JP5701349B2 - Life extension method for high temperature piping, life extension structure for high temperature piping, and metal temperature control method for high temperature piping - Google Patents

Description

The present invention is, life-prolonging method and survival structures of high-temperature pipe of the hot pipes such as high-temperature piping and pressure vessels for use in for example thermal and nuclear power plants and chemical plants, etc., a method for controlling the metal temperature of the high-temperature pipe.

  Since, for example, a boiler or the like constituting a thermal power plant is operated in a high temperature and high pressure environment, damage due to creep or the like may be accumulated in the heat-resistant steel that is a material constituting the thermal plant due to long-term operation. Therefore, in the operation of this type of plant, it is important to ensure the stable operation over a long period of time by performing the life evaluation of the heat-resistant steel with high accuracy and maintaining the reliability of the pressure-resistant portion.

High-temperature piping used in thermal power plants and the like has a function of carrying the above heated by a boiler to a steam turbine, but creep damage occurs due to progress of creep damage due to high temperature and long-time use, When these voids are connected, a crack is generated, and eventually the fracture occurs.
In order to prevent final fracture, the degree of creep void growth is analyzed by periodic nondestructive inspection to derive the degree of creep damage for each member, and the remaining life of the member is evaluated (Patent Document 1, 2). Generally, since the risk of creep rupture of the pipe welded portion is higher than that of the base material portion, the inspection location is mainly a welded portion.

JP 2004-85347 A JP 2008-122345 A

As a result of this nondestructive inspection, there is a member with a high degree of creep damage, and if the risk of creep rupture is high until the next periodic inspection, replace the member or lower the operating temperature of the entire plant, Measures are taken to lower the metal temperature of the entire pipe and reduce the risk of creep rupture.
However, there is a problem that lowering the operating temperature of the entire plant results in a decrease in operating efficiency of the plant.

  Therefore, the advent of a technique capable of extending the remaining life of the high temperature member without lowering the overall operation temperature of the plant and without reducing the plant operation efficiency is desired.

In view of the above problems, the present invention provides a method for extending the life of a high-temperature pipe and a high-temperature pipe capable of extending the remaining life of a high-temperature member without lowering the overall operation temperature of the plant and without reducing the plant operation efficiency. It is an object of the present invention to provide a life extension structure and a method for controlling the metal temperature of high-temperature piping.

ここで、νはポアソン比であり、ａは配管の平均半径、ｈは配管の板厚である。 The first aspect of the present invention to solve the above problems, the remaining life evaluation of creep rupture of the welded portion of the high-temperature pipe, when it is determined that can not continue to use the steady creep rupture of the high-temperature pipe removing a portion of the heat insulator covering the high-risk points, the high-temperature pipe locally reduce the outer surface temperature of FIG Rutotomoni the extension of life of the high creep rupture risk locations, the thermal insulation material The width of the exposed portion that removes a part is changed from the tensile stress to the compressive stress by changing the stress between the tensile stress and the compressive stress generated in the high-temperature pipe by removing the heat insulating material from the peeled end portion of the exposed portion. The distance at which the compressive stress asymptotically approaches 0 after being changed to 0 is greater than or equal to twice, and the distance at which the compressive stress asymptotically approaches 0 after changing from the tensile stress to the compressive stress is according to the following (1): in the life-prolonging method of piping
βx = 5 (1)
β is represented by the following formula (2).

Here, ν is the Poisson's ratio, a is the average radius of the pipe, and h is the thickness of the pipe.

According to a second aspect of the present invention, in the first aspect of the invention, there is provided a method for extending the life of the high-temperature pipe , wherein the surface of the member from which the heat insulating material has been removed is cooled.

According to a third aspect of the present invention, in the second aspect of the invention, there is provided a method for extending the life of the high-temperature pipe , wherein the cooling is cooling with air or cooling with cooling water.

According to a fourth aspect of the present invention, in the first aspect of the invention, there is provided a method for extending the life of the high-temperature pipe , characterized in that a heat dissipation member is installed on the surface of the member from which the heat insulating material has been removed.

A fifth invention is the high-temperature pipe according to any one of the first to fourth inventions, wherein the temperature of the surface of the member from which the heat insulating material has been removed is measured to determine that the cooling capacity is appropriate. There is in life extension method.

Sixth invention, in the fifth aspect, the case cooling capacity is not proper, in prolonging method of high temperature piping and changes so that proper cooling capacity.

ここで、νはポアソン比であり、ａは配管の平均半径、ｈは配管の板厚である。 A seventh aspect of the invention, the residual life evaluation of creep rupture of high-temperature pipe, when it is determined that can not continue to use the constant, part of the heat insulator covering the high point of the creep rupture risk of the high-temperature pipe The external surface temperature of the high-temperature pipe is locally reduced , and the width of the exposed portion for removing a part of the heat insulating material is removed from the peeling end portion of the exposed portion 14. Thus, the stress change between the tensile stress and the compressive stress generated in the high-temperature pipe is at least twice the distance at which the compressive stress gradually approaches 0 after the change from the tensile stress to the compressive stress. The distance at which the compressive stress asymptotically approaches 0 after changing to is in the structure for extending the life of the high-temperature pipe characterized by the following (1) .
βx = 5 (1)
β is represented by the following formula (2).

Here, ν is the Poisson's ratio, a is the average radius of the pipe, and h is the thickness of the pipe.

According to an eighth aspect of the present invention, in the seventh aspect of the invention, there is provided a life extension structure of the high-temperature pipe , characterized by comprising a cooling means for cooling the surface of the member from which the heat insulating material has been removed.

A ninth aspect of the eighth invention, the cooling means is in the extended life structure of the hot pipe, which is a water-cooled by air cooling means or cooling water with air.

According to a tenth aspect of the invention, in the seventh aspect of the invention, there is provided a structure for extending the life of the high-temperature pipe , characterized in that a heat dissipation member is installed on the surface of the member from which the heat insulating material has been removed.

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

FIG. 1 is a schematic diagram of a structure for extending the life of a high-temperature pipe according to the first embodiment. FIG. 2 is a diagram illustrating a portion where the heat insulating material of the piping is peeled off. FIG. 3 is a diagram showing 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 diagram of a structure for extending the life of high-temperature piping according to the second embodiment. FIG. 5 is a perspective view of FIG. FIG. 6 is a schematic diagram of a structure for extending the life of another high-temperature pipe according to the second embodiment. FIG. 7 is a schematic diagram of a structure for extending the life of high-temperature piping according to the third embodiment. FIG. 8 is a perspective view showing an example of air supply means for supplying cooling air. FIG. 9 is a schematic diagram of the structure for extending the life of high-temperature piping according to the fourth embodiment. FIG. 10 is a schematic diagram of another high temperature piping life extension structure according to the fourth embodiment. FIG. 11 is a schematic diagram of the protective structure of the exposed portion of the high-temperature pipe . FIG. 12 is a process diagram of a metal temperature control method for high-temperature piping.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by this Example, Moreover, when there exists multiple Example, what comprises combining each Example is also included.

FIG. 1 is a schematic diagram of a structure for extending the life of a high-temperature pipe according to 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 evaluation of the remaining life of the creep rupture of the welded portion 12 of the high temperature pipe (hereinafter referred to as “pipe”) 11 which is a high temperature member. When it is determined that a high part (welded part with a high creep damage degree) is confirmed and cannot be used continuously, a part of the heat insulating material 13 covering the part of the pipe 11 where the risk of creep rupture is high is rotated. It removes in the direction, and it is set as the exposed part 14, and the external surface temperature of the piping 11 is reduced locally, and the lifetime of a creep rupture location is extended.
In FIG. 1, reference numeral 15 indicates boiler steam. For example, high-temperature steam at 600 ° C. flows in the pipe 11.

  In the welded portion 12 of the pipe 11 determined to have a high creep rupture risk by nondestructive inspection, the heat insulating material 13 that is permanently installed is removed as shown in FIG. By releasing heat, the metal temperature of the pipe 11 is lowered.

In this case, by removing the heat insulating material 13 to form the exposed portion 14, natural convection heat transfer with the outside air (for example, 100 ° C.) is performed, and the heat transfer coefficient is about ^{2 to} 12 W / m ² K.

  Thus, by lowering the metal temperature of the pipe 11, the creep rupture life of the pipe is extended, and it is possible to extend the life of the pipe.

  As a result, it is possible to extend the life by only lowering the local temperature of the piping. Therefore, reducing the operating temperature of the entire plant as before, lowering the metal temperature of the entire piping and reducing the risk of creep rupture. This eliminates the adverse effect of lowering the operation efficiency of the plant.

  As described above, according to the present embodiment, when a portion having a high risk of creep damage in a high-temperature pipe is confirmed, the heat insulating material 13 covering the pipe 11 is removed by a predetermined distance (L), and the exposed portion 14 is removed. By reducing the metal temperature and reducing the risk of creep damage, it is possible to extend the life without lowering the operation efficiency of the entire plant. Here, the reduction in the metal temperature is effective not only in the creep rupture life but also in the extension of the crack propagation life.

  Here, when the outer diameter of the piping 11 is 460 mm, for example, the width L for removing the heat insulating material 13 is preferably about 900 mm or more as will be described later, but depending on the width for removing the heat insulating material 13 Compressive stress is generated by local deformation in the out-of-plane direction, and life extension can be expected by reducing stress.

Next, the width L for removing a part of the heat insulating material 13 will be described.
In Figure 2, which from the pipe 11 to remove the heat insulator 13 on the left side will be described distance for removing heat insulating material from the end x ₀ removal of heat insulating material 13 (L / 2).
Since the tensile stress and the compressive stress are applied to the pipe 11 by removing the heat insulating material 13, if the distance from the place x ₀ where the heat insulating material 13 is peeled off is x (x ₁ , x ₂ , x ₃ ), the stress The distance at which the change of asymptotically approaches 0 is expressed by the following equation.
βx = 5 (1)
Here, since β is expressed by the following equation (2), the value of x may be obtained.

  For example, when the outer diameter of the pipe 11 is 460 mm and the plate thickness is 70 mm, a = 195 mm, h = 70 mm, the value of x when βx = 2.4 is 218 mm, and the value of x when βx = 5 Is 454 mm. Further, since β∝1 / √ (ah), the value of x and √ (ah) are related values, and when a and h are changed, the value of x is changed.

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

The distance (L) which peels the heat insulating material 13 of the piping 11 and makes it the exposed part 14 is demonstrated using FIG.2 and FIG.3.
FIG. 2 is a diagram illustrating a portion where the heat insulating material of the piping is peeled off. Note that the heat insulating material is peeled off with the welded portion at the center, but FIG. 2 illustrates the left peeled portion.

3, the distance from the release point x ₀ of insulation material and (mm), a diagram showing the relationship between such tensile and compressive stresses in the piping.
In the piping of FIG. 2, a case where the outer diameter of the piping is 460 mm and the thickness of the piping is 70 mm will be described.

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

If this is combined with the peeled portion on the left side of the pipe 11 and the peeled portion on the right side, the separation distance L is 45 4 mm × 2 = 908 mm.
Therefore, the separation distance L is preferably about 900 mm or more.

Moreover, what is necessary is just to determine the range which removes the heat insulating material 13 based on the following numerical formula, when extending lifetime further by compressive stress.
2.4 ≦ βx <5 (3)
For example, in the case of an outer diameter of 460 mm and a plate thickness of 70 mm, it is necessary to peel at least a distance X ₁ (= 218 mm) at which no tensile stress is applied, and for a convergent X ₃ (45 4 mm) or more, the heat insulating material needs to be peeled off Disappears.

FIG. 4 is a schematic diagram of a structure for extending the life of high-temperature piping according to the second embodiment. FIG. 5 is a perspective view of FIG. In addition, the same code | symbol is attached | subjected to the member which overlaps with the structure which concerns on Example 1, and the description is abbreviate | omitted. As shown in FIGS. 4 and 5, the structure for extending the life of the high-temperature pipe according to the second embodiment has a multilayer fin 17 as a heat dissipation member around the exposed portion 14 from which the heat insulating material 13 is removed in the first embodiment. It is provided in close contact.

As shown in FIG. 5, an upper fin 17 </ b> A having a plurality of fins 18 and a lower fin 17 </ b> B having a plurality of fins 18 are fastened by a fastening member 20 together with the flanges 19.
The fin 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 this embodiment, in the welded portion of the high-temperature pipe determined to have a high creep rupture risk by nondestructive inspection, the heat insulating material 13 that is permanently installed is removed as shown in FIGS. 4 and 5 to form the exposed portion 14. The upper fin 17A and the lower fin 17B are provided so as to be in close contact with the exposed portion 14. Thus, the metal temperature of piping can be lowered | hung rather than Example 1 by increasing the area which releases heat using a multilayer fin structure.

  According to the present embodiment, the heat insulating material 13 is removed, and the area where heat is released by the multilayer fins 17 installed on the exposed portion 14 is increased, and the heat flux is increased in proportion to the area increase rate. This makes it possible to cool the metal temperature quickly.

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

FIG. 6 is a schematic diagram of a structure for extending the life of another high-temperature pipe according to the second embodiment.
As shown in FIG. 6, multi-layer fins 17 are installed in the longitudinal joint pipe 11 </ b> A formed by the weld portion 12 in the longitudinal direction. In this way, by installing the multi-layer fins 17 and increasing the heat flux and cooling the pipes by natural convection heat transfer with the outside air, compressive stress is applied to the pipes 11 due to the difference in thermal expansion between the multi-layer fins 17 and the pipes 11. The stress reduction effect can be achieved.

FIG. 7 is a schematic diagram of a structure for extending the life of high-temperature piping according to the third embodiment. In addition, the same code | symbol is attached | subjected to the member which overlaps with the structure which concerns on Example 1, and the description is abbreviate | omitted. As shown in FIG. 7, the structure for extending the life of the high-temperature pipe according to the third embodiment is a surface of the exposed portion 14 from which the heat insulating material 13 is removed in the first embodiment. It is cooled by. Here, as the cooling medium 21, miscellaneous exhaust gas, inert gas, or the like may be used in addition to air.

FIG. 8 is a perspective view showing an example of air supply means for supplying cooling air.
As shown in FIG. 8, an annular air supply means 22 is provided along the outer periphery of the exposed portion 14 of the pipe 11, and air 23 is blown from the air ejection holes (not shown) of the annular air supply means 22 over the entire circumference. And forced cooling.

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

As shown in FIG. 7 and FIG. 8, the permanent heat insulating material 13 is removed and forced by the cooling medium (air) 21 in the welded portion of the high-temperature pipe determined to have a high creep rupture risk by nondestructive inspection. Heat is dissipated by cooling to lower the metal temperature of the pipe 11.
In this case, by removing the heat insulating material 13 and forcibly cooling the exposed portion 14 with the cooling medium (air) 21, forced convection heat transfer with the outside air is performed, and the heat transfer rate is 20 to 100 W / m. It is about ² K.

  In the third embodiment, unlike the first and second embodiments, the creep rupture life of the pipe 11 is extended by forcibly lowering the metal temperature by the cooling medium 21, and the remaining life of the pipe can be extended. .

FIG. 9 is a schematic diagram of the structure for extending the life of high-temperature piping according to the fourth embodiment. In addition, the same code | symbol is attached | subjected to the piping which overlaps with the structure which concerns on Example 1, and the description is abbreviate | omitted. As shown in FIG. 9, in the structure for extending the life of the high-temperature pipe according to the fourth embodiment, a water jacket 31 as a cooling unit is installed around the exposed portion 14 from which the heat insulating material 13 is removed in the first embodiment. By installing this water jacket 31, the pipe is cooled by natural heat transfer with water, thereby exchanging heat with the internal fluid and reducing the metal temperature.

  In a welded part of a pipe that has been determined to have a high risk of creep rupture by nondestructive inspection, the pipe is formed by removing the heat insulation that is permanently installed as shown in FIG. 9 and forcibly releasing heat using a water jacket 31 or the like. Reduce the metal temperature.

In this case, the heat insulating material 13 is removed, and the water jacket 31 is disposed on the exposed portion 14, whereby natural convection heat transfer with the cooling water is performed, and the heat transfer coefficient is about 500 to 600 W / m ² K. As a result, the metal temperature is lowered, the creep rupture life of the pipe 11 is extended, and the remaining life of the pipe can be extended.

FIG. 10 is a schematic diagram of another high temperature piping life extension structure according to the fourth embodiment.
In FIG. 10, the cooling pipe 32 is disposed on the surface of the exposed portion 14 from which the heat insulating material 13 has been removed, and the cooling water 33 is caused to dissipate heat by passing through the cooling water 33, thereby reducing the metal temperature of the pipe 11. I have to.

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

FIG. 11 is a schematic diagram of the protective structure of the exposed portion of the high-temperature pipe .
Further, as shown in FIG. 11, in order to prevent the exposed portion 14 from being exposed to rain by removing the heat insulating material 13 of the pipe 11, the protective member 29 such as a rain finish is removed from the range L of the exposed portion 14. However, it is preferable to install it over a long range so that it does not become a thermal barrier against the pipe 11. In addition to measures against thermal barriers, a protective member 29 is provided so that the sun is not affected by heat and proper cooling is achieved.

FIG. 12 is a process diagram of a metal temperature control method for high-temperature piping.
In this embodiment, when the cooling medium 21 or cooling means such as cooling water is used for cooling, the temperature of the surface of the pipe from which the heat insulating material 13 has been removed is measured by the temperature measuring means to determine that the cooling capacity is appropriate. ing.

  In the welded portion of the high-temperature pipe that has been determined to have a high risk of creep rupture by nondestructive inspection, after removing the heat insulating material 13 that is permanently installed, a thermocouple of the temperature measuring means is attached to a part of the exposed portion 14, The metal temperature is measured and the remaining life is evaluated. The thermocouples are preferably installed at a plurality of locations separated from the heat affected zone by 10 to 20 mm.

  In this case, it is required by measuring whether it is possible to determine whether the required remaining life can be achieved by measuring the temperature, and by combining with the forced cooling by the air blowing of the third embodiment and the water jacket of the fourth embodiment. By controlling the cooling capacity so as to satisfy the remaining life, it is possible to extend the piping life.

  For example, when the remaining time until the next periodic inspection is 10,000 hours, for example, when the cooling pipe 32 as shown in FIG. When it is determined that the actual cooling water 33 is cooled by only 30 ° C. due to temperature measurement, cooling that further lowers the shortage of 20 ° C. can be performed, for example, forced cooling by air cooling or cooling By controlling the cooling capacity of the medium (control such as further reducing the cooling water with a refrigerant, etc.), it is possible to extend the pipe life so as to achieve the required remaining life.

FIG. 12 is a process diagram of such a metal temperature control method for high-temperature piping.
In the first step, the heat insulating material 13 of the pipe 11 is removed at the welded part of the pipe determined to have a high creep rupture risk by nondestructive inspection, and the cooling function of the third or fourth embodiment is imparted (S -1).
In the second step, the metal temperature of the exposed portion 14 of the pipe 11 during operation is measured (S-2).
As a determination of the result of temperature measurement in the second step (S-2), it is determined whether or not the pipe life satisfies the required remaining life by temperature measurement (S-3).
In the third step (S-3), if the remaining life is satisfied (Yes), the operation is continued without changing the cooling capacity (S-4).
On the other hand, in the third step (S-3), when the remaining life is not satisfied (No), an operation of increasing the cooling capacity to the metal temperature for satisfying the required life is performed (S-5). ).
As a result, it is possible to carry out a sound operation until the remaining life.

  Further, by performing temperature measurement, it can be determined whether or not the current cooling is sound.

11 High temperature piping (piping)
12 Welding part 13 Thermal insulation material 14 Exposed part 15 Boiler steam

Claims (10)

When it is judged that continuous continuous use is not possible based on the evaluation of the remaining life of creep rupture of the welded part of high-temperature piping ,
Removing a portion of the heat insulator covering the high point of the creep rupture risk of the high-temperature pipe, locally reduce the outer surface temperature of the hot pipe, Ru FIG prolonged life of high creep rupture risk locations With
The width of the exposed portion for removing a part of the heat insulating material is such that the change in the stress between the tensile stress and the compressive stress generated in the high-temperature pipe by removing the heat insulating material from the peeling end portion of the exposed portion is tensile. More than twice the distance where the compressive stress asymptotically approaches zero after changing from stress to compressive stress,
The distance at which the compressive stress gradually approaches 0 after changing from the tensile stress to the compressive stress is according to the following (1):
βx = 5 (1)
β is represented by the following formula (2).

Here, ν is the Poisson's ratio, a is the average radius of the pipe, and h is the thickness of the pipe. In claim 1,
A method for extending the life of a high-temperature pipe , wherein the surface of the member from which the heat insulating material has been removed is cooled. In claim 2,
A method for extending the life of high-temperature piping , wherein the cooling is cooling with air or cooling with cooling water. In claim 1,
A method for extending the life of a high-temperature pipe , wherein a heat radiating member is installed on the surface of the member from which the heat insulating material has been removed. In any one of Claims 1 thru | or 4,
A method for extending the life of a high-temperature pipe , wherein the temperature of the surface of the member from which the heat insulating material has been removed is measured to determine that the cooling capacity is appropriate. In claim 5,
A method for extending the life of a high-temperature pipe , wherein the cooling capacity is changed to be appropriate when the cooling capacity is not appropriate. When it is determined that the continuous life of the high temperature piping creep rupture remaining life cannot be used,
Together with the portion of the insulation material covering the high point of the creep rupture risk high-temperature pipe was removed and formed by locally lowering the external surface temperature of the high-temperature pipe,
The width of the exposed portion for removing a part of the heat insulating material is a change in stress between the tensile stress and the compressive stress generated in the high-temperature pipe by removing the heat insulating material from the peeling end portion of the exposed portion 14. After changing from tensile stress to compressive stress, the compressive stress is more than twice the distance asymptotic to 0,
The distance extension at which the compressive stress gradually approaches 0 after the change from the tensile stress to the compressive stress is according to the following (1):
βx = 5 (1)
β is represented by the following formula (2).

Here, ν is the Poisson's ratio, a is the average radius of the pipe, and h is the thickness of the pipe. In claim 7 ,
A structure for extending the life of a high-temperature pipe , comprising cooling means for cooling the surface of the member from which the heat insulating material has been removed. In claim 8 ,
The structure for extending the life of high-temperature piping , wherein the cooling means is air-cooling means using air or water-cooling cooling using cooling water. In claim 7 ,
A structure for extending the life of a high-temperature pipe , wherein a heat radiating member is installed on the surface of the member from which the heat insulating material has been removed.

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