TW201627646A - Method of extending life expectancy of high-temperature piping and life expectancy extension structure for high-temperature piping - Google Patents

Abstract

If it is determined that steady and continuous use is not possible according to a life expectancy evaluation at a weld section of a high-temperature piping based on creep ruptures, insulation material covering a site of the high-temperature piping at high risk of creep rupture is partially removed to locally lower the temperature of the outer surface of the high-temperature piping and to extend the life expectancy of the site at high risk of creep rupture. In addition, the width of an exposed part where the insulation material was partially removed is at least twice the distance where the change in stress between the tensile stress and compressive stress generated on the high-temperature piping due to removing the insulation material from the stripped end of the exposed part changes from tensile stress to compressive stress and the compressive stress gradually approaches zero. The distance where the compressive stress approaches zero after the tensile stress changes to compressive stress is calculated according to the following formula (1). I2x=5 (1), where I2 is represented by the following formula (2). Here, v is the Poisson ratio, a is the average radius of the piping, and h is the thickness of the piping.

Description

Longevity method of high temperature piping and extended life structure of high temperature piping

The present invention relates to a method for extending the life of a high-temperature pipe such as a high-temperature pipe or a pressure vessel used in a thermal power plant, a nuclear power plant, or a chemical plant, and a structure for extending the life of a high-temperature pipe.

For example, a boiler or the like that constitutes a thermal power plant is operated in a high-temperature and high-pressure environment, and the heat-resistant steel constituting the material accumulates damage caused by creep or the like with long-term operation. Therefore, in the operation of such a plant, the high-precision life evaluation of the heat-resistant steel described above is performed to maintain the reliability of the pressure-resistant portion, and it is important to ensure long-term stable operation.

A high-temperature pipe used in a thermal power plant or the like has a function of transporting steam heated by a boiler to a steam turbine, and a latent change hole is developed as a result of high temperature and long-term use, and these holes are connected. Cracks are generated and eventually break.

In order to prevent the final fracture, the degree of creep of each member is analyzed by periodic non-destructive inspection to derive the degree of creep damage of each member, and the remaining life of the member is evaluated (Patent Documents 1 and 2). In general, compared with the base metal part, the risk of latent fracture of the pipe fusion joint is high, the inspection department The position is mainly the fusion joint.

Prior technical literature Patent literature

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2004-85347

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2008-122345

As a result of the non-destructive inspection, when there is a member having a high creep damage degree, there is a risk of high creeping fracture during the period until the next periodic inspection, and the operating temperature is lowered by changing the member or the entire plant. The risk of latent fracture is reduced by reducing the metal temperature of the entire pipe.

However, when the overall operating temperature of the plant is lowered, there is a problem that the plant operating efficiency is deteriorated.

Therefore, it is desirable to have a technique that does not lower the overall operating temperature of the plant, does not cause a decrease in the operating efficiency of the plant, and can prolong the remaining life of the high temperature component.

The present invention has been developed in view of the above problems, and an object of the present invention is to provide a method for extending the life of a high-temperature pipe and a structure for extending the life of a high-temperature pipe, without lowering the overall operating temperature of the plant, without causing a decrease in the operating efficiency of the plant, and enabling the high-temperature component. The remaining life is extended.

In the first aspect of the present invention, the method of extending the life of the high-temperature pipe is characterized in that it is covered by the remaining life evaluation of the creeping fracture of the welded portion of the high-temperature pipe. A part of the heat insulating material at the high-latency fracture risk portion of the high-temperature pipe is removed, and the outer surface temperature of the high-temperature pipe is locally lowered, so that the life of the high-latency fracture risk portion is prolonged, and a part of the heat insulating material is removed. The width is twice or more the distance from which the tensile stress and the compressive stress generated in the high-temperature pipe are removed from the peeling end of the exposed portion, and the stress is changed from the tensile stress. After changing to compressive stress, the compressive stress gradually approaches the distance of 0. The distance from the tensile stress to the compressive stress and the compressive stress gradually approaches 0 satisfies the following formula (1), β x=5. . . (1) β is expressed by the following formula (2),

Here, v is a Poisson ratio, a is the average radius of the pipe, and h is the plate thickness of the pipe.

According to a second aspect of the invention, in the first aspect of the invention, the surface of the member from which the heat insulating material is removed is cooled.

According to a third aspect of the invention, in the second aspect of the invention, the cooling is Cool with air or use cooling water for cooling.

According to a fourth aspect of the invention, in the first aspect of the invention, the heat dissipating member is provided on a surface of the member from which the heat insulating material is removed.

According to a fifth aspect of the invention, in the first aspect of the invention, the temperature of the surface of the member from which the heat insulating material is removed is measured, and whether the cooling ability is appropriate is determined.

According to a sixth aspect of the invention, in the fifth aspect of the invention, when the cooling ability is not appropriate, the cooling capacity is changed to be appropriate.

According to a seventh aspect of the invention, there is provided a structure for extending the life of a high-temperature pipe, wherein the risk of high-latency fracture of the high-temperature pipe is covered when the remaining life of the welded portion of the high-temperature pipe is estimated to be unsustainable. A part of the heat insulating material of the portion is removed, and the temperature of the outer surface of the high temperature pipe is locally lowered. The width of the exposed portion where the heat insulating material is removed is twice or more the distance from the exposure. The peeling end portion of the portion removes the heat insulating material and changes the tensile stress and the compressive stress generated by the high temperature pipe from the tensile stress to the compressive stress, and the compressive stress gradually approaches a distance of 0, from the tensile stress. The distance at which the compressive stress gradually approaches 0 after changing to compressive stress satisfies the following formula (1), β x = 5. . . (1) β is expressed by the following formula (2),

Here, v is a Poisson ratio, a is the average radius of the pipe, and h is the plate thickness of the pipe.

According to a seventh aspect of the invention, in the seventh aspect of the invention, there is provided a cooling means for cooling a surface of a member from which the heat insulating material is removed.

According to a ninth invention, in the eighth aspect of the invention, the cooling means is an air cooling means using air or a water cooling means using cooling water.

According to a tenth aspect of the invention, in the seventh aspect of the invention, the heat dissipating member is provided on a surface of the member from which the heat insulating material is removed.

According to the present invention, by lowering the metal temperature of the piping, the creep rupture life of the piping is prolonged, and the life of the remaining life of the piping can be extended.

11‧‧‧High temperature piping (pipe)

12‧‧‧welding department

13‧‧‧Insulation

14‧‧‧Exposed Department

15‧‧‧Boiler Vapor

Fig. 1 is a schematic view showing a structure of a life extension of the high temperature pipe of the first embodiment.

Fig. 2 shows a portion after peeling off the heat insulating material of the piping.

Fig. 3 shows the relationship between the distance from the peeled portion of the heat insulating material and the tensile stress and compressive stress applied to the inside of the pipe.

Fig. 4 is a schematic view showing a structure of a life extension of the high temperature pipe of the second embodiment.

Figure 5 is a perspective view of Figure 4.

Fig. 6 is a schematic view showing a structure of a life extension of another high temperature pipe of the second embodiment.

Fig. 7 is a schematic view showing a structure of a life extension of the high temperature pipe of the third embodiment.

Fig. 8 is a perspective view showing an example of an air supply means for supplying cooling air.

Fig. 9 is a schematic view showing a structure of a life extension of the high temperature pipe of the fourth embodiment.

Fig. 10 is a schematic view showing a structure of a life extension of another high temperature pipe of the fourth embodiment.

Fig. 11 is a schematic view showing a protective structure of an exposed portion of a high temperature pipe.

Fig. 12 is a view showing the steps of a metal temperature control method for a high temperature pipe.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Further, this embodiment is not intended to limit the present invention, and in addition, when there are a plurality of embodiments, the configuration in which the embodiments are combined is also included.

[Example 1]

Fig. 1 is a schematic view showing a structure of a life extension of the high temperature pipe of the first embodiment.

As shown in Fig. 1, the life extension structure of the high-temperature pipe according to the present embodiment is based on the remaining life evaluation of the creeping fracture of the welded portion 12 of the high-temperature pipe, that is, the high-temperature pipe (hereinafter referred to as "pipe") 11, and the high-potential is confirmed. When the fracture risk portion (the welded portion having a high degree of creep damage) is judged to be incapable of being used normally, one portion of the heat insulating material 13 of the high creep potential fracture risk portion of the covered pipe 11 is removed in the rotational direction to become the exposed portion 14 ,borrow This causes the temperature of the outer surface of the pipe 11 to be locally lowered to achieve an extension of the life of the latent fracture site.

In Fig. 1, reference numeral 15 denotes a boiler vapor, and a high-temperature vapor of, for example, 600 °C flows in the pipe 11.

The welded portion 12 of the pipe 11 having a high risk of latent fracture according to the non-destructive inspection is removed as shown in FIG. 1 to form the exposed portion 14 and the heat is released from the exposed portion 14. The metal temperature of the pipe 11 is lowered.

In this case, the exposed portion 14 is formed by removing the heat insulating material 13, and natural convective heat transfer occurs with the outside air (for example, 100 ° C), and the thermal conductivity is about 2 to 12 W/m ² K.

In this way, by lowering the metal temperature of the pipe 11, the creeping fracture life of the pipe 11 is prolonged, and the life of the remaining life of the pipe can be extended.

As a result, it is possible to achieve longevity by merely lowering the temperature of the pipe locally, and it is possible to prevent the conventional disadvantages, that is, to lower the operating temperature of the entire plant, and to lower the metal temperature of the entire pipe, thereby reducing the risk of creeping fracture. The efficiency of the plant has deteriorated.

As described above, according to the present embodiment, when the high-latency damage risk portion of the high-temperature pipe is confirmed, the heat insulating material 13 of the covered pipe 11 is removed by the width (L) of the predetermined distance to form the exposed portion 14, thereby lowering the metal temperature. The risk of latent damage is reduced, and the overall operating efficiency of the plant is not reduced, and the life can be extended. Here, the decrease in the temperature of the metal is not only the latent fracture life but also effective for the life extension of the crack growth life.

Here, the removal width L of the heat insulating material 13 is preferably 460 mm when the outer diameter of the pipe 11 is, for example, a range of about 900 mm or more as will be described later, and the outer surface direction is deformed depending on the removal width of the heat insulating material 13. Compressive stress is generated, and the life extension caused by the stress reduction is also expected.

Next, the width L in which a part of the heat insulating material 13 is removed will be described.

In FIG. 2, the distance (L/2) in which the heat insulating material 13 is removed from the end portion x ₀ from which the heat insulating material 13 is removed is described by removing the heat insulating material 13 on the left side from the pipe 11.

When the heat insulating material 13 is removed, tensile stress and compressive stress are applied to the pipe 11, and the distance from the place where the heat insulating material 13 is peeled off is ₀ (x ₁ , x ₂ , x ₃ ), and the stress is changed. The distance gradually approaching 0 is expressed by the following formula.

β x=5. . . (1)

Here, β is represented by the following formula (2), and it is only required to take the value of x.

Here, v is the Poisson ratio (material properties), in general, a metal material pipe 11 is approximately 0.3. In addition, a is the average radius and h is the plate thickness.

For example, when the outer diameter of the pipe 11 is 460 mm and the thickness is 70 mm, a = 195 mm, h = 70 mm, the value of x when β x = 2.4 is 218 mm, and the value of x when β x = 5 is 454 mm. In addition, because of β 1 / √ (ah), x value and √ (ah) are related values, if a, h change, the value of x will change.

Therefore, for example, when the outer diameter is 460 mm and the thickness is 70 mm, x = 218 to 454 mm.

The distance (L) at which the heat insulating material 13 of the pipe 11 is peeled off to form the exposed portion 14 will be described with reference to FIGS. 2 and 3 .

Fig. 2 shows a portion after peeling off the heat insulating material of the piping. Further, the peeling of the heat insulating material is performed by peeling the center of the welded portion, and FIG. 2 is a description of the peeled portion on the left side.

Fig. 3 shows the relationship between the distance (mm) from the peeling portion x _{0 of the} heat insulating material, the tensile stress applied to the inside of the pipe, and the compressive stress.

The piping of Fig. 2 is described with respect to a case where the outer diameter of the pipe is 460 mm and the pipe thickness is 70 mm.

As shown in Fig. 3, when the peeling portion 0 mm of the heat insulating material of the pipe is set to x ₀ , as described above, the tensile stress becomes 0 at a predetermined distance x ₁ (= 218 mm). The compressive stress becomes maximum at a predetermined distance x ₂ (= 273 mm) from the predetermined distance x ₁ . At a predetermined distance x ₃ (= 454 mm) from the predetermined distance x ₂ , the compressive stress becomes zero and converges.

When the left side peeling portion and the right side peeling portion of the pipe 11 are added together, the distance is doubled, and the peeling distance L becomes 454 mm × 2 = 908 mm.

Therefore, the distance L to be peeled off is preferably about 900 mm or more.

In addition, it is necessary to use compressive stress to achieve further life extension. In the case of a long length, the range in which the heat insulating material 13 is removed can be determined according to the following formula (3).

2.4≦β x<5. . . (3)

For example, when the outer diameter is 460 mm and the thickness is 70 mm, at least the distance x ₁ (= 218 mm) to which the tensile stress is not applied must be peeled off, and at the time of convergence x ₃ (454 mm) or more, the heat insulating material does not need to be peeled off.

[Embodiment 2]

Fig. 4 is a schematic view showing a structure for extending the life of the high temperature pipe of the second embodiment. Fig. 5 is a perspective view of Fig. 4; The same components as those of the first embodiment are denoted by the same reference numerals, and their description will be omitted. As shown in FIG. 4 and FIG. 5, in the life-extending structure of the high-temperature pipe of the second embodiment, the heat-dissipating member is provided so as to be in close contact with the exposed portion 14 in which the heat-insulating material 13 is removed in the first embodiment. Multilayer heat sink 17.

As shown in FIG. 5, the heat sink 17A having the plurality of fins 18 and the fins 17B having the lower fins 18 are fastened by the fastening member 20 in such a manner that the flanges 19 are aligned with each other.

The heat sink 18 has a thickness (d ₁₁ ) of, for example, 70 mm and a height (h ₁₁ ) of about 300 mm to form a multilayer fin structure.

In the present embodiment, the welded portion of the high-temperature pipe which is determined to be a high-latency fracture risk by non-destructive inspection removes the permanent heat insulating material 13 as shown in FIGS. 4 and 5 to form the exposed portion 14 to The upper fins 17A and the lower fins 17B are provided so that the exposed portions 14 are in close contact with each other. borrow By adopting such a multi-layer fin structure, the area for releasing heat is increased, and the metal temperature of the piping can be lowered to be lower than that of Embodiment 1.

According to the present embodiment, by providing the multilayer heat sink 17 of the exposed portion 14 after the heat insulating material 13 is removed, the area for releasing heat is increased, and the heat flux is increased in proportion to the area increase rate, compared to the first embodiment. Can make the metal temperature cool faster.

As a result, the metal temperature is lowered to extend the creep rupture life of the pipe 11, and the life of the remaining life of the pipe can be extended.

Fig. 6 is a schematic view showing a structure of a life extension of another high temperature pipe of the second embodiment.

As shown in Fig. 6, a plurality of fins 17 are provided in the length joint pipe 11A formed by the welded portion 12 in the longitudinal direction. In this manner, the heat flux is increased by the provision of the plurality of fins 17, and the piping is cooled by the natural convection heat conduction with the outside air, and the compressive stress is applied to the piping 11 by the difference in thermal elongation between the multilayer fins 17 and the piping 11. And seek stress reduction effect.

[Example 3]

Fig. 7 is a schematic view showing a structure of a life extension of the high temperature pipe of the third embodiment. The same components as those of the first embodiment are denoted by the same reference numerals, and their description will be omitted. As shown in Fig. 7, the life-extending structure of the high-temperature pipe of the third embodiment is the surface of the exposed portion 14 after the heat insulating material 13 is removed in the first embodiment, and the surface is cooled by a medium (for example, air) 21 Cool down. Here, as the cooling medium 21, in addition to air In addition, exhaust gas, inert gas, and the like can be used for various purposes.

Fig. 8 is a perspective view showing an example of an air supply means for supplying cooling air.

As shown in Fig. 8, an annular air supply means 22 is provided along the outer circumference of the exposed portion 14 of the pipe 11, and the air 23 is spread over the entire circumference from the air discharge hole (not shown) of the annular air supply means 22. Air is supplied and forced cooling is implemented.

The wind speed of the air forcibly cooled by the cooling medium 21 is preferably, for example, about 10 m/s.

As shown in Figs. 7 and 8, the permanent heat insulating material 13 is removed by the cooling medium (air) 21 as shown in Figs. 7 and 8 in the welded portion of the high temperature pipe which is judged to be a high latent fracture risk by non-destructive inspection. The forced cooling is performed to dissipate heat, and the metal temperature of the pipe 11 is lowered.

In this case, the exposed portion 14 from which the heat insulating material 13 has been removed is forcibly cooled by the cooling medium (air) 21 to cause forced convection heat transfer with the outside air, and the thermal conductivity is about 20 to 100 W/m ² K. .

In the third embodiment, unlike the first and second embodiments, the metal temperature is forcibly lowered by the cooling medium 21, and the creeping fracture life of the pipe 11 is prolonged, so that the life of the remaining life of the pipe can be extended.

[Example 4]

Fig. 9 is a schematic view showing a structure of a life extension of the high temperature pipe of the fourth embodiment. The same components as those of the first embodiment are denoted by the same reference numerals, and their description will be omitted. As shown in FIG. 9, the high temperature piping of Example 4 The life extension structure is a water jacket 31 as a cooling means in the periphery of the exposed portion 14 in which the heat insulating material 13 is removed in the first embodiment. By providing the water jacket 31, the piping is cooled by natural heat conduction with water, and heat exchange with the internal fluid is performed to reduce the metal temperature.

In the welded portion of the pipe which is judged to be a high-latency fracture risk by the non-destructive inspection, as shown in FIG. 9, the permanent heat insulating material 13 is removed, and the heat is forcibly released by the water jacket 31 or the like to make the metal temperature of the pipe reduce.

In this case, the water jacket 31 is disposed in the exposed portion 14 after the heat insulating material 13 is removed, and natural convection heat is generated from the cooling water, and the thermal conductivity is about 500 to 600 W/m ² K. As a result, the metal temperature is lowered, the creeping fracture life of the pipe 11 is prolonged, and the life of the remaining life of the pipe can be extended.

Fig. 10 is a schematic view showing a structure of a life extension of another high temperature pipe of the fourth embodiment.

In FIG. 10, the cooling pipe 32 is placed on the surface of the exposed portion 14 after the heat insulating material 13 is removed, and the cooling water 33 is passed through the portion thereof, and the cooling water 33 is used to dissipate heat, whereby the metal temperature of the pipe 11 is lowered.

The speed of the cooling water 33 for forced cooling is preferably, for example, about 1 m/s. Further, the diameter of the wound cooling pipe 32 is, for example, about 20 mm.

Fig. 11 is a schematic view showing a protective structure of an exposed portion of a high temperature pipe.

Further, as shown in FIG. 11, in order to prevent the heat insulating material of the pipe 11 The exposed portion 14 after the removal 13 is in a rainy state, and it is preferable to provide the protective member 29 such as a flashing plate over a range longer than the range L of the exposed portion 14, thereby avoiding the formation of a thermal barrier to the pipe 11. Further, in addition to the thermal barrier countermeasure, by providing the protective member 29, it is possible to prevent the heat influence by the sun and to perform appropriate cooling.

[Example 5]

Fig. 12 is a view showing the steps of a metal temperature control method for a high temperature pipe.

In the present embodiment, when cooling is performed using a cooling medium such as the cooling medium 21 or cooling water, the temperature of the surface of the pipe after the heat insulating material 13 is removed is measured by the temperature measuring means, and it is judged whether or not the cooling ability is appropriate.

After the permanent heat insulating material 13 is removed by the welded portion of the high-temperature pipe which is determined to be a high-latency fracture risk by non-destructive inspection, a thermocouple serving as a temperature measuring means is attached to a part of the exposed portion 14, and the metal of the pipe 11 is measured. The remaining life was evaluated by temperature. Preferably, the thermocouple is disposed 10 to 20 mm away from the heat-affected portion and disposed at a plurality of locations.

In this case, by measuring the temperature, it can be judged whether or not the required remaining life is reached, and the cooling capacity is controlled to be satisfied by combining with the forced cooling by the air supply of Embodiment 3 or the water jacket of the fourth embodiment. The remaining life required can extend the life of the pipe.

For example, if there is still 10,000 hours from the next periodic inspection, for example, the cooling pipe 32 is wound by the cooling water as shown in FIG. 33. In the case of forced cooling, when it is judged that the temperature must be lowered by about 50 ° C, the cooling by the actual use of the cooling water 33 can only be lowered by 30 ° C via the temperature measurement, for example, by forced cooling by air cooling, or By controlling the cooling capacity of the cooling medium (control that the cooling water is further cooled by the refrigerant, etc.), cooling is performed to further reduce the temperature by 20 ° C, and the life of the piping can be extended to the required remaining life.

Next, the steps of the metal temperature control method of the high temperature piping will be described using FIG.

In the first step, the heat insulating material 13 of the pipe 11 is removed by the welded portion of the pipe which is determined to have a high creeping fracture risk by non-destructive inspection, and the cooling function (S-1) of the third embodiment or the fourth embodiment is given. .

In the second step, the metal temperature (S-2) of the exposed portion 14 of the pipe 11 during operation is measured.

As a result of the temperature measurement result of the second step (S-2), it is determined by temperature measurement whether or not the pipe life satisfies the required remaining life (S-3).

In the third step (S-3), when the remaining life (Yes) is satisfied, the operation is performed without changing the cooling capacity (S-4).

On the other hand, in the third step (S-3), the remaining life (No) is not satisfied, and the operation is performed to lower the cooling capacity and lower the temperature to a metal temperature (S-5) that satisfies the required life.

As a result, normal operation can be performed up to the remaining life.

In addition, by performing temperature measurement, it can be judged whether the current cooling is normal.

11‧‧‧High temperature piping (pipe)

12‧‧‧welding department

13‧‧‧Insulation

14‧‧‧Exposed Department

15‧‧‧Boiler Vapor

Claims (10)

A method for extending the life of a high-temperature pipe, characterized in that, according to the remaining life evaluation of the latent fracture of the welded portion of the high-temperature pipe, when it is judged that the normal use cannot be continued, the heat-insulating material of the high-latency fracture risk portion of the high-temperature pipe is covered. Partially removing, the outer surface temperature of the high-temperature pipe is locally lowered, and the life of the high-latency fracture risk portion is prolonged, and the width of the exposed portion where a part of the heat insulating material is removed is twice or more of the following distance. When the stress of the tensile stress and the compressive stress generated in the high-temperature pipe is changed from the tensile stress to the compressive stress by the removal of the heat insulating material from the peeling end portion of the exposed portion, the compressive stress gradually approaches zero. The distance from the aforementioned tensile stress to the compressive stress and the compressive stress gradually approaches 0 satisfies the following formula (1), β x=5. . . (1) β is expressed by the following formula (2), Here, v is a Poisson ratio, a is the average radius of the pipe, and h is the plate thickness of the pipe. The method for extending the life of a high-temperature pipe according to the first aspect of the invention, wherein the surface of the member from which the heat insulating material is removed is cooled. For example, the longevity side of the high temperature piping mentioned in the second paragraph of the patent application scope The method wherein the cooling is performed by using air for cooling or cooling with cooling water. The method for extending the life of a high-temperature pipe according to the first aspect of the invention, wherein the heat-dissipating member is provided on a surface of the member from which the heat insulating material is removed. The method for extending the life of a high-temperature pipe according to the first aspect of the invention, wherein the temperature of the surface of the member from which the heat insulating material is removed is measured, and whether the cooling ability is appropriate is determined. The method for extending the life of a high-temperature pipe according to the fifth aspect of the invention, wherein the cooling capacity is appropriately changed when the cooling capacity is not appropriate. A structure for extending the life of a high-temperature pipe, which is characterized in that, according to the remaining life evaluation of the creeping fracture of the welded portion of the high-temperature pipe, when it is judged that the normal use cannot be continued, the heat-insulating material of the high-latency fracture risk portion of the high-temperature pipe is covered. Part of the removal causes the outer surface temperature of the high temperature pipe to be locally lowered, and the width of the exposed portion from which a part of the heat insulating material is removed is twice or more the distance from the peeling end of the exposed portion. After the heat insulating material is removed, the tensile stress and compressive stress generated by the high temperature pipe change from a tensile stress to a compressive stress, and the compressive stress gradually approaches a distance of 0, and the tensile stress is changed to a compressive stress. The distance at which the post-compression stress gradually approaches 0 satisfies the following formula (1), β x=5. . . (1) β is expressed by the following formula (2), Here, v is a Poisson ratio, a is the average radius of the pipe, and h is the plate thickness of the pipe. The structure for extending the life of the high-temperature pipe according to the seventh aspect of the invention is the cooling means for cooling the surface of the member from which the heat insulating material is removed. The structure for extending the life of the high-temperature pipe according to the eighth aspect of the invention, wherein the cooling means is an air cooling means using air or a water cooling means using cooling water. The life-extending structure of the high-temperature pipe according to the seventh aspect of the invention, wherein the heat-dissipating member is provided on a surface of the member from which the heat insulating material is removed.