Studies on the behavior of part-through circumferential crack at intrados in elbows under in-plane bending moment

Srivastava, Ankit; Prabhakaran, K.M.; Ghosh, Ashish

doi:10.1016/j.nucengdes.2011.04.042

Cited by 4 publications

(4 citation statements)

References 18 publications

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“…For all sizes Rb/Rm=3 and Rm/t was 5, 6, 7.5, 9, 12, 15, 20 and 25. These choices reflect the sizes of pipeline most applicable to high-pressure environments, such as in the oil, gas and nuclear industries (Srivastava et al, 2011). Table 1 shows detailed information about each elbow.…”

Section: Elbow Size and Modellingmentioning

confidence: 99%

Condition assessment of damaged elbow in subsea pipelines

Lee

Seo

Paik

2016

Ships and Offshore Structures

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The evaluation of the performance of aged structures is essential in the oil and gas industry, where inaccurate predictions of structural performance may lead to significant hazardous consequences. Elbows are critical structures subject to continuous corrosion that can lead to a burst or collapse. It is important to be able to predict both burst strength in continually corroding structures and the behaviour of the structures after critical corrosion takes place. Structural failures due to a significant reduction in wall thickness make it very complicated for pipeline operators to maintain pipeline serviceability. This paper discusses the plastic limit pressure of elbows without defects and with several local thinned areas. Finite element analysis (FEA) and the Goodall formula were used to evaluate the new formula. The results of the FEA show that the limit load of elbows under internal pressure differs with position and depth of damage. An empirical formula for the limit load of elbows with local thinned areas is proposed. Eight sizes of elbow were considered in this study, with Rm/t of 5, 6, 7.5, 9, 12, 15, 20 and 25. This range covers most of the piping used in high-pressure environments, such as nuclear and subsea situations. The method of numerical analysis was validated by experiment and with FEA results from the literature. The results of the study can be applied to both the operation and assessment of pipelines. A formula to predict the maximum burst strength of damaged elbows is presented, which will enable more accurate estimates of the time until pipelines need to be replaced or repaired .

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Section: Elbow Size and Modellingmentioning

confidence: 99%

Condition assessment of damaged elbow in subsea pipelines

Lee

Seo

Paik

2016

Ships and Offshore Structures

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“…The pipeline system is still the most important way to transport an oil and gas to worldwide where the energy demand has been increasing for decade [1]. The transportation of hydrocarbons based to improve the fabrication defects of pipeline which may be among the reasons that lead to cracks.…”

Section: Introductionmentioning

confidence: 99%

“…The transportation of hydrocarbons based to improve the fabrication defects of pipeline which may be among the reasons that lead to cracks. Most cracks have grown from small defects that were showed during operation of piping systems product or weld [1]. The piping system is regularly needed to manufacture the pipeline elbows by bending the length of pipelines to the necessary geometry forms [2].…”

Section: Introductionmentioning

confidence: 99%

Finite element method investigation of geometrical influences of adhesive and patch in the safety for 90° elbow piping system

Gadi

Meriem-Benziane

Bouiadjra³

2019

JMES

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Piping system elbow study is the most important part in all fields of hydrocarbons transportation which presents the behaviour of circumferential crack at elbow extrados. The effect of geometry of adhesive and patch in the crack elbow is important in pipeline safety. This study shows the details for along the direction of the circumferential elbow crack by three dimensional (FEM) which is used to determine the stress intensity factor at 90° elbow for two cases: firstly, without patch and secondly, repaired with composite patch. This method allows to predict the behaviour of cracked elbow through the analysis of crack propagation under the internal different pressures taking into consideration the operating conditions. The geometry and nature of composite patch proved that the increase of patch thickness leads to decrease the SIF from 7 MPa.m 1/2 to 6.15 MPa.m 1/2 . It can be concluded that the repairing by composite materials leads to reduce the stress intensity factor with patch which not only can augment the lifetime of pipeline but also decreasing the costs and the pollution.

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“…[10][11][12] For circumferentially cracked elbows subjected to combined internal pressure and in-plane closing bending, published findings on plastic loads are very limited, which may be ascribed to the complexities contained in solving the problem. The performance of cracked elbows with part-through crack at the intrados under bending moment was investigated by Srivastava et al 13 based on nonlinear (both geometric and material) finite element analysis (FEA) on different sizes of elbows having different crack sizes. Prabhakaran et al 14 conducted nonlinear elastic-plastic FEAs of 90 long radius elbows with a through-wall axial crack at crown under in-plane bending.…”

Section: Introductionmentioning

confidence: 99%

Determination of critical angle of circumferential throughwall crack for structurally distorted 90° pipe bends under bending moment with and without internal pressure

Sumesh

Veerappan

Shanmugam

2017

Proceedings of the Institution of Mechanical Engineers, Part L:

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Throughwall circumferential cracks (TWC) in elbows can considerably minimize its collapse load when subjected to in-plane bending moment. The existing closed-form collapse moment equations do not adequately quantify critical crack angles for structurally distorted cracked pipe bends subjected to external loading. Therefore, the present study has been conducted to examine utilizing elastic-plastic finite element analysis, the influence of structural distortions on the variation of critical TWC of 90° pipe bends under in-plane closing bending moment without and with internal pressure. With a mean radius ( r) of 50 mm, cracked pipe bends were modeled for three different wall thickness, t (for pipe ratios of r/ t = 5,10,20), each with two different bend radius, R (for bend ratios of R/r = 2,3) and with varying degrees of ovality and thinning (0 to 20% with increments of 5%). Finite element analyses were performed for two loading cases namely pure in-plane closing moment and in-plane closing bending with internal pressure. Normalized internal pressures of 0.2, 0.4, and 0.6 were applied. Results indicate the modification in the critical crack angle due to the pronounced effect of ovality compared to thinning on the plastic loads of pipe bends. From the finite element results, improved closed-form equations are proposed to evaluate plastic collapse moment of throughwall circumferential cracked pipe bends under the two loading conditions.

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Studies on the behavior of part-through circumferential crack at intrados in elbows under in-plane bending moment

Cited by 4 publications

References 18 publications

Condition assessment of damaged elbow in subsea pipelines

Condition assessment of damaged elbow in subsea pipelines

Finite element method investigation of geometrical influences of adhesive and patch in the safety for 90° elbow piping system

Determination of critical angle of circumferential throughwall crack for structurally distorted 90° pipe bends under bending moment with and without internal pressure

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