JPH0815115A - Thermal stress monitor - Google Patents

Abstract

PURPOSE:To obtain a thermal stress monitor in which the stress caused by a reaction load from the piping side, as well as the stress generated from the pipe base part itself, can be evaluated. CONSTITUTION:The thermal stress monitor 20 comprises a fatigue monitoring/ operating section 21, a pipe base part data base 22, and a piping part data base 23, wherein the pipe base part data base 22 stores the Green function 22a of pipe base stress, a temperature variation diagram 22b, and a stress 22c for a unit reaction load. The piping part data base 23 stores the pipe base reaction 23a due to an equivalent thermal bending stress and a temperature variation diagram 23b. The fatigue monitoring/operating section 21 receives a temperature variation 2a on the outer surface of the pipe base part, a temperature variation 3a on the outer surface of the piping, and a pressure variation 4a from sensors 2, 3, 4, executes crack stability evaluation and fatigue damage calculation using the data stored in the data bases 22, 23, and presents the results on a display.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal stress monitoring device applied to a power plant or the like, and particularly to a thermal stress monitoring for a pipe pipe base thermal stratification for evaluating fatigue damage coefficient and crack stability in a pipe part. Regarding the device.

[0002]

2. Description of the Related Art Conventionally, a thermal stress monitoring system applied to a power plant or the like, as shown in FIG. In FIG. 4, reference numeral 1 denotes a thermal stress fatigue monitoring device, which is composed of a fatigue monitoring calculation unit 11 and a database unit 12. The database section 12 stores an equivalent thermal bending stress database 12a, a Green function of stress 12b, and a temperature change diagram 12c.

The equivalent thermal bending stress database 12a has a unit linear temperature distribution 12a1 of the inner wall temperature on the cross section of the pipe to be evaluated.
Beam model FEM analysis (Finite Element Method analysis) 12a2 was carried out assuming a temperature distribution where the temperature difference between the top and bottom of the horizontal pipe is 1 ° C when viewed from the side. I am asking for. The beam model is one of FEM analyzes and is often used when analyzing a piping system. In the FEM analysis, the structure to be analyzed is divided into fine mesh elements, and a balance equation regarding displacement and force is created for each element. Next, the boundary conditions of the target model are given to the equilibrium equations, and the simultaneous equations are solved, so that the stress, the amount of deformation, etc. in each element can be calculated.

The Green function of stress 12b is a change in stress with respect to a stepwise temperature change of 1 ° C., which is a boundary condition such as a fluid temperature.
For the unit temperature change 12b1 of the inner wall, F of the axis symmetric model
EM analysis 12b2 is carried out to obtain. Further, the temperature change diagram 12c is obtained as a relationship between the value obtained by subtracting the outer surface temperature from the inner surface temperature and the time change rate of the outer surface temperature.

A plurality of pipe outer surface temperature sensors 3 and pressure sensors 4 are provided in the pipe portion. The fatigue monitoring calculation unit 12 of the fatigue monitoring calculation device 1 inputs the signals of the outer surface temperature change 3a from the pipe outer surface temperature sensor 3 and the pressure change 4a from the pressure sensor 4 and uses the data stored in the database unit 12 Conduct crack stability evaluation and fatigue damage evaluation.

The display device 5 is provided at a predetermined position such as a central control room and displays the evaluation result. Next, the operation of the thermal stress monitoring device will be described with reference to the flowchart of FIG. The fatigue monitoring calculation unit 11 uses the outer surface temperature change 3a measured by the pipe outer surface temperature sensor 3 as an input signal, and obtains the inner wall temperature distribution 11a of the evaluation point cross section and its time change 11b using the temperature change diagram 12c. . This estimated inner wall temperature change 11b and Green's function of stress 1
Calculation 11d of thermal shock stress is implemented using the Green's function method 11c extracted from 2b.

Further, according to the inner wall temperature distribution 11a of the evaluation point cross section, the calculation 11e of the local thermal stress in the pipe cross section is executed for the nonlinear temperature distribution component by the self-balancing equation of the moment and the force in the pipe cross section. Fatigue monitoring calculation unit 11
At the same time, the equivalent thermal bending stress calculation 11f is performed using the equivalent thermal bending stress database 12a. Further, the pressure change 4a signal input from the pressure sensor 4 is multiplied by a coefficient multiple to perform internal pressure stress calculation 11g.

Fatigue damage calculation 11h is executed from the calculation results of the internal pressure stress calculation 11g, the thermal shock stress calculation 11d, the pipe cross-section local thermal stress calculation 11e, and the equivalent thermal bending stress calculation 11f. Also, calculation of thermal bending stress 11
Based on the calculation result of f and internal pressure stress calculation 11g, a crack stability evaluation 11i based on the net stress concept for an assumed crack is performed.

[0009]

In the above-mentioned conventional system, the thermal stress evaluation flow is assembled for the piping portion, but it is necessary to consider the influence from the piping side on the piping base portion. Unlike the part in which the thermal stress evaluation logic evaluates the stress of a part of the pipe, the conventional method cannot be applied when focusing on the pipe stub.

Since the present invention has been made in view of the above circumstances, it is possible to evaluate the stress due to the reaction force load from the piping side in addition to the stress generated in the nozzle part itself, and to evaluate the stress in the nozzle part. Moreover, it is an object of the present invention to provide a thermal stress monitoring device capable of estimating the life by fatigue damage calculation.

[0011]

The thermal stress monitoring device according to the present invention subtracts the outer surface temperature from the data measured by the outer surface temperature sensor mounted near the evaluation point and the inner surface temperature obtained in advance. A means for obtaining the estimated inner wall temperature distribution near the above evaluation points and the estimated inner wall temperature time change from the data and the time change rate of the outer surface temperature of the nozzle part, and the local thermal stress in the pipe cross section from the estimated inner wall temperature distribution obtained by this means And means to evaluate the equivalent thermal bending stress by estimating the external force load from the piping side, means to obtain the thermal shock stress using the Green's function method from the estimated internal wall temperature change over time, and the pressure sensor A means for determining internal pressure stress from the data, a pipe fatigue damage evaluation from the local thermal stress in the pipe cross section, the equivalent thermal bending stress, the thermal shock stress, and the internal pressure stress. Characterized by comprising a means for performing can 裂安 qualitative assessment.

[0012]

[Operation] Data is input from the outer surface temperature sensor installed near the evaluation points of the pipe and the nozzle part, and the time change of the outer surface temperature of the nozzle part prepared in advance and the change from the inner surface temperature to the outer surface temperature The estimated internal wall temperature change near the evaluation point is obtained using the relationship curve with the data obtained by subtracting, and the thermal shock stress in the plate thickness direction is evaluated using the Green's function method of the axial symmetric model. That is, when the liquid temperature in the pipe changes instantaneously due to thermal shock, the local thermal stress in the plate thickness direction is evaluated using the Green's function method for the stub part axis symmetrical model.

The asymmetric stress component due to the temperature distribution in the section of the nozzle section is formulated from the self-balance of the moment and force in the section of the pipe from the temperature distribution. Further, since the nozzle part is connected to the pipe and serves as a fixed point on the pipe side, it receives a reaction force load of thermal stress generated in the pipe part. In order to evaluate this reaction force (external force for the nozzle part), an outer surface temperature sensor is installed at a representative location on the pipe side, the inner wall temperature distribution is obtained, and it is separated into a linear component and a non-linear component. Since the linear component acts as a reaction force on the nozzle, the reaction force load at the nozzle fixing side for the unit linear temperature distribution on the piping side is calculated and stored in the database. If the stress generated at the point of interest when a unit external force acts on the nozzle side is stored as a database,
If the linear temperature generated on the pipe side is obtained, the stress due to the reaction load can be obtained. By these methods, it becomes possible to evaluate the thermal stress of the pipe stub.

[0014]

An embodiment of the present invention will be described below with reference to the drawings. 1 and 2 show the thermal stress monitoring device of the present invention and its peripheral structure. In FIG. 1, reference numeral 15 denotes a pipe, which is composed of a low temperature water pipe portion 15a and a high temperature water pipe portion 15b, and is connected to and supported by a nozzle 16. The pipe 15 is provided with a pipe outer surface temperature sensor 3 for measuring a rough surface temperature of a representative cross section of the pipe portion, and a pipe nozzle outer surface temperature sensor 2 in the vicinity of the nozzle 16. Although not shown in FIG. 1, a pressure sensor 4 for detecting the pressure in the pipe 15 is also installed.

As shown in FIG. 2, the thermal stress monitoring device 20 receives the signals of the temperature change 2a of the outer surface of the nozzle stub, the temperature change 3a of the outer surface of the pipe, and the pressure change 4a from the respective sensors 2, 3, 4. input. The thermal stress monitoring device 20 includes a fatigue monitoring calculation unit 21, a nozzle section database 22, and a piping section database 23. The nozzle surface outside surface temperature change 2a from each of the sensors 2, 3 and 4 and the piping outside surface temperature. The signals of change 3a and pressure change 4a are input to the fatigue monitoring calculation unit 21.

In the nozzle part database 22, the Green function 22a of the nozzle stress and the temperature change diagram (inner surface temperature-
The relationship between the outer surface temperature and the outer surface time change rate) 22b and the stress 22c for the unit reaction force load are stored. In addition, the pipe part database 23 stores a nozzle base reaction force 23a due to equivalent thermal bending stress and a temperature change diagram (relationship between inner surface temperature-outer surface temperature and outer surface time change rate) 23b.

Green function 22a of nozzle stress and temperature change diagram 22b stored in nozzle database 22
When the unit temperature change 22a1 of the nozzle inner wall by a large-scale computer (not shown) is input in advance,
The EM analysis 22a2 is carried out for the calculation. Further, the stress 22c against the unit reaction force load causes the unit reaction force load 22c1 to act on the connecting portion between the nozzle 16 and the pipe 15, and the nozzle FE FE
It is determined by M analysis 22c2.

In addition, the nozzle base reaction force 23a due to the equivalent thermal bending stress in the piping database 23 is the unit linear temperature distribution 23a1 of the inner wall temperature (when the horizontal piping is viewed from the side,
The beam model FEM analysis 23a2 is performed by assuming a temperature distribution in which the temperature difference between the top and bottom of the pipe is 1 ° C.). Further, the temperature change diagram 23b is obtained by performing the pipe axis symmetric model FEM analysis 23b2 using the unit temperature change 23b1 of the pipe inner wall as input data.

The fatigue monitoring calculation unit 21 receives the signals of the nozzle surface outer surface temperature change 2a, the pipe outer surface temperature change 3a, and the pressure change 4a from the sensors 2, 3 and 4, respectively.
Fatigue damage calculation and crack stability evaluation are performed using the data stored in the nozzle part database 22 and the piping part database 23, and the results are displayed on the display device.

Next, the above embodiment will be described with reference to the flow chart shown in FIG. Fatigue monitoring calculation unit 21
First, the calculation is performed on the nozzle 16 portion. That is, the evaluation point cross-section inner wall temperature distribution 30 and the estimated inner wall temperature time change 31 are obtained by using the nozzle surface outer surface temperature change 2a detected by the nozzle surface outer surface temperature sensor 2 and the temperature change diagram 22b. Calculation 33 of the local thermal stress in the pipe cross section is executed from the circumferential distribution of the inner wall temperature. Green function method 32 from estimated inner wall temperature time change 31 and Green function 22a of nozzle stress
Thus, the thermal shock stress calculation 34 is executed. The Green's function method obtains a change in stress (Green's function) with respect to a stepwise temperature change of a boundary temperature such as a fluid temperature of 1 ° C. according to a predetermined procedure, holds this as a database, and stores it as input data such as a fluid. This is a method of calculating the temperature change at each time step by using the time change of the temperature and calculating the time history of the thermal stress by multiplying the Green's function by proportional multiplication. By using this Green's function method, the time history of thermal stress can be calculated in a very short time.

Next, the fatigue monitoring calculation unit 21 executes a calculation for the pipe 15 part. That is, the pipe cross section inner wall temperature distribution 37 is obtained from the pipe outer surface temperature change 3a detected by the pipe outer surface temperature sensor 3 and the temperature change diagram 23b, and from this temperature distribution 37, the pipe cross section inner wall linear temperature distribution 3
Separate 8 A calculation 39 of the piping base reaction force is performed using the database of the pipe cross section inner wall linear temperature distribution 38 and the pipe base reaction force 23a based on the equivalent thermal bending stress. From the reaction force estimated by this and the stress 22c for the unit reaction force load of the nozzle part, the stress calculation 35 by the reaction force load is executed.

Further, the signal of the pressure change 4a detected by the pressure sensor 4 is multiplied by a coefficient to calculate the internal pressure stress 36.
The fatigue damage calculation 40 is performed in combination with the stress component obtained by the calculation 33 of the local thermal stress in the pipe cross section, the calculation 34 of the thermal shock stress, and the stress calculation 35 by the reaction force load.

By combining the stresses calculated by the reaction load stress calculation 35 and the internal pressure stress calculation 36, a crack stability evaluation 41 based on the net stress concept for an assumed crack is performed, and a comprehensive soundness evaluation of the nozzle part is performed. Do. The evaluation result is output and displayed on the display device 5.

[0024]

As described above in detail, according to the present invention, by measuring and processing the outer surface temperature in the vicinity of the nozzle section evaluation point and the outer surface temperature of the representative cross section of the tube section, the nozzle section itself can be processed. In addition to the generated stress, stress due to reaction force from the piping side can be evaluated, and since the asymmetric distribution of temperature is also considered, it is possible to evaluate the stress of the nozzle stub and the life by fatigue damage calculation. Estimates are also possible.

[Brief description of drawings]

FIG. 1 is a diagram showing a sensor installation state in a pipe and a nozzle part according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an overall configuration of a thermal stress monitoring device according to an embodiment of the present invention and its peripheral configuration.

FIG. 3 is a flowchart showing the operation of the embodiment.

FIG. 4 is a block diagram showing an overall configuration of a conventional thermal stress monitoring device and its peripheral configuration.

FIG. 5 is a flowchart showing the operation of a fatigue monitoring calculation unit in the conventional thermal stress monitoring device.

[Explanation of symbols]

2 ... Pipe outer surface temperature sensor, 3 ... Pipe outer surface temperature sensor, 4 ... Pressure sensor, 5 ... Display device, 15 ... Piping, 16
... Stubstock, 20 ... Thermal stress monitoring device, 21 ... Fatigue monitoring calculation unit, 22 ... Stub database, 22a
… Green function of nozzle stress, 22b… Temperature change diagram, 2
2c ... Stress for unit reaction force load, 22a1 ... Unit temperature change of nozzle inner wall, 22a2 ... Model of FEM for nozzle axis FEM analysis, 22c1 ... Unit reaction force load, 22c2 ... Tube part FEM
Analysis, 23 ... Piping part database, 23a ... Piston part reaction force by equivalent thermal bending stress, 23b ... Temperature change diagram, 23a
1 ... Unit linear temperature distribution of inner wall temperature, 23a2 ... Beam model FEM analysis, 23b1 ... Unit temperature change of pipe inner wall,
23b2 ... Pipe axis symmetric model FEM analysis, 30 ... Evaluation point cross-section inner wall temperature distribution, 31 ... Estimated inner wall temperature change with time, 32
... Green function method, 33 ... Calculation of local thermal stress in piping section, 34 ... Calculation of thermal shock stress, 35 ... Stress calculation by reaction load, 36 ... Internal pressure stress calculation, 37 ... Pipe section inner wall temperature distribution, 38 ... Piping Cross-section inner wall linear temperature distribution, 39 ... Calculation of reaction force of pipe nozzle, 40 ... Fatigue damage calculation, 41 ... Crack stability evaluation.

Front page continued (72) Inventor Takashi Umehara 1-1-1, Wadasaki-cho, Hyogo-ku, Kobe-shi, Hyogo Mitsubishi Heavy Industries Ltd. Kobe Shipyard (72) Inventor Shin-ichi Takano 2-chome, Niihama, Arai-cho, Takasago-shi, Hyogo No.25 Takahishi Engineering Co., Ltd. (72) Inventor Yasuhiro Morimoto 2-8-25, Niihama, Arai-cho, Takasago, Hyogo Prefecture Takahishi Engineering Co., Ltd.

Claims (1)

[Claims] 1. From the data measured by an outer surface temperature sensor mounted near the evaluation point, the data obtained by subtracting the outer surface temperature from the inner surface temperature obtained in advance, and the time rate of change of the outer surface temperature of the nozzle part, A means for obtaining the estimated inner wall temperature distribution near the evaluation point and the estimated inner wall temperature change with time. Equivalent by estimating the local thermal stress in the pipe cross section from the estimated inner wall temperature distribution obtained by this means and estimating the external force load from the pipe side. Means for evaluating the thermal bending stress, means for obtaining the thermal shock stress using the Green's function method from the estimated internal wall temperature change over time, means for obtaining the internal pressure stress from the data measured by the pressure sensor, A means for evaluating fatigue damage and crack stability of a pipe from thermal stress, the equivalent thermal bending stress, the thermal shock stress, and the internal pressure stress is provided. Heat stress monitoring device that.