JP7702837B2 - Life evaluation system and life evaluation method - Google Patents

Description

This disclosure relates to a lifespan assessment system and a lifespan assessment method.

In the boiler equipment and piping equipment installed in thermal power plants, high chromium steel, which is classified as high strength heat resistant steel, is used as the operating temperature rises. However, the joints between the header pipes, such as the headers and piping, and the pipes that are connected to them and make up the pipe stub are in a severe stress environment where thermal stress, internal pressure, and bending stress due to self-weight are added, making it essential to evaluate creep damage. Conventionally, creep damage analysis of pipe stubs has been performed by non-destructive testing or using the finite element method (see, for example, Patent Document 1).

Patent No. 5848224

However, pipe stubs come in a variety of shapes and sizes, and the tendency for stress to occur varies depending on the shape and size. Therefore, in order to properly evaluate the life span, evaluation using FEM elastic creep analysis is necessary. However, because there is a wide variety of pipe stub shapes used in thermal power plants, evaluation using FEM elastic creep analysis requires a great deal of time and effort.

In view of the above circumstances, at least one embodiment of the present disclosure aims to perform a relatively accurate evaluation of the life span of a nozzle in a short period of time.

(1) A life assessment system according to at least one embodiment of the present disclosure,
a first stress calculation unit which defines at least one of a nozzle stub welded portion of a header or piping of a thermal power plant or a base material portion around a nozzle stub hole of the header or piping as a first evaluation portion to be subjected to a life evaluation, and calculates a life evaluation stress to be used in evaluating the life of the first evaluation portion based on a nozzle stub type, a parent pipe dimension, a nozzle stub dimension, an evaluation pressure, an evaluation temperature, and a steel type related to the first evaluation portion;
and a first life evaluation unit that evaluates the life of the first evaluation portion based on the life evaluation stress.

(2) A life evaluation method according to at least one embodiment of the present disclosure,
A step of setting at least one of a nozzle stub welded portion of a header or piping of a thermal power plant or a base material portion around a nozzle stub hole of the header or piping as a first evaluation portion to be subjected to a life evaluation, and calculating a life evaluation stress to be used in evaluating the life of the first evaluation portion based on a nozzle stub type, a parent pipe dimension, a nozzle stub dimension, an evaluation pressure, an evaluation temperature, and a steel type related to the first evaluation portion;
and evaluating the life of the first evaluation portion based on the life evaluation stress.

According to at least one embodiment of the present disclosure, the lifespan of a pipe stub can be evaluated with relatively high accuracy in a short period of time.

1 is a block diagram showing a configuration of a life assessment system according to an embodiment of the present invention. 10 is a flowchart illustrating an outline of a life assessment procedure for a first evaluation portion of the life assessment system according to the present embodiment. 1 is an example of a cross-sectional view of a piping in the vicinity of a nozzle weld; FIG. 13 is a diagram showing an example of a nozzle type. FIG. 13 is a diagram showing an example of a nozzle type. FIG. 13 is a diagram showing an example of a nozzle type. FIG. 13 is a diagram showing an example of a nozzle type. FIG. 13 is a diagram showing an example of a nozzle type. FIG. 13 is a diagram showing an example of a nozzle type. 1 is an example of a graph showing a relationship between a stress coefficient β and a variable βx. 13 is an example of a table showing the results of life evaluation of the first evaluation portion displayed on the output unit. 10 is a flowchart illustrating an outline of a life assessment procedure for a second evaluation portion of the life assessment system according to the present embodiment. 1 is an example of a graph showing a time history of a life evaluation stress σ and a change over time in a cumulative life consumption rate. 13 is an example of a table showing the results of life evaluation of the second evaluation portion displayed on the output unit.

Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as the embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure.
For example, expressions expressing relative or absolute configuration, such as "in a certain direction,""along a certain direction,""parallel,""orthogonal,""center,""concentric," or "coaxial," not only strictly express such a configuration, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained.
For example, expressions indicating that things are in an equal state, such as "identical,""equal," and "homogeneous," not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained.
For example, expressions describing shapes such as a rectangular shape or a cylindrical shape do not only refer to rectangular shapes, cylindrical shapes, etc. in the strict geometric sense, but also refer to shapes that include uneven portions, chamfered portions, etc., to the extent that the same effect is obtained.
On the other hand, the expressions "comprise,""include,""have,""includes," or "have" of one element are not exclusive expressions excluding the presence of other elements.

(Overall configuration of life evaluation system 100)
FIG. 1 is a block diagram showing the configuration of a life assessment system according to this embodiment.
The life assessment system according to this embodiment is a system for assessing the life of pipes in a thermal power plant.
The life assessment system 100 according to this embodiment includes a processing unit 101 , an input unit 103 , a storage unit 105 , and an output unit 107 .
The processing unit 101 is a computer system provided together with the input unit 103, the storage unit 105, and the output unit 107. The life assessment system 100 may be a server provided on a network and having the functions of the processing unit 101. If the processing unit 101 is a server provided on a network, the storage unit 105 may be a database provided on the network, and the input unit 103 and the output unit 107 may be part of a terminal connected via the network.

The input unit 103 is an input device such as a keyboard or mouse, and is used to input various data required for life assessment of piping in a thermal power plant.

The processing unit 101 is composed of a CPU and the like, and executes various programs stored in the memory unit 105 to perform various processes required for the life evaluation system 100. In this embodiment, the processing unit 101 has a first stress calculation unit 111, a first life evaluation unit 113, a second stress calculation unit 121, a time history calculation unit 122, and a second life evaluation unit 123 as functional blocks. The first stress calculation unit 111, the first life evaluation unit 113, the second stress calculation unit 121, the time history calculation unit 122, and the second life evaluation unit 123 will be described in detail later.

The memory unit 105 stores various programs used for processing by the processing unit 101, as well as various data required to execute the programs.

The output unit 107 is a so-called monitor or other notification device, and outputs the evaluation results of the life span of the piping of the thermal power plant calculated by the processing unit 101 as output data.

(Life evaluation of piping in thermal power plants)
In the boiler equipment and piping equipment installed in thermal power plants, high-chromium steel, which is classified as a high-strength heat-resistant steel, is used as the operating temperatures rise. However, the joints between the parent pipes of headers and piping and the pipes connected to them that make up the pipe stubs are in a severe stress environment where thermal stress, internal pressure, and bending stress due to self-weight are added, making it essential to evaluate creep damage.
There are various shapes and sizes of nozzles, and the tendency of generated stress varies depending on the shape and size. Therefore, in order to properly evaluate the life span, evaluation by FEM elastic creep analysis is necessary. However, since the nozzle shapes used in thermal power plants are diverse, evaluation by FEM elastic creep analysis requires a lot of time and effort.

After careful consideration, the inventors discovered that by performing an FEM elastic creep analysis in advance for multiple patterns with different nozzle stub types and dimensions of each part of the nozzle stub, and parameterizing the life evaluation stress based on the analysis results, it is possible to easily calculate the life evaluation stress from the nozzle stub type, parent pipe dimensions, nozzle stub dimensions, evaluation pressure, evaluation temperature, and steel type. This allows the life evaluation of the nozzle stub to be evaluated relatively accurately when evaluating the life of the first evaluation portion, without having to perform a new FEM elastic creep analysis.

(Regarding life evaluation of the first evaluation portion in the life evaluation system 100)
Hereinafter, the life assessment in the life assessment system 100 according to this embodiment will be described.
FIG. 2 is a flow chart that outlines a procedure for evaluating a life span of the first evaluation portion of the life span evaluation system 100 according to this embodiment.
The life assessment method using the life assessment system 100 of this embodiment includes step S1 of inputting data regarding the first evaluation portion, step S3 of calculating the life assessment stress, step S5 of evaluating the life, and step S7 of outputting the results of the life assessment.

(Step S1 of inputting data on the first evaluation site)
In this embodiment, step S1 of inputting data related to the first evaluation portion is a step of inputting various data related to the first evaluation portion to the processing unit 101.
Here, the first evaluation portion according to the present embodiment is a header of a thermal power plant or a nozzle stub welded portion of a piping of a thermal power plant, and a base material portion around a nozzle stub hole of the header or the piping. Note that the first evaluation portion may be either a header of a thermal power plant or a nozzle stub welded portion of a piping of a thermal power plant, or a base material portion around a nozzle stub hole of the header or the piping.
In the following description, the headers and piping of a thermal power plant may be simply referred to as piping.

Fig. 3 is an example of a cross-sectional view of a pipe near a nozzle stub welded portion. In the example of Fig. 3, the first evaluation portion 5 according to the present embodiment is the nozzle stub welded portion 41 and the base material portion (base material portion around the nozzle stub hole) 23 around the nozzle stub hole 21 of the pipe 10 (parent pipe 20).
The nozzle stub welded portion 41 of the piping of the thermal power plant may be, for example, a nozzle stub welded portion of a boiler header, or may be a nozzle stub welded portion of the piping of the thermal power plant other than the boiler header. The nozzle stub hole surrounding base material portion 23 of the piping of the thermal power plant may be, for example, a portion where the nozzle stub hole 21 is formed in the parent pipe 20 of the boiler header, or may be a portion where the nozzle stub hole 21 is formed in the parent pipe 20 of the boiler piping other than the boiler header.

In step S1 of inputting data related to the first evaluation area 5, various data related to the first evaluation area 5 may be input from the input unit 103, or data stored in the memory unit 105 may be read out and input to the processing unit 101.

In step S1 of inputting data relating to the first evaluation portion 5, the various data relating to the first evaluation portion 5 input to the processing unit 101 include data relating to the nozzle 30 related to the first evaluation portion 5, which is the subject of life evaluation, the evaluated pressure, the evaluated temperature, the type of steel, etc.
Data relating to the nozzle 30 for the first evaluation portion 5 includes the nozzle type, main pipe dimensions, and nozzle dimensions, which will be described later.
Here, the evaluated pressure is the internal pressure of the pipe 10 associated with the first evaluation portion 5 , and the evaluated temperature is the temperature of the pipe 10 associated with the first evaluation portion 5 .
The type of steel refers to the type of material of the piping 10 related to the first evaluation portion, such as modified 2Cr steel, modified 9Cr steel, 12Cr steel, etc., which are classified as high-strength heat-resistant steel.

(About the type of pipe stand)
The nozzle stub type included in the data regarding the nozzle 30 relating to the first evaluation portion 5 is information indicating what type the nozzle stub type is classified from at least one of the following perspectives: the positional relationship between the parent pipe 20 and the connecting pipe (pipe stub) 30, whether the connecting pipe 30 penetrates the parent pipe 20, or the shape of the nozzle stub weld 41.
4A to 4F are diagrams showing examples of nozzle types classified from the above perspective.
The nozzle 30 (nozzle 31) as shown in Fig. 4A is called Type A, the nozzle 30 (nozzle 32) as shown in Fig. 4B is called Type B, and the nozzle 30 (nozzle 33) as shown in Fig. 4C is called Type C. The nozzle 30 (nozzle 34) as shown in Fig. 4D is called Type E, the nozzle 30 (nozzle 35) as shown in Fig. 4E is called Type F, and the nozzle 30 (nozzle 36) as shown in Fig. 4F is called Type G.

In this embodiment, the nozzle types are classified according to, for example, the positional relationship between the mother pipe 20 and the connecting pipe (nozzle stub 30). In this case, the nozzle types are classified according to whether they are set-on or set-in nozzles. A set-on nozzle is a type of nozzle in which the connecting pipe (nozzle stub 30) sits on top of the mother pipe 20, such as type A nozzle stub 31 shown in Figure 4A. A set-in nozzle is a type of nozzle in which the mother pipe 20 is countersunk and the connecting pipe is inserted into the countersunk hole, such as type B nozzle stub 32 shown in Figure 4B.

In this embodiment, the nozzle types are classified according to whether or not the connecting pipe passes through the mother pipe. For example, in the F-type nozzle 35 shown in FIG. 4E, the connecting pipe (nozzle 35) passes through the mother pipe 20, while in the other types of nozzle stubs 30 shown in FIGS. 4A to 4D and 4F, the connecting pipe (nozzle stub 30) does not pass through the mother pipe 20.

In this embodiment, the nozzle types may be classified according to, for example, the shape of the nozzle weld or the shape of the groove.
In this embodiment, the nozzle types may be classified, for example, by the depth of the countersunk hole in the set-in nozzle, the taper angle, etc. For example, in the B-type nozzle 32 shown in Fig. 4B, the depth of the countersunk hole is relatively shallow, and in the G-type nozzle 36 shown in Fig. 4F, the depth of the countersunk hole is relatively deep.

(Step S3 of calculating life evaluation stress)
In this embodiment, step S3 of calculating the life evaluation stress is a step of calculating the life evaluation stress σ to be used for evaluating the life of the first evaluation portion 5 based on the various data input in step S1 of inputting data regarding the first evaluation portion.

After extensive research, the inventors discovered that the life evaluation stress can be easily calculated by multiplying the stress that serves as the basis for the life evaluation stress σ, such as the outer surface hoop stress σθsurface of the parent pipe 20, by a stress coefficient β, which is determined in advance based on the pipe stub type, parent pipe dimensions, pipe stub dimensions, evaluation pressure, and evaluation temperature, as described below.

FIG. 5 is an example of a graph showing the relationship between the stress coefficient β and the variable βx.
The stress coefficient β according to this embodiment is determined as a value proportional to a variable βx described below.
The variable βx is expressed as a function having variables such as the outer diameter D of the mother pipe 20, the outer diameter d of the nozzle stub 30, the wall thickness T of the mother pipe 20, the wall thickness t of the nozzle stub, the depth z of the countersunk hole, the groove angle h, the weld leg length b0, etc., as in the following formula (1). Note that these variables are data input in step S1 of inputting data related to the first evaluation portion 5.
βx=f(D, d, T, t, z, h, b0) ... (1)

The function for calculating the variable βx is determined in advance for each nozzle type and for each of the first evaluation portions (the nozzle stub welded portion 41 and the nozzle stub hole-surrounding base material portion 23) and is stored in the storage unit 105. In addition, the relationship between the stress coefficient β and the variable βx as shown in FIG. 5 is also determined in advance for each nozzle type and for each of the first evaluation portions (the nozzle stub welded portion 41) and is stored in the storage unit 105.
In addition, for the first evaluation portion (the base material portion 23 around the nozzle hole), stress coefficients and variables according to the outer diameter and thickness of the mother pipe and the nozzle are predetermined and stored in the memory unit 105.
In step S3 of calculating the life evaluation stress, the first stress calculation unit 111 in the processing unit 101 reads out a function for calculating the variable βx and information on the relationship between the stress coefficient β and the variable βx from the storage unit 105 based on the nozzle type and the part of the first evaluation part input in step S1 of inputting data on the first evaluation part. Then, the first stress calculation unit 111 calculates the variable βx and the stress coefficient β.

Next, the first stress calculation unit 111 calculates a stress that is a reference for the life evaluation stress σ, such as the outer surface hoop stress σθsurface of the mother pipe 20, from the evaluation pressure input in step S1 of inputting data related to the first evaluation portion. Then, the first stress calculation unit 111 multiplies the calculated stress by a stress coefficient β to calculate the life evaluation stress σ, for example, as in the following formula (2).
σ=σθsurface×β...(2)

(Regarding the correction coefficient Ψ)
In step S3 of calculating the life assessment stress, the first stress calculation unit 111 may further calculate the life assessment stress σ by taking into account a correction coefficient Ψ that is predetermined based on the inspection results of the piping 10 and the internal pressure creep test results, for example, as shown in the following equation (3).
The correction coefficient Ψ is a correction coefficient that is determined in advance based on the inspection results and the internal pressure creep test results of the pipe 10 in order to improve the accuracy of the life evaluation for the first evaluation portion based on the life evaluation stress σ. The correction coefficient Ψ is stored in the storage unit 105.
σ=σθsurface×β×Ψ...(3)

As described above, in the life assessment system 100 of this embodiment, the first stress calculation unit 111 calculates the life assessment stress σ taking into account the stress coefficient β that is predetermined based on the nozzle type, main pipe dimensions, nozzle dimensions, evaluation pressure, and evaluation temperature.
This makes it possible to immediately determine the stress coefficient β from the nozzle type, the mother pipe dimensions, the nozzle dimensions, the evaluation pressure, and the evaluation temperature, and to easily calculate the life evaluation stress σ by multiplying the determined stress coefficient β by the stress that is the basis of the life evaluation stress σ. This makes it possible to evaluate the life of the nozzle 30 relatively accurately in a short time.

In the life assessment system 100 according to this embodiment, the first stress calculation unit 111 may calculate the life assessment stress σ taking into account a predetermined correction coefficient Ψ based on the inspection results of the piping 10 and the internal pressure creep test results.
This improves the accuracy of the life evaluation of the nozzle 30.

In the life assessment system 100 according to this embodiment, the accuracy of the life assessment of the nozzle 30 can be improved by taking into account the nozzle type as described above.

(Step S5 of evaluating the lifespan)
Step S5 of evaluating the life according to this embodiment is a step of evaluating the life of the first evaluation portion 5 based on the life evaluation stress σ calculated in step S3 of calculating the life evaluation stress. In step S5 of evaluating the life, the first life evaluation unit 113 in the processing unit 101 calculates the life of the first evaluation portion 5 based on the life evaluation stress σ calculated in step S3 of calculating the life evaluation stress. Specifically, the first life evaluation unit 113 calculates the life by determining the creep damage rate of the first evaluation portion 5 for each small time period based on the life evaluation stress σ.
Here, the first life evaluation unit 113 may calculate the life of the first evaluation portion 5 based on the life evaluation stress σ obtained by the above-mentioned formula (3). The first life evaluation unit 113 may also calculate the life of the first evaluation portion 5 based on the life evaluation stress σ obtained by the above-mentioned formula (2).

The life calculated in step S5 of evaluating the life is at least one of the initial crack initiation life of the nozzle stub weld toe 41a (see FIG. 3) related to the first evaluation portion 5, the life of the nozzle stub hole surrounding base material portion 23 related to the first evaluation portion 5, or the fracture life of the nozzle stub weld portion 41 related to the first evaluation portion 5. In the following description, the life calculated in step S5 of evaluating the life is the initial crack initiation life of the nozzle stub weld toe 41a (see FIG. 3) related to the first evaluation portion 5, the crack propagation life from the nozzle stub weld toe 41a or the nozzle stub internal weld unwelded portion 42a (see FIG. 3), the life of the nozzle stub hole surrounding base material portion 23 related to the first evaluation portion 5, and the fracture life of the nozzle stub weld portion 41 related to the first evaluation portion 5.

As described above, the life assessment system 100 of this embodiment includes a first stress calculation unit 111 that calculates a life assessment stress σ to be used for assessing the life of the first evaluation portion 5 based on the nozzle type, parent pipe dimensions, nozzle dimensions, evaluated pressure, evaluated temperature, and steel type related to the first evaluation portion 5, and a first life assessment unit 113 that evaluates the life of the first evaluation portion 5 based on the life assessment stress σ.
As a result, the life of the piping 10 including the nozzle 30 can be evaluated relatively accurately without newly performing an FEM elastic creep analysis when evaluating the life of the first evaluation portion 5. Therefore, according to the life evaluation system 100 according to the present embodiment, the life of the piping 10 including the nozzle 30 can be evaluated relatively accurately in a short period of time.

In the life assessment system 100 of this embodiment, the first life assessment unit 113 calculates at least one of the initial crack initiation life of the nozzle stub weld toe 41a relating to the first evaluation portion 5, the life of the nozzle stub hole-surrounding base material portion 23 relating to the first evaluation portion 5, or the fracture life of the nozzle stub weld portion 41 relating to the first evaluation portion 5, based on the life assessment stress σ.
This allows a life evaluation to be performed corresponding to the type of damage in the piping 10 including the nozzle 30.

In the life assessment system 100 according to this embodiment, the first life assessment unit 113 calculates the propagation life of a crack from the nozzle stub weld toe 41a or the nozzle stub internal unwelded portion 42a (see FIG. 3) related to the first evaluation portion 5 based on the life assessment stress σ.
This allows for a life evaluation based on cracks generated from the nozzle stub weld toe 41a.

The life assessment method using the life assessment system 100 according to this embodiment includes step S3 of calculating the life assessment stress and step S5 of assessing the life.
As a result, as described above, the life of the nozzle 30 can be evaluated relatively accurately without newly performing an FEM elastic creep analysis when evaluating the life of the first evaluation portion 5. Therefore, according to the life evaluation method using the life evaluation system 100 according to the present embodiment, the life of the piping 10 including the nozzle 30 can be evaluated relatively accurately in a short period of time.

(Step S7 of outputting the result of the life evaluation)
Step S7 of outputting the result of the lifespan evaluation according to this embodiment is a step of outputting the lifespan of the first evaluation part 5 calculated in step S5 of evaluating the lifespan to the output unit 107 as the result of the lifespan evaluation. In step S7 of outputting the result of the lifespan evaluation, the first lifespan evaluation unit 113 generates display data for displaying the lifespan of the first evaluation part 5 calculated in step S5 of evaluating the lifespan on the output unit 107 and outputs the display data to the output unit 107. Note that the first lifespan evaluation unit 113 may generate the lifespan of the first evaluation part 5 calculated in step S5 of evaluating the lifespan as, for example, audio data and output the audio data to the output unit 107. That is, the data output in step S7 of outputting the result of the lifespan evaluation is not limited to display data.
FIG. 6 is an example of a table showing the results of the life evaluation of the first evaluation portion 5 displayed on the output unit 107.

As shown in Figure 6, the result 70 of the lifespan evaluation of the first evaluation portion 5 displayed on the output unit 107 includes various data 71 input in step S1 of inputting data regarding the first evaluation portion 5, and the result 73 of the lifespan evaluation of the first evaluation portion 5.
As shown in Figure 6, the result 73 of the life evaluation of the first evaluation portion 5 includes an initial crack initiation life 731 of the nozzle stub weld toe 41a relating to the first evaluation portion 5, a crack propagation life 733 from the nozzle stub weld toe 41a or the nozzle stub internal unwelded portion 42a (see Figure 3), a life 735 of the nozzle stub hole-surrounding base material portion 23 relating to the first evaluation portion 5, and a fracture life 737 of the nozzle stub weld portion 41 relating to the first evaluation portion 5.

In addition, the evaluated stress σ1 shown in the life evaluation result 73 of the first evaluation portion 5 is the life evaluation stress σ used to calculate the fracture life 737 of the nozzle stub weld portion 41 related to the first evaluation portion 5.
The evaluated stress σ2 shown in the life evaluation result 73 of the first evaluation portion 5 is the life evaluation stress σ used to calculate the initial crack initiation life 731 of the pipe stub weld toe 41a related to the first evaluation portion 5.
The evaluated stress σ3 shown in the result 73 of the life evaluation of the first evaluation portion 5 is the life evaluation stress σ used to obtain the propagation life 733 of a crack from the nozzle stub weld toe 41a.
The evaluated stress σ4 shown in the result 73 of the life evaluation of the first evaluation portion 5 is the life evaluation stress σ used to determine the life 735 of the base material portion 23 around the nozzle hole related to the first evaluation portion 5.

(Regarding life evaluation of the second evaluation portion in the life evaluation system 100)
Further, the lifespan assessment in the lifespan assessment system 100 according to this embodiment will be described.
Thermal stress and stresses generated by external forces, such as stress due to internal pressure and bending stress due to the weight, act on the base material of the pipe 10 of a thermal power plant, the longitudinal welded portion of the pipe 10, and the circumferential welded portion of the pipe 10. Since a relaxation phenomenon occurs in which this thermal stress decreases over time, in order to grasp an appropriate lifespan, it is necessary to perform an evaluation taking this relaxation phenomenon into consideration. Conventionally, FEM elastic creep analysis has been performed for creep damage evaluation (lifespan evaluation) taking the relaxation phenomenon into consideration, which required a great deal of time and effort.
In the following description, when the base material portion of the piping 10 of a thermal power plant, the longitudinal welded portion of the piping 10, or the circumferential welded portion of the piping 10 is the subject of life evaluation, these portions are referred to as the second evaluation portions.

The life evaluation initial stress used to evaluate the life of the second evaluation part is calculated based on the initial stress at the time of design of the second evaluation part, the type of the second evaluation part, the evaluation pressure, the evaluation temperature, and the type of steel, and the life of the second evaluation part can be evaluated by calculating the time history of the life consumption rate of the second evaluation part based on the calculated life evaluation initial stress, taking into account stress relaxation of the thermal expansion stress in the second evaluation part.
Here, for the initial stress at the time of designing the second evaluation portion, the life of the second evaluation portion can be evaluated with relatively high accuracy without performing FEM elastic creep analysis for life evaluation considering the relaxation phenomenon by using the analysis results of a general-purpose piping stress analysis system that is generally used when designing the piping 10. In other words, since the analysis results of the general-purpose piping stress analysis system are obtained at the time of designing the piping 10, by acquiring the initial stress at the time of designing the second evaluation portion that is included in this analysis result, the life evaluation initial stress used for evaluating the life of the second evaluation portion can be easily calculated.
Therefore, in the lifespan assessment system 100 according to this embodiment, the lifespan of the second assessment portion is assessed as follows.

FIG. 7 is a flow chart that outlines a procedure for evaluating a life span of the second evaluation portion of the life span evaluation system 100 according to this embodiment.
The life assessment method using the life assessment system 100 of this embodiment includes step S11 of inputting data regarding the second evaluation portion, step S12 of inputting an initial stress, step S13 of calculating the life assessment stress, step S14 of calculating a time history, step S15 of evaluating the life, and step S17 of outputting the results of the life assessment.

(Step S11 of inputting data related to the second evaluation site)
In this embodiment, step S11 of inputting data related to the second evaluation portion is a step of inputting various data related to the second evaluation portion to the processing unit 101.
Here, the second evaluation portion according to the present embodiment is a base material portion of the piping 10 of a thermal power plant, a longitudinal welded portion of the piping 10, and a circumferential welded portion of the piping 10. Note that the second evaluation portion may be any of the base material portion of the piping 10 of a thermal power plant, the longitudinal welded portion of the piping 10, and the circumferential welded portion of the piping 10.
The piping 10 may be a boiler header piping or may be a boiler piping other than a boiler header. The piping 10 may be a main pipe 20 or a nozzle 30.

In step S11 of inputting data related to the second evaluation area, various data related to the second evaluation area may be input from the input unit 103, or data stored in the memory unit 105 may be read out and input to the processing unit 101.

In step S11 of inputting data on the second evaluation portion, the various data on the second evaluation portion input to the processing unit 101 include data on the dimensions of the piping 10, the evaluated pressure, the evaluated temperature, the type of steel, etc., related to the second evaluation portion that is the subject of life evaluation.
Here, the evaluated pressure is the internal pressure of the pipe 10 associated with the second evaluation portion, and the evaluated temperature is the temperature of the pipe 10 associated with the second evaluation portion.
In addition, the type of steel refers to the type of material of the piping 10 related to the second evaluation portion, such as modified 2Cr steel, modified 9Cr steel, 12Cr steel, etc., which are classified as high-strength heat-resistant steel.

(Step S12 for inputting initial stress)
In the present embodiment, step S12 of inputting the initial stress is a step of inputting the initial stress at the time of designing the second evaluation portion. In step S12 of inputting the initial stress, the initial stress at the time of designing the second evaluation portion is acquired from the analysis result of the general-purpose piping stress analysis system obtained at the time of designing the piping 10.
For example, if the analysis results of a general-purpose piping stress analysis system, or the initial stress at the time of design of the second evaluation portion included in the analysis results, are stored in advance in the memory unit 105, then in step S12 of inputting the initial stress, the initial stress at the time of design of the second evaluation portion can be read out and obtained from the memory unit 105.

(Step S13 of calculating life evaluation stress)
Step S13 of calculating the life evaluation stress according to this embodiment is a step of calculating an initial stress (life evaluation initial stress) of the life evaluation stress σ used in evaluating the life of the second evaluation portion based on various data input in step S11 of inputting data related to the second evaluation portion and various data input to the processing unit 101 in step S12 of inputting the initial stress. In step S13 of calculating the life evaluation stress, the second stress calculation unit 121 of the processing unit 101 calculates the life evaluation initial stress from the initial stress at the time of designing the second evaluation portion, taking into consideration the various data input in step S11 of inputting data related to the second evaluation portion and the data on the dimensions of the pipe 10 related to the second evaluation portion among the various data input to the processing unit 101 in step S12 of inputting the initial stress.

(Step S14 of calculating time history)
In this embodiment, step S14 of calculating the time history is a step of calculating the time history of the stress relaxation trajectory of the second evaluation portion (time history of the life evaluation stress σ) taking into account the stress relaxation of the thermal expansion stress in the second evaluation portion based on the life evaluation initial stress calculated in step S13 of calculating the life evaluation stress.
8 is an example of a graph showing the time history of the life evaluation stress σ and the change over time in the cumulative life consumption rate. In the graph shown in FIG. 8, the horizontal axis is a logarithmic axis relating to elapsed time.
In step S14 of calculating the time history, the time history calculation unit 122 of the processing unit 101 calculates the stress relaxation trajectory in terms of time history, taking into account the primary creep 91, which has a relatively high speed, and the secondary creep 92, which has a relatively low speed.

(Step S15 for evaluating the lifespan)
In this embodiment, the step S15 of evaluating the life is a step of calculating the life (accumulated life consumption rate) of the second evaluation portion based on the time history of the life evaluation stress σ calculated in the step S14 of calculating the time history. In the step S15 of evaluating the life, the second life evaluation unit 123 of the processing unit 101 calculates the cumulative life consumption rate by calculating the creep damage degree for each minute time based on the time history of the life evaluation stress σ calculated in the step S14 of calculating the time history.
The cumulative life consumption rate is set to 0 in the initial state of the pipe 10 where no creep damage has accumulated, and 1 in the state where creep damage has accumulated to the point where the pipe 10 breaks.

(Step S17 of outputting the result of the life evaluation)
Step S17 of outputting the result of the lifespan evaluation according to this embodiment is a step of outputting the lifespan of the second evaluation part calculated in step S15 of evaluating the lifespan to the output unit 107 as the result of the lifespan evaluation. In step S17 of outputting the result of the lifespan evaluation, the second lifespan evaluation unit 123 generates display data for displaying the lifespan of the second evaluation part calculated in step S15 of evaluating the lifespan on the output unit 107 and outputs the display data to the output unit 107. Note that the second lifespan evaluation unit 123 may generate the lifespan of the second evaluation part calculated in step S15 of evaluating the lifespan as, for example, audio data and output the audio data to the output unit 107. That is, the data output in step S17 of outputting the result of the lifespan evaluation is not limited to display data.
FIG. 9 is an example of a table showing the results of the life evaluation of the second evaluation portion displayed on the output unit 107.

As shown in Figure 9, the result 80 of the life evaluation of the second evaluation part displayed on the output unit 107 includes various data 81 input in step S11 of inputting data related to the second evaluation part, data 82 such as initial stress at the time of designing the second evaluation part obtained in step S12 of inputting the initial stress, and the result 83 of the life evaluation of the second evaluation part.
In the example shown in Figure 9, the result 83 of the life evaluation of the second evaluation portion includes, for example, the life of the circumferential weld of the weld joint if the second evaluation portion is the welded portion of a welded joint, and includes the life of the base material portion of the piping 10 if the second evaluation portion is the base material of the piping 10.

When the second evaluation portion is a bend portion such as an elbow or a bent pipe, the second stress calculation unit 121 may calculate the initial stress for life evaluation taking into account the circumferential thickness distribution of the elbow or bend portion. When the second evaluation portion is an elbow or a bend portion, the time history calculation unit 122 may calculate the above-mentioned time history taking into account the thickness distribution.
That is, the elbows and bent portions of the piping 10 of a thermal power plant are manufactured by bending a straight pipe, and therefore the elbows and bends have a distribution of wall thickness in the circumferential direction.
As described above, by taking into consideration the circumferential thickness distribution at the elbow or bend portion, the accuracy of the life evaluation of the second evaluation portion can be improved.

(About the types of steel)
In some embodiments, the type of steel material for the pipe 10 has been described as being high-strength heat-resistant steel, but is not limited to this.
That is, in some embodiments, each portion of the piping 10 may be formed of, for example, high chromium steel containing about 9 to 12 mass % chromium or low alloy steel containing about 1 to 3 mass % chromium. In some embodiments, the type of steel material for the piping 10 may be any of various steel materials used in the creep temperature range.

The present disclosure is not limited to the above-described embodiments, but also includes variations of the above-described embodiments and appropriate combinations of these embodiments.

The contents described in each of the above embodiments can be understood, for example, as follows.
(1) A life assessment system 100 according to at least one embodiment of the present disclosure has at least one of a nozzle stub welded portion 41 of a header or piping 10 of a thermal power plant or a nozzle stub hole-around base material portion 23 of the header or piping 10 as a first evaluation portion 5 which is the subject of life assessment, and is equipped with a first stress calculation unit 111 which calculates a life assessment stress σ to be used in assessing the life of the first evaluation portion 5 based on the nozzle stub type, parent pipe dimensions, nozzle stub dimensions, evaluated pressure, evaluated temperature, and steel type related to the first evaluation portion 5, and a first life assessment unit 113 which evaluates the life of the first evaluation portion 5 based on the life assessment stress σ.

After careful consideration, the inventors discovered that by performing an FEM elastic creep analysis in advance for multiple patterns with different nozzle stub types and dimensions of each part of the nozzle stub, and parameterizing the life evaluation stress σ based on the analysis results, the life evaluation stress σ can be easily calculated from the nozzle stub type, parent pipe dimensions, nozzle stub dimensions, evaluation pressure, evaluation temperature, and steel type. This allows the life evaluation of the piping 10 including the nozzle stub 30 to be evaluated relatively accurately when evaluating the life of the first evaluation portion 5, without having to perform a new FEM elastic creep analysis. Therefore, according to the above configuration (1), the life of the piping 10 including the nozzle stub 30 can be evaluated relatively accurately in a short period of time.

(2) In some embodiments, in the configuration of (1) above, the first life evaluation unit 113 may calculate at least one of the initial crack initiation life of the nozzle stub weld toe 41a relating to the first evaluation portion 5, the life of the nozzle stub hole surrounding base material portion 23 relating to the first evaluation portion 5, or the fracture life of the nozzle stub weld portion 41 relating to the first evaluation portion 5 based on the life evaluation stress σ.

The above configuration (2) allows for a life evaluation that corresponds to the type of damage in the piping 10, including the pipe base 30.

(3) In some embodiments, in the configuration of (2) above, the first life evaluation unit 113 may calculate the propagation life of a crack from the nozzle stub weld toe 41a or the nozzle stub internal unwelded portion 42a (see FIG. 3) related to the first evaluation portion 5 based on the life evaluation stress σ.

The above configuration (3) allows for life evaluation based on cracks that occur at the nozzle stub weld toe 41a or the nozzle stub internal unwelded portion 42a (see Figure 3).

(4) In some embodiments, in any of the configurations (1) to (3) above, the first stress calculation unit 111 may calculate the life evaluation stress σ taking into account a predetermined stress coefficient β based on the nozzle type, main pipe dimensions, nozzle dimensions, evaluation pressure, and evaluation temperature.

According to the above configuration (4), the above stress coefficient β can be immediately calculated from the nozzle stub type, the parent pipe dimensions, the nozzle stub dimensions, the evaluation pressure, and the evaluation temperature, and the life evaluation stress σ can be easily calculated by multiplying the calculated stress coefficient β by the stress that is the basis for the life evaluation stress σ. This allows the life of the piping 10 including the nozzle stub 30 to be evaluated relatively accurately in a short period of time.

(5) In some embodiments, in the configuration of (4) above, the first stress calculation unit 111 may calculate the life evaluation stress σ taking into account the inspection results of the pipe 10 and a predetermined correction coefficient Ψ based on the internal pressure creep test results.

The above configuration (5) can improve the accuracy of the life evaluation of the piping 10 including the pipe stand 30.

(6) In some embodiments, in any of the configurations (1) to (5) above, the nozzle type may be classified from at least one of the following perspectives: the positional relationship between the main pipe 20 and the connecting pipe (nozzle stub 30), whether the connecting pipe (nozzle stub 30) penetrates the main pipe 20, or the shape of the nozzle stub weld 41.

According to the above configuration (6), by taking into account the nozzle types classified from the above viewpoints, the accuracy of the life evaluation of the piping 10 including the nozzle 30 can be improved.

(7) In some embodiments, in any of the configurations (1) to (6) above, at least one of the base material portion of the pipe 10, the longitudinal weld portion of the pipe 10, and the circumferential weld portion of the pipe 10 is the second evaluation portion to be evaluated for life, and a second stress calculation unit 121 is provided that calculates a life evaluation initial stress to be used in evaluating the life of the second evaluation portion based on the initial stress at the time of design of the second evaluation portion, the type of the second evaluation portion, the evaluation pressure, the evaluation temperature, and the steel type, a time history calculation unit 122 that calculates the time history of the stress relaxation trajectory of the second evaluation portion based on the life evaluation initial stress and taking into account the stress relaxation of the thermal expansion stress in the second evaluation portion, and a second life evaluation unit 123 that evaluates the life of the second evaluation portion based on the time history.

According to the above configuration (7), the life evaluation initial stress used to evaluate the life of the second evaluation part is calculated based on the initial stress at the time of designing the second evaluation part, the type of the second evaluation part, the evaluation pressure, the evaluation temperature, and the type of steel, and the life of the second evaluation part can be evaluated by calculating the time history of the life consumption rate of the second evaluation part based on the calculated life evaluation initial stress and taking into account the stress relaxation of the thermal expansion stress in the second evaluation part.

(8) In some embodiments, in the configuration of (7) above, when the second evaluation portion is an elbow or a bend, the second stress calculation unit 121 may calculate the initial life evaluation stress taking into account the circumferential thickness distribution at the elbow or bend. When the second evaluation portion is an elbow or a bend, the time history calculation unit 122 may calculate the above time history taking into account the thickness distribution.

Bends such as elbows and bent pipes of the piping 10 of a thermal power plant are manufactured by bending a straight pipe, and therefore the bent portion has a distribution of wall thickness in the circumferential direction.
According to the above configuration (8), by taking into consideration the circumferential thickness distribution in the bent portion, it is possible to improve the accuracy of the life evaluation of the second evaluation portion.

(9) In some embodiments, in any of the configurations (1) to (8) above, the type of steel may include high-chromium steel, which is a high-strength heat-resistant steel.

Like configuration (9) above, configurations (1) to (8) above are suitable for evaluating the life span of piping 10 in a thermal power plant that is made of high chromium steel.

(10) A life assessment method according to at least one embodiment of the present disclosure includes a first evaluation portion 5 that is the subject of life assessment, which is at least one of the nozzle stub welded portion 41 of a piping 10 of a thermal power plant and the base material portion 23 around the nozzle stub hole of the piping 10, and includes a step of calculating a life assessment stress σ to be used in assessing the life of the first evaluation portion 5 based on the nozzle stub type, parent pipe dimensions, nozzle stub dimensions, evaluation pressure, evaluation temperature, and steel type related to the first evaluation portion 5 (step S3 of calculating life assessment stress σ), and a step of evaluating the life of the first evaluation portion 5 based on the life assessment stress σ (step S5 of evaluating the life).

According to the method (10) above, as described above, when evaluating the life of the first evaluation portion 5, the life of the pipe stub can be evaluated relatively accurately without performing a new FEM elastic creep analysis. Therefore, according to the method (10) above, the life of the piping 10 including the pipe stub 30 can be evaluated relatively accurately in a short time.

5 First evaluation portion 10 Pipe 20 Main pipe 21 Pipe stub hole 23 Base material portion around pipe stub hole 30 Pipe stub (connecting pipe)
Reference Signs List 41: nozzle stub welded portion 41a: nozzle stub weld toe 42a: nozzle stub internal unwelded portion 100: life assessment system 101: processing portion 103: input portion 105: memory portion 107: output portion 111: first stress calculation portion 113: first life assessment portion 121: second stress calculation portion 122: time history calculation portion 123: second life assessment portion

Claims (9)

a first stress calculation unit which defines at least one of a nozzle stub welded portion of a header or piping of a thermal power plant or a base material portion around a nozzle stub hole of the header or piping as a first evaluation portion to be subjected to a life evaluation, and calculates a life evaluation stress to be used in evaluating the life of the first evaluation portion based on a nozzle stub type, a parent pipe dimension, a nozzle stub dimension, an evaluation pressure, an evaluation temperature, and a steel type related to the first evaluation portion;
a first life evaluation unit that evaluates a life of the first evaluation portion based on the life evaluation stress ,
The first stress calculation unit calculates the life evaluation stress in consideration of a stress coefficient that is predetermined based on the nozzle type, the mother pipe dimension, the nozzle dimension, the evaluation pressure, and the evaluation temperature.
Life assessment system. 2. The life assessment system according to claim 1, wherein the first life assessment unit calculates, based on the life assessment stress, at least one of an initial crack initiation life of a nozzle stub weld toe related to the first evaluation portion, a life of the nozzle stub hole-surrounding base material portion related to the first evaluation portion, or a fracture life of a nozzle stub weld related to the first evaluation portion. The life assessment system according to claim 2 , wherein the first life assessment unit calculates a propagation life of a crack from the nozzle weld toe related to the first evaluation portion based on the life assessment stress. The life assessment system according to any one of claims 1 to 3, wherein the first stress calculation unit calculates the life assessment stress taking into account a predetermined correction coefficient based on the inspection results of the piping and the results of an internal pressure creep test. A life assessment system as described in any one of claims 1 to 3, wherein the nozzle stub types are classified from at least one of the following perspectives: the positional relationship between the main pipe and the connecting pipe, whether or not the connecting pipe penetrates the main pipe, or the shape of the nozzle stub weld. a second stress calculation unit that sets at least one of a base metal portion of the piping, a longitudinal welded portion of the piping, and a circumferential welded portion of the piping as a second evaluation portion to be subjected to a life evaluation, and calculates a life evaluation initial stress to be used in evaluating the life of the second evaluation portion based on an initial stress at the time of design of the second evaluation portion, a type of the second evaluation portion, an evaluation pressure, an evaluation temperature, and a steel type;
a time history calculation unit that calculates a time history of a stress relaxation trajectory of the second evaluation portion based on the life evaluation initial stress and taking into account stress relaxation of the thermal expansion stress in the second evaluation portion;
a second life evaluation unit that evaluates a life of the second evaluation portion based on the time history;
The life evaluation system according to claim 1 , further comprising: the second stress calculation unit calculates the life evaluation initial stress in consideration of a circumferential thickness distribution at the elbow or the bend portion when the second evaluation portion is an elbow or a bend portion;
The life evaluation system according to claim 6 , wherein the time history life calculation unit calculates the time history taking into account the wall thickness distribution when the second evaluation portion is the elbow or the bend portion. The life evaluation system according to claim 1 , wherein the type of steel material includes high chromium steel, which is a high strength heat resistant steel. A step of setting at least one of a nozzle stub welded portion of a header or piping of a thermal power plant or a base material portion around a nozzle stub hole of the header or piping as a first evaluation portion to be subjected to a life evaluation, and calculating a life evaluation stress to be used in evaluating the life of the first evaluation portion based on a nozzle stub type, a parent pipe dimension, a nozzle stub dimension, an evaluation pressure, an evaluation temperature, and a steel type related to the first evaluation portion;
and evaluating a life of the first evaluation portion based on the life evaluation stress ,
In the step of calculating the life evaluation stress, the life evaluation stress is calculated in consideration of a stress coefficient that is predetermined based on the nozzle type, the mother pipe dimension, the nozzle dimension, the evaluation pressure, and the evaluation temperature.
Life assessment method.

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