A method for evaluating the residual life of a boiler heating surface tube

Abstract

The application discloses a kind of boiler heating surface tube residual life evaluation methods, comprising the following steps:1) determine the information of the evaluated tube section, at least including the cumulative service time t op Of the evaluated tube section;2) determine the equivalent calculation temperature of the tube wall of the evaluated tube section;3) determine the tube wall calculation pressure of the evaluated tube section;4) determine the Larson-Miller parameter equation reflecting the material endurance strength performance of the evaluated tube section;5) calculate the corrosion thinning rate of the wall thickness of the evaluated tube section;6) calculate the service life t n Of the new tube of the evaluated tube section under the wall thickness thinning rate when corrosion thinning and long-time creep are main failure modes;7) the residual life of the evaluated tube section is the service life t n Of the new tube obtained in step 6) minus the cumulative service time t op Of the evaluated tube section in step 1).The boiler high-temperature heating surface tube service life evaluation method of the application has important significance for precise evaluation of the service life of the boiler high-temperature pressure-bearing component life evaluation.

Description

Technical Field

[0001] This invention relates to the field of nuclear power component remaining service life assessment technology, and in particular to a method for assessing the service life of boiler high-temperature heated surface tubes based on the interaction of corrosion thinning and creep damage. Background Technology

[0002] The life assessment of boiler heating surfaces should be based on their failure modes. The main causes of damage to superheater and reheater tubes include short-term superheating, long-term creep, corrosion on the fire-facing side, erosion, and welding failure of dissimilar steels. Damage to water-cooled walls is mainly caused by working fluid-side corrosion and high-temperature corrosion on the fire-facing side. If the tube wall temperature does not exceed the metal creep temperature, the remaining life is calculated based on the tube wall thinning rate. If it is high-temperature corrosion, the same analysis method as for superheater and reheater tubes is used. The main causes of economizer damage are pitting corrosion, wear, and low-temperature corrosion. Corrosion-related life calculations are based on strength verification theory, using the tube wall thinning rate to calculate the life. The remaining life assessment of boiler heating surfaces mainly targets failure modes such as corrosion thinning, long-term creep, high-temperature corrosion thinning, and welding failure of dissimilar steels. Currently, there is no method to accurately assess the corrosion thinning life of high-temperature heating surfaces. Summary of the Invention

[0003] In view of this, in order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a method for evaluating the service life of boiler high-temperature heating surface tubes based on the interaction of corrosion thinning and creep damage.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A method for assessing the remaining life of boiler heating surface tubes includes the following steps:

[0006] 1) Determine the background information of the pipe section being evaluated, including at least the cumulative service time t of the pipe section being evaluated. op information;

[0007] 2) Determine the equivalent calculated temperature of the pipe wall of the pipe segment being evaluated;

[0008] 3) Determine the calculated pressure of the pipe wall of the pipe segment being evaluated;

[0009] 4) Determine the Larson-Miller parametric equations that reflect the creep strength properties of the pipe section material being evaluated;

[0010] 5) Calculate the corrosion thinning rate of the pipe section being evaluated;

[0011] 6) Calculate the service life t of the new pipe section under the evaluated wall thickness reduction rate when corrosion thinning and long-term creep are the main failure modes. n ;

[0012] 7) The remaining life of the evaluated pipe section is the lifespan t of the new pipe obtained in step 6). n Subtract the cumulative service time t of the evaluated pipe section in step 1). op .

[0013] According to some preferred embodiments of the invention, the information of the pipe segment being evaluated includes the material of the pipe segment being evaluated, its outer diameter D, etc. o Initial wall thickness δ0, current wall thickness δ1.

[0014] According to some preferred embodiments of the invention, the initial wall thickness δ0 and the current wall thickness δ1 are only the thicknesses of the metal substrate layer on the pipe wall.

[0015] According to some preferred embodiments of the invention, the equivalent service temperature T c Design temperature T of the pipe wall d Pipe wall thickness design calculation temperature T s and equivalent temperature of the pipe wall T d The aging status of the pipe wall material is determined together.

[0016] According to some preferred embodiments of the present invention, the calculated pressure P of the pipe wall is the normal operating pressure P of the pipe wall. op .

[0017] According to some preferred embodiments of the present invention, the Larson-Miller parametric equations are as shown in equations (1) and (2):

[0018] P(σ)=(T+273.15)(C+lg t r (1)

[0019] P(σ)=C0+C1 lgσ+C2 lg 2 σ+C3 lg 3 σ+C4 lg 4 σ (2)

[0020] In the formula: T is the temperature in Celsius, °C; t r σ is the creep failure time, h; σ is the initial creep loading stress, MPa; C is the Larson-Miller constant, and C0, C1, C2, C3, and C4 are material constants.

[0021] According to some preferred embodiments of the present invention, the parameters of the material LM can be determined by solving the corresponding material constant values ​​using formula (3) through multiple linear regression:

[0022] lgt r =(C1 lgσ+C2 lg 2 σ+C3 lg 3 σ+C4 lg4 σ+C0) / (T+273.15)-C (3).

[0023] According to some preferred embodiments of the invention, the corrosion thinning rate v of the evaluated pipe section wall thickness is expressed by the formula Calculated.

[0024] According to some preferred embodiments of the invention, when the heat-receiving surface tube fails primarily through corrosion thinning and long-term creep, its cumulative life loss D tc The result is obtained by formula (4):

[0025]

[0026] In the formula: C is the Larson-Miller constant, C0, C1, C2, C3, and C4 are material constants; k1 is the stress coefficient, which is taken as 1.5 for heated surface components; k2 is the dimensional safety factor for wall thickness corrosion thinning, which is taken as 1.1 for heated surface components; m is the material service environment parameter, n is the material service environment parameter, P is the calculated pressure of the pipe wall, and x is the integral independent variable.

[0027] According to some preferred embodiments of the invention, the dimensional safety factor for the wall thickness corrosion reduction is 1.0 for components that result in general failure and 1.1 for components that result in severe failure.

[0028] According to some preferred embodiments of the present invention, m is calculated by formula (5):

[0029]

[0030] In the formula: A represents the material service environment parameter, and B represents the material service environment parameter.

[0031] According to some preferred embodiments of the present invention, n is calculated by formula (6):

[0032]

[0033] In the formula: A represents the material service environment parameter, B represents the material service environment parameter, and C represents the material service environment parameter. i LMP(σ) is the material constant in the Larson-Miller fitted curve.

[0034] According to some preferred embodiments of the present invention, A is calculated by formula (7):

[0035] A = T c +273.15 (7)

[0036] In the formula: T c This is the equivalent service temperature.

[0037] According to some preferred embodiments of the present invention, B is calculated by formula (8):

[0038] B = (T) c +273.15)·C (8)

[0039] In the formula: T c The equivalent service temperature is given by C, which is the Larson-Miller constant.

[0040] Due to the adoption of the above technical solutions, the advantages of the present invention compared with the prior art are as follows: The boiler high-temperature heating surface tube service life assessment method of the present invention is applicable to the remaining service life assessment of boiler heating surfaces with corrosion thinning and high-temperature creep as the main failure modes. It can also be used for the service life assessment of other high-temperature pressure-bearing pipelines in the fields of thermal power, petroleum and petrochemicals with long-term creep and corrosion thinning as the main failure modes. It is of great significance for the accurate assessment of the service life of boiler high-temperature pressure-bearing components. Detailed Implementation

[0041] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0042] The boiler high-temperature heating surface tube service life assessment method based on the interaction of corrosion thinning and creep damage in this embodiment specifically includes the following steps:

[0043] Step 1) Determine the information of the pipe segment being evaluated.

[0044] Information about the evaluated pipe section includes the material of the evaluated pipe section (determined based on the LMP function determined by the material) and the cumulative service time t. op Outer diameter D o Initial wall thickness δ0, current wall thickness δ1. Wherein, initial wall thickness δ0 and current wall thickness δ1 should only refer to the thickness of the metal substrate layer of the pipe wall.

[0045] Step 2) Determine the equivalent calculated temperature T of the pipe wall of the pipe segment being evaluated. c .

[0046] Equivalent service temperature T c Take the pipe wall design temperature T d Pipe wall thickness design calculation temperature T s and equivalent temperature of the pipe wall T d The maximum value.

[0047] Step 3) Determine the calculated wall pressure P of the pipe segment being evaluated.

[0048] The calculated pressure P of the pipe wall is taken as the normal operating pressure of the pipe wall. op .

[0049] Step 4) Determine the Larson-Miller parametric equations that reflect the creep strength properties of the pipe section material being evaluated.

[0050] The Larson-Miller parametric equations are shown in Equations (1) and (2). The parameters of the material LM can be determined by solving Equation (3) using multiple linear regression to obtain the corresponding material constant values.

[0051] P(σ)=(T+273.15)(C+lg t r (1)

[0052] P(σ)=C0+C1 lgσ+C2 lg 2 σ+C3 lg 3 σ+C4 lg 4 σ (2)

[0053] lgt r =(C1 lgσ+C2 lg 2 σ+C3 lg 3 σ+C4 lg 4 σ+C0) / (T+273.15)-C (3)

[0054] In the formula: T is the temperature in Celsius, °C; t r σ is the creep failure time, h; σ is the initial creep loading stress, MPa; C is the Larson-Miller constant, and C0, C1, C2, C3, and C4 are material constants.

[0055] Step 5) Calculate the corrosion thinning rate v of the pipe section being evaluated.

[0056] Step 6) Calculate the service life t of the new pipe section under the evaluated pipe segment at this wall thickness reduction rate, with corrosion thinning and long-term creep (high-temperature creep) as the main failure modes. n .

[0057] Specifically, when corrosion thinning and long-term creep are the main failure modes of the heated surface tube, its cumulative life loss D increases with the length of service life. tc It can be calculated using formula (4).

[0058]

[0059] In the formula: C is the Larson-Miller constant, C0, C1, C2, C3, and C4 are material constants; k1 is the stress coefficient, which is 1.5 for the heated surface tube; k2 is the dimensional safety factor for wall thickness corrosion thinning, which is 1.0 for components that cause general failure and 1.1 for components that cause serious failure; m is the material service environment parameter, which is calculated by formula (5); n is the material service environment parameter, which is calculated by formula (6); P is the calculated pressure of the tube wall, and x is the integral independent variable.

[0060]

[0061]

[0062] In the formula: A is the material service environment parameter, calculated using formula (7); B is the material service environment parameter, calculated using formula (8); C i These are the material parameters in the LM function.

[0063] A = T c +273.15 (7)

[0064] B = (T) c +273.15)·C (8)

[0065] When the cumulative lifespan loss D tc When = 1, the corresponding time t is the service life t of the new pipe in the evaluated pipe section. n Equation (4) can be solved numerically by iteratively incrementing time x by dx and calculating the corresponding D in each iteration. tc When D tc When the value is ≥1, the loop exits and the corresponding previous time t is output. This time t is the service life t of the new pipe in the evaluated pipe segment. n .

[0066] Step 7) Calculate the remaining life t of the pipe segment being evaluated. left =t n -t op .

[0067] The remaining service life assessment of heated surfaces mainly targets failure modes such as corrosion thinning, long-term creep, high-temperature corrosion thinning, and welding failure of dissimilar steels. Addressing the current lack of an accurate method for assessing the service life of high-temperature heated surfaces due to corrosion thinning, this invention presents a method for assessing the service life of boiler high-temperature heated surface tubes based on the interaction of corrosion thinning and creep damage. This method is applicable to the remaining service life assessment of boiler heated surfaces where corrosion thinning and high-temperature creep are the main failure modes. It can also be used for the service life assessment of other high-temperature pressure-bearing pipelines in thermal power, petroleum and petrochemical fields where long-term creep and corrosion thinning are the main failure modes. This method is of great significance for the accurate assessment of the service life of high-temperature pressure-bearing components in boilers.

[0068] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for assessing the remaining life of boiler heating surface tubes, characterized in that, Includes the following steps: 1) Determine the information of the pipe section being evaluated, including at least the cumulative service time t of the pipe section being evaluated. op information; 2) Determine the equivalent service temperature of the pipe wall of the pipe section being evaluated; 3) Determine the calculated pressure of the pipe wall of the pipe segment being evaluated; 4) Determine the Larson-Miller parametric equations that reflect the creep strength properties of the pipe section material being evaluated; 5) Calculate the corrosion thinning rate of the pipe section being evaluated; 6) Calculate the service life t of the new pipe section under the evaluated wall thickness reduction rate when corrosion thinning and long-term creep are the main failure modes. n ; 7) The remaining life of the evaluated pipe section is the lifespan t of the new pipe obtained in step 6). n Subtract the cumulative service time t of the evaluated pipe section in step 1). op ; When the main failure modes of the heated surface tube are corrosion thinning and long-term creep, its cumulative life loss D tc The cumulative lifetime loss D is calculated using the following formula. tc When = 1, the corresponding time t is the service life t of the new pipe in the evaluated pipe section. n : ； In the formula: C is the Larson-Miller constant; C0, C1, C2, C3, and C4 are material constants; k1 is the stress coefficient, which is taken as 1.5 for heated surface components; k2 is the dimensional safety factor for wall thickness reduction due to corrosion, which is taken as 1.1 for heated surface components; m and n are both material constants; P is the calculated pressure of the pipe wall; x is the independent variable of integration; D o δ is the outer diameter, δ0 is the initial wall thickness, and v is the corrosion thinning rate of the pipe section being evaluated.

2. The evaluation method according to claim 1, characterized in that, The information of the pipe segment being evaluated includes the material of the pipe segment and its outer diameter D. o Initial wall thickness δ0, current wall thickness δ1.

3. The evaluation method according to claim 2, characterized in that, The initial wall thickness δ0 and the current wall thickness δ1 are only the thicknesses of the metal substrate layer on the pipe wall.

4. The evaluation method according to claim 1, characterized in that, The calculated pressure P of the pipe wall is the normal operating pressure P of the pipe wall. op .

5. The evaluation method according to claim 1, characterized in that, The Larson-Miller parametric equations are shown in equations (1) and (2): P(σ)=(T+273.15)(C+lgt r ) (1); P(σ)=C0+C1lgσ+C2lg 2 σ+C3lg 3 σ+C4lg 4 p (2); In the formula: T is the temperature in Celsius, °C; t r σ is the creep failure time, h; σ is the initial creep loading stress, MPa; C is the Larson-Miller constant, and C0, C1, C2, C3, and C4 are material constants.

6. The evaluation method according to claim 5, characterized in that, The parameters of the Larson-Miller parametric equation are determined by solving the corresponding material constant values ​​using formula (3) through multiple linear regression: lgt r =(C1lgσ+C2lg 2 σ+C3lg 3 σ+C4lg 4 σ+C0) / (T+273.15)-C (3).

7. The evaluation method according to claim 2, characterized in that, The corrosion thinning rate v of the evaluated pipe section wall thickness is expressed by the formula... Calculated.

8. The evaluation method according to claim 1, characterized in that, The dimensional safety factor for the wall thickness corrosion reduction is 1.0 for components that cause general failure and 1.1 for components that cause serious failure.

9. The evaluation method according to claim 1, characterized in that, m is calculated using formula (5): (5)； In the formula: A and B are both parameters of the material's service environment.

10. The evaluation method according to claim 1, characterized in that, n is calculated using formula (6): (6)； In the formula: A and B are both material service environment parameters, C i is a material constant.

11. The evaluation method according to claim 9 or 10, characterized in that, A is calculated using formula (7): A=T c +273.15 (7); In the formula: T c This is the equivalent service temperature.

12. The evaluation method according to claim 9 or 10, characterized in that, B is calculated using formula (8): B=(T c +273.15)·C (8); In the formula: T c The equivalent service temperature is given by C, which is the Larson-Miller constant.

13. The evaluation method according to claim 12, characterized in that, The equivalent service temperature T c Design temperature T of the pipe wall d Pipe wall thickness design calculation temperature T s and equivalent temperature of the pipe wall T d The aging status of the pipe wall material is determined together.

14. The evaluation method according to claim 6, characterized in that, The material constants are calculated using formula (9): (9)； In the formula: T c For the equivalent service temperature, C i is a material constant.

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