Effect of Torsion on Collapse Bending Moment for 24-Inch Diameter Schedule 80 Pipes With Wall Thinning

2012 ◽  
Author(s):  
Kunio Hasegawa ◽  
Yinsheng Li ◽  
Bostjan Bezensek ◽  
Phuong Hoang
Keyword(s):  
Power Plants ◽  
Bending Moment ◽  
Combined Loading ◽  
Bending Moments ◽  
Compressive Stresses ◽  
Wall Thinning ◽  
Nominal Thickness ◽  
Calculation Results ◽  
Loading Modes ◽  
Local Wall Thinning

Piping items in power plants may experience combined bending and torsion moments during operation. Currently, there is a lack of guidance in the ASME B&PV Code Section XI for combined loading modes including pressure, torsion and bending. Finite element analyses were conducted for 24-inch diameter Schedule 80 pipes with local wall thinning subjected to tensile and compressive stresses. Plastic collapse bending moments were calculated under constant torsion moments. From the calculation results, it can be seen that collapse bending moment for pipes with local thinning subjected to tensile stress is smaller than that subjected to compressive stress. In addition, equivalent moment is defined as the root the sum of the squares of the torsion and bending moments. It is found that the equivalent moments can be approximated with the pure bending moments, when the wall thinning length is equal or less than 7.73R·t for the wall thinning depth of 75% of the nominal thickness, where R is the mean radius and t is the wall thickness of the pipe.

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

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.

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.

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.

Testing of Elastic Stresses and Limit Close-Bending Moments of Reducer Bends Subject to In-Plane Close-Bending Moments

2013 ◽  
Vol 838-841 ◽  
pp. 2236-2241 ◽  
Author(s):  
Sun Yi Chen ◽  
Si Hong Chen
Keyword(s):  
Neutral Line ◽  
Circumferential Stress ◽  
Bending Moment ◽  
Inside Surface ◽  
Tension Stress ◽  
Bending Moments ◽  
Element Analysis ◽  
Elastic Stresses ◽  
Compressive Stresses ◽  
Calculation Results

Elastic stresses and limit close-bending moments of reducing elbows subject to in–plane close-bending moments were validated by limit element analysis (LMA) and testing. Results of LMA show that if the end bend moment M acts on small end while the large end is fixed, the largest movement acts on neutral line near the larger end, and large circumferential stress lies on inside surface near neutral lines but deflect to intrados of large end. For the same model, if the end bend moment M acts on large end while the small end is fixed, the largest movement acts on near the small end and lies on neutral line, and larger stress acts on small end and nearby. Results of testing show that stress character in tension stress and compressive stresses are consistent with the calculation results from formula. The limit bending moment calculation results from formula of reducing elbow is conservative, but is consistent with the formula of the limit bending moment, which is controlled by small end of reducing elbow.

Application of Laser-Generated Ultrasound for Evaluation of Thickness Reduction in Carbon Steel Pipes

2006 ◽  
Vol 321-323 ◽  
pp. 743-746 ◽  
Author(s):  
Jong Ho Park ◽  
Joon Hyun Lee ◽  
Gyeong Chul Seo ◽  
Sang Woo Choi
Keyword(s):  
Carbon Steel ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Guided Wave ◽  
Thickness Reduction ◽  
Steel Pipes ◽  
Time Frequency ◽  
Wall Thinning ◽  
Local Wall Thinning

In carbon steel pipes of nuclear power plants, local wall thinning may result from erosion-corrosion or flow-accelerated corrosion(FAC) damage. Local wall thinning is one of the major causes for the structural fracture of these pipes. Therefore, assessment of local wall thinning due to corrosion is an important issue in nondestructive evaluation for the integrity of nuclear power plants. In this study, laser-generated ultrasound technique was employed to evaluate local wall thinning due to corrosion. Guided waves were generated in the thermoelastic regime using a Q-switched pulsed Nd:YAG laser with a linear slit array. . In this paper, time-frequency analysis of ultrasonic waveforms using wavelet transform allowed the identification of generated guided wave modes by comparison with the theoretical dispersion curves. Modes conversion and group velocity were employed to detect thickness reduction.

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.

Development of Engineering Formulae for Stress Concentration Factors of Local Wall Thinning in CANDU Feeder Pipe Under Pressure

2011 ◽  
Author(s):  
Jong Sung Kim ◽  
Jae Seok Seo
Keyword(s):  
Stress Concentration ◽  
Power Plants ◽  
Degradation Mechanism ◽  
Peak Stress ◽  
Design Stage ◽  
Fatigue Assessment ◽  
Wall Thinning ◽  
Concentration Factors ◽  
Stress Concentration Factors ◽  
Local Wall Thinning

Feeder pipes that connect the inlet and outlet headers with the in-reactor fuel channels in CANDU nuclear power plants are considered as safety Class 1 piping items. Therefore, fatigue of the feeder pipes should be assessed at design stage in order to verify structural integrity during design lifetime. In accordance with the fatigue assessment result, cumulative usage factors of some feeder pipes have significant values. An active degradation mechanism for the outlet feeder piping made of SA-106 Grade B carbon steel is local wall thinning due to flow-accelerated corrosion. This local wall thinning can cause increase of peak stress due to stress concentration by notch effect. The increase of peak stress results in increase of the cumulative usage factor. However, present fatigue assessment doesn’t consider the stress concentration due to the local wall thinning. Therefore, it is necessary to assess the effect of local wall thinning on the stress concentration. This study developed the engineering formulae for stress concentration factors of the local wall thinning in the CANDU feeder pipe under internal pressure by using the engineering procedure of Kinectrics Co.. Finally, the developed formulae were applied to the elbow feeder pipes and compared with the finite element analysis results. As a result of comparison, it is identified that the engineering formulae is valid.

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.

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