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.

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.

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

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.

Analysis of 4” Schedule 160 Pipe With a Wall Thinning Subject to Torsion, Bending and Pressure Loads

2012 ◽  
Author(s):  
Bostjan Bezensek
Keyword(s):  
Pressure Vessel ◽  
Axial Loads ◽  
Modes Of Failure ◽  
Ellipsoidal Shape ◽  
Wall Thinning ◽  
Planar Wall ◽  
Planar Crack ◽  
Current Guidance ◽  
Bending Loading ◽  
Local Wall Thinning

Pipes with local wall thinning can be simultaneously subject to multi-axial loads such as the internal pressure loads, axial loads, bending and torsion (twist) moments. Continued operation of such items makes use of fitness-for-service assessments using codes such as the ASME Boiler and Pressure vessel Code, Section XI. Currently the non-mandatory Appendix C of the Code gives guidance for performing assessment for various modes of failure. However in the current guidance there is no provision for inclusion of the torsion loads for either planar (crack) or non-planar (wall thinning) type flaws under predominant membrane and bending loading. This paper is a continuation of the study reported at the earlier PVP conferences, whereby the intent is to provide guidance on inclusion of small amounts of torsion with the dominant pressure and bending loading for a pipe containing a wall thinning. In this paper the results are reported for a 4″ (100mm) nominal diameter Schedule 160 pipe. Two shapes of the wall thinning are examined; a cylindrical with round edges and an ellipsoidal shape. These are chosen to span a range of real shapes. The limits on the applicability of the equivalent moment, defined as the root of the sum of the squares (RSS) in construction codes is presented in terms of the wall thinning dimensions.

Low Cycle Fatigue Behavior and Seismic Assessment for Elbow Pipe Having Local Wall Thinning

2010 ◽  
Author(s):  
Yoshio Urabe ◽  
Koji Takahashi ◽  
Kotoji Ando
Keyword(s):  
Fatigue Crack ◽  
Pipe Wall ◽  
Low Cycle Fatigue ◽  
Safety Margin ◽  
Seismic Loading ◽  
Cycle Fatigue ◽  
Wall Thinning ◽  
Erosion Corrosion ◽  
Technical Issues ◽  
Local Wall Thinning

One of the concerned technical issues in the nuclear piping under operation is pipe wall thinning caused by flow accelerated corrosion. Recently it has been reported that the elbow section is more suspicious on pipe wall thinning by erosion-corrosion. Some researchers including authors have been studied static and fatigue strength of elbows with local wall thinning. However, still more experiment and analysis data are needed to clarify the technical issues. Accordingly, further experiments and their evaluations were carried out by the authors. This paper presents the influences of size and location on fatigue life. Also as one of the application of the test results, safety margin of elbows with wall thinning against seismic loading is discussed. Low cycle fatigue tests were conducted using elbow specimens made of STPT410 steel with local wall thinning. The local wall thinning was machined on the inside of elbow specimens in order to simulate erosion/corrosion metal loss. The local wall thinning areas were located at three different areas, called extrados, crown and intrados. Eroded ratio (eroded depth/wall thickness) is 0.5 and 0.8 and eroded angle is 90deg. and 180deg..The elbow specimens were subjected to cyclic in-plane bending under displacement control (±20mm) without and with internal pressure of 3MPa. Obtained main conclusions are shown bellow. (1) Existence of local wall thinning in extrados does not have an important effect on fatigue life. Especially, fatigue crack does not initiate at the extrados where the extreme local wall thinning exists (eroded ratio = 0.8 and eroded angle = 180 deg.). (2) Regardless of existence of internal pressure, fatigue crack initiates at the crown where local wall thinning does not exist. (3) Even if the eroded ratio and the eroded angle reached up to 0.8 and 180 deg., the elbows with local wall thinning have high safety margin against seismic loading, comparing to ASME Boiler and Pressure Vessel Code Sec. III allowable seismic stress criteria.

scholarly journals Special Phased Array Applications for Pipeline Girth Weld Inspections

2006 ◽  
Author(s):  
Michael Moles ◽  
Simon Labbe´
Keyword(s):  
Wall Thickness ◽  
Temperature Compensation ◽  
Phased Array ◽  
Phased Arrays ◽  
Pipe Wall ◽  
Small Diameter ◽  
Thin Wall ◽  
Seamless Pipe ◽  
Pipe Wall Thickness ◽  
Girth Welds

Ultrasonic phased arrays present major improvements over conventional multiprobe ultrasonics for inspecting pipeline girth welds, both for onshore and for offshore use. Probe pans are lighter and smaller, permitting less cutback; scans are quicker due to the smaller probe pan; phased arrays are considerably more flexible for changes in pipe dimensions or weld profiles, and for different scan patterns. More important, some of the potential advantages of phased arrays are now becoming commercially available. These include: • Compensating for variations in seamless pipe wall thickness. • Wedge temperature compensation. • Improved focusing for thick and thin wall inspections. • Premium inspections for risers, tendons and other components. • Small diameter pipes. • Multiple displays. • Clad pipe. The paper describes the latest phased array UT results for special applications.

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.

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.

Low Cycle Fatigue Behavior and Seismic Assessment for Elbow Pipe Having Local Wall Thinning

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Yoshio Urabe ◽  
Koji Takahashi ◽  
Kotoji Ando
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Pipe Wall ◽  
Low Cycle Fatigue ◽  
Safety Margin ◽  
Seismic Loading ◽  
Crack Penetration ◽  
Wall Thinning ◽  
Technical Issues ◽  
Local Wall Thinning

One of the concerned technical issues in the nuclear piping under operation is pipe wall thinning caused by flow accelerated corrosion. Recently, it has been reported that the elbow section is more suspicious on pipe wall thinning by erosion–corrosion. Some researchers including authors have been studied static and fatigue strength of elbows with local wall thinning. However, still more experiment and analysis data are needed to clarify the technical issues. Accordingly, further experiments and their evaluations were carried out by the authors. This paper presents the influences of size and location on fatigue life. Also as one of the application of the test results, safety margin of elbows with wall thinning against seismic loading is discussed. Low cycle fatigue tests were conducted using elbow specimens made of STPT410 steel with local wall thinning. The local wall thinning was machined on the inside of elbow specimens in order to simulate erosion/corrosion metal loss. The local wall thinning areas were located at three different areas, called extrados, crown, and intrados. Eroded ratio (eroded depth/wall thickness) is 0.5 and 0.8 and eroded angle is 90 deg and 180 deg. The elbow specimens were subjected to cyclic in-plane bending under displacement control (±20 mm) without and with internal pressure of 3 MPa using a universal testing machine. Fatigue life was defined as fatigue crack penetration through the thickness and crack penetration was watched by naked eyes during the test through the protection window made of a transparent plastic plate. Obtained main conclusions are as follows: (1) Existence of local wall thinning in extrados does not have an important effect on fatigue life. Especially, fatigue crack does not initiate at the extrados where the extreme local wall thinning exists (eroded ratio = 0.8 and eroded angle = 180 deg). (2) Regardless of existence of internal pressure, fatigue crack initiates at the crown where local wall thinning does not exist for an elbow with local wall thinning at extrados. This conclusion should be confirmed using eroded elbow specimens under more high pressure. (3) Even if the eroded ratio and the eroded angle reached up to 0.8 and 180 deg, the elbows with local wall thinning have high safety margin against seismic loading, comparing to ASME Boiler and Pressure Vessel Code Section 3 allowable seismic stress criteria.

Application Scope of Limit Load Criterion for Ductile Material Pipes With Circumferentially External Cracks

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Kunio Hasegawa ◽  
Yinsheng Li ◽  
Valery Lacroix ◽  
Vratislav Mares
Keyword(s):  
Pipe Wall ◽  
Internal Surface ◽  
Limit Load ◽  
Ductile Material ◽  
Plastic Collapse ◽  
Surface Cracks ◽  
Pipe Wall Thickness ◽  
Asme Code ◽  
Bending Capacity ◽  
New Equation

Abstract Bending stress at plastic collapse for a circumferentially cracked pipe is predicted by limit load criterion provided by the Appendix C of the ASME Code Section XI. The equation of the Appendix C is applicable for pipes with both external and internal surface cracks. On the other hand, the authors have developed a more precise equation taking into account the pipe mean radii at noncracked area and at cracked ligament area. From the comparison of Appendix C equation and the new equation, the plastic collapse stress estimated by the Appendix C equation gives about 20% less conservative bending capacity prediction for external cracked pipes with large crack angle and small Rm/t, where Rm is the pipe mean radius and t is the pipe wall thickness. This paper discusses the limitation scope to use the limit load criterion of the Appendix C equation.

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