Prediction of Collapse Stress for Pipes With Arbitrary Multiple Circumferential Surface Flaws

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
Yinsheng Li ◽  
Kunio Hasegawa ◽  
Kunio Onizawa ◽  
Nathaniel G. Cofie
Keyword(s):  
Stainless Steel ◽  
Nuclear Power ◽  
Numerical Solutions ◽  
Estimation Method ◽  
Limit Load ◽  
Arbitrary Distribution ◽  
Piping System ◽  
Load Estimation ◽  
As Stress ◽  
Steel Piping

When a flaw is detected in a stainless steel piping system of a nuclear power plant during in-service inspection, the limit load estimation method provided in codes such as ASME Section XI or JSME S NA-1-2008 can be applied to evaluate the integrity of the pipe. However, in the current editions of these codes, a limit load estimation method is only provided for pipes containing a single flaw. Independent multiple flaws, such as stress corrosion cracks, have actually been detected in the same plane of stainless steel piping systems. In this paper, a failure estimation method by formula is proposed for any number and arbitrary distribution of multiple independent circumferential flaws in the same plane of a pipe. Using the proposed method, numerical solutions are compared with experimental results to validate the model, and several numerical examples are provided to show its effectiveness.

Fracture Estimation Method for Pipe With Multiple Circumferential Surface Flaws

2009 ◽  
Author(s):  
Yinsheng Li ◽  
Kunio Hasegawa ◽  
Kunio Onizawa ◽  
Masayoshi Shimomoto
Keyword(s):  
Stainless Steel ◽  
Nuclear Power ◽  
Numerical Solutions ◽  
Estimation Method ◽  
Arbitrary Distribution ◽  
Piping System ◽  
Piping Systems ◽  
Asme Code ◽  
As Stress ◽  
Steel Piping

When a flaw is detected in a stainless steel piping system of a nuclear power plant during in-service inspection, the fracture estimation method provided in the codes such as the ASME Code Section XI or the JSME S NA-1-2004 can be applied to evaluate the integrity of the pipe. However, in these current codes, the fracture estimation method is only provided for the pipe containing a single flaw, although independent multiple flaws such as stress corrosion cracks have actually been detected in the same circumference of stainless steel piping systems. In this paper, a fracture estimation method is proposed by formula for multiple independent circumferential flaws with any number and arbitrary distribution in the same circumference of the pipe. Using the proposed method, the numerical solutions are compared with the experimental results to verify its validity, and several numerical examples are provided to show its effectiveness.

Fracture Assessment of Austenitic Stainless Steel Piping With Multiple Flaws in Heat-Affected Zone

2010 ◽  
Author(s):  
Chihiro Narazaki ◽  
Toshiyuki Saito ◽  
Masao Itatani ◽  
Takuya Ogawa ◽  
Takao Sasayama
Keyword(s):  
Stainless Steel ◽  
Heat Affected Zone ◽  
Nuclear Power ◽  
Power Plants ◽  
Estimation Method ◽  
Limit Load ◽  
Low Carbon ◽  
Fracture Assessment ◽  
Steel Piping ◽  
Weld Heat

Stress corrosion cracking (SCC) has been observed as circumferential multiple flaws in the weld heat-affected zone of primary loop recirculation system piping and core shrouds made of low carbon stainless steel. In the Japan Society of Mechanical Engineers code, Rules on Fitness-for-Service for Nuclear Power Plants, there is no fracture assessment of piping with multiple flaws which are not subject to flaw combination rule criteria. Through fracture testing of piping with two circumferential flaws in the weld heat-affected zone, the limit load estimation method was used for fracture assessment of stainless steel piping.

Experimental Investigation on the Limit Load Estimation Method for Pipes Containing a Circumferential Surface Flaw With Complicated Shape

2011 ◽  
Author(s):  
Yinsheng Li ◽  
Kunio Hasegawa ◽  
Naoki Miura ◽  
Katsuaki Hoshino
Keyword(s):  
Stainless Steel ◽  
Nuclear Power ◽  
Power Plants ◽  
Estimation Method ◽  
Limit Load ◽  
Surface Flaw ◽  
Experimental Results ◽  
Load Estimation ◽  
Bending Moments ◽  
Steel Pipes

When a flaw is detected in the stainless steel pipes at nuclear power plants during in-service inspections, the limit load estimation method provided in the codes such as JSME Rules on Fitness-for-Service for Nuclear Power Plants or ASME Boiler and Pressure Vessel Code Section XI can be applied to evaluate the integrity of the flawed pipe. However, in these current codes, the limit load estimation method is only derived for pipes containing a flaw with uniform depth, although many flaws with complicated shapes, such as stress corrosion cracks, have actually been detected in pipes. In order to evaluate the integrity of the flawed pipes in a more rational way, a limit load estimation method has been proposed by authors considering the complicated circumferential surface flaw in its shape. In this study, failure bending experiments are performed for stainless steel pipes containing a circumferential surface flaw with a complicated asymmetrical shape. The proposed method is verified by comparing with experimental results of failure bending moments obtained in this study and in previous experiments. It is observed that the predicted failure bending moments by the proposed method are consistent with the experimental results, and the proposed method is applicable to estimate the realistic load-carrying capacity of flawed pipes.

Experimental Investigation on Failure Estimation Method for Circumferentially Cracked Pipes Subjected to Combined Bending and Torsion Loads

2013 ◽  
Author(s):  
Yinsheng Li ◽  
Kunio Hasegawa ◽  
Michiya Sakai ◽  
Shinichi Matsuura ◽  
Naoki Miura
Keyword(s):  
Experimental Investigation ◽  
Pressure Vessel ◽  
Nuclear Power ◽  
Power Plants ◽  
Structural Integrity ◽  
Estimation Method ◽  
Bending Moment ◽  
Limit Load ◽  
Piping System ◽  
Torsion Moment

When a crack is detected in a nuclear piping system during in-service inspections, the failure estimation method provided in codes such as the ASME Boiler and Pressure Vessel Code Section XI or JSME Rules on Fitness-for-Service for Nuclear Power Plants can be applied to evaluate the structural integrity of the cracked pipe. In the current codes, the failure estimation method for circumferentially cracked pipes includes bending moment and axial force due to pressure. Torsion moment is not considered. The Working Group on Pipe Flaw Evaluation for the ASME Boiler and Pressure Vessel Code Section XI is developing guidance for combining torsion load within the existing solutions provided in Appendix C for bending and pressure loadings on a pipe. A failure estimation method for circumferentially cracked pipes subjected to general loading conditions including bending moment, internal pressure and torsion moment with general magnitude has been proposed based on analytical investigations on the limit load for cracked pipes. In this study, experimental investigation was conducted to confirm the applicability of the proposed failure estimation method. Experiments were carried out on 8-inch diameter Schedule 80 stainless steel pipes containing a circumferential surface crack. Based on the experimental results, the proposed failure estimation method was confirmed to be applicable to cracked pipes subjected to combined bending and torsion moments.

Experimental Investigation on the Failure Estimation Method of Cracked Cylinders Subjected to Multi-Axial Loads

2011 ◽  
Author(s):  
Yinsheng Li ◽  
Kunio Hasegawa ◽  
Naoki Miura ◽  
Katsuaki Hoshino
Keyword(s):  
Stainless Steel ◽  
Nuclear Power ◽  
Power Plants ◽  
Estimation Method ◽  
Bending Moment ◽  
Limit Load ◽  
Analytical Investigation ◽  
Failure Behavior ◽  
Axial Loads ◽  
Torsion Moment

When a crack is detected in a stainless steel pipe during in-service inspections, the failure estimation method given in the codes such as ASME Boiler and Pressure Vessel Code Section XI or JSME Rules on Fitness-for-Service for Nuclear Power Plants can be applied to evaluate the integrity of the cracked pipe. In the current codes, the failure estimation method considers the bending moment and axial force due to pressure. The torsion moment is assumed to be relatively small and is not considered in the method. Recently, an analytical investigation has been carried out by several of our authors on the limit load considering multi-axial loads including torsion, and a failure estimation method for combined bending moment, torsion moment and internal pressure is proposed. In this study, to investigate the failure behavior of cracked pipes subjected to multi-axial loads, including the torsion, and to provide experimental support for the failure estimation method, experiments were carried out on small sized stainless steel cylinders containing a circumferential surface and a through-wall crack, taking into consideration the combined tensile and torsion loads. Based on the experimental results, the proposed failure estimation method is verified for cracked pipes subjected to multi-axial loads.

Experimental Investigation of Failure Estimation Method for Circumferentially Cracked Pipes Subjected to Combined Bending and Torsion Moments

2014 ◽  
Vol 137 (2) ◽  
Author(s):  
Yinsheng Li ◽  
Kunio Hasegawa ◽  
Michiya Sakai ◽  
Shinichi Matsuura ◽  
Naoki Miura
Keyword(s):  
Experimental Investigation ◽  
Nuclear Power ◽  
Power Plants ◽  
Structural Integrity ◽  
Estimation Method ◽  
Bending Moment ◽  
Limit Load ◽  
Estimation Methods ◽  
Piping System ◽  
Steel Pipes

When a crack is detected in a nuclear piping system during in-service inspections, failure estimation method provided in codes such as ASME Boiler and Pressure Vessel Code Section XI or JSME Rules on Fitness-for-Service for Nuclear Power Plants can be applied to evaluate the structural integrity of the cracked pipe. In the current codes, the failure estimation method for circumferentially cracked pipes is applicable for both bending moment and axial force due to pressure. Torsion moment is not considered. Recently, two failure estimation methods for circumferentially cracked pipes subjected to combined bending and torsion moments were proposed based on analytical investigations on the limit load for cracked pipes. In this study, experimental investigation was conducted to confirm the applicability of the failure estimation method for cracked pipes subjected to bending and torsion moments. Experiments were carried out on 8-in. diameter Schedule 80 stainless steel pipes containing a circumferential surface crack. Based on the experimental results, the proposed failure estimation methods were confirmed to be applicable to cracked pipes subjected to combined bending and torsion moments.

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.

Research on Ultrasonic Inspection of Cast Austenitic Stainless Steel Piping

2012 ◽  
Author(s):  
Kazunobu Sakamoto ◽  
Takashi Furukawa ◽  
Ichiro Komura ◽  
Yoshinori Kamiyama ◽  
Tsuyoshi Mihara
Keyword(s):  
Stainless Steel ◽  
Wave Propagation ◽  
Austenitic Stainless Steel ◽  
Ultrasonic Wave ◽  
Research Program ◽  
Ultrasonic Inspection ◽  
Piping System ◽  
Pressurized Water ◽  
Ultrasonic Wave Propagation ◽  
Steel Piping

Japan Nuclear Energy Safety Organization (JNES) has been carrying out the research program entitled “Nondestructive Inspection Technologies for the Cast Stainless Steel Piping” since 2009FY to comprehend the unique ultrasonic wave propagation in the Cast Austenitic Stainless Steel (CASS) and to confirm detection and sizing capability for cracks in the material by currently available ultrasonic testing techniques. The research is also intended to provide inspection staff with the fundamental information of ultrasonic wave propagation in CASS, for educational purpose. In this research program, specimens whose material, size, dimension and welding method are identical to the main coolant piping system in Japanese pressurized water reactors (PWRs) are examined. Results from the study on the capability for inspection of CASS and the unique wave propagation phenomena such as beam skewing are discussed in this paper.

Effect of Circumferential Location of Local Wall Thinning Defect on the Collapse Moment of Elbow

2006 ◽  
Author(s):  
Jin Weon Kim ◽  
Yeon Soo Na ◽  
Chi Yong Park
Keyword(s):  
Carbon Steel ◽  
Internal Pressure ◽  
Nuclear Power ◽  
Three Dimensional ◽  
Piping System ◽  
Main Concern ◽  
Wall Thinning ◽  
Bending Load ◽  
Local Wall Thinning ◽  
Steel Piping

Local wall-thinning due to flow-accelerated corrosion is one of the degradation mechanisms of carbon steel piping in nuclear power plant (NPP). It is a main concern in carbon steel piping systems in terms of the safety and operability of the NPP. Recently, the integrity of piping components containing local wall-thinning has become more important for maintaining the reliability of a nuclear piping system, and has been the subject of several studies. However, although wall-thinning in pipe bends and elbows has been frequently reported, its effect on the integrity of pipe bends and elbows has not yet been systematically investigated. Thus, the purpose of this study was to investigate the effect of the circumferential location of a local wall-thinning defect on the collapse behavior of an elbow. For this purpose, the present study used three-dimensional finite element analyses on a 90-degree elbow containing local wall-thinning at the crown of the bend region and evaluated the collapse moment of the wall-thinned elbow under various thinning geometries and loading conditions. The combined internal pressure and bending loads were considered as an applied load. Internal pressure of 0∼20 MPa and both closing-and opening-mode bending were applied. The results of the analyses showed that a reduction in the collapse moment of the elbow due to local wall-thinning was more significant when a defect was located at the crown than when a defect was located at the intrados and extrados. Also, the effect of the internal pressure on the collapse moment depended on the circumferential location of the thinning defect and mode of the bending load.

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