Interaction and Assessment of Multiple Local Wall Thinning Defects

2013 ◽  
Author(s):  
Jian Peng ◽  
Changyu Zhou ◽  
Qiao Dai
Keyword(s):  
Critical Stress ◽  
Safety Assessment ◽  
Load Condition ◽  
Assessment Method ◽  
Relative Depth ◽  
Finite Element Analyses ◽  
Pure Bending ◽  
Defect Assessment ◽  
Wall Thinning ◽  
Local Wall Thinning

The safety assessment of pipes with multiple local wall thinning defects (LWTs) is systematically investigated by finite element analyses (FEA) with special attention to the interaction of multiple LWTs. It is interesting that the arrangement of LWTs (axial arrangement and circumferential arrangement), the load condition (pure pressure, pure bending and complicated load) and the relative depth play important roles in the interaction of multiple LWTs. The effective stress area and critical stress can be used to explain their influences. Moreover, existing assessment methods of multiple LWTs in some defect assessment standards such as API 579/ASME FFS, ASME B31G, BS 7910 and GB 19624 are reviewed. It’s noticed that the influences of arrangement, load condition and relative depth are ignored in existing standard methods, but they can influence the assessment results significantly. In order to consider these issues, an improved assessment of multiple LWTs based on API 579/ASME FFS is proposed. This improved assessment method has considered the influences of arrangement, load condition and relative depth, and can give better results.

Technical Basis for Application of Collapse Moments for Locally Thinned Pipes Subjected to Torsion and Bending Proposed for ASME Section XI

2014 ◽  
Author(s):  
Kunio Hasegawa ◽  
Yinsheng Li ◽  
Bostjan Bezensek ◽  
Phuong H. Hoang ◽  
Howard J. Rathbun
Keyword(s):  
Power Plants ◽  
Bending Moments ◽  
Finite Element Analyses ◽  
Pure Bending ◽  
Plastic Bending ◽  
Evaluation Procedures ◽  
Wall Thinning ◽  
Applicable Range ◽  
Technical Basis ◽  
Local Wall Thinning

Piping components in power plants may experience combined bending and torsion moments during operation. There is a lack of guidance for pipe evaluation for pipes with local wall thinning flaws under the combined bending and torsion moments. ASME B&PV Code Section XI Working Group is currently developing fully plastic bending pipe evaluation procedures for pressurized piping components containing local wall thinning subjected to combined torsion and bending moments. Using elastic fully plastic finite element analyses, plastic collapse bending moments under torsions were obtained for 4 (114.3) to 24 (609.6) inch (mm) diameter pipes with various local wall thinning flaw sizes. The objective of this paper is to introduce an equivalent moment, which combines torsion and bending moments by a vector summation, and to establish the applicable range of wall thinning lengths, angles and depths, where the equivalent moments are equal to pure bending moments.

Inclusion of Torsion With Bending and Pressure Loads for Pipes With Thin-Wall Regions

2011 ◽  
Author(s):  
Bostjan Bezensek ◽  
Yinsheng Li ◽  
Kunio Hasegawa ◽  
Phuong H. Hoang
Keyword(s):  
Pipe Wall ◽  
Plastic Collapse ◽  
Thin Wall ◽  
Finite Element Analyses ◽  
Pure Bending ◽  
Pipe Wall Thickness ◽  
Wall Thinning ◽  
Equivalent Load ◽  
Bending Loading ◽  
Local Wall Thinning

Piping installations may experience local wall thinning under predominant pressure and bending loading with a small amount of torsion loading. Assessment of the remaining pipe integrity must account for all loads and can benefit from resolving the multiaxial loads into an equivalent load. This paper presents results of the finite element analyses of straight pipes containing non-planar flaws (i.e. local wall thinning areas) subject to combination of pressure, bending and torsion. The pressure is 8 MPa and the torsion stresses are limited to 20% of the material’s flow stress. Flaws are introduced into a 4 inch OD pipe with an R/t of 6.64 and 9.36. The incipient plastic collapse moment at a given torsion moment is determined and compared with the plastic collapse moment of the pure bending case. The results show that for flaws with a depth less than 60% of the nominal pipe wall thickness the bending and torsion moments can be combined into an equivalent moment by vector summation (the Root of the Sum of Squares approach). For deeper flaws the effect of pipe and flaw geometry is observed.

Capacity Analysis and Safety Assessment of Polyethylene Pipeline With Local Wall-Thinning Defect

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Weijie Jiang ◽  
Jianping Zhao
Keyword(s):  
Safety Assessment ◽  
Mechanical Performance ◽  
Orthogonal Design ◽  
Bending Moment ◽  
Limit Load ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Assessment Procedure ◽  
Wall Thinning ◽  
Local Wall Thinning

The purpose of this study is to propose a safety assessment procedure for polyethylene (PE) pipe with local wall-thinning defect. A uniaxial tensile test is performed to test the mechanical performance of PE. Then, the constitutive model for PE can be established. The limit load of the PE pipe with local wall-thinning defect can be studied with the method of combining the orthogonal design of experiment and finite element (FE) analysis. Then, the factors of local wall-thinning defect can be analyzed. The results show that the depth of the defect has a great effect on the limit load (internal pressure and bending moment) of PE pipe. The effects that the axial length of the defect and the circumferential length of the defect have on the limit load are not significant. Referring to the safety assessment of metal pipe proposed by GB/T19624-2004, a safety assessment for PE pipe with local wall-thinning defect is revised.

Limit Load Analysis of Elbow with Local Wall Thinning under Combined Loads

2015 ◽  
Vol 750 ◽  
pp. 198-205
Author(s):  
Peng Cui ◽  
Chang Yu Zhou
Keyword(s):  
Safety Assessment ◽  
Bending Moment ◽  
Limit Load ◽  
Orthogonal Experimental Design ◽  
Limit Loads ◽  
Pressure Pipe ◽  
Combined Loads ◽  
Wall Thinning ◽  
Volume Defect ◽  
Local Wall Thinning

The local wall thinning(LWT) is a kind of common volume defect in pressure pipe. The limit loads of elbows with LWT under pressure, bending moment, torque and their combined loads have been studied in detail by orthogonal experimental design and finite element method. The results have shown that the influence of depth and circumferential length of LWT on the limit load is more obvious compared to that of axial length when an elbow is under pressure, bending moment or torque. The change of limit bending moment and torque with the depth of LWT and circumferential length is significant for an elbow under combined bending moment and torque. At last, the safety assessment equations for elbow under combined in-plane closing bending moment and torque were proposed by regression analysis.

Failure Strength Assessment of Pipes With Local Wall Thinning Under Combined Loading Based on Finite Element Analyses

2004 ◽  
Vol 126 (2) ◽  
pp. 179-183 ◽  
Author(s):  
Do-Jun Shim ◽  
Jae-Boong Choi ◽  
Young-Jin Kim
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Nuclear Power ◽  
Bending Moment ◽  
Combined Loading ◽  
Assessment Procedure ◽  
Finite Element Analyses ◽  
Maximum Moment ◽  
Wall Thinning ◽  
Local Wall Thinning

Failure assessment of a pipe with local wall thinning draws increasing attention in the nuclear power plant industry. Although many guidelines have been developed and are used for assessing the integrity of a wall-thinned pipeline, most of these guidelines consider only pressure loading and thus neglect bending loading. As most pipelines in nuclear power plants are subjected to internal pressure and bending moment, an assessment procedure for locally wall-thinned pipeline subjected to combined loading is urgently needed. In this paper, three-dimensional finite element (FE) analyses are carried out to simulate full-scale pipe tests conducted for various shapes of wall-thinned area under internal pressure and bending moment. Maximum moments based on ultimate tensile stress were obtained from FE results to predict the failure of the pipe. These results are compared with test results, showing good agreement. Additional finite element analyses are then performed to investigate the effect of key parameters, such as wall-thinned depth, wall-thinned angle and wall-thinned length, on maximum moment. Moreover, the effect of internal pressure on maximum moment was investigated. Change of internal pressure did not show significant effect on the maximum moment.

Safety assessment of pipes with multiple local wall thinning defects under pressure and bending moment

2011 ◽  
Vol 241 (8) ◽  
pp. 2758-2765 ◽  
Author(s):  
Jian Peng ◽  
Chang-Yu Zhou ◽  
Ji-Lin Xue ◽  
Qiao Dai ◽  
Xiao-Hua He
Keyword(s):  
Safety Assessment ◽  
Bending Moment ◽  
Wall Thinning ◽  
Local Wall Thinning

Evaluation of Torsion and Bending Collapse Moments for Pipes With Local Wall Thinning

2011 ◽  
Author(s):  
Kunio Hasegawa ◽  
Yinsheng Li ◽  
Bostjan Bezensek ◽  
Phuong Hoang
Keyword(s):  
Power Plants ◽  
Bending Moment ◽  
Combined Loading ◽  
Bending Moments ◽  
Pure Bending ◽  
Evaluation Procedures ◽  
Wall Thinning ◽  
Loading Modes ◽  
Bending Fracture ◽  
Local Wall Thinning

ASME B&PV Code Section XI provides fully plastic bending fracture evaluation procedures for pressurized piping components containing flaws subjected to bending and membrane loads. The piping components in power plants may experience only bending moments but also occasionally small torsion moments, simultaneously. Currently, there is a lack of guidance in the Section XI for combined loading modes including torsion. Finite element analyses were conducted in this paper for 24-inch diameter straight pipes with local wall thinning. The pipe was subject to combined bending and torsion moments. It is shown that the effect of torsion moment on plastic collapse bending moment for the pipes depends on the local wall thinning sizes. In addition, it is found that the equivalent moments defined as the root of the sum of the squares (RSS) of the torsion and bending moments is equal to pure bending moments, when wall thinning depth is shallow.

Technical Basis for Application of Collapse Moments for Locally Thinned Pipes Subjected to Torsion and Bending Proposed for ASME Section XI

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Kunio Hasegawa ◽  
Yinsheng Li ◽  
Bostjan Bezensek ◽  
Phuong H. Hoang ◽  
Howard J. Rathbun
Keyword(s):  
Power Plants ◽  
Plastic Collapse ◽  
Bending Moments ◽  
Pure Bending ◽  
Plastic Bending ◽  
Evaluation Procedures ◽  
Wall Thinning ◽  
Applicable Range ◽  
Technical Basis ◽  
Local Wall Thinning

Piping components in power plants may experience combined bending and torsion moments during operation. There is a lack of guidance for pipe evaluation for pipes with local wall-thinning flaws under the combined bending and torsion moments. ASME boiler and pressure vessel (B&PV) Code Section XI Working Group is currently developing fully plastic bending pipe evaluation procedures for pressurized piping components containing local wall thinning subjected to combined torsion and bending moments. Using elastic fully plastic finite element (FE) analyses, plastic collapse bending moments under torsions were obtained for 4 (114.3)–24 (609.6) in. (mm) diameter pipes with various local wall-thinning flaw sizes. The objective of this paper is to introduce an equivalent moment, which combines torsion and bending moments by a vector summation, and to establish the applicable range of wall-thinning lengths, angles, and depths, where the equivalent moments are equal to pure bending collapse moments.

A Novel Safety Assessment Method based on Fault Dependent Matrix

2019 ◽  
Vol 15 (9) ◽  
pp. 2392 ◽  
Author(s):  
Dong Haiyong ◽  
Gu Qingfan ◽  
Wang Guoqing ◽  
Zhai Zhengjun ◽  
Lu Yanhong
Keyword(s):  
Safety Assessment ◽  
Assessment Method
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