Leak-before-break analysis of a pipe containing circumferential defects

2015 ◽  
Vol 58 ◽  
pp. 369-379 ◽  
Author(s):  
X.B. Ren ◽  
B. Nyhus ◽  
H.L. Lange ◽  
M. Hauge
Keyword(s):  
Circumferential Defects ◽  
Leak Before Break

Effect of the Yield to Tensile Ratio on Structural Integrity of Line Pipes Subjected to Bending Loads

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Hugo A. Ernst ◽  
Richard E. Bravo
Keyword(s):  
Structural Integrity ◽  
Defect Tolerance ◽  
Deformation Control ◽  
Critical Defect ◽  
Bending Loads ◽  
Critical Defect Size ◽  
Circumferential Defects ◽  
T Values ◽  
Lower Limits ◽  
Leak Before Break

This work studies the effect of the yield (Y) to tensile (T) ratio, Y∕T, on the structural integrity of line pipes with part through the thickness (PTT) circumferential defects subject to bend loading. A model based on elastic-plastic fracture mechanics and plasticity theory was developed for that purpose. The analysis handles situation with load or deformation control conditions. The results are shown in terms of curves of critical defect size versus the controlling variable, i.e., load or deformation. For each one of the different materials studied, cases with different Y∕T values were considered. Even for the lower limits of experimental data, i.e., larger Y∕T, the materials have adequate defect tolerance. A leak before break analysis of a PTT circumferential defect growing into a through the thickness defect growing circumferentially was performed.

Probabilistic Leak Before Break Using the R6 Methodology

2020 ◽  
Author(s):  
Peter Gill
Keyword(s):  
Monte Carlo ◽  
Nuclear Reactor ◽  
Probabilistic Method ◽  
Limit Load ◽  
Monte Carlo Analysis ◽  
Two Phase ◽  
Weld Residual Stress ◽  
Circumferential Defects ◽  
Further Development ◽  
Leak Before Break

Abstract The integrity of a component in a safety critical industry is determined by carrying out Engineering Critical Assessments (ECA). These are designed to provide a conservative estimate of the life of a component based on conservative inputs/methodology. It is becoming increasingly apparent that for many applications these methods are overly conservative. The only physical way to really assess the reliability of a component is by producing many thousands, if not millions of a specific component and calculating a failure probability based on testing/OPEX. This is simply not feasible for the components in, for example, a nuclear reactor, and probabilistic techniques are becoming increasingly important as a means to understand the reliability of a component. This information can then be used to assess risk and inform inspection programmes. Typically a probabilistic method relies on assigning distributions to various input parameters and evaluating a probability integral, usually by Monte-Carlo analysis. A previous PVP paper developed Monte Carlo methods using the R6 fracture mechanics procedure. Although providing good insight into the likelihood of failure, these analyses were simplified and not readily applied to realistic plant situations. Further development would enable much more of the technology contained within R6 to be applied within probabilistic software. The following new features of the software are presented in this paper: • the latest K and limit load solutions from R6 for through wall circumferential defects • Simplified V factor approach to account for secondary stresses • two phase flow (water) based on the latest SQUIRT methodology • global bending, through wall bending, weld residual stress This enables a full probabilistic leak detection calculation for circumferential through wall cracks in pipes. Examples of probabilistic Leak-before-Break calculations for PWR pipework are presented in the paper.

Effect of the Yield to Tensile Ratio, Y/T, on Structural Reliability of Linepipes Subject to Bend Loading

2004 ◽  
Author(s):  
Hugo A. Ernst ◽  
Richard E. Bravo ◽  
Jose´ A. Villasante ◽  
Alfonso Izquierdo
Keyword(s):  
Structural Reliability ◽  
Defect Tolerance ◽  
Deformation Control ◽  
Critical Defect ◽  
Control Situations ◽  
Critical Defect Size ◽  
Circumferential Defects ◽  
T Values ◽  
Lower Limits ◽  
Leak Before Break

A model based on elastic-plastic fracture mechanics (EPFM) and plasticity theory, was developed to study the effect of the Yield (Y) to Tensile (T) ratio, Y/T, on the structural reliability of linepipes with part through the thickness (PTT) circumferential defects subject to bend loading. The analysis allows for load or deformation control situations. The results are shown in terms of curves of critical defect size vs. the controlling variable, i.e. load or deformation. For each one of the materials studied, different cases with different Y/T values were considered. Even for the lower limits of experimental data, i.e. larger Y/T, the materials have adequate defect tolerance. A Leak Before Break Analysis was also conducted.

A Probabilistic Application of the R6 Detectable Leakage Leak-Before-Break Procedure

2002 ◽  
Author(s):  
D. W. Beardsmore ◽  
S. F. Yellowlees ◽  
J. K. Sharples ◽  
R. A. Ainsworth ◽  
P. J. Budden
Keyword(s):  
Fracture Toughness ◽  
Defect Size ◽  
Minimum Size ◽  
Probabilistic Assessment ◽  
Monte Carlo Calculations ◽  
Statistical Coupling ◽  
Crack Stability ◽  
The Stability ◽  
Circumferential Defects ◽  
Leak Before Break

This paper presents an assessment of circumferential defects in pipes which combines the Detectable Leakage, leak-before-break Procedure of R6 with the probabilistic assessment principles contained in R6. It shows how the equations which determine the stability of cracks and those that describe the rate of leakage can be formulated, and how Monte Carlo calculations can be carried out, to determine the limiting crack sizes for leakage detectability and crack stability. A leak-before-break case can be made if the minimum size required for a detectable leak is less than the size at which disruptive fracture would occur. A large number of independent calculations can be carried out, from which the probability of making a leak-before-break case can be established for any specified defect size. Results of calculations are presented using a series of histograms to demonstrate the probabilities obtained. The effect of including a statistical coupling between the material’s yield stress and fracture toughness is also examined.

scholarly journals Leak-before-break analysis of thermally aged nuclear pipe under different bending moments

2015 ◽  
Vol 47 (6) ◽  
pp. 712-718 ◽  
Author(s):  
Xuming Lv ◽  
Shilei Li ◽  
Hailong Zhang ◽  
Yanli Wang ◽  
Zhaoxi Wang ◽  
...  
Keyword(s):  
Bending Moments ◽  
Leak Before Break

LEAK-BEFORE-BREAK CONDITIONS OF PLATES AND PIPES UNDER HIGH FATIGUE STRESSES

1992 ◽  
Vol 15 (8) ◽  
pp. 809-824 ◽  
Author(s):  
Ki Woo Nam ◽  
Kotoji Ando ◽  
Sakai Yuzuru ◽  
Nobukazu Ogura
Keyword(s):  
High Fatigue ◽  
Leak Before Break

scholarly journals Leak-before-break considerations for LMFBR structures

1986 ◽  
Vol 24 (4) ◽  
pp. 337-346 ◽  
Author(s):  
L. Grüter ◽  
H. Zeibig ◽  
B.Percie du Sert ◽  
S. Bhandari
Keyword(s):  
Leak Before Break

Simplified LBB Guidance: Stage 1 — Development of a New Software Tool and Initial Scoping Calculations

2018 ◽  
Author(s):  
Peter Gill ◽  
John Sharples ◽  
Chris Aird
Keyword(s):  
Fracture Toughness ◽  
Material Properties ◽  
Software Tool ◽  
Pipe Material ◽  
Loading Conditions ◽  
Design Rules ◽  
Inner Radius ◽  
Inner Diameter ◽  
Stage 1 ◽  
Leak Before Break

This study is focussed on establishing more simplified Leak-before-Break (LbB) guidance for inclusion into Section III.11 of the R6 procedure. The approach adopted has involved the development of a universal software tool for LbB simplified assessments which can be used to perform initial scoping calculations to demonstrate typical LbB cases. It is envisaged that this simplified methodology will enable plant assessment engineers to be more informed on which sites on plant are likely to have LbB successfully applied and to be able to undertake LbB assessments in a more simplistic way than is currently available. Using the developed software tool, a range of LbB calculations for different cracks and loading conditions have been performed to provide guidance on where LbB is more likely to be applied on plant. Loading conditions include primary and secondary stresses, where through-wall changes have been accounted for. The pipe geometries included in this study have been defined by the inner radius and the wall thickness, calculated by minimum pipe thickness required according to meet the design rules of ASME III. The pipe inner radius varies from 40mm to 200mm (80mm to 400mm inner diameter (ID)). All pipe outer diameters are less than 0.5m. All cracks considered in this study are through-wall and circumferential. Pipe material properties are chosen to be broadly representative of an Austenitic Stainless Steel, where the fracture toughness varies from 100 to 180MPa√m and the yield stress is 150MPa.

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