JP2965716B2 - Piping life diagnosis - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pipe life diagnosing method,
In particular, the present invention relates to a pipe life diagnostic method for accurately evaluating the life of a pipe in consideration of a discontinuous portion of an inner surface shape of a pipe welding joint of a power plant or the like.

[0002]

2. Description of the Related Art Electric power demand in Japan is rapidly increasing with rapid growth, and various power generation plants such as thermal power plants have been expanding to meet this demand. In particular, thermal power plants have been increasing in temperature and pressure in order to increase their output, and have achieved large capacities, thus playing a major role in power supply. On the other hand, under such circumstances, each unit of the thermal power plant is subject to severe operating conditions such as continuous use over a long period of time to balance with the output of nuclear power generation and adjust the power supply and demand balance between day and night. It has been placed. Therefore, in order to maintain and improve the reliability of the thermal power generation equipment used for a long time, it is necessary to systematically implement measures for aging deterioration of each equipment of the power generation equipment. As one of measures against aging deterioration of equipment, a method of judging a deterioration state of a main part in advance and grasping a remaining life of the main part for the purpose of appropriately determining a member renewal time has been adopted. In addition, for the steam turbine, the boiler, and the like among the thermal power generation facilities, the inspection site, the inspection item, the inspection interval, and the like are specified by a guideline or the like. On the other hand, in this guideline, in operation, the cumulative operation time of the target steam equipment exceeds 100,000 hours or the cumulative
If the number exceeds 500, the remaining life of the main parts of the target steam equipment has been properly diagnosed, and the age of the main parts has not reached the remaining life calculated based on the diagnosis results. It is stated that if it is satisfied, the period of the predetermined periodic inspection can be extended. In addition, there is a guideline regarding the above-mentioned remaining life diagnosis, and in this guideline, the first time of the life diagnosis, the target part, the deterioration factor and method, the remaining life diagnosis method, the remaining life diagnosis method, the re-execution time of the remaining life diagnosis In addition, there is shown a point of various operations such as a change of a periodic inspection time based on a result of the remaining life diagnosis.

In the case of boiler equipment, boiler pipes, boiler pipes, and boiler pipe stubs are the target parts of the thermal power generation equipment where the strictest design conditions are set.
The turbine equipment includes a turbine casing, a turbine axle, and a turbine rotor blade. It is particularly important to know the remaining life of these parts, and various methods for diagnosing remaining life have been proposed according to the deterioration factors of each part. Creep and fatigue are known as factors of deterioration of these members, and both of them deteriorate depending on elapsed time. Creep phenomena always appear at such a part under a certain stress, and the member is deformed and eventually leads to creep rupture over time. On the other hand, the fatigue phenomenon is likely to appear in a portion where a repeated stress acts.

[0004] The remaining life diagnosis method has been established for the creep life and fatigue life caused by the above-described creep and fatigue, and it is possible to judge the remaining life based on the diagnosis method.

[0005] As methods for diagnosing the remaining life with respect to the creep life, there are a destructive inspection method, a hardness measurement method, a texture inspection method and the like.

In the destructive inspection method, a sample is taken from a used material, three test pieces are prepared under approximately three kinds of stress conditions or temperature conditions, and a creep rupture test is performed. An extrapolation regression curve is calculated using the Larson Miller parameter PP = T (C + log t) where T: absolute temperature, C: material constant, and t: time. This is an inspection method in which a lower limit line of a confidence interval is created and compared with an unused material curve to calculate a consumption life and an estimated remaining life.

[0007] The hardness measurement method is to select a high temperature portion or a high stress portion of a member, and to measure Vickers hardness (H) at nine or more points.
V) was measured, and the lower limit of the hardness of the 99% confidence interval was determined from the measurement results of 9 or more points, and the lower limit line of the 99% confidence interval was plotted on the extrapolation curve between the rupture stress according to this hardness and the Larson Miller parameter P. This is a measurement method for calculating the consumption life and the estimated remaining life by comparing with the same curve of an unused material.

Further, in the microscopic examination method, the creep damage and the amount of minute voids generated in the structure of the member are defined as the A parameter (the ratio of the grain boundaries formed by voids to the number of grain boundaries per unit area) and the creep life consumption. This is a method of estimating the creep life consumption by measuring the amount of vacancies since there is a correlation with the rate.

On the other hand, methods for diagnosing the remaining life with respect to the fatigue life include a destructive inspection method, a hardness measuring method, and an analyzing method.

In the destructive inspection method, a sample is taken from a used material, three test pieces are prepared under about three kinds of stress conditions, and a low cycle fatigue test is performed. Inspection to calculate extrapolation regression curve using Larson Miller parameter on relational diagram, draw lower limit line of 99% confidence interval, compare with unused material same curve, and calculate consumption life and estimated remaining life Is the law.

[0011] The hardness measurement method is to select a high temperature part or a high stress part of a member and to measure Vickers hardness (HV) at nine or more points.
Is measured, and the lower limit value of the hardness of the 99% confidence interval is determined from the measurement results of 9 or more points, and a lower limit line of the 99% confidence interval is created on an extrapolation curve of the stress amplitude and the number of times of crack generation according to this hardness. This is a measurement method for calculating the consumption life and the estimated remaining life by comparing with the same curve of an unused material.

The analysis method is a method of performing an analytical calculation from the fluctuation stress during operation and the history of the number of startups, and estimating the remaining life from the result.

Although various policies have been proposed for diagnosing the remaining life of the main components of the thermal power plant which have deteriorated over time, in practice, it is necessary to individually perform the diagnosing of the remaining life of each piping component. Here, for example, if the diagnosis target is a main steam pipe from a boiler to a turbine, and a high-temperature and high-pressure steam pipe such as a reheat steam pipe, the destructive inspection method, the hardness measurement method, and the tissue inspection method can be applied. it can.

[0014]

However, the piping section to be subjected to each of the above-mentioned inspection methods is generally a part connected to a boiler, a turbine, a valve, and the like. And cannot inspect the inside. For this reason, inspection and inspection of these high-temperature and high-pressure steam pipes are usually performed on site from the outside of the pipes, and there is a problem that the internal conditions cannot be considered.

One of the most susceptible parts of the high-temperature and high-pressure steam pipe is a discontinuous part in the vicinity of the inner weld of the pipe weld joint. The hardness measurement method and histological inspection method described above cannot directly inspect the inner surface of the pipe, and the only way is to estimate the internal state from inspection on the outer surface of the pipe, and the estimated life of the shape discontinuity on the inner surface of the pipe where high local stress occurs is too short. There is a risk of evaluation. Therefore, in order to grasp the state of deterioration of the inner surface of the pipe, it is necessary to directly collect a test piece from the pipe member by a destructive inspection method or the like. However, since the test piece is removed from a part of the tube, there is a problem that the strength of the member is reduced. Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, appropriately estimate the life of the shape discontinuous portion of the pipe inner surface where high local stress occurs, and consider other factors in the piping member. It is an object of the present invention to provide a piping life diagnosing method for predicting the life diagnosing of a pipe with higher accuracy.

[0016]

In order to achieve the above object, the present invention measures the shape of a measurement site on the inner surface of a pipe, creates an analysis shape model using the measurement results, and performs stress analysis. While calculating the local stress value of the part, the hardness of the outer surface of the tube is measured, and an extrapolation curve showing the relationship between the tube stress value and the extrapolation parameter is created based on the hardness. It is characterized in that the consumption life of a pipe is estimated by plotting local stress values.

[0017]

The operation of the present invention will be described with reference to FIG.
FIG. 1 shows a processing flow of life diagnosis of a pipe in a high-temperature and high-pressure state, and will be described along this processing flow.

First, the shape and dimensions of the inner surface of a pipe portion to be diagnosed are measured. By this measurement, it is possible to accurately measure the dimensions of the inner surface of the pipe, especially the discontinuous portion of the inner surface shape such as the excess portion at the welded joint of the pipe, and create a shape model for analytical calculation based on this measurement result. The stress analysis calculation is performed in consideration of predetermined analysis conditions. With this stress analysis calculation, the stress, displacement, etc. of each part of the analysis model can be known, and at the same time, the maximum local stress can be calculated by comparing the stress at each part, and the maximum stress on the inner surface of the pipe can be obtained with high accuracy. Can be.

On the other hand, the hardness is measured at a predetermined measurement point on the outer surface of the pipe, and based on the hardness, the deterioration state of the material of the pipe is determined from the relation between the creep rupture strength and the pipe strength characteristics such as low cycle fatigue limit and the extrapolation parameters. Create the extrapolated curve shown. The local stress value obtained from the above analytical calculation is plotted on the extrapolation curve and a curve showing the material strength characteristics of the unused material, and the consumption life of the pipe can be calculated from the position of the intersection with the curve.

[0020]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded perspective view showing an embodiment of the present invention;

FIG. 1 shows a processing flow for performing a life diagnosis of a pipe in a high temperature and high pressure state. In FIG.
This diagnostic method is roughly composed of four processing blocks. In the first block 100, measurement and measurement result processing are performed. That is, the shape and hardness of the pipe are measured, and the measurement result data is analyzed to create an analysis model used for stress analysis or to calculate a regression curve for diagnostic evaluation.

In a second block 200, the operating conditions of the plant are investigated. In this investigation, input data for the stress analysis calculation performed in the third block 300 (piping pressure during operation, temperature and temperature history in the pipe during operation, temperature distribution in each part) and the piping performed in the fourth block 400 Collects operating condition data (operation results, number of start / stops, operation time, etc.) for life assessment / evaluation of the system.

In the third block 300, the first block 10
A stress analysis calculation is performed using the analysis shape model created in step S0. This stress analysis calculation is performed by using a computer to create a two-dimensional or three-dimensional model by finite element method analysis (FEM) or the like. At this time, as the shape data and material data of the analysis shape model, those measured or set in advance in the first block 100 and the second block 200 are used. The stress analysis includes a stress analysis for an applied load corresponding to various design conditions such as an operating pressure, and a thermal stress analysis based on a thermal stress obtained by the temperature distribution analysis performed in the second block 200.

In a fourth block 400, based on the extrapolated regression curve obtained from the measurement results, the local maximum stress calculated in the third block 300, operating condition data, a future plant operation plan, and the like are taken into consideration. Estimate lifetime and evaluate.

The above evaluation is performed, and finally, based on the above data, the periodic inspection of the power generation equipment and the planning and determination of the replacement time of the members are performed.

Next, the processing procedure of the first block 100, such as measurement, will be described in detail. In a thermal power plant, a main steam pipe, a main steam lead pipe, and the like are arranged in a pipeline system from a boiler to a steam turbine, and a seamless pipe is usually used for these pipes. These seamless pipes are processed into members having a shape such as a straight pipe, a bent pipe, an elbow, and a tee (T), and these are appropriately combined and welded to form a piping route having a predetermined shape. Usually, the discontinuity in the shape of the welded joint of these pipes is the starting point of the damage, so that a predetermined measurement is performed by focusing on this portion.

FIG. 2 shows an embodiment for measuring the shape of the discontinuity in the inner surface of the pipe of the welded joint. This pipe 1 is provided with a taper 2 having a predetermined angle at a pipe end 1a by machining to obtain a welding groove. Route 3
Is formed with a spare part 4. Due to the taper 2 and the excess portion 4, a shape discontinuous portion 6 having irregularities is formed on the inner surface of the pipe of the welded joint portion 5, and stress concentration is likely to occur. In order to accurately measure the shape of the shape discontinuity portion, the present embodiment employs a putty molding method. This putty molding method will be described with reference to FIG. In FIG. 2, reference numeral 5 denotes a pipe welding joint, and a small-diameter seat 7 is formed in a pipe surface near the welding joint 5. The small-diameter seat 7 is a small hole provided for inserting a gamma ray generator (not shown) for performing a radiation inspection of the pipe welding joint portion 5. After the inspection, the small-diameter seat 7 is sealed with a plug (not shown). In this embodiment, the shape measurement of the shape discontinuous portion 6 on the inner surface of the pipe is performed by using the small diameter seat 7. That is, the molding device 8 is inserted into the pipe via the small-diameter seat 7. The molding device 8 is a device for removing the putty of the shape discontinuity portion 6 and has a dish-shaped putty press 9 having a built-in electromagnet (not shown) at the end of the device. A putty 10 for molding is attached to one surface of the putty presser 9, and the putty presser 9 itself is assembled by a link mechanism so that the putty presser 9 can be easily inserted from the small-diameter seat 7. Further putty presser 9
Is mounted with a wire-shaped operation guide frame 11 that can freely operate the link mechanism. An operation handle 12 is connected to a hand side of the operation guide frame 11, so that an operation of fixing the putty presser 9 at a predetermined position on the inner surface of the tube can be performed at hand. Also, putty holder 9
A pressurizing portion 13 for pressing the putty presser 9 against the inner surface of the tube is provided on the surface opposite to the side where the putty 10 is attached,
The pressure unit 13 is connected to an air supply pipe 14 extending inside the operation guide frame 11.

Next, a method of measuring the shape of the shape discontinuous portion 6 on the inner surface of the pipe by using the above-described molding device 8 will be briefly described. First, the condition of the shape discontinuous portion 6 to be measured is confirmed by observing the state of the inner surface of the tube with a fiber scope (not shown) via the small-diameter seat 7 in advance. Then, the molding device 8 is inserted from the small-diameter seat 7, the operation guide frame 11 is operated by the operation handle 12, and the putty presser 9 is guided to the measurement position, and when the putty presser 9 reaches the predetermined position,
The putty presser 9 is fixed to the inner surface of the tube by operating the built-in electromagnet. Next, compressed air is supplied to the pressurizing section 1 through the air supply pipe 14.
Then, the putty 10 inside the putty presser 9 is pressed against the surface of the shape discontinuous portion 6 to form a mold. After molding, putty holder 9
The part is taken out from the inside of the pipe, the putty put is put on a three-dimensional measuring device or the like, and the three-dimensional shape is traced to measure the dimensions. Then, an analysis shape model for stress analysis such as a finite element method is created based on the measured dimensions.

On the other hand, the hardness of the outer surface of the tube is tested by selecting a predetermined measurement position so as to include the vicinity of the position where the shape of the inner surface is sampled. In this embodiment, the Vickers hardness test (H
The hardness is determined by V). Further, based on this hardness, an extrapolation regression curve showing the material deterioration state of the pipe is created from the relation between the extrapolation parameters and the pipe strength characteristics such as creep rupture strength and low cycle fatigue limit. The extrapolation regression curve is obtained using a Larson-Miller parameter P which is an extrapolation method parameter, and this parameter P is expressed by the following equation. P = T (C + log t) where T: absolute temperature, C: material constant, t: time In addition, a lower limit line of the 99% confidence interval of the extrapolated regression curve is created, and an unused material curve is also set. I do. At this time, creep rupture strength characteristics are considered as a base for creep damage evaluation, and low cycle fatigue characteristics are considered as a base for fatigue damage evaluation.

Next, an example of the result of the stress analysis calculation of the third block 300 will be described. FIG. 3 shows the results of pipe stress analysis in the vicinity of the discontinuous shape by the finite element method in the form of a diagram output, and is an iso-stress diagram obtained by comparing stress values of respective elements and connecting iso-stress values. It can be seen that stress concentration occurs at the shape discontinuity portion 6 as indicated by the arrow. The local stress value at this location is used for diagnosis in the fourth block 400.

FIG. 4 shows an extrapolated regression curve (solid line) and an unused material curve (dashed line) created in the first block 100. The consumption life of each part can be estimated by plotting the stress value σ on the vertical axis against these curves. At this time, σ ₁ indicates a local maximum stress when the shape discontinuity 6 is considered, and σ ₂ indicates a local stress when the shape discontinuity 6 is not considered. It can be seen that the case of σ ₁ has a longer consumption life and a shorter remaining life. From this result, by considering the shape discontinuity portion 6, the evaluation of the member can be estimated on the safe side, and more accurate pipe life diagnosis can be performed.

In order to measure the shape of the shape discontinuous portion 6 on the inner surface of the pipe, in addition to the putty molding method, the thickness of a predetermined position is measured by an ultrasonic thickness measuring device, or the welding shape result by radiation inspection is measured. It is also possible to use together. Further, a thermocouple can be attached as data for estimating the remaining life, and the temperature records at the time of starting operation and at the time of normal operation can be measured.

[0033]

As is apparent from the above description, according to the present invention, it is possible to directly measure the shape discontinuity of the inner surface of the pipe and perform a stress analysis to accurately grasp the local stress in a non-destructive state. The extra life is obtained by accurately evaluating the remaining life of the pipe by the extrapolation method and performing an appropriate diagnosis on the life of the pipe.

[Brief description of the drawings]

FIG. 1 is a processing flowchart showing one embodiment of a piping diagnosis method according to the present invention.

FIG. 2 is a schematic side view showing one embodiment of a shape measuring device used in the present invention.

FIG. 3 is an iso-stress diagram showing an example of a stress analysis calculation result.

FIG. 4 is a diagram showing a relationship between extrapolation parameters and stress.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pipe 5 Weld joint part 6 Discontinuity part 8 Modeling device 100 1st block (measurement / measurement processing block) 200 2nd block (operation condition investigation block) 300 3rd block (stress analysis calculation block) 400 4th block (Piping life diagnosis evaluation block)

Claims (1)

(57) [Claims] 1. A method for measuring the shape of a measured portion on the inner surface of a pipe, creating an analytical shape model using the measurement results, performing stress analysis, calculating a local stress value of the portion, and measuring the hardness of the outer surface of the pipe. Perform an extrapolation curve showing the relationship between the pipe stress value and the extrapolation parameter based on this hardness, and estimate the consumption life of the pipe by plotting the local stress value on the extrapolation curve. A pipe life diagnosis method characterized by the following.