Development of Analytical Evaluation Procedures and Acceptance Criteria for Pipe Wall Thinning in ASME Code Section XI

2004 ◽  
Author(s):  
Kunio Hasegawa ◽  
Gery M. Wilkowski ◽  
Lee F. Goyette ◽  
Douglas A. Scarth
Keyword(s):  
Pipe Wall ◽  
Evaluation Methodology ◽  
Current Status ◽  
Evaluation Procedure ◽  
Analytical Evaluation ◽  
Acceptance Criteria ◽  
New Class ◽  
Wall Thinning ◽  
Class 1 ◽  
Asme Code

As the worldwide fleet of nuclear power plants ages, the need to address wall thinning in pressure boundary materials becomes more acute. The 2001 ASME Code Case N-597-1, “Requirements for Analytical Evaluation of Pipe Wall Thinning,” provides procedures and criteria for the evaluation of wall thinning that are based on Construction Code design concepts. These procedures and criteria have proven useful for Code Class 2 and 3 piping; but, they provide relatively little flexibility for Class 1 applications. Recent full-scale experiments conducted in Japan and Korea on thinned piping have supported the development of a more contemporary failure strength evaluation methodology applicable to Class 1 piping. The ASME B&PV Code Section XI Working Group on Pipe Flaw Evaluation has undertaken the codification of new Class 1 evaluation methodology, together with the existing Code Case N-597-1 rules for Class 2 and 3 piping, as a non-mandatory Appendix to Section XI. This paper describes the current status of the development of the proposed new Class 1 piping acceptance criteria, along with a brief review of the current Code Case N-597-1 evaluation procedure in general.

Pressure Blow Out Assessment for Class 1 Piping With Local Wall Thinning

2006 ◽  
Author(s):  
Kunio Hasegawa ◽  
Katsuyuki Shibata
Keyword(s):  
Internal Pressure ◽  
Nuclear Power ◽  
Tensile Load ◽  
Evaluation Methodology ◽  
Evaluation Procedure ◽  
Seismic Load ◽  
Analytical Evaluation ◽  
Wall Thinning ◽  
Bending Load ◽  
Class 1

Wall thinning caused by the flow of water in power piping systems became a major concern to the nuclear power industries. ASME Code Case N-597-3, “Requirements for Analytical Evaluation of Pipe Wall Thinning,” provides procedures and criteria for Code Class 2 and 3 piping for the evaluation of wall thinning. However, analytical evaluation procedure for Class 1 piping is not provideed in the Code Case. Recent full-scale experiments on locally thinned pipes have supported the development of more contemporary failure strength evaluation methodology for Class 1 piping. These evaluation methodologies are applicable for the loading type of bending, tensile or cyclic bending load. Prior to the failure by bending moment, tensile load or cyclic/seismic load, locally wall thinned pipes shall be considered pressure blow out by the internal pressure itself. This paper introduces the failure of a uniformly thinned cylinder by an internal pressure and describes limitation on wall thinning depth to avoid pressure blow out for Class 1 piping.

Load Factor for Evaluating Non-Planar Flaws in Carbon Steel Piping Using Limit Load Methodology

2016 ◽  
Author(s):  
Phuong H. Hoang
Keyword(s):  
Carbon Steel ◽  
Nuclear Power ◽  
Power Plants ◽  
Pipe Wall ◽  
Local Strain ◽  
Limit Load ◽  
Evaluation Methodology ◽  
Load Factor ◽  
Wall Thinning ◽  
Steel Piping

Non-planar flaw such as local wall thinning flaw is a major piping degradation in nuclear power plants. Hundreds of piping components are inspected and evaluated for pipe wall loss due to flow accelerated corrosion and microbiological corrosion during a typical scheduled refueling outage. The evaluation is typically based on the original code rules for design and construction, and so often that uniformly thin pipe cross section is conservatively assumed. Code Case N-597-2 of ASME B&PV, Section XI Code provides a simplified methodology for local pipe wall thinning evaluation to meet the construction Code requirements for pressure and moment loading. However, it is desirable to develop a methodology for evaluating non-planar flaws that consistent with the Section XI flaw evaluation methodology for operating plants. From the results of recent studies and experimental data, it is reasonable to suggest that the Section XI, Appendix C net section collapse load approach can be used for non-planar flaws in carbon steel piping with an appropriate load multiplier factor. Local strain at non-planar flaws in carbon steel piping may reach a strain instability prior to net section collapse. As load increase, necking starting at onset strain instability leads to crack initiation, coalescence and fracture. Thus, by limiting local strain to material onset strain instability, a load multiplier factor can be developed for evaluating non-planar flaws in carbon steel piping using limit load methodology. In this paper, onset strain instability, which is material strain at the ultimate stress from available tensile test data, is correlated with the material minimum specified elongation for developing a load factor of non-planar flaws in various carbon steel piping subjected to multiaxial loading.

Fatigue-Strength-Reduction Factors for Welds in Pressure Vessels and Piping

2000 ◽  
Vol 122 (3) ◽  
pp. 297-304 ◽  
Author(s):  
Carl E. Jaske
Keyword(s):  
Fatigue Strength ◽  
Weld Joint ◽  
Pressure Vessels ◽  
Strength Reduction ◽  
Current Status ◽  
Published Data ◽  
Weld Joints ◽  
Class 1 ◽  
Asme Code ◽  
Reduction Factors

Fatigue-strength-reduction factors (FSRFs) are used in the design of pressure vessels and piping subjected to cyclic loading. This paper reviews the background and basis of FSRFs that are used in the ASME Boiler and Pressure Vessel Code, focusing on weld joints in Class 1 nuclear pressure vessels and piping. The ASME Code definition of FSRF is presented. Use of the stress concentration factor (SCF) and stress indices are discussed. The types of welds used in ASME Code construction are reviewed. The effects of joint configuration, welding process, cyclic plasticity, dissimilar metal joints, residual stress, post-weld heat treatment, the nondestructive inspection performed, and metallurgical factors are discussed. The current status of weld FSRFs, including their development and application, are presented. Typical fatigue data for weldments are presented and compared with the ASME Code fatigue curves and used to illustrate the development of FSRF values from experimental information. Finally, a generic procedure for determining FSRFs is proposed and future work is recommended. The five objectives of this study were as follows: 1) to clarify the current procedures for determining values of fatigue-strength-reduction factors (FSRFs); 2) to collect relevant published data on weld-joint FSRFs; 3) to interpret existing data on weld-joint FSRFs; 4) to facilitate the development of a future database of FSRFs for weld joints; and 5) to facilitate the development of a standard procedure for determining the values of FSRFs for weld joints. The main focus is on weld joints in Class 1 nuclear pressure vessels and piping. [S0094-9930(00)02703-7]

Technical Basis for Flaw Acceptance Criteria for Cast Austenitic Stainless Steel Piping

2020 ◽  
Vol 142 (2) ◽  
Author(s):  
Do Jun Shim ◽  
Nathanial Cofie ◽  
Dilipkumar Dedhia ◽  
Tim Griesbach ◽  
Kyle Amberge
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Evaluation Procedure ◽  
Correction Factors ◽  
Acceptance Criteria ◽  
Regulatory Guidance ◽  
Asme Code ◽  
Tensile Data ◽  
Equivalent Factor ◽  
Technical Basis

Abstract According to the current ASME Code Section XI, IWB-3640 and Appendix C flaw evaluation procedure, cast austenitic stainless steel (CASS) piping with ferrite content (FC) less than 20% is treated as wrought stainless steel. For CASS piping with FC equal or greater than 20%, there was no flaw evaluation procedure in the ASME Code prior to the 2019 Edition. In this paper, the technical basis for the recently approved Code change containing flaw acceptance criteria for CASS piping is presented. The procedure utilizes the current rules in ASME Code Section XI, IWB 3640/Appendix C and the existing elastic-plastic correction factors (i.e., Z-factors) for other materials in the Code. The appropriate Z-factor to use for the CASS piping is determined based on the FC (using Hull's equivalent factor). Experimentally measured fully saturated fracture toughness and tensile data of the three most common grades of CASS material in the U.S. (CF3, CF8, and CF8M) were used to determine the flaw acceptance criteria in the Appendix C Code method. As described here, the method is conservative since it utilizes the fully saturated condition of CASS materials. In addition, it is simple and consistent with the current regulatory guidance on aging management of CASS piping.

Effects of Bending Moment and Torsion on the Internal Pressure Limit Load of Locally Thinned Pipes

2011 ◽  
Author(s):  
Phuong H. Hoang ◽  
Kunio Hasegawa ◽  
Bostjan Bezensek ◽  
Yinsheng Li
Keyword(s):  
Internal Pressure ◽  
Pipe Wall ◽  
Large Strain ◽  
Bending Moment ◽  
Limit Load ◽  
Evaluation Procedure ◽  
Structural Factors ◽  
Stress Evaluation ◽  
Pressure Limit ◽  
Wall Thinning

The pipe wall thinning stress evaluation procedures in Code-Case N-597-2 [1] of the ASME Boiler and Pressure Vessel (B&PV) Code are essentially based on Construction Code [2] stress evaluation. Stresses in the hoop and the axial directions are evaluated separately to meet the Construction Code allowable stress. Using Construction Code rules for local pipe wall thinning stress evaluation in Class 2 & 3 piping may be too restrictive. An alternative approach is to use the limit loads of locally wall thinned pipe in conjunction with an appropriate Z-Factor and the structural factors of the ASME B&PV Section XI, Appendix C [3]. Such approach may require a combined effect of pressure, bending, axial load and torsion loads on locally thinned pipe. In this paper, the effects of bending moment and torsion on the internal pressure limit load of locally thinned straight pipes are investigated. Large strain finite element limit load analysis with elastic - perfectly plastic materials are performed for a parametric matrix of piping models with various pipe R/t ratios, flaw depths, axial and transverse flaw extents. Based on the results, the allowable pressure for axial flaws in C-5420 of the ASME B&PV Section XI, Appendix C [3] may be used for piping local wall thinning as an alternative evaluation procedure to the current minimum pipe wall thickness evaluation procedure in the Code Case N-597-2 [1].

Code Aspects Related to Combination of Stresses due to Hydrogen Detonations: Local Effects

2012 ◽  
Author(s):  
John C. Minichiello ◽  
Stephen D. Ahnert ◽  
Thomas C. Ligon ◽  
David J. Gross
Keyword(s):  
Fatigue Damage ◽  
Pipe Wall ◽  
Axial Strain ◽  
Evaluation Methodology ◽  
Local Effects ◽  
Bending Waves ◽  
Piping Systems ◽  
Asme Code ◽  
Fatigue Evaluation ◽  
Hoop Stresses

This paper addresses the local effects of hydrogen detonations inside piping. It is the first in a two-part series of papers which assess the effects of detonations in piping systems relative to ASME Code allowables. The effects of internal detonations in piping systems are typically separated into two regimes: local effects and system effects. Local effects are often simplistically represented as pure hoop stresses resulting from the pressure acting radially on the inside circumference of the pipe. In reality, the interaction of the pipe wall and the propagating detonation wave is relatively complex, resulting in “waves” or “ripples” in the pipe wall. These areas of local, through-wall curvature lead to substantial axial stresses which may even exceed the hoop stresses. Furthermore, in the elastic regime, there is very little damping present in the pipe wall, leading to numerous stress cycles as the local bending waves move axially along the pipe wall. Fatigue effects of the combined hoop and axial cycling were evaluated using ASME Code Section VIII, Division 2 fatigue evaluation methodology. Analysis of strain gage data from a number of hydrogen detonation experiments in 2-inch and 4-inch Schedule 40 piping showed that the fatigue damage is generally driven by fewer than 10 large-magnitude fatigue cycles, which account for an average of 75% of the total fatigue damage. However, the results also demonstrate that for two detonation events with similar measured peak hoop or axial strain, the number of fatigue allowable events may vary dramatically depending on the shape of the strain response.

Supplementary Technical Basis for ASME Section XI Code Case N-597-2

2006 ◽  
Author(s):  
Douglas A. Scarth ◽  
Kunio Hasegawa ◽  
Lee F. Goyette ◽  
Phil Rush
Keyword(s):  
Wall Thickness ◽  
Nuclear Power ◽  
Pressure Vessels ◽  
Code Design ◽  
Acceptance Criteria ◽  
Accelerated Corrosion ◽  
Wall Thinning ◽  
Class 1 ◽  
American Society ◽  
Technical Basis

Section XI of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code provides rules and requirements for maintaining pressure boundary integrity of components, piping, and equipment during the life of a nuclear power plant. Code Case N-597-2 of Section XI, Requirements for Analytical Evaluation of Pipe Wall Thinning, provides evaluation procedures and acceptance criteria to justify continued operation of Class 1, 2 and 3 piping items subjected to wall thinning by a mechanism such as flow-accelerated corrosion. The acceptance criteria ensure that margins equivalent to those of the ASME B&PV Code are maintained. The technical basis for Code Case N-597-2 was previously presented at the 1999 ASME Pressure Vessels and Piping Conference. Since then, the ASME Section XI Working Group on Pipe Flaw Evaluation has identified the need for further explanation of the technical basis for the Code Case, such as the procedures for evaluation of wall thickness less than the Construction Code Design Pressure-based minimum allowable wall thickness, tmin. This paper provides an additional description of the Code Case technical basis and validation against experimental and historic wall thinning events.

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