JPH0769229B2 - Tube stress relief method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a method for releasing stress generated in a pipe material in order to ensure the safety of a structure such as a pipe material by using a magnetostrictive stress measuring device. The present invention relates to a method of releasing stress in a pipe that enables adjustment work in a pipe state.

[Prior Art] For example, in the case of a structure such as a pipeline, if there is a fixing portion somewhere, uneven settlement may occur due to ground subsidence, which may cause a problem in safety of the structure. In such a case, the stress due to uneven settlement is generally released to ensure the safety of the structure.

In order to release the bending stress of a pipe, it is first necessary to measure the bending stress acting on the pipe. Conventionally, for example, in stress relief construction of a governor station of a pipeline, a strain gauge is used to measure the bending stress acting on the pipe.

[Problems to be Solved by the Invention] In the case of stress measurement using a conventional strain gauge as described above, since only relative strain can be measured, one end of the pipeline is disassembled at the flange portion to eliminate bending stress. The actual measurement was performed after adjusting the zero point of the measuring instrument.
Since a fluid such as a liquid or a gas usually flows through the pipeline, there is a problem that the fluid flowing through the pipeline needs to be stopped by a valve or the like in order to disconnect the pipeline.

Further, in order to attach the strain gauge, it is necessary to perform the surface treatment on the measured position, and the pipeline coating is peeled off, so that there is a problem that re-coating is required after the measurement.

On the other hand, although it is possible to apply an X-ray stress measurement method that is a non-destructive residual stress measurement method, in the case of an X-ray stress measurement device,
Since the device itself is large, it is difficult to set the X-ray device in a narrow space on site, and even if it can be set, it takes time for pretreatment and damages the surface by electropolishing, and it takes time for measurement. There were problems such as.

The present invention has been made to solve such a problem, and is an adjustment work for releasing the stress generated in the pipe material without disconnecting the connection of the pipe material that has been piped, that is, in a live pipe state in which a fluid is allowed to flow inside. The purpose of the present invention is to obtain a method for releasing stress in a pipe.

[Means for Solving the Problem] A method for releasing stress in a pipe according to the present invention is a method for releasing stress generated in a pipe material in order to ensure the safety of a structure formed by piping such as a pipe material. Using a magnetostrictive stress measuring device that relatively moves on the outer peripheral surface or the inner peripheral surface in a non-contact state, the bending stress distribution in the pipe circumferential direction of the pipe material is measured by SI.
Approximately calculated by N curve, adjust the structure so that the calculated value does not exceed the reference value for safety of the structure or the minimum value, and release the stress generated in the pipe material The above-mentioned magnetostrictive stress measuring device is provided.

[Operation] In the present invention, in the method of relieving the stress generated in the pipe material in order to ensure the safety of the structure made of the pipe material such as the pipe material, the magnetostrictive sensor is in a non-contact state on the outer peripheral surface or the inner peripheral surface of the pipe material. Using a magnetostrictive stress measuring device that moves relative to
The bending stress distribution in the pipe circumferential direction of the pipe material is calculated by approximation with a SIN curve, and the structure is adjusted so that the calculated value does not exceed a reference value for safety of the structure or a minimum value. The stress generated in the pipe material is released.

[Example] The present invention is a magnetostrictive stress measuring method disclosed in Japanese Patent Application No. 63-153622 filed previously for the work of releasing bending stress of a pipe working on a structure such as a pipeline. Is applied to enable stress relief work in a live pipe state while the pipeline is connected, and the work efficiency can be improved.

First, the outline of the magnetostrictive stress measuring method according to the prior application will be described, then the configuration and operation of the magnetostrictive stress measuring apparatus according to the present invention will be described, and finally the stress of the pipe using the magnetostrictive stress measuring method of the present invention. The releasing method will be described in detail.

As a method of measuring the stress and residual stress of a steel material or a steel structure, there is a method using a magnetostriction sensor in addition to X-rays and ultrasonic waves. As a method for measuring the stress of a cylindrical material such as a magnetizable round bar or pipe using this magnetostrictive sensor, there is a magnetostrictive stress measuring method disclosed in Japanese Patent Application No. 63-153622 filed previously.

In the magnetostrictive stress measurement method, when a load is applied to a magnetic material, anisotropy occurs in the magnetic permeability, the magnetic permeability in the load direction increases, and the magnetic permeability in the direction perpendicular to the load direction decreases. This is a method of measuring the direction and magnitude of the principal stress by detecting the difference by a magnetostrictive sensor (also called a magnetic anisotropy sensor) that connects the exciting coil and the detecting coil.
According to this measurement method, the measurement time for one point is 10 to 100 msec.
As a result, handling is extremely convenient.

However, since the conventional magnetostrictive stress measuring method is generally performed by bringing the magnetostrictive sensor into contact with the surface to be measured, the magnetic resistance at the contact surface greatly differs depending on the state of the surface to be measured. Therefore, there is a drawback that the measurement error becomes large.

Therefore, the idea is to measure in a non-contact state, that is, in the state where the magnetostrictive sensor is separated from the measured surface by a certain distance, but in this case, the magnetostrictive sensitivity decreases, so the setting of the magnetostrictive sensor There was another problem that required very subtle adjustments.

In the invention of the prior application, a device for solving the problems in the non-contact measurement and developing a magneto-striction stress measuring method for a columnar material such as a magnetizable round bar or a pipe by a non-contact method, and measuring device therefor have been developed. We have provided a method to measure the stress distribution in the circumferential direction of a cylindrical material with higher accuracy than before.

FIG. 1 is a diagram for explaining the magnetostrictive stress measuring method according to the previous application. In FIG. 1 (a), a bending load is applied to the columnar material 1 so that the upper side of the columnar material 1 has a tensile stress + σ and the lower side thereof has a compression stress. Stress-σ
Indicates that is working. Further, FIG. 2B shows the columnar material 1
The magnetostrictive sensor 2 is rotated in a clockwise direction from the uppermost point of the columnar material 1, that is, the angular position of 0 °, while maintaining lift-off (gap) at a constant distance h from the central axis of the columnar material and its outer peripheral surface. 1 shows a method of continuously measuring the magnetostrictive signal detected by the magnetostrictive sensor 2 at each angular position between 0 ° and 360 ° by making one rotation along the circumferential direction.

FIG. 2 is a diagram for explaining the SIN approximation method based on the magnetostrictive stress measurement method of FIG. 1, and FIG. 2A shows the angle indicating the orientation of the magnetostrictive sensor 2 on the outer circumference of the cylindrical material 1 and its stress distribution. Since the maximum tensile stress occurs at an angle of 0 ° (that is, directly above the columnar material 1) and the maximum compressive stress occurs at an angle of 180 ° (that is, immediately below the columnar material 1,) the stress distribution is similar to the SINθ curve. To do.

FIG. 2 (b) shows the measured value of the stress by the strain gauge and the SINθ approximate value when a load of −20 kg / mm ² was applied to the cylindrical material. From this figure, it can be seen that the actual stress distribution and the SINθ curve are very similar.

The description of the magnetostrictive pressure measuring method is completed as described above, and then the magnetostrictive stress measuring device is described.

FIG. 3 is a block diagram of a magnetostrictive stress measuring device for a pipe to which the stress releasing method for a pipe according to the present invention is applied. In the figure, reference numeral 10 denotes a traveling device section, which incorporates a magnetic anisotropy sensor 11 and a traveling carriage 12. The magnetic anisotropy sensor 11 is a sensor for detecting the magnetic anisotropy in the circumferential direction of the pipe material in a non-contact manner, and includes, for example, an exciting coil and a detecting coil that are orthogonal to each other, and a constant exciting current is applied to the exciting coil. Then, the magnetic anisotropy caused by the action of stress is detected as a voltage signal obtained from the detection coil. The traveling carriage 12 is, for example, a traveling mechanism that travels on rails and / or gears provided on the outer circumference of the pipe and moves the magnetic anisotropy sensor 11 in the circumferential direction of the pipe to perform measurement. Reference numeral 13 is a magnetostriction measuring unit, which supplies a constant current to the exciting coil of the magnetic anisotropy sensor 11, and at the same time amplifies the detection signal obtained from the detection coil of the sensor 11 to obtain a voltage signal proportional to the magnetic anisotropy. It is a magnetostriction measuring unit for outputting. Reference numeral 14 denotes a motor driver, which supplies a traveling drive signal to the traveling vehicle 12 to cause the traveling vehicle 12 to travel, and an encoder signal is returned as position information of the traveling result. 15 is an A / D converter, 16
Is an interface such as RS232C, 17 is a personal
A computer (hereinafter referred to as a personal computer), 18 is a data display unit using a CRT or liquid crystal.

The operation of FIG. 3 will be described. To measure the stress in the circumferential direction of the pipe material, for example, a rail or / and a gear (not shown) is attached to the outer peripheral surface of the pipe material on a curve perpendicular to the central axis of the pipe material, and a holder is mounted on the rail or / and gear via the holder. Mount the traveling device unit 10 so that it can travel. Next, the personal computer 17 gives a running command for one rotation to the motor driver 14 via the interface 16, and the motor driver 14 sends the running command to the rail or / or
Also, the traveling device 10 on the gear is caused to travel once along the circumference of the pipe. During this running, the magnetic anisotropy sensor 11 (magnetostriction sensor 2
The same as the above) is detected by the magnetostriction measuring unit 13 at each angular position between 0 ° and 360 ° on the outer peripheral surface of the pipe material shown in FIG. 1 (b). The amplified signal is output, and the output is quantized by the A / D converter 15 and supplied to the personal computer 17. The personal computer 17 displays the measured value from the magnetostriction measuring unit 13 for each angle indicating the azimuth on the outer circumference of the magnetic anisotropy sensor 11 and / or the data obtained by approximating this measured value by the SIN approximation curve in a graphic or numerical display format. Then, the data is displayed on the data display unit 18, and if necessary, a hard copy is output by a printer (not shown). The stress relieving work of the pipe according to the present invention can be performed based on the data displayed on the data display unit 18 of the measurement device or the hard copy data output by the printer.

Further, in the above-described embodiment, the example in which the magnetostrictive sensor is made to travel on the outer peripheral surface of the pipe material in a non-contact manner has been shown, but the magnetostrictive sensor may be made to travel on the inner peripheral surface of the pipe material in a non-contact manner as well. Further, in this case, the magnetostrictive sensor may be fixed by rotating the pipe with respect to its central axis without running the magnetostrictive sensor. In either case, the magnetostrictive sensor and the pipe member may be moved relative to each other, and the same effect can be obtained by fixing one and moving the other.

The tube stress relieving method of the present invention is described below.

FIG. 4 is a structural diagram of a gas governor station which is an embodiment to which the present invention is applied. In the figure, the pipelines from the outside are piped to the central valve through curved pipes and valves in the governor station, respectively. The places where the tubes on both ends of this central valve are thin are usually the parts where the greatest stress acts.

In the conventional stress relief method, strain gauges were attached to the pipes at both ends of the central valve, where the gas flow inside the pipe was stopped by the left and right valves, and the flange on one side of the central valve was disassembled. After making the bending stress zero and performing the zero point cooking of the measuring instrument, the actual stress was measured and the valve level was adjusted so that this stress would be small.

The stress relieving method of the pipe of the present invention is performed in the following procedure.

(1) Magnetostriction was measured by the magnetostrictive stress measuring device shown in Fig. 3 for the part where both ends of the central valve in the governor station were thin, and the amplitude value of the SIN approximation curve approximated from the measured value Is calculated and the bending stress distribution of the pipe is output to a display unit or a printer by a graphic display. The direction of maximum amplitude value of the SIN approximation curve displayed in this figure indicates the direction of maximum tensile stress, the direction of minimum amplitude value indicates the direction of maximum compressive stress, and the signal amplitude value indicates the magnitude of stress. . Therefore, the operator can visually understand the direction and the magnitude of the bending stress by this graphic display, and can easily determine the level adjustment direction.

(2) If a calibration curve of the bending stress and the signal amplitude of the SIN approximate curve obtained by the magnetostrictive stress measuring device for the pipe as shown in Fig. 5 is obtained in advance, the calibration curve is used now. Measure the bending stress. In FIG. 5, the circles and the triangles indicate the measured values of bending stress actually measured by a strain gauge or the like in two measuring systems, and a curve approximating these measured values becomes a calibration curve. (However, it is approximated by a straight line in Fig. 5.) If a calibration curve that allows quantitative measurement is not available, the bending stress vs. Set two calibration curves for maximum and minimum signal amplitude slopes and estimate the worst case bending stress from within these two calibration curves or use the minimum slope calibration curve can do.

FIG. 6 is a diagram showing the variation of the calibration curve of the magnetostrictive stress measuring device due to the tube.

(3) Adjust the bulp level so that the bending stress of the pipe measured or estimated in (2) becomes small.

(4) Bending stress is measured again with the magnetostrictive stress measuring device, and it is confirmed whether the stress is within the standard value specified for safety. If it is not within the standard value, the adjustment is repeated and the value is smaller than the standard value. Value. For example, the calibration curve shown in Fig. 5 was obtained, and the bending stress was 5 kg / mm ²
If you want to set it below, set the amplitude of the SIN approximation curve to 0.8V or less. Further, in the case of the estimation shown in FIG. 6, even in the worst case, if the amplitude of the SIN approximate curve is set to 0.5 V or less, the bending stress is estimated to be 5 kg / mm ² or less. Even if there is no calibration curve at all, if the adjustment is repeated so as to minimize the amplitude of the SIN approximation curve, the bending stress can be minimized even when the quantitative stress value cannot be grasped and the pipeline is in the live pipe state. Can be adjusted as follows.

In this way, the stress release method by the magnetostrictive stress measurement method allows work in a live tube state with the pipeline connected, does not damage the tube by non-contact measurement, and the measurement time is only a few minutes. There is a great advantage that cannot be obtained by other methods, such that it is sufficient and the magnitude of bending stress can be visually understood because it is displayed graphically.

[Effects of the Invention] As described above, according to the present invention, in the method of releasing the stress generated in the pipe material in order to secure the safety of the structure made of the pipe such as the pipe material, the value approximated to the measurement value of the magnetostrictive stress measuring device Based on the amplitude value of the SIN approximate curve, the structure was adjusted to release the stress generated in the pipe material, so the effects listed below can be obtained.

1. Compared with the conventional stress relief method using strain gauges, it is possible to carry out the work in a live tube condition.

2. Since the stress can be measured without contacting the pipe, it can be measured from above the paint without damaging the pipe. Therefore, pretreatment and repainting treatment after measurement are unnecessary.

3. Since the time required for measurement is only a few minutes, work can be performed quickly.

4. Since the magnitude of the bending stress is displayed in a graph, the operator can visually understand that the bending stress is small, which facilitates adjustment.

[Brief description of drawings]

1 (a) and 1 (b) are diagrams for explaining the magnetostrictive stress measuring method according to the prior application, and FIGS. 2 (a) and 2 (b) are for explaining the SIN approximation method by the magnetostrictive stress measuring method of FIG. FIG. 3 is a block diagram of a magnetostrictive stress measuring device for a pipe to which the stress releasing method for a pipe of the present invention is applied, and FIG. 4 is a structural view of a gas governor station which is an embodiment to which the present invention is applied. FIG. 5 is a diagram showing a calibration curve of the bending stress and the signal amplitude of the SIN approximate curve obtained by the magnetostrictive stress measuring device for the pipe, and FIG. 6 is a diagram showing the variation of the calibration curve of the magnetostrictive stress measuring device due to the pipe. . In the figure, 1 is a cylindrical material, 2 is a magnetostrictive sensor, 10 is a traveling device section, 11 is a magnetic anisotropy sensor, 12 is a traveling carriage, 13 is a magnetostrictive measuring section, 14 is a motor driver, and 15 is an A / D conversion. Bowl, 16
Is an interface, 17 is a personal computer, and 18 is a data display unit.

Continuation of front page (72) Inventor Sadaaki Sakai Nihon Kokan Co., Ltd. 1-2-1, Marunouchi, Chiyoda-ku, Tokyo (56) Reference JP-A-1-308933 (JP, A)

Claims (1)

[Claims] 1. A method of relieving stress generated in a pipe material for ensuring the safety of a structure made of piping such as a pipe material, wherein a magnetostrictive sensor relatively moves on an outer peripheral surface or an inner peripheral surface of the pipe material in a non-contact state. Using a magnetostrictive stress measuring device to calculate the bending stress distribution in the pipe circumferential direction of the pipe material by approximating with a SIN curve, and the calculated value does not exceed the reference value for the security of the structure or a minimum value A method for releasing stress in a pipe, comprising: adjusting the structure so that the stress generated in the pipe material is released.