JPH05256731A - System for evaluating fatigue strength of small-diameter pipe - Google Patents

Abstract

PURPOSE:To obtain a system for evaluating the fatigue-strength of a small- diameter pipe, which can generally monitor, evaluate and control the fatigue strength of the small-diameter pipe by combining the factors of high/low cycle- fatigue and the factor of outer/inner-surface crack development. CONSTITUTION:With respect to the outer-surface-crack development caused by high/low-cycle fatigue, welded-part-surface inspection (PT, VT and the like) 9 is performed, and evaluation 13 is performed. With respect to the inner- surface-crack development caused by high-cycle fatigue, welded-part-inner-face inspection (RT, UT and the like) 10 is performed. At the same time, pipe vibration measurement 11 is performed. A finite-element-analysis program 15 is performed. The results are analyzed 16 and evaluated 17. With regard to the inner-surface-crack development cuased by low-cycle fatigue, the welded-part- inner-face inspection 10 is performed, the pipe-vibration measurement 11 is performed, the finite-element analysis 15 is performed and the results are analyzed 16 and evaluated 17. When the results are not sound, countermeasures 14, which are necessary for both cases, are performed. The results are stored into a database 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small-diameter pipe fatigue strength evaluation system, and in particular, it accurately evaluates the fatigue strength of small-diameter pipes and manages fatigue strength data for efficient maintenance of small-diameter pipes. Relates to means for performing.

[0002]

2. Description of the Related Art Small diameter pipes having a diameter of about 2 B or less are often used in piping systems of power plants and the like, and socket type welded joints are usually used as welded joints in these small diameter pipes. ..

[0003]

[Problems to be Solved by the Invention] In fatigue strength control of medium-sized / large-diameter pipes in existing power plants, in-service inspection, non-destructive inspection of welded parts as ISI and internal inspection Pipe wall thickness erosion / corrosion monitoring by fluids is systematized and implemented. Since the piping system of medium / large-diameter piping in the power plant is manufactured and managed by high-level safety design, manufacturing technology, welding technology, construction quality control, etc., there are very few cases of damage due to fatigue. Moreover, if any damage is found, it is immediately replaced with a new one.

On the other hand, even small-diameter pipes are manufactured and controlled by high-level safety design, manufacturing technology, welding technology, construction quality control, etc. The measurement of pipe wall thickness as a material erosion / corrosion monitor has not been carried out sufficiently. Also,
If any damage is found, it cannot be concluded that it should be replaced with a new one immediately. In particular, there was no systematic evaluation and management method for fatigue strength, which is presumed to be a frequent cause of damage to small-diameter pipes.

That is, there are the following problems. As a fatigue strength control means for small-diameter pipes, we evaluated both high-cycle fatigue and low-cycle fatigue of the socket weld, which is the weakest point, and the crack propagation from the outer surface such as the toe of the socket weld was evaluated by them. In other words, small diameter that comprehensively manages all fatigue strength problems of small-diameter pipes by monitoring and evaluating both the crack growth on the outer surface and the crack growth from the inner surface such as the inner surface of the socket welded portion, that is, the inner surface crack growth. There was no pipe fatigue strength evaluation system.

Based on the piping specification data and the actual measurement data obtained by the nondestructive inspection and the vibration measurement, stress analysis,
There was no small-diameter pipe fatigue strength evaluation system that could consistently perform vibration analysis, fatigue analysis, fatigue evaluation, etc.

The non-destructive inspection target portion of the socket welded portion is selected, the repair / replacement / remodeling is instructed based on the fatigue strength evaluation result, and there is no determination function to clearly indicate the next measurement time or the end of evaluation. There was also no database to efficiently manage information on locations, evaluation results, and next measurement time.

An object of the present invention is to combine the factors of high cycle fatigue and low cycle fatigue with the factors of outer surface crack growth and inner surface crack growth to comprehensively monitor / evaluate / manage the fatigue strength of small diameter pipes. The purpose is to provide a pipe pipe fatigue strength evaluation system.

Another object of the present invention is to make it possible to consistently execute stress analysis, vibration analysis, fatigue analysis, fatigue evaluation, etc. based on piping specification data and actual measurement data obtained by nondestructive inspection and vibration measurement. The purpose is to provide a pipe pipe fatigue strength evaluation system.

Another object of the present invention is to select a non-destructive inspection target portion of a socket weld, instruct repair / replacement / remodeling based on the fatigue strength evaluation result, and clearly indicate the next measurement time or evaluation end. It is an object of the present invention to provide a small-diameter pipe fatigue strength evaluation system that has a function and has a database that efficiently manages these inspection target locations, evaluation results, and next measurement time information.

[0011]

In order to achieve the above object, the present invention provides a means for nondestructively inspecting the outer surface of a socket type welded joint portion of a small diameter pipe having a diameter of about 2B or less, and an outer surface nondestructive inspection. A method for analyzing / evaluating the fatigue strength of the outer surface of the pipe based on the outer surface defect of the welded joint obtained in to determine the soundness, a means for non-destructive inspection of the inner surface of the socket type welded joint of the pipe, and a vibration of the pipe. And the means for determining the soundness by analyzing / evaluating the fatigue strength of the inner surface of the pipe based on the inner surface defects and vibration measurement results of the welded joint obtained by the inner surface non-destructive inspection, and the result of the judgment is unhealthy. In this case, we propose a small-diameter pipe fatigue strength evaluation system consisting of means for displaying the necessary countermeasures.

For future reference, it is desirable to provide a database that stores the above-mentioned non-destructive inspection results, fatigue strength analysis / evaluation results, pipe soundness determination results, and necessary measures in association with each other.

The means for analyzing / evaluating the fatigue strength of the outer surface of the pipe may be a means for analyzing and evaluating both high cycle fatigue and low cycle fatigue, or based on the outer surface defect of the welded joint and the vibration measurement result. It can also be used as a means for analyzing and evaluating high cycle fatigue and low cycle fatigue separately.

On the other hand, the means for analyzing / evaluating the fatigue strength of the inner surface of the pipe is a means for separately analyzing and evaluating high cycle fatigue and low cycle fatigue based on the inner surface defect of the welded joint and the vibration measurement result. ..

In any case, the display means can also display the next measurement time for each socket-type welded joint portion.

[0016]

In the present invention, the pipe stress analysis procedure analyzes the stress based on the pipe specification data and the vibration acceleration or the assumed acceleration for evaluation obtained by the vibration measuring device, and the vibration stress and the nominal stress (thermal stress + thermal stress + Self-weight stress) is calculated.

In the fatigue analysis procedure, fatigue is analyzed by the vibration stress, the nominal stress, the pipe specification data, the inner surface crack size obtained by the nondestructive inspection device, and the estimated crack size for evaluation, and the fatigue strength reduction coefficient and Calculate the stress intensity factor fluctuation range.

In the fatigue evaluation procedure, the fatigue strength reduction coefficient and the stress intensity coefficient fluctuation range are compared with the fatigue limit and the crack growth limit, respectively, and the quality of the small diameter pipe is judged.

The database stores piping specification data, actual measurement data, evaluation results, whether countermeasures are required at the fatigue strength evaluation target location,
Accumulate information such as whether or not countermeasures have been implemented.

Therefore, the small-diameter pipe fatigue strength evaluation system of the present invention is a consistent system including a stress analysis procedure, a vibration analysis procedure, a fatigue analysis procedure, a fatigue evaluation procedure, and a database construction procedure.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a small diameter pipe fatigue strength evaluation system according to the present invention will be described with reference to FIGS.

FIG. 1 is a block diagram showing the device construction of an embodiment of a small diameter pipe fatigue strength evaluation system according to the present invention. The small diameter pipe fatigue strength evaluation system of the present embodiment is
It comprises a display 1, an input device 2 such as a keyboard, an arithmetic processing device 3 for performing various analyzes and evaluations, and a storage device 4 for storing data and / or processing procedures necessary for the analysis and evaluation. The arithmetic processing unit 3 sequentially calls the processing procedure of the processing procedure storage unit 3b to the operation unit 3a and executes it. Input unit 3c and data output unit 3d of the arithmetic processing unit 3
The storage data calling unit 3e is an interface for the input device 2, the display 1, and the storage device 4. The arithmetic processing unit 3 fetches data required for analysis / evaluation from the input unit 2 or the storage unit 4, and executes vibration analysis, fatigue analysis and evaluation. The arithmetic processing unit 3 displays the processing result on the display 1 and outputs it to the storage unit 4.

FIG. 2 is a system diagram showing the construction of the evaluation system of the small diameter pipe fatigue strength evaluation system according to the present invention. This small-diameter pipe fatigue strength evaluation system considers all of high cycle fatigue strength evaluation and low cycle fatigue strength evaluation, and external crack growth and internal crack growth, and includes all fatigue problems of small-diameter piping. There is.

Four types of evaluation procedures can be considered by combining the factors of high / low cycle and the factors of crack growth on the inner / outer surface, but the crack growth on the outer surface can be confirmed comparatively by a visual test or a penetrant flaw detection test. In practice, three evaluation procedures are sufficient because they are easy and reliable. That is, in the present embodiment, the evaluation procedure A5 for high cycle / low cycle outer surface crack growth and the evaluation procedure B6 for high cycle inner surface crack growth.
And the evaluation procedure C7 of the low cycle inner surface crack growth.

FIG. 3 is a flowchart showing an execution procedure in the small diameter pipe fatigue strength evaluation system according to the present invention. This flow chart shows how the three evaluation procedures are carried out, based on the basic concept of FIG. First, in step 8, select the target range,
Execute three evaluation procedures A, B, and C. The order of executing these evaluation procedures A, B, and C is not particularly limited, and one or two kinds of evaluation procedures can be executed to end the process, if necessary.

In step 8, when the high cycle / low cycle outer surface crack growth evaluation procedure A is selected, in step 9, the outer surface of the weld is inspected by a penetrant test, ie, PT or a visual test, ie, visual.
Execute test, VT. The crack size (defect data) of the outer surface is input, and in step 13, the high cycle / low cycle outer surface crack growth is evaluated to determine whether or not the small diameter pipe is sound. If there is no defect on the outer surface and the small diameter pipe is sound, the evaluation result is the small diameter pipe fatigue strength management database 1
Accumulate in 2 and finish the evaluation. If a defect is confirmed on the outer surface and the small-diameter pipe is not sound, in step 14, necessary measures are displayed to the operator by the display 1,
The evaluation results are accumulated in the small diameter pipe fatigue strength management database 12, and the evaluation is completed.

When the high cycle internal crack growth evaluation procedure B is selected in step 8, in step 10, a radiation transmission test, ie, ra, is performed as an internal surface inspection of the weld.
dio-graphic test, RT and ultrasonic testing, ie ultra
Execute sonic test, UT and input the crack size of the inner surface due to high cycle factor as defect data. On the other hand, in step 11, the vibration of the pipe due to the high cycle factor is measured, and in step 15, the vibration stress is obtained by the finite element method analysis program or the like. In step 16, fatigue due to a high cycle factor is analyzed from the defect data and the vibration stress. In step 17, based on the result of fatigue analysis, it is determined whether or not the small diameter pipe is sound. If there is no defect on the inner surface and the small diameter pipe is sound, the evaluation result is accumulated in the small diameter pipe fatigue strength management database 12, and the evaluation is completed. If a defect is confirmed on the inner surface and the small-diameter pipe is not sound, the necessary measures are displayed on the display 1 to the operator in step 14, the evaluation result is stored in the small-diameter pipe fatigue strength management database 12, and the evaluation is completed. ..

When the evaluation procedure C of the low cycle inner surface crack growth is selected in Step 8, the radiation transmission test RT and the ultrasonic flaw detection test UT are executed as the inner surface inspection of the welded portion in Step 10, and the inner surface is caused by the low cycle factor. Enter the defect data as the crack size. On the other hand, in step 11, the vibration of the pipe due to the low cycle factor is measured, and in step 15, the sum of the thermal stress and the self-weight stress, that is, the nominal stress is obtained by the finite element method analysis program or the like. In step 16, the fatigue caused by the low cycle factor is analyzed based on the defect data and the nominal stress. In step 17, based on the result of fatigue analysis, it is determined whether or not the small diameter pipe is sound. If there is no defect on the inner surface and the small diameter pipe is sound, the evaluation result is accumulated in the small diameter pipe fatigue strength management database 12, and the evaluation is completed. If a defect is confirmed on the inner surface and the small-diameter pipe is not sound, the necessary measures are displayed on the display 1 to the operator in step 14, the evaluation result is stored in the small-diameter pipe fatigue strength management database 12, and the evaluation is completed. ..

FIG. 4 is a flow chart showing an evaluation procedure A for evaluating both the high cycle external crack growth and the low cycle external crack growth in the small diameter pipe fatigue strength evaluation system according to the present invention. First, in step 8, an evaluation target pipe, that is, an evaluation range is selected and registered in the small-diameter pipe fatigue strength management database 12. In step 9, a nondestructive inspection of the outer surface of the welded portion, that is, a penetrant flaw detection test PT and a visual inspection VT are performed. In step 13, the soundness of the small diameter pipe is evaluated. If there is no defect here, the evaluation result is registered in the small-diameter pipe fatigue strength management database 12, and the process ends. On the other hand, if a defect is confirmed, in step 14, necessary measures are instructed to the operator by the display 1, the evaluation result is registered in the small diameter pipe fatigue strength management database 12, and the process is ended.

FIG. 5 is a flow chart showing a data processing procedure of inner surface crack growth common to the evaluation procedures B and C in the small diameter pipe fatigue strength evaluation system according to the present invention. In step 18, evaluation data such as piping specification data, crack size data, and vibration measurement data are input. Next, in step 19, stress analysis, vibration analysis, and fatigue analysis are executed. In step 20, a fatigue strength evaluation procedure for small-diameter piping is executed. Fatigue strength evaluation result 21
In step 22, is combined with other fatigue strength evaluation results to form a fatigue strength evaluation table.

Analysis work such as data input / output, stress analysis, and vibration analysis is executed in, for example, an engineering workstation, and various data and results are obtained from the engineering workstation in, for example, a small-diameter computer built in a large computer. Piping fatigue strength management database 1
It is sent to 2 and registered.

FIG. 6 is a flow chart showing an evaluation procedure B for evaluating the high cycle inner surface crack propagation in the small diameter pipe fatigue strength evaluation system according to the present invention. In step 8, an evaluation target pipe, that is, an evaluation range is selected. In step 11, the vibration of the piping system is measured.
In step 23, the design vibration load is selected, and in step 24, the damping constant is selected. Step 25
In, the vibration stress is calculated from the vibration measurement value, the design vibration load, and the damping constant. Further, in step 10, a nondestructive inspection of the inner surface of the welded portion, that is, a radiation transmission test RT and an ultrasonic flaw detection test UT are executed. In step 26, the fatigue strength reduction coefficient is calculated from the defect data. In step 17, the soundness of the small diameter pipe is evaluated based on the calculated vibration stress and the calculated fatigue strength reduction coefficient. If it is sound, the evaluation result is registered in the small-diameter pipe fatigue strength management database 12, and the process ends. On the other hand, if a defect is confirmed, in step 14, necessary measures are instructed to the operator by the display 1, the evaluation result is registered in the small diameter pipe fatigue strength management database 12, and the process is ended.

FIG. 7 is a flowchart showing an evaluation procedure C for evaluating the low cycle internal crack propagation in the small diameter pipe fatigue strength evaluation system according to the present invention. In step 8, an evaluation target pipe, that is, an evaluation range is selected. Next, in step 10, a nondestructive inspection of the inner surface of the weld, that is, a radiation transmission test RT or an ultrasonic flaw detection test UT.
To execute. In step 27, the fluctuation range of the stress intensity factor is calculated from the defect data. In step 28, the sum of the thermal stress and the self-weight stress of the piping system, that is, the nominal stress is calculated. In step 17, based on the calculated fluctuation range of the stress intensity factor and the calculated nominal stress,
Assess soundness. If it is sound, the evaluation result is registered in the small-diameter pipe fatigue strength management database 12, and the process ends.
On the other hand, if a defect is confirmed, in step 14, necessary measures are instructed to the operator by the display 1,
The evaluation result is registered in the small-diameter pipe fatigue strength management database 12, and the process ends.

Here, an example in which the evaluation procedure is executed in the order of A → B → C has been described, but if necessary, A → C →
It will be apparent that the various orders may be performed in the order B, B → A → C, A → B, A → C, B → A, C → A.

Regarding the outer surface crack growth, the high cycle fatigue strength evaluation and the low cycle fatigue strength evaluation were performed together by the processing procedure of FIG. 4. It is also possible to separately perform the evaluation and the low cycle fatigue strength evaluation.

Further, repair / repair based on the fatigue strength evaluation result
In addition to instructing replacement / modification, it is possible to provide a function to clearly indicate the next measurement time or the end of evaluation.

[0037]

According to the present invention, it is possible to comprehensively monitor / evaluate / manage the fatigue strength of small-diameter pipes by combining the factors of high cycle fatigue and low cycle fatigue and the factors of external crack growth and internal crack growth. ..

Further, since stress analysis, vibration analysis, fatigue analysis, fatigue evaluation and the like can be consistently executed based on the piping specification data and the actual measurement data obtained by the nondestructive inspection and the vibration measurement, the situation can be grasped and the piping can be understood. It is possible to quickly and accurately respond to replacements, etc.

Further, a non-destructive inspection target portion of the socket weld portion is selected, and repair / replacement / replacement is performed based on the fatigue strength evaluation result.
It has a function of instructing remodeling and clearly indicating the next measurement time or the end of evaluation, and since it has a database that efficiently manages information on these inspection target points, evaluation results, and next measurement time, the burden on maintenance workers Can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a device configuration of an embodiment of a small diameter pipe fatigue strength evaluation system according to the present invention.

FIG. 2 is a system diagram showing a configuration of an evaluation system of a small diameter pipe fatigue strength evaluation system according to the present invention.

FIG. 3 is a flowchart showing an execution procedure in the small diameter pipe fatigue strength evaluation system according to the present invention.

FIG. 4 is a flowchart showing an evaluation procedure A for evaluating high cycle / low cycle outer surface crack growth in the small diameter pipe fatigue strength evaluation system according to the present invention.

FIG. 5 is a flowchart showing a data processing procedure of inner surface crack growth common to the evaluation procedures B and C in the small diameter pipe fatigue strength evaluation system according to the present invention.

FIG. 6 is a flowchart showing an evaluation procedure B for evaluating the high cycle internal crack growth in the small diameter pipe fatigue strength evaluation system according to the present invention.

FIG. 7 is a flowchart showing an evaluation procedure C for evaluating low cycle inner surface crack propagation in the small diameter pipe fatigue strength evaluation system according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 display 2 input device 3 arithmetic processing device 3a arithmetic unit 3b processing procedure storage unit 3c input unit 3d data output unit 3e stored data recall unit 4 storage device 5 high cycle / low cycle external crack growth evaluation procedure A 6 high cycle internal surface Crack growth evaluation procedure B 7 Low cycle inner surface crack growth evaluation procedure C 8 Target range selection 9 Weld surface inspection 10 Weld inner surface inspection 11 Pipe vibration measurement 12 Small diameter pipe fatigue strength management database 13 Evaluation of evaluation procedure A 14 Measures 15 Finite element analysis program 16 Analysis 17 Evaluation of evaluation procedures B and C 18 Evaluation data 19 Pipe stress analysis and vibration analysis 20 Fatigue analysis / evaluation 21 Fatigue strength evaluation result 22 Fatigue strength evaluation result summary table 23 Design vibration load selection 24 Selection of damping constant 25 Calculation of vibration stress 26 Calculation of fatigue strength reduction coefficient 27 Calculation of fluctuation range of stress intensity factor 28 Calculation of nominal stress

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Akira Maeda 3-2-1, Sachimachi, Hitachi City, Ibaraki Prefecture Hitachi Engineering Co., Ltd. (72) Eiji Suzuki 3-2-1, Saiwaicho, Hitachi City, Ibaraki Prefecture No. 1 in Hitachi Engineering Co., Ltd. (72) Inventor Toshihiro Hishinuma 3-2-1, Sachimachi, Hitachi City, Ibaraki Hitachi Engineering Co., Ltd.

Claims (6)

[Claims] 1. A means for nondestructively inspecting an outer surface of a socket-type welded joint portion of a small-diameter pipe having a bore diameter of about 2B or less, and the pipe based on an outer surface defect of the welded joint portion obtained by the outer surface nondestructive inspection. Means for analyzing / evaluating fatigue strength of outer surface to determine soundness, means for non-destructive inspection of inner surface of socket-type welded joint portion of the pipe, means for measuring vibration of the pipe, and inner non-destructive inspection And means for determining the soundness by analyzing / evaluating the fatigue strength of the inner surface of the pipe based on the inner surface defect of the welded joint portion and the vibration measurement result obtained in, and necessary when the result of the judgment becomes unhealthy Small pipe piping fatigue strength evaluation system consisting of means for displaying various measures. 2. A means for nondestructively inspecting an outer surface of a socket-type welded joint portion of a small-diameter pipe having a diameter of about 2B or less, and the pipe based on an outer surface defect of the welded joint portion obtained by the outer surface nondestructive inspection. Means for analyzing / evaluating fatigue strength of outer surface to determine soundness, means for non-destructive inspection of inner surface of socket-type welded joint portion of the pipe, means for measuring vibration of the pipe, and inner non-destructive inspection And means for determining the soundness by analyzing / evaluating the fatigue strength of the inner surface of the pipe based on the inner surface defect of the welded joint portion and the vibration measurement result obtained in, and necessary when the result of the judgment becomes unhealthy Small-diameter pipe fatigue strength evaluation consisting of means for displaying various measures, a database for associating and storing each nondestructive inspection result, fatigue strength analysis / evaluation result, pipe integrity judgment result, and necessary measures System. 3. The small diameter pipe fatigue strength evaluation system according to claim 1, wherein the means for analyzing / evaluating the fatigue strength of the outer surface of the pipe analyzes and evaluates both high cycle fatigue and low cycle fatigue. A small-diameter pipe fatigue strength evaluation system characterized by being a means. 4. The small-diameter pipe fatigue strength evaluation system according to claim 1, wherein the means for analyzing / evaluating the fatigue strength of the outer surface of the pipe includes an outer surface defect of the welded joint portion and the vibration measurement result. A small-diameter pipe fatigue strength evaluation system, which is a means for analyzing and evaluating high cycle fatigue and low cycle fatigue separately based on the above. 5. The small-diameter pipe fatigue strength evaluation system according to claim 1, wherein the means for analyzing / evaluating the fatigue strength of the inner surface of the pipe is the inner surface defect of the welded joint portion and the A small-diameter pipe fatigue strength evaluation system, characterized in that it is means for separately analyzing and evaluating high cycle fatigue and low cycle fatigue based on vibration measurement results. 6. The small diameter pipe fatigue strength evaluation system according to claim 1, wherein the display means also displays the next measurement time for each socket-type welded joint portion. A small-diameter pipe fatigue strength evaluation system characterized in that