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CN-115712984-B - Evaluation method for residual life of boiler heating surface tube

CN115712984BCN 115712984 BCN115712984 BCN 115712984BCN-115712984-B

Abstract

The invention discloses an assessment method for residual life of a boiler heating surface pipe, which comprises the following steps of 1) determining information of an assessed pipe section at least comprising accumulated service time t op of the assessed pipe section, 2) determining pipe wall equivalent calculation temperature of the assessed pipe section, 3) determining pipe wall calculation pressure of the assessed pipe section, 4) determining Larson-Miller parameter equation reflecting material durability strength performance of the assessed pipe section, 5) calculating wall thickness corrosion thinning rate of the assessed pipe section, 6) calculating service life t n of a new pipe of the assessed pipe section under the corrosion thinning rate when long-term creep is taken as a main failure mode, and 7) subtracting accumulated service time t op of the assessed pipe section in step 1) from service life t n of the new pipe obtained in step 6). The service life assessment method for the boiler high-temperature heating surface pipe has important significance for accurately assessing the service life of the boiler high-temperature pressure-bearing member.

Inventors

  • ZHU BAOYIN
  • ZHOU JIANCONG
  • JIN XIAO
  • MA QINZHENG
  • XIA XIANXI
  • LAI YUNTING
  • Luan Gaocan
  • FU YANGYANG

Assignees

  • 苏州热工研究院有限公司
  • 广东省粤泷发电有限责任公司
  • 中国广核集团有限公司
  • 中国广核电力股份有限公司

Dates

Publication Date
20260512
Application Date
20221021

Claims (14)

  1. 1. The method for evaluating the residual life of the heating surface tube of the boiler is characterized by comprising the following steps of: 1) Determining the information of the estimated pipe section, wherein the information at least comprises the accumulated service time t op information of the estimated pipe section; 2) Determining the equivalent service temperature of the pipe wall of the pipe section to be evaluated; 3) Determining the pipe wall calculation pressure of the pipe section to be evaluated; 4) Determining Larson-Miller parameter equations reflecting the durability strength properties of the pipe section materials being evaluated; 5) Calculating the wall thickness corrosion thinning rate of the estimated pipe section; 6) Calculating the service life t n of a new pipe of the estimated pipe section under the wall thickness thinning speed when the corrosion thinning and the long-time creep are taken as main failure modes; 7) The residual life of the estimated pipe section is the service life t n of the new pipe obtained in the step 6), minus the accumulated service time t op of the estimated pipe section in the step 1); When the heating surface pipe takes corrosion thinning and long-term creep as main failure modes, the accumulated service life loss D tc is calculated by the following formula, and when the accumulated service life loss D tc =1, the corresponding time t is the service life t n of the new pipe of the estimated pipe section: ; Wherein C is Larson-Miller constant, C 0 、C 1 、C 2 、C 3 、C 4 is material constant, k 1 is stress coefficient, 1.5 is taken for a heated surface component, k 2 is wall thickness corrosion thinning dimension safety coefficient, 1.1 is taken for a heated surface component, m and n are both material constants, P is pipe wall calculation pressure, x is integral independent variable, D o is outer diameter, delta 0 is initial wall thickness, and v is estimated pipe section wall thickness corrosion thinning rate.
  2. 2. The method of evaluating according to claim 1, wherein the information of the evaluated pipe section includes a material of the evaluated pipe section, an outer diameter D o , an initial wall thickness δ 0 , a current wall thickness δ 1 .
  3. 3. The method of evaluation according to claim 2, wherein the initial wall thickness δ 0 and the current wall thickness δ 1 are only thicknesses of the metal substrate layer on the pipe wall.
  4. 4. The method of claim 1, wherein the calculated pressure P is a normal operating pressure P op of the pipe wall.
  5. 5. The evaluation method according to claim 1, wherein the Larson-Miller parameter equation is shown in the following formulas (1) and (2): P(σ)=(T+273.15)(C+lgt r ) (1); P(σ)＝C 0 +C 1 lgσ+C 2 lg 2 σ+C 3 lg 3 σ+C 4 lg 4 σ (2); wherein T is the temperature in degrees centigrade, T r is the creep rupture time, h, sigma is the initial creep loading stress, MPa, C is Larson-Miller constant, and C 0 、C 1 、C 2 、C 3 、C 4 is the material constant.
  6. 6. The method of claim 5, wherein the parameter determination of the Larson-Miller parameter equation is based on equation (3) by solving for the corresponding material constant value via multiple linear regression ：lgt r ＝(C 1 lgσ+C 2 lg 2 σ+C 3 lg 3 σ+C 4 lg 4 σ+C 0 )/(T+273.15)-C (3).
  7. 7. The method of evaluating according to claim 2, wherein the rate of wall thickness corrosion reduction v of the pipe section being evaluated is calculated by the formula And (5) calculating to obtain the product.
  8. 8. The method of evaluating according to claim 1, wherein the wall thickness corrosion reduction measures a dimensional safety factor of 1.0 for a component with a general failure result and 1.1 for a component with a severe failure result.
  9. 9. The evaluation method according to claim 1, wherein m is calculated by the formula (5): (5); wherein A, B are all the service environment parameters of the material.
  10. 10. The evaluation method according to claim 1, wherein n is calculated by the formula (6): (6); wherein A, B is a material service environment parameter, and C i is a material constant.
  11. 11. The evaluation method according to claim 9 or 10, wherein a is calculated by the formula (7): A=T c +273.15 (7); Wherein T c is the equivalent service temperature.
  12. 12. The evaluation method according to claim 9 or 10, wherein B is calculated by the formula (8): B=(T c +273.15)·C (8); Wherein T c is the equivalent service temperature, and C is Larson-Miller constant.
  13. 13. The method of claim 12, wherein the equivalent service temperature T c is determined by a combination of a wall design temperature T d , a wall thickness design calculation temperature T s , a wall equivalent temperature T d , and a wall material aging state.
  14. 14. The evaluation method according to claim 6, wherein the material constant is calculated by the formula (9): (9); Wherein T c is equivalent service temperature, and C i is material constant.

Description

Evaluation method for residual life of boiler heating surface tube Technical Field The invention relates to the technical field of residual life assessment of nuclear power components, in particular to a service life assessment method of a boiler high-temperature heating surface pipe based on interaction of corrosion thinning and creep damage. Background The service life assessment of the heating surface of the boiler is based on failure modes of the boiler, the main reasons of damage to the superheater and the reheater pipe are short-time overheat, long-time creep, corrosion to the fire surface, erosion, dissimilar steel welding failure and the like, the reasons of damage to the water cooling wall are mainly working medium side corrosion and fire side high-temperature corrosion, if the pipe wall temperature does not exceed the metal creep temperature, the residual service life is calculated by the pipe wall thinning rate, if the pipe wall temperature is high-temperature corrosion, the same analysis method as that of the superheater and the reheater pipe is adopted, the main reasons of damage to the coal economizer are pitting corrosion, abrasion and low-temperature corrosion, the corrosion life calculation is based on the strength checking theory, and the service life is calculated by the pipe wall thinning rate. The residual service life assessment of the heating surface of the boiler is mainly aimed at taking corrosion thinning, long-term creep, high-temperature corrosion thinning and dissimilar steel welding failure as main failure modes, and no method capable of accurately assessing the corrosion thinning service life of the heating surface at present exists. Disclosure of Invention In view of the above, in order to overcome the defects of the prior art, the invention aims to provide a service life assessment method for a high-temperature heating surface pipe of a boiler based on the interaction of corrosion thinning and creep damage. In order to achieve the above purpose, the present invention adopts the following technical scheme: A method for evaluating the residual life of a heating surface tube of a boiler comprises the following steps: 1) Determining background information of the estimated pipe section, wherein the background information at least comprises accumulated service time t op information of the estimated pipe section; 2) Determining the equivalent calculated temperature of the pipe wall of the pipe section to be evaluated; 3) Determining the pipe wall calculation pressure of the pipe section to be evaluated; 4) Determining Larson-Miller parameter equations reflecting the durability strength properties of the pipe section materials being evaluated; 5) Calculating the wall thickness corrosion thinning rate of the estimated pipe section; 6) Calculating the service life t n of a new pipe of the estimated pipe section under the wall thickness thinning speed when the corrosion thinning and the long-time creep are taken as main failure modes; 7) The remaining life of the estimated pipe section is the new pipe life t n obtained in step 6) minus the accumulated length of service t op of the estimated pipe section in step 1). According to some preferred embodiments of the invention, the information about the pipe section being evaluated includes the pipe section being evaluated, the outer diameter D o, the initial wall thickness delta 0, and the current wall thickness delta 1. According to some preferred embodiments of the invention, the initial wall thickness δ 0 and the current wall thickness δ 1 are only the thicknesses of the metal substrate layers on the pipe wall. According to some preferred embodiments of the present invention, the equivalent service temperature T c is determined by the pipe wall design temperature T d, the pipe wall thickness design calculation temperature T s, the pipe wall equivalent temperature T d, and the aging state of the pipe wall material. According to some preferred embodiments of the invention, the calculated pressure P is the normal operating pressure P op of the pipe wall. According to some preferred embodiments of the invention, the Larson-Miller parameter equation is shown in formula (1) and formula (2): P(σ)=(T+273.15)(C+lg tr) (1) P(σ)＝C0+C1 lgσ+C2 lg2σ+C3 lg3σ+C4 lg4σ (2) wherein T is the temperature in degrees centigrade, T r is the creep rupture time, h, sigma is the initial creep loading stress, MPa, C is Larson-Miller constant, and C 0、C1、C2、C3、C4 is the material constant. According to some preferred embodiments of the invention, the parameter determination of the material L-M may be solved for the corresponding material constant value by multiple linear regression using equation (3): lgtr＝(C1 lgσ+C2 lg2σ+C3 lg3σ+C4 lg4σ+C0)/(T+273.15)-C (3). According to some preferred embodiments of the invention, the estimated pipe section wall thickness corrosion thinning rate v is calculated by the formula And (5) calculating to obtain the product. According to