JP2014070976A - Piping stress evaluation device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piping stress evaluation device and a method for calculating stress with high accuracy and performing stress evaluation at an arbitrary evaluation point by using easy measurement.SOLUTION: A piping stress evaluation device has: a vibration frequency specification section 32 which specifies a first vibration frequency of a branch pipe based on a time history waveform of acceleration when arbitrary vibration is given to the branch pipe; an analytic model determination section 33 which calculates a second vibration frequency of the branch pipe based on a first analytic model obtained by modeling a header by rotational rigidity, horizontal rigidity, and concentrated mass, modeling the branch pipe by a beam element, and modeling a connection part between the header and the branch pipe by the rotational rigidity, and determines a second analytic model in which the second vibration frequency matches to the first vibration frequency; a steady response measurement section 34 which calculates a third acceleration spectrum based on the time history waveform of the acceleration in a steady operation of a plant; and a generated stress evaluation section 35 which calculates peak stress based on the second analytic model and the third acceleration spectrum, compares and evaluates allowable stress of the peak stress and the branch pipe.

Description

  The present invention relates to a piping stress evaluation apparatus and method.

  When performing stress evaluation of piping, for example, as shown in FIG. 21, a branch pipe 52 provided in a mother pipe 51 has a valve 53, and the branch pipe 52 is fixed to a fixed wall 54 by a support 55. In the configuration, when stress evaluation of the branch pipe 52 is performed, conventionally, a strain gauge 56 is attached to the evaluation target portion of the branch pipe 52, and an output signal of the strain gauge 56 is supplied to an amplifier 57 and an A / D converter 58. As shown in FIG. 22, the strain time history waveform (see FIG. 22 (a)) is converted into the stress time history waveform (see FIG. 22 (b)). The fatigue stress was evaluated by calculating the generated stress in terms of

  23, the displacement is calculated from accelerometers 61 and 62 installed in the branch pipe 52, and the generated stress is evaluated from the relationship between the displacement and the stress based on the piping specifications (member specifications). As shown in FIG. 24, using an analysis model 70 of the mother pipe 51 and the branch pipe 52, stress is calculated from measurement data at the acceleration measurement points P1 and P2.

JP 2001-153719 A JP 2002-162298 A Japanese Patent Laid-Open No. 11-014782

  However, when the strain gauge 56 described with reference to FIGS. 21 and 22 is used, the measurement is troublesome, and the generated stress can be grasped only at the pasted portion. As described with reference to FIGS. 23 and 24, there is a method for calculating stress from the measurement data of the accelerometers 61 and 62 in order to perform measurement relatively easily. However, if the analysis model 70 is insufficient, Highly accurate fatigue evaluation was difficult.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a piping stress evaluation apparatus and method for performing stress evaluation by calculating high-precision stress at an arbitrary evaluation point using easy measurement. And

A piping stress evaluation apparatus according to the first invention for solving the above-mentioned problems is as follows.
A plurality of accelerometers attached to the branch pipe branched from the mother pipe of the plant, or to the mother pipe and the branch pipe;
In the pipe stress evaluation apparatus provided with stress evaluation means for calculating and evaluating the stress generated in the branch pipe using the measurement value measured by the accelerometer,
The stress evaluation means includes
The frequency analysis is performed from the time history waveforms of acceleration in the plurality of accelerometers when arbitrary vibration is applied to the branch pipe, and the first acceleration spectrum in the accelerometer far from the mother pipe and the first acceleration spectrum A first acceleration function is calculated by calculating a second acceleration spectrum that is closer to the mother tube or the accelerometer of the mother tube, and dividing the first acceleration spectrum by the second acceleration spectrum. A frequency specifying unit for specifying the first frequency of the branch pipe from the spectrum peak of the first transfer function;
The first pipe is modeled with rotational rigidity, horizontal rigidity, and concentrated mass, the branch pipe is modeled with a beam element, and a first analysis model is created in which the connection between the mother pipe and the branch pipe is modeled with rotational rigidity. Then, based on the first analysis model, eigenvalue analysis is performed to calculate a second frequency of the branch pipe, so that the second frequency matches the first frequency, An analysis model determination unit that determines a second analysis model in which the second frequency matches the first frequency by changing the rotational rigidity and horizontal rigidity of the mother pipe;
During steady operation of the plant, from a time history waveform of acceleration in the accelerometer arranged at an arbitrary measurement point of the branch pipe, by performing frequency analysis, a steady response measurement unit that calculates a third acceleration spectrum;
Using the second analysis model, frequency response analysis of the second analysis model is performed to calculate a fourth acceleration spectrum at the measurement point and a first stress spectrum at an arbitrary evaluation point of the branch pipe. And dividing the first stress spectrum by the fourth acceleration spectrum to calculate a second transfer function, multiplying the second transfer function by the third acceleration spectrum, and Is generated in the branch pipe by calculating a second stress spectrum at, calculating a peak stress by frequency integrating the second stress spectrum, and comparing the peak stress with an allowable stress of the branch pipe And a generated stress evaluation unit that performs stress evaluation.

A piping stress evaluation apparatus according to the second invention for solving the above-mentioned problems is as follows.
In the piping stress evaluation apparatus according to the first invention,
When the branch pipe is provided with a valve, the analysis model determination unit models the valve with a concentrated mass to create the first analysis model.

A piping stress evaluation apparatus according to a third invention for solving the above-mentioned problem is as follows.
In the piping stress evaluation apparatus according to the first invention,
The analysis model determination unit creates the first analysis model by modeling the entire valve including a handle of the valve with a distributed mass when the branch pipe is provided with a valve. It is characterized by.

The pipe stress evaluation method according to the fourth invention for solving the above-mentioned problem is as follows.
The acceleration of the plurality of accelerometers when an arbitrary vibration is applied to the branch pipe, using a branch pipe branched from the main pipe of the plant or a plurality of accelerometers attached to the main pipe and the branch pipe. A frequency analysis is performed from the time history waveform, and a first acceleration spectrum at the accelerometer far from the mother tube and a second acceleration spectrum at the accelerometer near or near the mother tube. The first acceleration spectrum is divided by the second acceleration spectrum to calculate a first transfer function, and the first vibration of the branch pipe is calculated from the spectrum peak of the first transfer function. Identify the number,
The first pipe is modeled with rotational rigidity, horizontal rigidity, and concentrated mass, the branch pipe is modeled with a beam element, and a first analysis model is created in which the connection between the mother pipe and the branch pipe is modeled with rotational rigidity. Then, based on the first analysis model, eigenvalue analysis is performed to calculate a second frequency of the branch pipe, so that the second frequency matches the first frequency, Changing the setting of rotational stiffness and horizontal stiffness of the mother pipe to determine a second analysis model in which the second frequency matches the first frequency;
During steady operation of the plant, from the time history waveform of acceleration in the accelerometer arranged at an arbitrary measurement point of the branch pipe, frequency analysis is performed to calculate a third acceleration spectrum,
Using the second analysis model, frequency response analysis of the second analysis model is performed to calculate a fourth acceleration spectrum at the measurement point and a first stress spectrum at an arbitrary evaluation point of the branch pipe. And dividing the first stress spectrum by the fourth acceleration spectrum to calculate a second transfer function, multiplying the second transfer function by the third acceleration spectrum, and Is generated in the branch pipe by calculating a second stress spectrum at, calculating a peak stress by frequency integrating the second stress spectrum, and comparing the peak stress with an allowable stress of the branch pipe It is characterized by evaluating stress.

The pipe stress evaluation method according to the fifth invention for solving the above-mentioned problem is as follows.
In the piping stress evaluation method according to the fourth invention,
When the branch pipe is provided with a valve, the valve is modeled by a concentrated mass to create the first analysis model.

The pipe stress evaluation method according to the sixth invention for solving the above-mentioned problems is as follows.
In the piping stress evaluation method according to the fourth invention,
When the branch pipe is provided with a valve, the first analysis model is created by modeling the entire valve including the valve handle with a distributed mass.

  According to the present invention, since the evaluation is performed using the acceleration data acquired from the accelerometer, it is possible to reduce the labor of measurement at the site. In addition, since the stress is calculated using an accurate analysis model, a highly reliable fatigue evaluation can be performed. Since the analysis model is used, the evaluation can be performed not only at the base of the branch pipe but also at any evaluation point.

It is the schematic explaining the piping stress evaluation apparatus which concerns on this invention. It is a block diagram of the piping stress evaluation apparatus shown in FIG. It is a flowchart explaining the piping stress evaluation method which concerns on this invention, and demonstrates the frequency specific | specification part in FIG. It is a flowchart explaining the piping stress evaluation method which concerns on this invention, and explains the analysis model determination part in FIG. It is a flowchart explaining the piping stress evaluation method based on this invention, and demonstrates the steady response measuring part in FIG. It is a flowchart explaining the piping stress evaluation method concerning this invention, and demonstrates the generated stress evaluation part in FIG. It is a graph which shows the time history waveform of the acceleration acquired by the tapping test, (a) is a branch pipe, (b) is measurement data on the mother pipe side. FIGS. 7A and 7B are graphs obtained by frequency analysis of the acceleration time history waveform shown in FIGS. 7A and 7B, where FIG. 7A shows a branch pipe and FIG. It is a graph which shows the transfer function of the main pipe and the branch pipe calculated | required from the acceleration spectrum shown to Fig.8 (a), (b). It is a figure which shows the analysis model used with the piping stress evaluation method which concerns on this invention. It is a figure explaining modeling of a mother pipe in the analysis model shown in FIG. In the analysis model shown in FIG. 10, it is a figure explaining the local rigidity of the connection part of a main pipe and a branch pipe. 13 is a graph used for obtaining the local rigidity described in FIG. 12. It is a figure explaining the frequency and vibration mode in a branch pipe, (a) is a primary mode, (b) is a secondary mode. (A) is a graph which shows the time history waveform of the acceleration of a branch pipe at the time of steady operation, (b) is a graph of the acceleration spectrum which frequency-analyzed the time history waveform of the acceleration shown to (a). It is a figure explaining the acceleration spectrum in the measurement point calculated using the analysis model, and the stress spectrum in an evaluation point. It is a graph which shows the transfer function of the stress-acceleration calculated | required from the acceleration spectrum in the measurement point shown in FIG. 16, and the stress spectrum in an evaluation point. It is a graph which shows the stress spectrum calculated | required from the acceleration spectrum of the branch pipe at the time of the steady operation shown in FIG.15 (b), and the transfer function of the stress-acceleration shown in FIG. It is a figure which shows another example of the analysis model used with the piping stress evaluation method which concerns on this invention, and is a model which shows only the part of a valve. It is a figure which shows the whole analysis model using the model shown in FIG. It is the schematic explaining the conventional stress evaluation using a strain gauge. (A) is a graph showing a time history waveform of strain, and (b) is a graph showing a time history waveform of stress converted from strain. It is the schematic explaining the conventional stress evaluation using an accelerometer. It is a figure which shows the analysis model of piping.

  Hereinafter, with reference to FIGS. 1-20, embodiment of the piping stress evaluation apparatus and method which concern on this invention is described. In the following description, in the plant piping structure, a pipe having a large radius is referred to as a mother pipe, a pipe provided by branching from the mother pipe and having a radius smaller than the mother pipe is referred to as a branch pipe, and vibration stress A branch pipe that has a large influence will be described as an evaluation target.

Example 1
Initially, with reference to FIG. 1, the piping stress evaluation apparatus of a present Example is demonstrated. Here, FIG. 1 is a schematic diagram illustrating the piping stress evaluation apparatus of the present embodiment.

  The pipe stress evaluation apparatus 20 of the present embodiment calculates the stress generated in the branch pipe 12 provided in the mother pipe 11 in the actually arranged pipe, and performs the fatigue evaluation thereof. For calculation and evaluation, accelerometers 21 and 22 are attached to a plurality of locations (at least two locations) of the branch pipe 12 to measure acceleration. The accelerometers 21 and 22 measure the acceleration of the branch pipe 12 caused by the vibration using the tapping hammer 15, the acceleration of the branch pipe 12 during the steady operation of the plant, and the like.

  The measurement data measured by the accelerometer 21 is supplied to a computer 27 via an amplifier 23 that amplifies the measurement data signal and an A / D converter 25 that performs A / D (analog / digital) conversion of the measurement data signal. To be recorded. Similarly, measurement data measured by the accelerometer 22 is input to a computer 27 via an amplifier 24 that amplifies the measurement data signal and an A / D converter 26 that A / D converts the measurement data signal. Recorded.

  As shown in FIG. 1, the branch pipe 12 may have a configuration having a valve 13, or may further have a configuration in which the branch pipe 12 is fixed to a fixed wall with a support as shown in FIG. 21. Moreover, the structure of only the branch pipe 12 without the valve 13 etc. may be sufficient.

  Moreover, it is desirable to install at least one of the accelerometers 21 and 22 installed in the branch pipe 12 at a position closer to the mother pipe 11 of the mother pipe 11 or the branch pipe 12, and at least the other is the mother pipe 11 from one side. It is desirable to install it at a position away from For example, in this embodiment, the accelerometer 21 is installed at the base of the branch pipe 12 connected to the mother pipe 11, and the accelerometer 22 is installed at a position away from the mother pipe 11.

  Next, with reference to FIGS. 2-18, the piping stress evaluation method in the piping stress evaluation apparatus of a present Example is demonstrated. Here, FIG. 2 is a block diagram for explaining the pipe stress evaluation apparatus of the present embodiment shown in FIG. 1, and FIGS. 3 to 6 are flowcharts for explaining the procedure in each block shown in FIG. is there. 7 to 18 are diagrams for explaining the flowcharts shown in FIGS.

  As shown in FIG. 2, the pipe stress evaluation apparatus 20 of the present embodiment mainly includes a vibration measurement unit 31, a vibration identification unit 32, a stress calculation unit 33, a steady response measurement unit 34, and a generated stress evaluation unit 35. ing. In the present embodiment, the computer 27 (stress evaluation means) includes a vibration specifying unit 32, a stress calculation unit 33, a steady response measurement unit 34, and a generated stress evaluation unit 35.

[Vibration measurement unit]
The vibration measurement unit 31 includes the accelerometers 21 and 22, amplifiers 23 and 24, and A / D converters 25 and 26 illustrated in FIG. 1, and the time history waveform of acceleration measured by the vibration measurement unit 31 is stored in the computer 27. The measurement data is input and recorded, and the measurement data is used by the vibration measurement unit 31 and the steady response measurement unit 34.

[Frequency specific part]
The frequency specifying unit 32 performs a tapping test using the pipe stress evaluation device 20 of the present embodiment, and specifies the frequency ν1 (natural frequency) of the pipe to be evaluated (here, the branch pipe 12). Yes. The frequency identification unit 32 will be described with reference to FIGS. 1 to 3 and FIGS. 7 to 9.

  First, as shown in FIG. 1, accelerometers 21 and 22 are installed in the branch pipe 12 to be evaluated. Here, the accelerometer 21 is arranged closer to the mother tube 11, and the accelerometer 22 is arranged farther from the mother tube 11 than the accelerometer 21. The tapping hammer 15 is used to give the tapping excitation, which is an arbitrary vibration, to the branch pipe 12, and the acceleration time is measured using the accelerometers 21 and 22, amplifiers 23 and 24, and A / D converters 25 and 26. History waveform measurement data is acquired (step S1; tapping test). From the acquired measurement data, as shown in FIGS. 7A and 7B, a time history waveform of acceleration due to tapping excitation is acquired for the branch pipe 12 and the parent pipe 11 side of the branch pipe 12.

  Then, by analyzing the frequency of the acceleration time history waveform shown in FIGS. 7A and 7B, as shown in FIGS. 8A and 8B, the branch pipe 12 and the branch pipe 12 An acceleration spectrum is calculated for the mother tube 11 side (step S2; frequency analysis). Here, the acceleration spectrum of the branch pipe 12 shown in FIG. 8A is an acceleration spectrum A (first acceleration spectrum), and the acceleration spectrum of the branch pipe 12 shown in FIG. Let B (second acceleration spectrum).

  Using the calculated acceleration spectrum A of the branch pipe 12 and the acceleration spectrum B of the branch pipe 12 on the side of the mother pipe 11, a transfer function F1 (first transfer function) between the mother pipe 11 and the branch pipe 12 is calculated. Specifically, by dividing the acceleration spectrum A of the branch pipe 12 by using the acceleration spectrum B on the side of the mother pipe 11 of the branch pipe 12, the transfer function F1, shown in FIG. A relationship can be sought. Based on the spectrum peak of the transfer function F1 shown in FIG. 9, the vibration mode and the frequency ν1 (first frequency) of the branch pipe 12 are specified (step S3; specification). The vibration mode and the frequency ν1 specified here are used in step 14 described later.

[Analysis model determination unit]
The analysis model determination unit 33 creates an analysis model of the pipe by setting the model specifications, and the frequency ν2 calculated using the analysis model matches the frequency ν1 specified by the frequency specification unit 32. The analysis model is tuned to determine the optimal analysis model. The analysis model determination unit 33 will be described with reference to FIGS. 1, 2, 4, and 10 to 14.

  First, model specifications for creating the analysis model M1 (first analysis model), for example, piping, valve specifications, local stiffness, support specifications, measurement point information, etc. are set (step S11; model). Specification settings).

  As the specifications of the piping and valves, specifically, the masses, rigidity, etc. of the mother pipe 11, the branch pipe 12, and the valve 13 are input, and the rigidity of the support (fixed location) of the mother pipe 11, the branch pipe 12 and the like. Set. For example, as shown in FIG. 11, when the mother pipe 11 is supported and fixed to a plurality of supports 14 as a multi-span mother pipe model, the mother pipe 11 can be modeled as rotational rigidity and horizontal rigidity. Modeling is performed using the rotary spring 41 and the horizontal springs 42 and 43, and the mass of the mother pipe 11 is modeled as a mother pipe concentrated mass 45. The mother pipe concentrated mass 45 is targeted at 50% of the mass of the mother pipe 11 between the two supports 14 sandwiching the branch pipe 12.

  For example, as shown in FIG. 10, the branch pipe 12 is modeled as a beam element J1, and the valve 13 is modeled as two valve concentrated masses 46 and 47. The valve concentrated mass 46 models the main body of the valve 13, and the valve concentrated mass 47 models the handle 13 a of the valve 13. The shape line L1 is illustrated to show the movement of the handle 13a in FIG. 14 described later.

  For example, as shown in FIG. 12, the local rigidity of the joint portion (connection portion) of the mother pipe 11 and the branch pipe 12, that is, the local rigidity of the surface 11a portion of the mother pipe 11 to which the branch pipe 12 is connected is Since it can be modeled as rotational rigidity, the rotational spring 44 is used for modeling. At this time, if the ratio of the radius and thickness of the mother pipe 11 and the radius ratio of the mother pipe 11 and the branch pipe 12 are known, the magnitude of local rigidity (rotational rigidity) can be obtained from the graph shown in FIG. The size of the local rigidity (rotational rigidity) can be set.

  In addition, information on measurement points where the accelerometers 21 and 22 are installed, for example, information on installation positions is set.

  By performing the above settings, the analysis model M1 shown in FIG. 10 is created for the pipe to be evaluated (branch pipe 12) (step S12; analysis model creation).

  Using the created analysis model M1, eigenvalue analysis is performed to calculate the frequency ν2 (second frequency) and the vibration mode (step S13; eigenvalue analysis). For example, when the eigenvalue analysis of the branch pipe 12 and the valve 13 is performed on the pipe shown in FIG. 1, the frequency of 62.9 Hz is obtained as the primary mode as shown in FIG. As shown in FIG. 14B, the frequency of 72.1 Hz can be calculated as the secondary mode. In FIGS. 14A and 14B, the dotted line represents the basic shape, and the solid line represents the mode shape (shape during vibration). As eigenvalue analysis, a known analysis method may be used.

  Then, the frequency ν1 specified in step S3 is compared with the frequency ν2 calculated in step S13. If they match, the process proceeds to step S31 described later, and if they do not match, the process proceeds to step S15 (step S14). ; Comparison). Here, the accuracy of the analysis model M1 created in step S12 is confirmed.

  If the frequency ν1 and the frequency ν2 do not match, the specifications of the piping and the support are reviewed and corrected (step S15; correction). At this time, since the rigidity and mass distribution of the branch pipe 12 can be accurately set based on the length and thickness of the branch pipe 12, the specifications thereof are not changed, and the local part of the joint portion between the mother pipe 11 and the branch pipe 12 is not changed. As described with reference to FIG. 13, the rigidity can be set accurately, so the specifications thereof are not changed, but the specifications of the mother pipe 11 that is likely to be an uncertain factor in the model specifications (mainly, the specifications of the mother pipe 11). Regarding horizontal rigidity and rotational rigidity, the horizontal rigidity and rotational rigidity of the support 14 are corrected, especially affected by the shape of the support 14 (gate type, cantilever type, etc.) and difficult to evaluate accurately. In some cases, the mother tube concentrated mass 45 of the mother tube 11 is corrected, and tuning is performed by repeating steps S11 to S15 until the frequency ν1 and the frequency ν2 coincide. The analysis model M2 (second analysis model) is determined by such a procedure. The determined analysis model M2 is optimized, and the accuracy as the analysis model is improved.

[Steady response measurement unit]
The steady response measuring unit 34 uses the pipe stress evaluation device 20 of the present embodiment to measure the acceleration of the branch pipe 12 during the steady operation of the plant in the actual pipe and calculate the acceleration spectrum during the steady operation. doing. The steady response measuring unit 34 will be described with reference to FIGS. 1, 2, 5, and 15.

  First, accelerometers 21 and 22 are installed in the branch pipe 12, and using the installed accelerometers 21 and 22, amplifiers 23 and 24, and A / D converters 25 and 26, a time history of acceleration during steady operation of the plant. Waveform measurement data is acquired (step S21; measurement). The position where the accelerometers 21 and 22 are installed may be the same position as the tapping test (see step S1) in the frequency identification unit 32. However, if information on the installation position of the measurement point is clear, any position of the branch pipe 12 may be set. The position may be measured, or only one of the accelerometers 21 and 22 may be measured. From the measurement data acquired using the accelerometers 21 and 22, a time history waveform of acceleration in the branch pipe 12 is obtained as shown in FIG.

  Then, by analyzing the frequency of the acceleration time history waveform shown in FIG. 15A, an acceleration spectrum in the branch pipe 12 is calculated as shown in FIG. 15B (step S22; analysis). Here, the acceleration spectrum of the branch pipe 12 shown in FIG. 15B is assumed to be an acceleration spectrum C (third acceleration spectrum). The acceleration spectrum C analyzed here is used in step 33 described later.

[Generated stress evaluation section]
The generated stress evaluation unit 35 uses the determined analysis model M2 to calculate the stress generated at the evaluation point based on the acceleration spectrum C analyzed in step S22, and performs fatigue evaluation from the calculated stress. The generated stress evaluation unit 35 will be described with reference to FIGS. 1, 2, 6 and 16 to 18. In the following description, as an example, the position of the base of the branch pipe 12 where the accelerometer 21 is installed is used as an evaluation point. However, in the following procedure, the evaluation is performed even if an arbitrary position of the branch pipe 12 is used as an evaluation point. Fatigue evaluation can be performed by calculating the stress generated at a point.

  A frequency response analysis is performed using the analysis model M2 determined in step S14. For example, as shown in FIG. 16, the frequency response of acceleration at the measurement point (in FIG. 16, the position where the accelerometer 22 is installed) and the frequency of stress at the evaluation point (the position where the accelerometer 21 is installed in FIG. 16). A response is calculated (step S31; frequency response analysis). Here, the acceleration spectrum at the measurement point shown in FIG. 16 is the acceleration spectrum D (fourth acceleration spectrum), and the stress spectrum at the evaluation point is the stress spectrum E (first stress spectrum).

  Using the acceleration spectrum D at the measurement point obtained in step S31 and the stress spectrum E at the evaluation point, a transfer function of stress and acceleration is calculated. Specifically, by dividing the stress spectrum E by using the acceleration spectrum D, the transfer function shown in FIG. 17, that is, the relationship between the stress-acceleration response magnification with respect to the frequency can be obtained (step S32; transfer function). Calculation). Here, the transfer function shown in FIG. 17 is defined as a transfer function F2 (second transfer function).

  The transfer function F2 obtained in step S32 is multiplied by the acceleration spectrum C analyzed in step S22. Thereby, the stress spectrum in an evaluation point can be calculated | required. For example, the stress spectrum corresponding to the frequency shown in FIG. 18 is obtained by multiplying the graph of the transfer function F2 shown in FIG. 17 by the graph of the acceleration spectrum C shown in FIG. 15B (step S33; Stress spectrum calculation). Here, let the stress spectrum shown in FIG. 18 be a stress spectrum G (second stress spectrum).

  The stress standard deviation σ is calculated by frequency integrating the stress spectrum G obtained in step S33. Since the value obtained by multiplying the standard deviation by three is close to the maximum value, the value obtained by multiplying the calculated standard deviation σ by three, that is, [3σ] is calculated as the peak stress (step S34; peak stress calculation). .

  By comparing the peak stress 3σ calculated in step S34 with the allowable stress of the branch pipe 12, the stress of the branch pipe 12 that is the target pipe is evaluated (step S35; stress evaluation). Thus, by judging whether or not the peak stress 3σ is within the allowable stress range of the branch pipe 12, the fatigue evaluation of the pipe is performed with high reliability.

  As described above, in the piping stress evaluation apparatus 20 of the present embodiment, the time history waveform data of acceleration acquired by the accelerometers 21 and 22 is used. it can.

  Further, in the generated stress evaluation unit 35, the analysis model M2 includes not only the model of the branch pipe 12 but also the model of the mother pipe 11, and further models the local rigidity of the joint between the mother pipe 11 and the branch pipe 12. Therefore, the accuracy as the analysis model is remarkably improved, the accuracy of the stress calculated from the analysis model M2 is also improved, and the calculated stress and the reliability of the fatigue evaluation become high. Note that the local rigidity of the joint between the mother pipe 11 and the branch pipe 12 is graphed under the piping conditions as described with reference to FIG. 13, and can be easily reflected in the analysis model M2.

  In addition, the analysis model M2 used in the generated stress evaluation unit 35 is tuned (optimized) so as to match the frequency specified by the tapping test. Built. The stress at the evaluation point is calculated by using the optimized analysis model M2 optimized in this way, and further using the acceleration spectrum C at the actual steady operation, so the stress corresponding to the actual steady operation is calculated. The calculation is performed with high accuracy, and a highly reliable fatigue evaluation can be performed.

  Moreover, since the stress is calculated using the analysis model M2, the stress can be calculated not only at the base of the branch pipe 12, but also at any evaluation point of the branch pipe 12, and the fatigue evaluation is performed. be able to.

(Example 2)
This embodiment uses the pipe stress evaluation apparatus 20 (see FIGS. 1 and 2) described in the first embodiment and is basically the same as the pipe stress evaluation method (see FIGS. 3 to 6) described in the first embodiment. Although the same procedure is performed, the analysis model M1 of the valve 13 attached to the branch pipe 12 is different from that of the first embodiment (see FIG. 10). Here, differences between the analysis models M1 will be described, and descriptions of equivalent points will be omitted.

  In Example 1, the branch pipe 12 was modeled as the beam element J1 and the valve 13 was modeled as the valve concentrated masses 46 and 47 as described with reference to FIG. On the other hand, in this embodiment, the valve 13 is not modeled as a concentrated mass, but is modeled as valve distribution masses 48 and 49. For example, in FIG. 19, 50% of the mass of the entire valve 13 is distributed at the center of gravity of the valve 13, 10% is distributed at the center of gravity of the handle 13a, and the remaining 40% is distributed throughout the valve 13. 49 as a model. As described above, in the present embodiment, the handle 13 a is also modeled as the valve distribution mass 49. Such valve distribution masses 48 and 49 may be arbitrarily changed according to the shape of the valve 13.

  Thus, by specifying the valve 13 of the branch pipe 12 with the valve distribution masses 48 and 49, the accuracy of specifying the vibration characteristics of the branch pipe 12 itself is improved. As a result, stress with higher reliability can be calculated, and the reliability of the fatigue evaluation becomes higher.

  The present invention is suitable for fatigue evaluation of a branch pipe of a pipe in a plant or the like.

DESCRIPTION OF SYMBOLS 11 Mother pipe 12 Branch pipe 13 Valve 15 Tapping hammer 21, 22 Accelerometer 23, 24 Amplifier 25, 26 A / D converter 27 Computer 31 Vibration measurement part 32 Frequency identification part 33 Analysis model determination part 34 Steady response measurement part 35 Generated stress evaluation unit 41 Rotating spring (Rolling rigidity of mother pipe)
42, 43 Horizontal spring (base pipe horizontal rigidity)
44 Rotating spring (Home pipe local rigidity (rotational rigidity))
45 Concentrated mass of mother pipe 46, 47 Concentrated mass of valve 48, 49 Distributed mass of valve J1 Beam element

Claims (6)

A plurality of accelerometers attached to the branch pipe branched from the mother pipe of the plant, or to the mother pipe and the branch pipe;
In the pipe stress evaluation apparatus provided with stress evaluation means for calculating and evaluating the stress generated in the branch pipe using the measurement value measured by the accelerometer,
The stress evaluation means includes
The frequency analysis is performed from the time history waveforms of acceleration in the plurality of accelerometers when arbitrary vibration is applied to the branch pipe, and the first acceleration spectrum in the accelerometer far from the mother pipe and the first acceleration spectrum A first acceleration function is calculated by calculating a second acceleration spectrum that is closer to the mother tube or the accelerometer of the mother tube, and dividing the first acceleration spectrum by the second acceleration spectrum. A frequency specifying unit for specifying the first frequency of the branch pipe from the spectrum peak of the first transfer function;
The first pipe is modeled with rotational rigidity, horizontal rigidity, and concentrated mass, the branch pipe is modeled with a beam element, and a first analysis model is created in which the connection between the mother pipe and the branch pipe is modeled with rotational rigidity. Then, based on the first analysis model, eigenvalue analysis is performed to calculate a second frequency of the branch pipe, so that the second frequency matches the first frequency, An analysis model determination unit that determines a second analysis model in which the second frequency matches the first frequency by changing the rotational rigidity and horizontal rigidity of the mother pipe;
During steady operation of the plant, from a time history waveform of acceleration in the accelerometer arranged at an arbitrary measurement point of the branch pipe, by performing frequency analysis, a steady response measurement unit that calculates a third acceleration spectrum;
Using the second analysis model, frequency response analysis of the second analysis model is performed to calculate a fourth acceleration spectrum at the measurement point and a first stress spectrum at an arbitrary evaluation point of the branch pipe. And dividing the first stress spectrum by the fourth acceleration spectrum to calculate a second transfer function, multiplying the second transfer function by the third acceleration spectrum, and Is generated in the branch pipe by calculating a second stress spectrum at, calculating a peak stress by frequency integrating the second stress spectrum, and comparing the peak stress with an allowable stress of the branch pipe A piping stress evaluation apparatus, comprising: a generated stress evaluation unit that performs stress evaluation. In the piping stress evaluation apparatus according to claim 1,
The said analysis model determination part models the said valve by concentrated mass, and produces the said 1st analysis model, when the valve is provided in the said branch pipe, The piping stress evaluation apparatus characterized by the above-mentioned. In the piping stress evaluation apparatus according to claim 1,
The analysis model determination unit creates the first analysis model by modeling the entire valve including a handle of the valve with a distributed mass when the branch pipe is provided with a valve. Piping stress evaluation device characterized by this. The acceleration of the plurality of accelerometers when an arbitrary vibration is applied to the branch pipe, using a branch pipe branched from the main pipe of the plant or a plurality of accelerometers attached to the main pipe and the branch pipe. A frequency analysis is performed from the time history waveform, and a first acceleration spectrum at the accelerometer far from the mother tube and a second acceleration spectrum at the accelerometer near or near the mother tube. The first acceleration spectrum is divided by the second acceleration spectrum to calculate a first transfer function, and the first vibration of the branch pipe is calculated from the spectrum peak of the first transfer function. Identify the number,
The first pipe is modeled with rotational rigidity, horizontal rigidity, and concentrated mass, the branch pipe is modeled with a beam element, and a first analysis model is created in which the connection between the mother pipe and the branch pipe is modeled with rotational rigidity. Then, based on the first analysis model, eigenvalue analysis is performed to calculate a second frequency of the branch pipe, so that the second frequency matches the first frequency, Changing the setting of rotational stiffness and horizontal stiffness of the mother pipe to determine a second analysis model in which the second frequency matches the first frequency;
During steady operation of the plant, from the time history waveform of acceleration in the accelerometer arranged at an arbitrary measurement point of the branch pipe, frequency analysis is performed to calculate a third acceleration spectrum,
Using the second analysis model, frequency response analysis of the second analysis model is performed to calculate a fourth acceleration spectrum at the measurement point and a first stress spectrum at an arbitrary evaluation point of the branch pipe. And dividing the first stress spectrum by the fourth acceleration spectrum to calculate a second transfer function, multiplying the second transfer function by the third acceleration spectrum, and Is generated in the branch pipe by calculating a second stress spectrum at, calculating a peak stress by frequency integrating the second stress spectrum, and comparing the peak stress with an allowable stress of the branch pipe A pipe stress evaluation method characterized by performing stress evaluation. In the piping stress evaluation method according to claim 4,
A pipe stress evaluation method characterized in that, when a valve is provided in the branch pipe, the first analysis model is created by modeling the valve with a concentrated mass. In the piping stress evaluation method according to claim 4,
When the branch pipe is provided with a valve, pipe stress evaluation is characterized in that the first analysis model is created by modeling the entire valve including a handle of the valve with a distributed mass. Method.

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