JP5596504B2 - Stress measurement method for high-temperature piping, measurement member - Google Patents

Description

  The present invention relates to a stress measurement method for high-temperature piping.

For example, in a thermal power plant, high-temperature and high-pressure steam heated by a boiler is sent to a turbine using a pipe. Pipes used at this type of high temperature are made of metal and cause thermal expansion and contraction. At present, a spring-type suspension device is used to support the high-temperature pipe, and the stress is dispersed by providing a bent portion in the pipe to release the thermal expansion and contraction of the high-temperature pipe.
Patent Document 1 listed below proposes a method for measuring a displacement amount of a structure using a sampling moire method.

JP 2009-264852 A

Conventionally, however, the thermal elongation / shrinkage amount is obtained by calculation at the time of design, but it has not been verified whether the thermal elongation / shrinkage amount or stress distribution of the actual piping is as calculated. In order to prevent the consumption of the life of the high-temperature pipe and the steam leakage from the joint, it is necessary to manage the stress of the high-temperature pipe, and it has been required to establish a method for measuring the stress distribution of the high-temperature pipe.
The present invention has been completed based on the above circumstances, and an object thereof is to enable stress measurement of high-temperature piping.

The present invention is a stress measurement method for a high-temperature pipe, wherein a first step of attaching a measurement member having a lattice pattern on the surface to a plurality of measurement points on the high-temperature pipe ; A second step in which the process of simultaneously photographing the lattice pattern of each measurement member attached to a measurement point with one or a plurality of cameras is performed in a state where the high-temperature pipe is at an initial temperature ; and a plurality of measurement points on the high-temperature pipe In the third step, the second step and the third step, wherein the high-temperature piping is in a high temperature state higher than the initial temperature, the process of simultaneously photographing the lattice pattern of each of the measurement members attached to one or more cameras From the captured image data of each lattice pattern, using the sampling moire method, the fourth step of determining the displacement amount of each measurement point accompanying the pipe temperature change, and the fourth step Based on the amount of displacement of each measuring point determined, having characterized in that including a fifth step of determining the stress distribution of the high-temperature pipe in the hot state. According to this invention, it is possible to measure the stress distribution of the high-temperature pipe.

The present invention is a stress measurement method for a high-temperature pipe, wherein a first step of attaching a measurement member having a lattice pattern on the surface to a plurality of measurement points on the high-temperature pipe ; A second step in which the process of simultaneously photographing the lattice pattern of each measurement member attached to a measurement point with one or a plurality of cameras is performed in a state where the high-temperature pipe is at an initial temperature ; and a plurality of measurement points on the high-temperature pipe A third step of performing a process of simultaneously photographing the lattice pattern of each of the measurement members attached to one or a plurality of cameras in a process in which the temperature of the high-temperature pipe rises from the initial temperature, and the second step From the image data of each lattice pattern photographed in the third step, the sampling point moire method is used to change each measurement point at each point in the pipe temperature rise process. A fourth step of determining the amount, and a fifth step of determining the stress distribution of the high-temperature pipe at each point in the temperature rise process based on the displacement amount of each measurement point determined in the fourth step. It has the characteristics. According to this invention, it is possible to measure the stress distribution of the high temperature pipe at each time in the temperature rising process.

As an embodiment of the present invention, the following configuration is preferable.
As the measurement member, a magnet plate having a step on the back surface and abutting at a plurality of points on the outer peripheral surface of the high-temperature pipe is used. If it does in this way, it is possible to stabilize the attitude | position of the magnet plate attached with respect to high temperature piping, and the displacement amount of each measurement point in high temperature piping can be measured correctly.

  According to the present invention, it is possible to measure the stress distribution of the high-temperature pipe.

The figure which shows the measurement principle of the sampling moire method in Embodiment 1 of this invention. Figure showing the measurement principle Schematic diagram of thermal power plant Enlarged view of high temperature piping Perspective view of magnet plate Sectional drawing which shows the state which attached the magnetic board to the high temperature piping 5 The perspective view which shows the state which attached the magnetic board to the high temperature piping 5. The figure which shows the stress distribution of the high temperature piping 5A-5B in a high temperature state The figure which shows the correlation of a generator output and piping temperature in Embodiment 2. The figure which shows stress distribution of the high temperature piping 5A-5B in imaging | photography time T1 The figure which shows stress distribution of the high temperature piping 5A-5B in imaging | photography time T5 The figure which shows the stress distribution of the high temperature piping 5A-5B in imaging | photography time T10.

<Embodiment 1>
A first embodiment of the present invention will be described with reference to FIGS.
1. Sampling moire method (phase shift moire method)
The sampling moire method measures the minute displacement amount of a structure by utilizing the fact that a minute displacement of a lattice pattern appears to expand to the displacement of a moire pattern. Hereinafter, the principle of measuring the displacement amount by the sampling moire method will be described taking a one-dimensional displacement amount as an example.

  The lattice pattern is a black and white striped pattern, and a moire pattern is obtained by image processing of the lattice pattern. For example, as shown in FIG. 1A, when a one-dimensional lattice pattern 50 in which a striped pattern is repeated in the X direction is photographed by the digital camera 20, an image shown in FIG. 1B is obtained. A small grid shown in FIG. 1B represents one pixel of the camera 20.

  Then, from the obtained image of the one-dimensional lattice pattern 50, as shown in FIG. 1C, for example, pixels are thinned out every four pixels, and interpolation is performed so that the density continuously changes between the thinned pixels. Then, as shown in FIG. 1D, a moire pattern 60 appears.

  The period of the moire pattern 60 is longer than the period of the one-dimensional lattice pattern 50. As shown in FIG. 2, if the displacement amount in the X direction of the one-dimensional lattice pattern 50 is “δ1”, the displacement amount in the X direction of the moire pattern 60 is “δ2”. A large amount of displacement appears on the moire pattern 60 in an enlarged manner. “Δ1” and “δ2” have the relationship of the following expression (1).

δ1 = δ2 (Ps / Pm) (1) Expression Ps is the pitch (length of one cycle) of the one-dimensional lattice pattern 50. Pm is the pitch of moire patterns (the length of one cycle).

  Therefore, the displacement amount of the measurement object can be measured from the above equation (1) by attaching the lattice pattern 50 to the measurement object in advance and examining the amount of change in the moire pattern 60.

  It is preferable to set the pixel thinning interval L2 as close as possible to the repetitive pitch L1 of the lattice pattern 50. This is because when L1 is close to L2, the measurement error of the displacement amount of the measurement object is reduced. When the magnitude relationship between L1 and L2 is set to L1> L2, the displacement of the moire pattern is opposite to the displacement of the measurement object, and when L2> L1, the displacement of the measurement object is set. It is known that the displacement of the moire pattern is in the same direction.

In the above description, the one-dimensional lattice pattern 50 has been described as an example. However, when the lattice pattern is expanded to two dimensions, the two-dimensional displacement amount (displacement amount in the X direction and the Y direction) of the measurement object can be measured.
2. Description of Structure of Measurement Object The thermal power plant U includes a boiler 3, a high temperature pipe 5, a turbine 7, a generator 9, and the like, and sends high-temperature and high-pressure steam heated by the boiler 1 to the turbine 7 through the high-temperature pipe 5. The generator 9 generates power.

  The high-temperature pipe 5 is a large pipe having an outer diameter of about 1 m and is made of carbon steel such as SB42. The high-temperature pipe 5 is supported in a state of being suspended by a spring-type suspension device. The high-temperature pipe 5 is configured to ensure airtightness at the joint portion by inserting packing between the flanges 6. When the output of the generator 9 changes from 0% to 100%, the pipe temperature (surface temperature) of the high-temperature pipe 5 increases from the initial temperature (about 20 ° C.) to about 280 ° C. Therefore, thermal elongation occurs and stress is generated in each part of the high temperature pipe 5.

  In the present embodiment, the stress distribution of the high-temperature pipe 5 accompanying a temperature change is measured with the high-temperature pipe 5 of part A shown in FIG. In addition, as shown in FIG. 4, the high temperature pipe 5 of the A part has a structure in which the high temperature pipe 5A and the high temperature pipe 5B are connected by a straight high temperature pipe 5C, and the total length is about 10 m. Each of the high temperature pipes 5A, 5B, 5C is connected by a flange 6 with a packing interposed therebetween.

3. Description of the structure of the magnet plate 10 for attaching the lattice pattern 12 to the high-temperature pipe 5 The magnet plate 10 (corresponding to the “measuring member” of the present invention) is obtained by sintering ferrite and has a square of about 100 mm. Yes. As shown in FIG. 5, a two-dimensional lattice pattern 12 is printed on the surface of the magnet plate 10. The two-dimensional lattice pattern 12 is a stripe pattern in which white and black are alternately repeated in two directions, the X direction and the Y direction.

  Further, a step 15 is formed on the back surface of the magnet plate 10 and on the right front side edge shown in FIG. The step portion 15 is obtained by stacking a small magnet plate on the back surface of the magnet plate 10 and extends over the entire length of the magnet plate 10. By providing such a step portion 15, as shown in FIG. 6, when the magnet plate 10 is attached to the high temperature pipe 5 to be measured, the magnet plate 10 is placed on the outer peripheral surface of the high temperature pipe 5 at two points. It becomes possible to make it.

4). Stress Measurement Method for High-Temperature Pipe 5 The stress measurement method is composed of five steps from a first step to a fifth step described below. It is assumed that the thermal power plant U is in a stopped state (the generator output is 0%) before starting the measurement, and the pipe temperature of the high temperature pipe 5 is the initial temperature (about 20 degrees).

  First, in the first step, the work of attaching the magnet plate 10 is performed with the surface on which the lattice pattern 12 is printed facing upward at a plurality of measurement points P on the high temperature pipe 5. As shown in FIG. 4, the measurement points P are set almost uniformly over the entire high-temperature pipes 5 </ b> A to 5 </ b> C (pipe outer peripheral surface, flange outer peripheral surface, etc.). In this embodiment, as shown in FIG. It is necessary to attach the magnet plate 10 to the entire high-temperature pipes 5A to 5C.

  In the second step, the lattice pattern 12 of the magnet plate 10 attached to each measurement point P of the high-temperature pipe 5 is moved in the Z direction (XY plane) by the camera 20 in a state where the high-temperature pipe 5 is at the initial temperature. The photographing process is performed for simultaneous photographing from a direction orthogonal to. As shown in FIG. 7, in this embodiment, the measurement area is divided into three and the camera 20 is installed for each area, and each of the high-temperature pipes 5 is used using three cameras 20A to 20C. The grid pattern 12 of the magnet plate 10 attached to the measurement point P is shared and photographed simultaneously.

  In this example, the number of measurement points P is set to about 150, and about 50 magnet plates 10 are photographed by one camera 20.

  The subsequent third step is performed after the operation of the thermal power plant U is started. More specifically, after the start of operation, the generator output increases and eventually reaches 100%, and the pipe temperature of the high temperature pipe 5 reaches a high temperature state of about 280 ° C. (the steam temperature is 300 ° C.). In the third step, when the pipe temperature reaches a high temperature state of about 280 ° C., the lattice pattern 12 of the magnet plate 10 attached to each measurement point P of the high temperature pipe 5 is moved by the three cameras 20 in the Z direction ( Simultaneous shooting is performed from a direction orthogonal to the XY plane.

  Next, in the fourth step, from the image data of each lattice pattern 12 photographed in the second step and the third step, the displacement amount in the X direction and the displacement in the Y direction of each measurement point P using the sampling moire method. Determine the amount.

  For example, if the amount of displacement in the X direction of the measurement point P1 located in front of the camera 20C shown in FIG. 7 is the Moire in the X direction at the initial temperature from the image data of the lattice pattern 12 of the magnet plate 10 attached to the measurement point P1. First, a pattern and a moire pattern in the X direction in a high temperature state are generated.

  Next, the amount of displacement in the X direction of the moire pattern is measured by comparing both moire patterns. Thereby, it is possible to obtain | require the displacement amount of the X direction of the measurement point P1 using said (1) Formula from the displacement amount of the measured X direction moire pattern. Similarly, the displacement amount in the Y direction of the measurement point P1 can be obtained from the displacement amount of the moire pattern in the Y direction using the above equation (1).

  Next, in the fifth step, a continuum model of the high-temperature pipe 5 is generated based on the displacement amount of each measurement point P determined in the fourth step. Specifically, the inverse problem analysis (using the finite element method for analysis) is performed using a computer, and the nodes of the continuum model corresponding to each measurement point P (when the continuum model is divided into each element) The amount of displacement of each node and the force applied to each node are determined so that the amount of displacement of each node) substantially matches the amount of displacement calculated in the fourth step. As a result, a continuum model of the high-temperature pipe 5 that simulates the displacement obtained in the fourth step is generated.

  By generating this continuum model, the amount of displacement of the high temperature pipes 5A to 5B in the high temperature state (the amount of displacement as a continuum) and the stress distribution of the high temperature pipes 5A to 5B in the high temperature state can be obtained. This is because, by accumulating the displacement amount of each node, it is possible to determine the displacement amount (displacement amount as a continuous body) of the high temperature pipes 5A to 5B in a high temperature state, and the force applied to each node is in a high temperature state. It is because it is the stress of the high temperature piping 5 in. And in this embodiment, as shown in FIG. 8, it is supposed that the stress distribution of the high temperature piping 5A-5B which is an analysis result will be displayed by the change of a color. In the example of FIG. 8, it can be seen that the stress in the tensile direction acts on the B part to the D part of the corners of the high temperature pipes 5A to 5B.

  The finite element method is a numerical analysis method in which the target is regarded as a collection of small and simple elements, divided into each element, analyzed for each element, and an approximate value of the overall behavior is obtained. It is a technique.

5. Explanation of Effects As described above, in this embodiment, the stress distribution of the high temperature pipe 5 can be measured. Therefore, it becomes possible to manage the stress of the high temperature pipe 5 based on the actually measured value, prevent the steam leakage from the joint, and extend the life by suppressing the deterioration of the high temperature pipe 5.

  For example, regarding steam leakage, the packing is easy to loosen and steam leakage is likely to occur where stress in the pulling direction is applied. Therefore, when a location where it is determined that a stress in the pulling direction is applied and steam leakage is likely to occur is found, the flange 6 of the portion is strongly tightened so that the packing does not loosen, or the suspension device By reviewing the suspension structure of the high-temperature pipe 5 by the above and by distributing the stress, it is possible to prevent steam leakage.

  In the present embodiment, a step is provided on the back surface of the magnet plate 10 so that the magnet plate 10 contacts the outer peripheral surface of the high temperature pipe 5 at a plurality of points. If it does in this way, it is possible to stabilize the attitude | position of the magnet plate 10 attached with respect to the high temperature piping 5, and the displacement amount of each measurement point P in the high temperature piping 5 can be measured correctly.

<Embodiment 2>
Next, a second embodiment of the present invention will be described with reference to FIGS. In Embodiment 1, the example which measured the stress distribution of the high temperature piping 5A-5B in a high temperature state was shown. In the second embodiment, the stress distribution of the high temperature pipe 5 at each time (time point) in the process in which the pipe temperature reaches the maximum temperature from the initial temperature is measured.

  If it demonstrates concretely, the stress measuring method of Embodiment 2 is comprised from five steps from the 1st step to the 5th step similarly to Embodiment 1. FIG.

  First, in the first step, as in the first embodiment, the operation of attaching the magnet plate 10 with the surface on which the lattice pattern 12 is printed facing upward is made at a plurality of measurement points P on the high temperature pipes 5A to 5C. Do.

  In the second step, the lattice pattern 12 of the magnet plate 10 attached to each measurement point P of the high temperature pipes 5A to 5C at the photographing time T0 when the high temperature pipe 5 is the initial temperature (about 20 degrees as an example) Simultaneous shooting is performed by the three cameras 20.

  In the subsequent third step, the lattice pattern 12 of the magnet plate 10 attached to each measurement point P of the high-temperature pipes 5A to 5C is taken by the three cameras 20 at regular intervals after the generator output starts to rise. Shoot at the same time. As shown in FIG. 9, there is a relationship between the output of the generator 9 and the piping temperature. Therefore, the image data of the lattice pattern 12 in the process in which the temperature of the high-temperature pipes 5A to 5C rises from the initial temperature can be obtained by performing imaging every certain time after the generator output starts to rise.

  In addition, T1-T13 of FIG. 9 has shown the imaging | photography time, and in this example, it is set to each measurement point P of high temperature piping 5A-5C until it reaches 100% after a generator output starts a raise. The lattice pattern 12 of the attached magnet plate 10 was photographed 13 times.

  Subsequently, in the fourth step, the displacement amount in the X direction and the displacement amount in the Y direction of each measurement point P for each photographing time T1 to T13 from the image data of each lattice pattern 12 photographed in the second step and the third step. Is determined using the sampling moire method.

  For example, when determining the displacement amount in the X direction and the displacement amount in the Y direction of each measurement point P at the photographing time T3, the image data of the grid pattern 12 photographed at the photographing time T0 and the photographing at the photographing time T3 are taken. From the image data of the lattice pattern 12, the displacement amount of the moire pattern in the X direction and the Y direction is obtained for each measurement point P, and the displacement amount in the X direction and the Y direction of each measurement point P is determined from the obtained displacement amount of the moire pattern. What is necessary is just to determine a displacement amount using said (1) Formula.

  Alternatively, from the image data of the lattice pattern 12 photographed at the photographing time T0 and the image data of the lattice pattern 12 photographed at the photographing time T1, the displacement amount of the moire pattern in the X direction and the Y direction is obtained for each measurement point P. Next, from the image data of the lattice pattern 12 photographed at the photographing time T1 and the image data of the lattice pattern 12 photographed at the photographing time T2, the displacement amount of the moire pattern in the X direction and the Y direction is obtained for each measurement point P. After repeating this in sequence, the amount of displacement in the X direction and the amount of displacement in the Y direction may be determined using the above equation (1) by integrating them.

  Subsequently, in the fifth step, from the amount of displacement in the X direction and the amount of displacement in the Y direction of each measurement point P at each photographing time T1 to T13 determined in the fourth step, the continuation of the high temperature pipe 5 at each photographing time T1 to T13. A body model is generated using the finite element method. And by producing | generating the continuum model in each imaging | photography time T1-T13, the displacement amount (displacement amount as a continuous body) of the high temperature piping 5A-5B in the high temperature state in each imaging | photography time T1-T13 simultaneously, and each imaging | photography time. Stress distribution of the high temperature pipes 5A to 5B in the high temperature state at T1 to T13 is obtained.

  As an example of the stress distribution of the high temperature pipes 5A to 5B in the high temperature state at each photographing time T1 to T13, FIG. 10 shows the stress distribution of the high temperature pipes 5A to 5B at the photographing time T1, and FIG. 11 shows the high temperature at the photographing time T5. The stress distribution of the pipes 5A to 5B is shown, and the stress distribution of the high temperature pipes 5A to 5B at the photographing time T10 is shown in FIG.

  As described above, in the second embodiment, it is possible to measure the stress distribution of the high temperature pipes 5A to 5B at each time point (shooting times T1 to T13) in the process in which the pipe temperature reaches the maximum temperature from the initial temperature. Therefore, it is possible to know how the stress distribution of the high temperature pipes 5A to 5B changes during the temperature rise process.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.

  (1) In the first and second embodiments, the steam pipe connecting between the boiler and the turbine is exemplified as an example of the high temperature pipe 5, but any pipe that causes a temperature change by the internal fluid may be used. It can also be used to measure the stress of pipes.

  (2) In the first and second embodiments, an example is shown in which a plurality of magnet plates attached to the high temperature pipe 5 are divided and photographed by three cameras, but the magnet plate 10 to be photographed is in the field of view of one camera. If it is within the range, it is possible to shoot with one camera.

5 ... High temperature piping 6 ... Flange 10 ... Magnet plate (equivalent to "measuring member" of the present invention)
20 (generic name for 20A to 20C) ... Camera

Claims (4)

A stress measurement method for high-temperature piping,
For a plurality of measurement points on the high-temperature pipe, a first step of attaching a measurement member with a lattice pattern on the surface;
A second step in which the process of simultaneously photographing the lattice pattern of each measurement member attached to a plurality of measurement points on the high-temperature pipe with one or a plurality of cameras is performed in a state where the high-temperature pipe is at an initial temperature;
A process of simultaneously photographing the lattice pattern of each measurement member attached to a plurality of measurement points on the high-temperature pipe by one or a plurality of cameras in a high temperature state in which the high-temperature pipe is higher than an initial temperature; and
From the image data of each lattice pattern photographed in the second step and the third step, using the sampling moire method, a fourth step of determining the displacement amount of each measurement point accompanying the pipe temperature change,
And a fifth step of determining a stress distribution of the high temperature pipe in the high temperature state based on the displacement amount of each measurement point determined in the fourth step. A stress measurement method for high-temperature piping,
For a plurality of measurement points on the high-temperature pipe, a first step of attaching a measurement member with a lattice pattern on the surface;
A second step in which the process of simultaneously photographing the lattice pattern of each measurement member attached to a plurality of measurement points on the high-temperature pipe with one or a plurality of cameras is performed in a state where the high-temperature pipe is at an initial temperature;
A process of simultaneously photographing the lattice pattern of each measurement member attached to a plurality of measurement points on the high-temperature pipe with one or a plurality of cameras is performed at regular intervals while the high-temperature pipe rises in temperature from the initial temperature. The third step,
A fourth step of determining a displacement amount of each measurement point for each time point in the pipe temperature rise process using the sampling moire method from the image data of each lattice pattern photographed in the second step and the third step; ,
A fifth step of determining a stress distribution of the high-temperature pipe at each point in the temperature rise process based on the displacement amount of each measurement point determined in the fourth step, Method.   The stress measurement method for a high temperature pipe according to claim 1 or 2, wherein a magnet plate having a step on the back surface and contacting the outer peripheral surface of the high temperature pipe at a plurality of points is used as the measurement member. A measurement member used for stress measurement of high-temperature piping,
  A measuring member comprising a magnet plate having a lattice pattern on the front surface, a step on the back surface, and abutting at a plurality of points on the outer peripheral surface of the high-temperature pipe.

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