Assessment of Overlapped Internal and External Volumetric Flaws in p-M Method

2009 ◽  
Author(s):  
Shinji Konosu ◽  
Hikaru Miyata
Keyword(s):  
Pressure Vessels ◽  
Assessment Procedure ◽  
Diagram Method ◽  
Common Problems ◽  
Good Agreement

Assessment of overlapped internal and external volumetric flaws is one of the most common problems relating to pressure vessels and piping components. Under the current Fitness for Service (FFS) rules, such as ASME, BS and so on, the procedures have not yet defined how to assess these flaws. In this paper, a new procedure for these volumetric flaws is proposed for assessing the flaws by the p-M (pressure-moment) diagram method, which is a simple assessment procedure. Numerous FEAs for a cylinder with overlapped internal and external flaws were conducted to verify the proposed procedure. There is good agreement among them.

Assessment Procedure for Multiple Volumetric Flaws in p-M Diagram

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Shinji Konosu
Keyword(s):  
Body Force ◽  
Pressure Vessels ◽  
The Body ◽  
Assessment Procedure ◽  
Force Method ◽  
Reference Stress ◽  
Body Force Method ◽  
Common Problems ◽  
Shielding Effects

Assessment of multiple volumetric flaws is one of the most common problems relating to pressure vessels and piping components. Under the current fitness for service rules, such as ASME, BS, and so on, multiple volumetric flaws are usually recharacterized as an enveloping volumetric flaw (defined as a single larger volumetric flaw) as well as multiple cracklike flaws, following their assessment rules. However, the rules proposed in their codes will not often agree and their justification is unknown. Furthermore, they can provide unrealistic assessment in some cases. In this paper, the interaction between two differently sized nonaligned volumetric flaws such as local thin areas is clarified by applying the body force method. Unlike multiple cracklike flaws, the effect of biaxial stresses on the interaction is evident. Based on the interaction that indicates the magnification and shielding effects and reference stress solutions, a new procedure for multiple volumetric flaws is proposed for assessing the flaws in the p-M (pressure-moment) diagram, which is a simple assessment procedure for vessels with volumetric flaws.

Assessment Procedure for Multiple Cracklike Flaws in Failure Assessment Diagram (FAD)

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Shinji Konosu
Keyword(s):  
Body Force ◽  
Pressure Vessels ◽  
The Body ◽  
Assessment Procedure ◽  
Failure Assessment Diagram ◽  
Reference Stress ◽  
Body Force Method ◽  
Failure Assessment ◽  
Common Problems ◽  
Shielding Effects

Assessment of multiple discrete cracklike flaws is one of the most common problems relating to pressure vessels and piping components. Under the current fitness for service (FFS) rules, such as ASME, BS, and so on, multiple cracklike flaws are usually recharacterized as an enveloping crack (defined as a single larger crack), following their assessment rules. The procedure, however, varies significantly in these FFS codes. In this paper, the interaction between nonaligned multiple unequal cracks is clarified by applying the body force method. Based on the interaction that indicates the magnification and shielding effects and the reference stress solutions, a newly developed assessment procedure for multiple discrete cracklike flaws in the failure assessment diagram is proposed.

Assessment of Overlapped Internal and External Volumetric Flaws in p-M Diagram

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Shinji Konosu ◽  
Hikaru Miyata
Keyword(s):  
Finite Element ◽  
Cross Section ◽  
Pressure Vessel ◽  
Effective Cross Section ◽  
Finite Element Analyses ◽  
Diagram Method ◽  
Reference Stress ◽  
Common Problems ◽  
Good Agreement

Assessment of overlapped internal and external volumetric flaws is one of the most common problems related to pressure vessel and piping components. Under the current fitness for service rules, such as those provided in ASME, BS, and so on, the procedures for the assessment of these flaws have not yet been defined. In this paper, a reference stress, incorporating the decrease in the effective cross section as a function of flaw depth and flaw angle in a cylinder, has been proposed in order to assess the flaws using the simple p-M (pressure-moment) diagram method. Numerous finite element analyses for a cylinder with overlapped internal and external flaws were conducted to verify the proposed procedure. There is good agreement among them.

Assessment Procedure for Multiple Volumetric Flaws (LTAs) in p-M Diagram

2008 ◽  
Author(s):  
Shinji Konosu
Keyword(s):  
Body Force ◽  
Pressure Vessels ◽  
The Body ◽  
Assessment Procedure ◽  
Multiple Crack ◽  
Force Method ◽  
Reference Stress ◽  
Body Force Method ◽  
Common Problems ◽  
Shielding Effects

Assessment of multiple volumetric flaws (LTAs) is one of the most common problems relating to pressure vessels and piping components. Under the current Fitness for Service (FFS) rules, such as ASME, BS and so on, multiple volumetric flaws are usually recharacterized as an enveloping volumetric flaw (defined as a single larger volumetric flaw) as well as multiple crack-like flaws, following their assessment rules. However, the rules proposed in their codes will not often agree and their justification is unknown. Furthermore, they can provide unrealistic assessment in some cases. In this paper, the interaction between two different sized non-aligned volumetric flaws such as local thin areas (LTAs) is clarified by applying the body force method. Unlike multiple crack-like flaws, the effect of biaxial stresses on the interaction is evident. Based on the interaction which indicates the magnification and shielding effects and reference stress solutions, a new procedure for multiple volumetric flaws is proposed for assessing the flaws in the p-M (pressure-moment) Diagram, which is a simple assessment procedure for vessels with LTAs.

Assessment Procedure for Multiple Crack-Like Flaws in Fracture Assessment Diagram (FAD)

2008 ◽  
Author(s):  
Shinji Konosu
Keyword(s):  
Body Force ◽  
Pressure Vessels ◽  
The Body ◽  
Assessment Procedure ◽  
Multiple Crack ◽  
Reference Stress ◽  
Discrete Crack ◽  
Fracture Assessment ◽  
Common Problems ◽  
Shielding Effects

Assessment of multiple discrete crack-like flaws is one of the most common problems relating to pressure vessels and piping components. Under the current Fitness for Service (FFS) rules, such as ASME, BS and so on, multiple crack-like flaws are usually recharacterized as an enveloping crack (defined as a single larger crack), following their assessment rules. The procedure, however, varies significantly in these FFS codes. In this paper, the interaction between non-aligned multiple unequal cracks is clarified by applying the body force method. Based on the interaction which indicates the magnification and shielding effects and the reference stress solutions, a newly developed assessment procedure for multiple discrete crack-like flaws in the Fracture Assessment Diagram (FAD) is proposed.

Fitness-for-Service Assessment for Pressure Equipment in Japan

2003 ◽  
Author(s):  
Takayasu Tahara
Keyword(s):  
High Pressure ◽  
Pressure Vessel ◽  
Working Group ◽  
Pressure Vessels ◽  
The Other ◽  
Task Group ◽  
Assessment Procedure ◽  
Storage Tanks ◽  
Task Groups ◽  
Petrochemical Industries

Pressure equipment in refinery and petrochemical industries in Japan has been getting old, mostly more than 30 years in operation. Currently, the Japanese regulations for pressure equipment in service are the same as those in existence during the fabrication of the pressure equipment. Accordingly, there is an immediate need for an up to date more advanced “Fitness For Service” (FFS) evaluation requirements for pressure equipment. In order to introduce the latest FFS methodologies to Japanese industries, the High Pressure Institute of Japan (HPI) has organized two task groups. One is a working group for development of a maintenance standard for non-nuclear industries. Its prescribed code “Assessment procedure for crack-like flaws in pressure equipment” is for conducting quantitative safety evaluations of flaws detected in common pressure equipment such as pressure vessels, piping, storage tanks. The other is a special task group to study of API RP579 from its drafting stage as a member of TG579. The FFS Handbook, especially for refinery and petrochemical industries, has been developed based on API RP579 with several modifications to meet Japanese pressure vessel regulations on April 2001. [1] It is expected that both the Standard and FFS handbook will be used as an exemplified standard with Japanese regulations for practical maintenance. This paper presents concepts of “Assessment procedure for crack-like flaws in pressure equipment” HPIS Z101, 2001 [2].

A Reinforcement Design Method Based on Analysis of Large Openings in Cylindrical Pressure Vessels

1996 ◽  
Vol 118 (4) ◽  
pp. 502-506 ◽  
Author(s):  
M. D. Xue ◽  
K. C. Hwang ◽  
W. Lu¨ ◽  
W. Chen
Keyword(s):  
Fourier Series ◽  
Present Method ◽  
Fourier Coefficients ◽  
Design Method ◽  
Large Diameter ◽  
Pressure Vessels ◽  
Diameter Ratio ◽  
Cylindrical Coordinates ◽  
Reinforcement Design ◽  
Good Agreement

The analytical solution is given for two orthogonally intersecting cylindrical shells with large diameter ratio d/D subjected to internal pressure. The modified Morley equation is used for the shell with cutout and the Love equation for the tube with nonplanar end. The continuity conditions of forces and displacements at the intersection are expressed in 3-D cylindrical coordinates (ρ, θ, z), and are expanded in Fourier series of θ. The Fourier coefficients are obtained by numerical quadrature. The present results are in good agreement with those obtained by tests and by FEM for ρ0 = d/D ≤ 0.8. The typical curves of SCF versus t/T and d/DT and reinforcement coefficients g, h versus D/T0 for each ρ0 are given on the present method.

Validity of Assessment Procedure in p-M Method for Multiple Volumetric Flaws

2008 ◽  
Author(s):  
Shinji Konosu ◽  
Masato Kano ◽  
Norihiko Mukaimachi ◽  
Shinichiro Kanamaru
Keyword(s):  
Internal Pressure ◽  
Yield Stress ◽  
Bending Moment ◽  
Pressure Vessels ◽  
Assessment Procedure ◽  
Plastic Collapse ◽  
Storage Tanks ◽  
Collapse Load ◽  
The Status ◽  
Single Flaw

General components such as pressure vessels, piping, storage tanks and so on are designed in accordance with the construction codes based on the assumption that there are no flaws in such components. There are, however, numerous instances in which in-service single or multiple volumetric flaws (local thin areas; volumetric flaws) are found in the equipment concerned. Therefore, it is necessary to establish a Fitness for Service (FFS) rule, which is capable of judging these flaws. The procedure for a single flaw or multiple flaws has recently been proposed by Konosu for assessing the flaws in the p–M (pressure-moment) Diagram, which is an easy way to visualize the status of the component with flaws simultaneously subjected to internal pressure, p and external bending moment, M due to earthquake, etc. If the assessment point (Mr, pr) lies inside the p–M line, the component with flaws is judged to be safe. In this paper, numerous experiments and FEAs for a cylinder with external multiple volumetric flaws were conducted under (1) pure internal pressure, (2) pure external bending moment, and (3) subjected simultaneously to both internal pressure and external bending moment, in order to determine the plastic collapse load at volumetric flaws by applying the twice-elastic slope (TES) as recommended by ASME. It has been clarified that the collapse (TES) loads are much the same as those calculated under the proposed p–M line based on the measured yield stress.

Estimation of Through-Wall Cracking Frequency of RPV Under PTS Events Using PFM Analysis Method for Identifying Conservatism Included in Current Japanese Code

2014 ◽  
Author(s):  
Kazuya Osakabe ◽  
Koichi Masaki ◽  
Jinya Katsuyama ◽  
Genshichiro Katsumata ◽  
Kunio Onizawa
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Crack Initiation ◽  
Structural Integrity ◽  
Probabilistic Approach ◽  
Pressure Vessels ◽  
Assessment Procedure ◽  
Analysis Method ◽  
Integrity Assessment ◽  
The U.S

To assess the structural integrity of reactor pressure vessels (RPVs) during pressurized thermal shock (PTS) events, the deterministic fracture mechanics approach prescribed in Japanese code JEAC 4206-2007 [1] has been used in Japan. The structural integrity is judged to be maintained if the stress intensity factor (SIF) at the crack tip during PTS events is smaller than fracture toughness KIc. On the other hand, the application of a probabilistic fracture mechanics (PFM) analysis method for the structural reliability assessment of pressure components has become attractive recently because uncertainties related to influence parameters can be incorporated rationally. A probabilistic approach has already been adopted as the regulation on fracture toughness requirements against PTS events in the U.S. According to the PFM analysis method in the U.S., through-wall cracking frequencies (TWCFs) are estimated taking frequencies of event occurrence and crack arrest after crack initiation into consideration. In this study, in order to identify the conservatism in the current RPV integrity assessment procedure in the code, probabilistic analyses on TWCF have been performed for certain model of RPVs. The result shows that the current assumption in JEAC 4206-2007, that a semi-elliptic axial crack is postulated on the inside surface of RPV wall, is conservative as compared with realistic conditions. Effects of variation of PTS transients on crack initiation frequency and TWCF have been also discussed.

Integral Mean of Yield Concept Applied to Thermal Hot Spots: Validation of a Level 2 Damage Assessment Method

2018 ◽  
Author(s):  
Henry Kwok ◽  
Simon Yuen ◽  
Jorge Penso
Keyword(s):  
Hot Spots ◽  
Damage Assessment ◽  
Hot Spot ◽  
Load Capacity ◽  
Assessment Method ◽  
Pressure Vessels ◽  
Assessment Procedure ◽  
Element Analysis ◽  
Level 3 ◽  
Level 2

The overall framework for a Level 2 assessment of local thermal hot spot in pressure vessels was first developed by Seshadri [1]. The assessment procedure invokes the concept of integral mean of yield and the concept on a reference volume to determine the reduction of load capacity caused by hot spot damage. This paper investigates the accuracy of this assessment by comparing the results of the Level 2 assessment with a Level 3 assessment (inelastic finite element analysis). Three examples with varying pressure component and hot spot sizes are considered. The comparison yielded a low variance between the Level 2 and Level 3 assessments with the Level 2 assessment being more conservative.

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