the lowermost gap due to the gravity acting on the moving blades. Becomes larger. For this reason, if the gap between the moving blades is inspected at the lowermost position of the all-round connecting blade while rotating the all-around connecting blade, the influence of the tension due to the weight of the moving blade as described above is minimized. Thus, the inspection of the spread of the gap between the rotor blades can be performed more efficiently and appropriately.

  Moreover, it is preferable that the manufacturing method of the steam turbine which concerns on aspect 5 of this invention contains the moving blade clearance gap inspection method in any one of the said aspects 1-4. According to the above method, it is possible to manufacture the steam turbine while appropriately managing the expansion of the gap between the moving blades while suppressing the cost by a simple method.

  According to one aspect of the present invention, there is an effect that it is possible to accurately measure the spread of the gap between the moving blades while suppressing the cost by a simple method.

It is a figure for demonstrating the inspection method which inserts a measurement member (henceforth "shim" is explained as an example) in the crevice between rotor blades concerning one embodiment of the present invention, and inspects the expansion of a crevice, (A) is a perspective view which shows a part of structure of a steam turbine, (b) shows the state of the clearance gap between shrouds before shim insertion, (c) is the state between shrouds after shim insertion Indicates. It is a figure for demonstrating the said inspection method, (a) shows the structure when a perimeter connection blade is seen from the turbine exhaust side regarding the said steam turbine, (b) is between shrouds after shim insertion. (C) is a figure for demonstrating each shim thickness of the shim which has two types of thickness, and the example of required number of sheets. It is a figure for demonstrating the procedure of the said inspection method, (a) is a figure which shows the procedure at the time of inserting a shim in the clearance gap between shrouds, (b) is related with the said inspection method. It is a figure for demonstrating the whole structure. It is a figure for demonstrating the fixing method of the moving blade by the caulking method by a taper pin in the case of a reverse Christmas tree type blade root, (a) shows a mode when pinning is performed, (b) , Shows the state when adjusting the length of the pin, (c) shows the state when the caulking process is performed with the striking device, (d) is when the unnecessary portion is removed with a lathe Show the state.

  The embodiment of the present invention will be described with reference to FIGS. Hereinafter, for convenience of explanation, components having the same functions as those described in the specific items may be denoted by the same reference numerals and description thereof may be omitted.

[Rotating blade clearance inspection method]
FIG. 1 is a diagram for explaining an inspection method (moving blade gap inspection method) for inspecting the spread of a gap by inserting a measurement member into the gap between moving blades according to an embodiment of the present invention. FIG. 1A is a perspective view showing a part of the configuration of the steam turbine 1 (particularly the final stage of the steam turbine 1). The figure shows a state when viewed from the turbine exhaust side in the direction (axial direction) along the rotation axis of the steam turbine 1.

  As shown in the figure, the last stage of the steam turbine 1 is mounted with all-round connection blades attached so as to expand in the radial direction with respect to a steam turbine rotor (hereinafter simply referred to as “rotor”). . A circumferentially connected blade is a torsion blade having a long blade length used in the low pressure stage of the steam turbine 1, and is shown in FIG. Adjacent steam turbine blades (robots) 2 and shrouds (robot blades) 3 at or near the top of the blades are in contact with adjacent blades, and the entire blades of that stage are connected together so that they can be regarded as a single unit. Thus, the moving blade can obtain a high structure damping effect against vibration stress such as resonance.

  That is, the feature of this all-circular connecting blade is that the steam turbine rotor blade 2 and the shroud 3 at the top of the blade are integrated with each other adjacent blades. Then, each moving blade comes into contact with the adjacent blade at the shroud 3 to form an all-around connection structure, and has high vibration resistance.

  Further, the all-around wings of this embodiment employ a so-called reverse Christmas tree type blade root, and a method in which attachment to the blade groove is loose (hereinafter referred to as “blade root fixed loose method”) is used. It is an all-around wing. The moving blade clearance inspection method of the present embodiment described below is a method suitable for managing the clearance between moving blades in the all-around connected blade to which the above-described fixed blade loose method is applied as a fixed blade root method. .

  The steam turbine 1 is designed and manufactured on the premise that high vibration resistance is always maintained, and since this vibration resistance maintenance is always maintained during a long-term turbine operation, the gap between the blade top shrouds 3 is maintained. 3a (hereinafter referred to as “shroud clearance” as appropriate) needs to be appropriately managed. Therefore, it is preferable to always inspect (or measure) the shroud clearance in accordance with the procedure described later during the periodic inspection and leave it in the record.

  The shroud clearance inspection (or determination or measurement) of this embodiment has three types: green (good state), yellow (needs attention), and red (needs full replacement of all-around connecting blades). Includes state determination. If it is red, it will be necessary to replace all the connecting blades around the circumference, but it will take some time to prepare (manufacture) the replacement blades, so periodic clearance measurements (for increasing the gap between the shrouds) (Inspection) must be carried out reliably.

  More specifically, as shown in FIG. 1 (c), a plurality of shims (measuring members) 4 are all shroud implanted on the stage to be measured shown in FIG. 1 (b). An inspection (or measurement) of the expansion of the gap 3a is performed by uniformly inserting the gap 3a between the three. As will be described later, the shim 4 is a plurality of plate-like members set to the same thickness based on an appropriate value related to the gap between the rotor blades. In this embodiment, the shim 4 is used as a measurement member used for the inspection of the spread of the gap 3a. However, the measurement member is not limited to this, and the measurement member is a plurality of members having the same thickness. Any member that can be used may be used. For example, the measurement member is not limited to a plate-like member such as the shim 4, and a round bar shape or a polygonal column (for example, triangular column) member may be employed.

  Hereinafter, a specific procedure of the moving blade gap inspection method of the present embodiment will be described in detail. FIG. 2 is a diagram for explaining the procedure of the moving blade gap inspection method. FIG. 2A shows the structure of the steam turbine 1 when the all-circular connecting blades are viewed from the turbine exhaust side. Further, in the same figure, a state is shown in which shims 4 are uniformly inserted into the gaps between all the shrouds 3. FIG. 2B shows a state of a gap between the shrouds 3 after the shim 4 is inserted.

  FIG. 2C shows the shim thickness and the required number of shims 4 having two kinds of thicknesses. As shown in the figure, two types (plural types) of shims 4 having different thicknesses are prepared. Specifically, a green determination shim 4 having a thickness of a (mm) and a red determination shim 4 having a thickness of b (mm) are prepared.

  The thickness a is set to a planned upper limit value of the shroud contact rotational speed, for example, 1.4 mm. Further, the thickness b (a <b) is set to an upper limit value on the strength accompanying an increase in the shroud contact rotation speed, for example, 1.8 mm. As a result, as will be described later, it is possible to confirm that the gap between the shrouds 3 is a delicate state that requires attention, although it is not immediately necessary to completely replace the all-round connecting blades. . For this reason, when it is confirmed that the above-mentioned subtle state is confirmed before it is determined that it is necessary to completely replace the all-round connection blades, the manufacture of the all-round connection blades to be replaced in advance is advanced. I can leave. Thereby, the stop period of the steam turbine 1 can be minimized.

  In this embodiment, the thickness types of the shim 4 used for the inspection are two types. However, the thickness type of the shim 4 is not limited to this, and for example, the shim 4 having three or more types of thickness is inspected. You may use for. It should be noted that as many green determination and red determination shims 4 as the number of moving blades are prepared.

  Next, the inspection of the shroud clearance is first performed using the shim 4 for green determination. If a shim 4 having the same thickness is inserted into the gaps between all the shrouds 3 in one measurement and the green judgment shim 4 fails, then use the red judgment shim 4 next. taking measurement. In addition, when it passes with the shim 4 for green determination, the measurement with the shim 4 for red determination is unnecessary.

  Next, (a) of FIG. 3 is a figure for demonstrating the procedure at the time of inserting the shim 4 in the clearance gap between the shrouds 3. FIG. As shown in the figure, the selected shims 4 are arranged in order from the lowest gap among the gaps between the plurality of shrouds 3 when the extending direction of the rotating shafts of the all-around connecting blades is along the horizontal direction. It is preferable to insert it toward the upper gap. The gap between the shrouds 3 of the all-circumferentially connected blades becomes smaller as it gets closer to the gap at the lowermost end due to the gravity acting on the moving blade, and conversely, the gap becomes larger as it gets closer to the gap at the uppermost end. For this reason, by starting the inspection of the gap from the lowermost gap, it is possible to reduce the influence of the tension due to the weight of the moving blade described above, and to efficiently and appropriately check the expansion of the gap between the shrouds 3. it can.

  In the example shown in FIG. 3A, after the shim 4 is inserted into the lowermost gap, the shim 4 is inserted into the uppermost (last) gap in turn alternately. However, the order of insertion is not particularly limited as long as the shim 4 is finally inserted uniformly into all the gaps.

  Further, it is possible to inspect the gap between all the shrouds 3 of the all-round connecting blades while rotating the all-around connecting blades clockwise or counterclockwise so as to check at the lowest end position of the all-around connecting blades. . As described above, the gap between the shrouds 3 of the all-circular connecting blades becomes smaller as it approaches the lowermost gap due to gravity acting on the moving blade, and conversely, the gap becomes wider as it approaches the uppermost gap. Becomes larger. For this reason, if the gap between the shrouds 3 is inspected at the lowermost position of the all-round connecting blade while rotating the all-around connecting blade, the influence of the tension due to the weight of the moving blade described above is minimized. It is possible to inspect the spread of the gap between the shrouds 3 more efficiently and appropriately.

(Sim insertion judgment)
By confirming the insertion state of the shim 4, a pass / fail determination is made and the determination result is recorded. The state of insertion of the shim 4 into the gap between the shrouds 3 is classified into the following three states (a) to (c).
(A) The state where the shim 4 cannot be inserted into all the gaps. When the shim 4 cannot be inserted into all the gaps, it can be determined that the gap (average) between the shrouds 3 is narrower than the thickness of the shim 4.
(B) A state in which the shims 4 can be surely inserted into all the gaps and all the shims 4 are held with an appropriate frictional force. If the shim 4 can be inserted into all the gaps and does not fall naturally, the gap (average) between the shrouds 3 can be determined to be equal to or smaller than the thickness of the shim 4.
(C) Some of the inserted shims 4 are loose, and at least one shim 4 naturally falls. If even one shim 4 falls naturally after all the shims 4 are inserted, it can be determined that the gap (average) between the shrouds 3 is wider than the thickness of the shim 4.

  In the above description, if the state is (a) or (b), it is determined that the inspection is acceptable. On the other hand, in the above case, if the state is (c), it is determined that the inspection is unacceptable.

[Determination of clearance status]
Next, the clearance state is determined according to the following criteria 1 to 3.

  Criteria 1 (green): Pass is determined by shim 4 for green determination. In this case, it can be confirmed that the state of the clearance is good.

  Criteria 2 (yellow): rejected with shim 4 for green judgment, and passed with shim 4 for red judgment. In this case, the clearance is slightly widened, and it is confirmed that the gap 3a between the shrouds 3 is in a delicate state that requires attention, although it is not immediately necessary to completely replace the all-around connecting blades. .

  Criteria 3 (red): Determined as unacceptable by the shim 4 for red determination. In this case, since the clearance exceeds the allowable value, it can be confirmed that it is necessary to completely replace the all-around connecting blades.

  When the above clearance state is determined to be green, the steam turbine 1 can be operated without any problem. In the case of yellow, the clearance is slightly widened, and attention is required. Therefore, when this yellow determination is made, the production of the alternative wing is started. In the case of red, the clearance exceeds the allowable value, and it is necessary to completely replace the all-around connecting wings.

[Effects of blade clearance inspection method]
In the above method, a plurality of plate-like shims 4 set to the same thickness based on appropriate values for the gaps between the rotor blades are formed in the gaps between all the shrouds 3 implanted in the stage to be measured. A simple method of inspecting the spread of the gap between the shrouds 3 by inserting uniformly is adopted. For this reason, by appropriately setting the thickness of the shim 4 according to the gap between the moving blades, for example, a method of directly measuring the spread of the gap between the shrouds with a gap gauge, transmitted light or reflected light with respect to the gap is used. Compared with the conventional method of measuring the gap value of the gap between the shrouds, it is possible to accurately measure the spread of the gap between the moving blades while suppressing the cost by a simple method.

  In the above method, shims having a plurality of types of thicknesses for green determination and red determination are used as the shims 4 to be inserted into the gaps between the shrouds 3. For this reason, it is possible to confirm that the gap between the shrouds 3 is in a delicate state that requires attention, although it is not immediately necessary to completely replace the all-round connecting blades. Therefore, when it is confirmed that the above-mentioned subtle state is confirmed before it is determined that it is necessary to completely replace the all-round connection blades, the all-round connection blade (alternative blade) to be replaced in advance is manufactured. Can be advanced. Thereby, the stop period of the steam turbine 1 can be minimized.

Moreover, according to said method, the following effects are acquired.
(1) It is possible to ensure long-term reliability (prevention of blade damage) of a steam turbine provided with all-round connection blades.
(2) Data of secular change of the gap between the shrouds 3 can be accumulated.
(3) The turbine stop period can be minimized by preparing the substitute blades in advance (by ensuring the production period of the substitute blades) by acquiring the expansion tendency data of the gap between the shrouds 3 in advance.

(Modification)
FIG. 3B shows the structure of one entire moving blade. As shown in the figure, the moving blade includes a steam turbine moving blade (moving blade) 2, a shroud (moving blade) 3, a stub (moving blade) 5, and a blade root 6. The blade root 6 is a so-called inverted Christmas tree-type blade root. In the embodiment described above, an example in which the gap between the shrouds 3 is inspected as an example of the gap between the rotor blades has been described. However, the gap between the rotor blades to be inspected is not limited to the gap between the shrouds 3, Any gap between the blades can be inspected.

  In particular, the method of uniformly inserting a plurality of measurement members set to the same thickness, such as the shim 4 described above, into the gaps between all the blades implanted in the stage to be measured is the shroud 3. The present invention can be applied not only to the management of the gap between the stubs, but also to the management of the gap between the stubs 5 that make contact with the adjacent wings in the middle part of the wing profile. Usually, it is very difficult to inspect the gap between the stubs 5 located in the middle part of the blade profile. However, according to the present method, it is possible to easily inspect the spread of the gap between the stubs 5.

(Application to steam turbine manufacturing method)
Moreover, you may include the moving blade clearance inspection method mentioned above in the manufacturing method of a steam turbine. According to such a manufacturing method, it is possible to manufacture the steam turbine while appropriately managing the expansion of the gap between the moving blades while suppressing the cost by a simple method.

[Additional Notes]
The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention. Furthermore, a new technical feature can be formed by combining the technical means disclosed in each embodiment.

  INDUSTRIAL APPLICABILITY The present invention can be used for a steam turbine provided with an all-around connecting blade to which a blade root fixing loose method is applied as a blade root fixing method, which requires clearance management between adjacent moving blades. .

1 Steam turbine 2 Steam turbine blade (roof blade)
3 Shroud
3a Clearance 4 Shim (Measuring member)
5 Stub (Robot)
6 Wing roots

Claims (5)

The blades at low rotational speed is a single wing, the entire circumference connecting wings, each of the plurality of rotor blades is all around connected structure in contact with the adjacent wing portions of the shroud in the vicinity of rated speed, the adjacent dynamic A moving blade clearance inspection method for inspecting clearance between blades,
Providing a plurality of measuring elements which are set to the same thickness on the basis of the proper values for the gap between the rotor blades, the gaps between the plurality of the blades, in a state of inserting a plurality of said measuring member, between the rotor blades A moving blade clearance inspection method, characterized by inspecting the expansion of the clearance of the blade.   2. The moving blade gap inspection method according to claim 1, wherein a plurality of types of measuring members having different thicknesses are used as the measuring member. A rotor blade gap inspection method for inspecting a gap between adjacent rotor blades of an all-around connecting blade,
By uniformly inserting a plurality of measurement members set to the same thickness based on an appropriate value regarding the gap between the rotor blades into the gap between the rotor blades, the spread of the gap between the rotor blades is inspected,
When the extending direction of the rotating shaft of the all-around connecting blade is along the horizontal direction, the inspection of the spread of the gap is started from the lowermost gap among the gaps between the plurality of moving blades. rotor blade clearance inspection how to.   The clearance between all the moving blades of the all-around connecting blade is inspected while rotating the all-around connecting blade so as to check at the position of the lowermost end of the all-around connecting blade. The moving blade clearance inspection method described in 1.   A method for manufacturing a steam turbine, comprising the moving blade gap inspection method according to any one of claims 1 to 4.

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