Structural Integrity Assessment of Steam Generator Tube by the Use of Heterogeneous Finite Element Method

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Xinjian Duan ◽  
Michael J. Kozluk ◽  
Sandra Pagan ◽  
Brian Mills
Keyword(s):  
Finite Element ◽  
Steam Generator ◽  
Failure Modes ◽  
Structural Integrity ◽  
Fretting Wear ◽  
Defect Depth ◽  
Steam Generator Tube ◽  
Integrity Assessment ◽  
Failure Pressure ◽  
Steam Generator Tubes

Aging steam generator tubes have been experiencing a variety of degradations such as pitting, fretting wear, erosion-corrosion, thinning, cracking, and denting. To assist with steam generator life cycle management, some defect-specific flaw models have been developed from burst pressure testing results. In this work, an alternative approach; heterogeneous finite element model (HFEM), is explored. The HFEM is first validated by comparing the predicted failure modes and failure pressure with experimental measurements of several tubes. Several issues related to the finite element analyses such as temporal convergence, mesh size effect, and the determination of critical failure parameters are detailed. The HFEM is then applied to predict the failure pressure for use in a fitness-for-service condition monitoring assessment of one removed steam generator tube. HFEM not only calculates the correct failure pressure for a variety of defects, but also predicts the correct change of failure mode. The Taguchi experimental design method is also applied to prioritize the flaw dimensions that affect the integrity of degraded steam generator tubes such as the defect length, depth, and width. It has been shown that the defect depth is the dominant parameter controlling the failure pressure. The failure pressure varies almost linearly with defect depth when the defect length is greater than two times the tube diameter. An axial slot specific flaw model is finally developed.

Failure Pressure for Steam Generator Tube With Two Different Collinear Axial Through-Wall Cracks

2006 ◽  
Author(s):  
Nam-Su Huh ◽  
Yoon-Suk Chang ◽  
Young-Jin Kim
Keyword(s):  
Steam Generator ◽  
Complex Shape ◽  
Structural Integrity ◽  
Failure Behavior ◽  
Multiple Cracks ◽  
Single Crack ◽  
Steam Generator Tube ◽  
3 Dimensional ◽  
Failure Pressure ◽  
Steam Generator Tubes

To maintain the structural integrity of steam generator tubes, 40% of wall thickness plugging criterion has been developed. The approach is for the steam generator tube with single crack, so that the interaction effect of multiple cracks can not be considered. Although, recently, several approaches has been proposed to assess the integrity of steam generator tube with two identical cracks whilst actual multiple cracks reveal more complex shape. In this paper, the failure pressure of steam generator tube containing multiple cracks of different length is evaluated based on the detailed 3-dimensional elastic-plastic finite element (FE) analyses. In terms of the crack shape, two collinear axial through-wall cracks with different length were considered. Furthermore, the resulting FE failure pressures are compared with FE failure pressures and experimental results for two identical collinear axial through-wall cracks to quantify the effect of crack length ratio on failure behavior of steam generator tube with multiple cracks.

Evaluation of the Creep Rupture Behavior of Alloy 690 Steam Generator Tubes Considering the Pressure Ramp Rate

2021 ◽  
Author(s):  
Jongmin Kim ◽  
Min-Chul Kim ◽  
Joonyeop Kwon
Keyword(s):  
Steam Generator ◽  
Creep Rupture ◽  
Parameter Method ◽  
Alloy 600 ◽  
Steam Generator Tube ◽  
Failure Pressure ◽  
Alloy 690 ◽  
Rupture Model ◽  
Temperature And Pressure ◽  
Steam Generator Tubes

Abstract The materials used previously for steam generator tubes around the world have been replaced and will be replaced by Alloy 690 given its improved corrosion resistance relative to that of Alloy 600. However, studies of the high- temperature creep and creep-rupture characteristics of steam generator tubes made of Alloy 690 are insufficient compared to those focusing on Alloy 600. In this study, several creep tests were conducted using half tube shape specimens of the Alloy 690 material at temperatures ranging from 650 to 850C and stresses in the range of 30 to 350 MPa, with failure times to creep rupture ranging from 3 to 870 hours. Based on the creep test results, creep life predictions were then made using the well-known Larson Miller Parameter method. Steam generator tube rupture tests were also conducted under the conditions of a constant temperature and pressure ramp using steam generator tube specimens. The rupture test equipment was designed and manufactured to simulate the transient state (rapid temperature and pressure changes) in the event of a severe accident condition. After the rupture test, the damage to the steam generator tubes was predicted using a creep rupture model and a flow stress model. A modified creep rupture model for Alloy 690 steam generator tube material is proposed based on the experimental results. A correction factor of 1.7 in the modified creep rupture model was derived for the Alloy 690 material. The predicted failure pressure was in good agreement with the experimental failure pressure.

Integrity Assessment of Subsea Pipeline Dent / Buckle Using ILI Data

2019 ◽  
Author(s):  
Gurumurthy Kagita ◽  
Gudimella G. S. Achary ◽  
Mahesh B. Addala ◽  
Balaji Srinivasan ◽  
Penchala S. K. Pottem ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Failure Modes ◽  
Structural Integrity ◽  
Mechanical Damage ◽  
Metal Loss ◽  
Stress Concentrations ◽  
Subsea Pipeline ◽  
Integrity Assessment ◽  
Finite Element Software

Abstract Mechanical damage in subsea pipelines in the form of local dents / buckles due to excessive bending deformation may severely threaten their structural integrity. A dent / buckle has two significant effects on the pipeline integrity. Notably, residual stresses are set up as result of the plastic deformation and stress concentrations are created due to change in pipe geometry caused by the denting / buckling process. To assess the criticality of a dent / buckle, which often can be associated with strain induced flaws in the highly deformed metal, integrity assessment is required. The objective of this paper is to evaluate the severity of dent / buckle in a 48” subsea pipeline and to make the rerate, repair or replacement decision. This paper presents a Level 3 integrity assessment of a subsea pipeline dent / buckle with metal loss, reported in in-line inspection (ILI), in accordance with Fitness-For-Service Standard API 579-1/ASME FFS-1. In this paper, the deformation process that caused the damage (i.e. dent / buckle) with metal loss is numerically simulated using ILI data in order to determine the magnitude of permanent plastic strain developed and to evaluate the protection against potential failure modes. For numerical simulation, elastic-plastic finite element analyses (FEA) are performed considering the material as well as geometric non-linearity using general purpose finite element software ABAQUS/CAE 2017. Based on the numerical simulation results, the integrity assessment of dented / buckled subsea pipeline segment with metal loss has been performed to assess the fitness-for-service at the operating loads.

Coalescence Criterion of Part-Through Wall Cracks in Steam Generator Tubes of Nuclear Power Plants

2004 ◽  
Author(s):  
Jeries Abou-Hanna ◽  
Timothy McGreevy ◽  
Saurin Majumdar ◽  
Amit J. Trivedi ◽  
Ashraf Al-Hayek
Keyword(s):  
Finite Element ◽  
Steam Generator ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Local Instability ◽  
Element Analysis ◽  
Failure Pressure ◽  
Ligament Failure ◽  
Steam Generator Tubes

In scheduling inspection and repair of nuclear power plants, it is important to predict failure pressure of cracked steam generator tubes. Nondestructive evaluation (NDE) of cracks often reveals two neighboring cracks. If two neighboring part-through cracks interact, the tube pressure, under which the ligament between the two cracks fails, could be much different than the critical burst pressure of an individual equivalent part-through crack. The ability to accurately predict the ligament failure pressure, called “coalescence pressure,” is important. The coalescence criterion, established earlier for 100% through cracks using nonlinear finite element analyses [1–3], was extended to two part-through-wall axial collinear and offset cracks cases. The ligament failure is caused by local instability of the radial and axial ligaments. As a result of this local instability, the thickness of both radial and axial ligaments decreases abruptly at a certain tube pressure. Good correlation of finite element analysis with experiments (at Argonne National Laboratory’s Energy Technology Division) was obtained. Correlation revealed that nonlinear FEM analyses are capable of predicting the coalescence pressure accurately for part-through-wall cracks. This failure criterion and FEA work have been extended to axial cracks of varying ligament width, crack length, and cases where cracks are offset by axial or circumferential ligaments. The study revealed that rupture of the radial ligament occurs at a pressure equal to the coalescence pressure in the case of axial ligament with collinear cracks. However, rupture pressure of the radial ligament is different from coalescence pressure in the case of circumferential ligament, and it depends on the length of the ligament relative to crack dimension.

Integrity Assessment of API 5L X65 and X70 Pipelines With Mechanical Damages

2012 ◽  
Author(s):  
Kyu Jung Yeom ◽  
Yong Kwang Lee ◽  
Kyu Hwan Oh ◽  
Cheol Man Kim ◽  
Woo Sik Kim
Keyword(s):  
Finite Element ◽  
Structural Integrity ◽  
Mechanical Damage ◽  
Local Stress ◽  
Assessment Method ◽  
Full Scale ◽  
Burst Pressure ◽  
Element Analysis ◽  
Integrity Assessment ◽  
Failure Pressure

Gas pipelines with mechanical damages could affect the structural integrity and causes local stress and strain concentration. Failures in gas pipeline as leakages that could affect the supply of gas, loss of production, and environmental pollution. It is important to determine if pipelines are fitness-for-service. ASME B31G code is still widely used criterion although the assessment method is the conservative method. Further examinations are needed on the effects of material grade and pipeline shape on the burst pressure of damaged pipelines. The goal of this paper is to predict the failure pressure of mechanical damaged made of API X65 and X70 pipelines, by conducting full scale burst tests and finite element analysis (FEA). Different pipeline grades, effects of gouges, and dent depths were considered for an integrity assessment. The full scale burst tests were performed for pipelines with artificial mechanical damage. The gouge defect was made in a V-notch shape and the dented pipeline was generated using a ball shaped indenter that was pressed into the pipe. A three dimensional FEA was performed to obtain the burst pressure of a pipe with gouge and dent defects as a function of defect depth and length. A FEA was used to simulate the and externally damaged pipes under internal pressure. Failure pressure was predicted with stress based and strain based assessments by the finite element method (FEM).

Assessment of Limit Loads for Circumferential Cracks in Steam Generator Tube Considering Constraining Effect of Tube Support

2005 ◽  
Author(s):  
Hyun Su Kim ◽  
Jong Sung Kim ◽  
Tae Eun Jin ◽  
Hong Deok Kim ◽  
Han Sub Chung
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Steam Generator ◽  
Nuclear Power ◽  
Three Dimensional ◽  
Fission Products ◽  
Limit Load ◽  
Steam Generator Tube ◽  
Integrity Assessment ◽  
Steam Generator Tubes

The steam generator in a nuclear power plant is a large heat exchanger that uses heat from reactor to generate steam to drive the turbine generators. Rupture of a steam generator tube can result in release of fission products to environment. Therefore, an accurate integrity assessment of the steam generator tubes with cracks is of great importance for maintaining safety of a nuclear power plant. The steam generator tubes are supported at periodic intervals by support plates and rotations of the tubes are constrained. Although it was reported that the limit load for a circumferential crack was significantly affected by boundary condition of the tube, existing limit load solutions do not include the constraining effect of tube supports. This paper provides detailed limit load solutions for circumferential cracks in steam generator tubes considering the actual boundary conditions to simulate the constraining effect of the tube supports. Such solutions are developed based on three dimensional (3D) finite element analyses. The resulting limit load solutions are given in a polynomial form, and thus can be simply used in practical integrity assessment of the steam generator tubes.

Analysis of Fluid-Elastic Instability for KSNP Steam Generator Tube and Its Plugging Effect at Central Region

2003 ◽  
Author(s):  
Ki-Wahn Ryu ◽  
Bong-Ho Cho ◽  
Chi-Yong Park ◽  
Su-Ki Park
Keyword(s):  
Steam Generator ◽  
Central Region ◽  
Outer Zone ◽  
Elastic Instability ◽  
Stability Ratio ◽  
Steam Generator Tube ◽  
Instability Analysis ◽  
Integrity Assessment ◽  
The Stability ◽  
Steam Generator Tubes

The characteristics of fluid-elastic instability for the KSNP steam generator tubes were investigated numerically. The information on the thermal-hydraulic data of the steam generator has been obtained by using the ATHOS3-MOD1 code and the fluid-elastic instability analysis has been conducted by using the PIAT (Program for Integrity Assessment of Steam Generator Tube) code. The KSNP steam generator has the concentrated plugging zone at the vicinity of the stay cylinder inside the steam generator. To investigate the cause of the concentrated plugging, the fluid-elastic instability analysis has been performed on various column and row number of the KSNP steam generator tubes. From the results of this study the stability ratio due to the fluid-elastic instability in the concentrated plugged zone tend to have larger values than those of the outer zone. Even though the further study will still be required, these results seem to be related with concentrated plugging inside the steam generator. And the stability ratio of plugged tube does not have any consistent advantages for all modes over the normal one. This seems to be caused by the decrease of mass, the increase of natural frequency, and the change of mode shape after plugging.

PWR and WWER Steam Generator Tube Integrity Assessment

2013 ◽  
Author(s):  
Roman Krautschneider
Keyword(s):  
Steam Generator ◽  
Operating Conditions ◽  
Degradation Mechanisms ◽  
Steam Generator Tube ◽  
Integrity Assessment ◽  
Steam Generator Tubes

Paper is describing and comparing degradation mechanisms and integrity assessment of PWR and WWER type of steam generator tubes. Because of different design, different used materials and also different operating conditions, there are significant differences in degradation mechanisms. Therefore both steam generator types have their specific codes dealing with inspection, monitoring and maintenance.

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