Evaluation of Pressurized Cold Bend Pipe Body Tensile Fractures Under Bending Loads

2014 ◽  
Author(s):  
Celal Cakiroglu ◽  
Muntaseer Kainat ◽  
Samer Adeeb ◽  
J. J. Roger Cheng ◽  
Millan Sen
Keyword(s):  
Experimental Study ◽  
Internal Pressure ◽  
Equivalent Plastic Strain ◽  
Vertical Plane ◽  
Steel Grade ◽  
Full Scale ◽  
Cold Bending ◽  
Steel Grades ◽  
Cold Bends ◽  
Full Scale Tests

Cold bending is applied at locations where the pipeline direction has to be changed in a horizontal or vertical plane. The process of cold bending usually results in residual stresses as well as changes in the material properties at the vicinity of the cold bend location which makes the study of the mechanical behaviour of cold bends indispensable. Due to discontinuous permafrost in arctic regions as well as slope instabilities and earthquakes cold bends within pipelines constructed in such locations can be subjected to significant tensile or compressive forces. Experimental studies were carried out by Sen et al [1][2][3]in order to investigate the buckling behaviour of pressurized cold bends. In these experiments the curvature of the cold bend is increased in the presence of a constant internal pressure. In their experimental study a total of 8 full scale tests were conducted with a variety of pipe diameters, diameter to wall thickness ratio and steel grade. In this set of full scale tests one of the pipes with grade X65 failed due to fracture at the extrados after buckling and formation of wrinkles at the intrados[1]. Our previous work [4], [5] on this subject showed the simulations of this case using finite element analysis. These simulations demonstrated that indeed pipe body tensile side fracture can be observed for this particular pipe specification. Whereby the tension side fractures are expected starting from a specific internal pressure level. The simulation results showed that the equivalent plastic strain values at the cold bend extrados increase dramatically starting from a certain level of applied curvature in load cases with an internal pressure higher than a transition value. In this paper the effect of steel grade on this transition from compressive to tensile failure is investigated. Parametric studies are conducted for the entire range of steel grades tested in the experimental study of Sen et al. It is found that there is a linear proportionality between the steel grade and the transition internal pressure for steel grades between X60 and X80.

Finite Element Analysis of Cold Bend Pipes Under Bending Loads

2010 ◽  
Author(s):  
Millan Sen ◽  
Roger Cheng
Keyword(s):  
Finite Element ◽  
Local Buckling ◽  
Vertical Direction ◽  
Element Model ◽  
Element Analysis ◽  
Cold Bending ◽  
Bending Process ◽  
Cold Bends ◽  
Full Scale Tests ◽  
The Right

Cold bends are required in pipelines at locations of changes in horizontal or vertical direction in the right of way. Due to this change of direction, pipeline deformations caused by geotechnical or operational loading conditions tend to accumulate at the site of cold bends. These deformations may become sufficient to cause local buckling at the bend. For pipeline design, it is important to understand the level of deformation that a cold bend can accumulate prior to local buckling so that the strain capacity can be compared to the expected pipeline deformations. Evaluating the buckling strain of cold bends is extremely complex due to the residual stresses, ripples, and material transformations cause by the cold bending process. Accordingly a finite element model was developed herein. This model accounted for the cold bend geometry, initial imperfections, and the material transformations caused by the cold bending process. This model was validated against 7 full scale tests of cold bend pipes that were subjected to bend loading and internal pressure. The global and local behavior of this model exhibited reasonable correlation against the tests.

SELECTION OF BASIC PARAMETERS OF HYDRAULIC SYSTEM OF STAND FOR FULL-SCALE TESTS OF PIPES FOR DURABILITY BY INTERNAL PRESSURE

2021 ◽  
pp. 22-27
Author(s):  
M. E. Goydo ◽  
A. A. Baturin ◽  
V. V. Bodrov ◽  
R. M. Bagautdinov
Keyword(s):  
Internal Pressure ◽  
Hydraulic System ◽  
Test Bench ◽  
Full Scale ◽  
Simple Method ◽  
Basic Parameters ◽  
Full Scale Tests ◽  
The Given ◽  
Consistent Application ◽  
Selection Of

A complex of formulas is presented, the consistent application of which allows, based on the given characteristics of the sinusoidal law of variation of the internal pressure in the test pipe, to calculate and select the main parameters of the hydraulic system of the test bench. An example is given of using a simple method for checking the correctness of the choice made.

Full-Scale Wrinkling Tests and Analyses of Large Diameter Corroded Pipes

1998 ◽  
Author(s):  
Marina Q. Smith ◽  
Daniel P. Nicolella ◽  
Christopher J. Waldhart
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Axial Compression ◽  
Wall Thickness ◽  
Full Scale ◽  
Operating Conditions ◽  
Material Behavior ◽  
Combined Loading ◽  
Longitudinal Bending ◽  
Full Scale Tests

The aging of pipeline infrastructures has increased concern for the integrity of pipelines exhibiting non-perforating wall loss and settlement induced bending. While pressure based guidelines exist which allow pipeline operators to define operational margins of safety against rupture (e.g.; ANSI/ASME B31-G and RSTRENG (Battelle, 1989)), reliable procedures for the prediction of wrinkling in degraded pipes subjected to combined loading are virtually non-existent. This paper describes full-scale testing and finite element investigations performed in support of the development of accurate wrinkling prediction procedures for the Alyeska Pipeline Service Company. The procedures are applicable to corroded pipes subjected to combined loading such as longitudinal bending, internal pressure, and axial compression. During the test program, full-scale 48-inch diameter sections of the trans-Alaska pipeline were subjected to internal pressure and loads designed to simulate longitudinal bending from settlement, axial compression from the transport of hot oil, and the axial restraint present in buried pipe. Load magnitudes were designed based on normal and maximum operating conditions. Corrosion in the pipe section is simulated by mechanically reducing the wall thickness of the pipe. The size and depth of the thinned region is defined prior to each test, and attempts to bound the dimensions of depth, axial length, and hoop length for the general corrosion observed in-service. The analytical program utilizes finite element analyses that include the nonlinear anisotropic material behavior of the pipe steel through use of a multilinear kinematic hardening plasticity model. As in the tests, corrosion is simulated in the analyses by a section of reduced wall thickness, and loads and boundary constraints applied to the numerical model exactly emulate those applied in the full-scale tests. Verification of the model accuracy is established through a critical comparison of the simulated pipe structural behavior and the full-scale tests. Results of the comparisons show good correlation with measurements of the pipe curvature, deflections, and moment capacity at wrinkling. The validated analysis procedure is subsequently used to conduct parameter studies, the results of which complete a database of wrinkling conditions for a variety of corrosion sizes and loading conditions.

Performance Evaluation of High Quality HFW Linepipe by a Series of Full-Scale Pipe Tests

2014 ◽  
Author(s):  
Satoshi Igi ◽  
Teruki Sadasue ◽  
Kenji Oi ◽  
Satoru Yabumoto ◽  
Shunsuke Toyoda
Keyword(s):  
Fracture Toughness ◽  
Low Temperature ◽  
Internal Pressure ◽  
Fatigue Test ◽  
Full Scale ◽  
Safety Performance ◽  
Small Scale ◽  
High Quality ◽  
Burst Test ◽  
Full Scale Tests

Newly-developed high quality high frequency electric resistance welded (HFW) linepipes have recently been used in pipelines in reel-lay applications and low temperature service environments because of their excellent low temperature weld toughness and cost effectiveness. In order to clarify the safety performance of these HFW linepipes, a series of full-scale tests including a hydrostatic burst test at low temperature, fatigue test and tension test under high internal pressure was conducted, together with small-scale tests such as impact energy and standard fracture toughness tests, which are generally used in mill production and pre-qualification tests. The Charpy transition curve of the developed HFW pipe occurred at a temperature much lower than −45°C. Based on the low-temperature hydrostatic burst test with a notched weld seam at −45°C, the weld of the HFW linepipe presented the same level of leak-before-break (LBB) behavior, as observed in UOE pipes. A full-pipe fatigue test of HFW pipes with repeated internal pressurizing was conducted. The fatigue strength of the developed HFW linepipe shows better performance than butt weld joints because of the smoothness at its weld portion, which is achieved by mechanical grinding of the weld reinforcement. Full-scale pipe tensile tests of girth welded joints were performed with an artificial surface notch at the heat affected zone in the girth weld. The influence of internal pressure was clearly observed in these tests. Based on the above-mentioned full-scale tests, the safety performance of high quality HFW linepipe is discussed in comparison with the mechanical properties in the small-scale tests such as the Charpy and standard fracture toughness tests, especially when the notch was placed in the welded seam.

Changes in Tensile Properties Due to Cold Bending of Line Pipes

2002 ◽  
Author(s):  
Naoki Fukuda ◽  
Hiroshi Yatabe ◽  
Tomoki Masuda ◽  
Masao Toyoda
Keyword(s):  
Tensile Properties ◽  
Analytical Model ◽  
Bauschinger Effect ◽  
Estimation Method ◽  
Tensile Tests ◽  
Full Scale ◽  
Small Scale ◽  
Cold Bending ◽  
Cold Bends ◽  
Good Agreement

The changes in the tensile properties of line pipes due to cold bending were experimentally and analytically investigated. Full-scale cold bending experiments were performed on API X60 and X80 grade line pipes. The reduction in the yield stress of the cold bends due to the Bauschinger effect was approximately 20% and 35% for X60 and X80, respectively. In order to evaluate the changes in the tensile properties of the pipes quantitatively, finite element (FE) analyses and small-scale experiments were conducted. The FE analytical model for simulating the strain distribution at various bending angles was verified with the results of the full-scale experiments. The tensile properties of the cold bends were in good agreement with those of the small-scale experiments using uni-axially prestrained specimens. Based on the present results, an estimation method was proposed for evaluating the distribution of the tensile properties after cold bending with the analytical model using the results of the tensile tests for prestrained specimens.

Evaluation of the Suitability of X100 Steel Pipes for High Pressure Gas Transportation Pipelines by Full Scale Tests

2004 ◽  
Author(s):  
G. Demofonti ◽  
G. Mannucci ◽  
H. G. Hillenbrand ◽  
D. Harris
Keyword(s):  
High Pressure ◽  
Fracture Propagation ◽  
Full Scale ◽  
Gas Pipeline ◽  
Defect Tolerance ◽  
Steel Pipes ◽  
Natural Gas Pipeline ◽  
Safe Level ◽  
Cold Bending ◽  
Full Scale Tests

In order to increase the knowledge necessary for the utilisation of grade X100 steel pipes, and to consolidate preliminary indications regarding the safe level of toughness required to control the ductile fracture propagation event within X100 gas pipeline, an ECSC-Demonstration Project, (DemoPipe), partially sponsored by EPRG, has been performed (2001–2004) using TMCP X100 pipes with a diameter of 36”. The project examines the problems of building a new high grade steel on-shore gas pipeline, with special emphasis given to the issues of the field welding technologies and selection of consumables, girth weld defect tolerance, field cold bending, and the fracture propagation behaviour in a high-pressure natural gas pipeline. In order to achieve these stated aims, a dedicated programme of laboratory and full scale tests was included in the project. This paper presents a summary of some of the results obtained, together with a discussion regarding their applicability to future X100 pipelines.

Ultra Heavy Wall Linepipe X65: Severe In-Service Straining of Lined Pipes

2013 ◽  
Author(s):  
Luigi Di Vito ◽  
Jan Ferino ◽  
Stefano Amato ◽  
Gianluca Mannucci ◽  
Stefano Crippa ◽  
...  
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Large Strain ◽  
Compressive Loading ◽  
Full Scale ◽  
Large Strains ◽  
Industrial Project ◽  
Axial Tensile ◽  
Full Scale Tests ◽  
Element Study

Tenaris and Centro Sviluppo Materiali (CSM) carried out a Joint Industrial Project aimed at developing heavy wall line pipes. The suitability for very severe applications, involving high service pressures and temperatures, the latter causing large strain fluctuations, in presence of an aggressive sour environment, is analyzed both theoretically and experimentally, including small and full pipe models and tests. Five papers have been already presented on this project, in previous OMAE conferences. The present paper focusses on Lined Heavy Wall Pipes for the adoption in presence of extremely aggressive conveyed fluids. As in-service large strains are involved in the JIP envisaged scenarios, the risk of liner buckling is necessarily concerned. To evaluate the suitability of lined heavy pipes in presence of in-service severe straining, a finite element study has been performed aimed at quantifying the limits for pipe deformability without occurrence of liner buckling. Two full scale tests on lined pipe strings have been also performed, imposing the very severe straining sequence previously determined as extreme for pipeline resistance. The sequence has been applied both in pure axial (tensile / compressive) loading and in bending conditions. The latter has been performed in very low internal pressure conditions to conservatively verify the resistance to liner buckling. In both cases, the lined heavy wall pipe resisted the severe straining sequence without any liner buckling, pipe excessive ratcheting or any other damage compromising the serviceability of the pipe.

Deformation Capacity of Weld Seam of the High Quality HFW Linepipe

2015 ◽  
Author(s):  
Satoshi Igi ◽  
Satoru Yabumoto ◽  
Teruki Sadasue ◽  
Hisakazu Tajika ◽  
Kenji Oi
Keyword(s):  
Low Temperature ◽  
Internal Pressure ◽  
Seismic Design ◽  
Weld Seam ◽  
Full Scale ◽  
Bending Test ◽  
Design Code ◽  
High Quality ◽  
Seismic Design Code ◽  
Full Scale Tests

Newly-developed high quality high frequency electric resistance welded (HFW) linepipes have recently been used in pipelines in reel-lay applications and low temperature service environments because of their excellent low temperature weld toughness and cost effectiveness. In order to clarify the applicability of these HFW linepipes to the seismic environment, a series of full-scale tests such as bending test with internal pressure and uniaxial compression test were conducted according to the seismic design code in Japan gas association (JGA). Based on the above-mentioned full-scale tests, the safety performance of high quality HFW linepipe to apply to the seismic region is discussed in comparison with the mechanical properties in the small-scale tests such as the tensile and compression property of the base material and weld seam, especially focused on the strain capacity of HFW linepipe from the view points of full-scale performance and geometrical imperfection. Test results of the bending test with internal pressure and the uniaxial compression were complied with the JGA seismic design code for the permanent ground deformation induced by lateral spreading and surface faults.

Strain Capacity and Deformation Behavior of HFW Linepipe

2016 ◽  
Author(s):  
Satoshi Igi ◽  
Satoru Yabumoto ◽  
Teruki Sadasue ◽  
Hisakazu Tajika ◽  
Kenji Oi
Keyword(s):  
Internal Pressure ◽  
Seismic Design ◽  
Full Scale ◽  
Bending Test ◽  
Uniaxial Compression Test ◽  
Design Code ◽  
Strain Capacity ◽  
Seismic Design Code ◽  
Full Scale Tests ◽  
Tensile Strain Capacity

Newly-developed high quality high frequency electric resistance welded (HFW) linepipes have recently been applied to offshore pipelines by using the reel-lay method and onshore in extremely low temperature environments because of their excellent low temperature weld toughness and cost effectiveness. In order to clarify the applicability of these HFW linepipes to seismic regions, a series of full-scale tests such as the bending test with internal pressure and the uniaxial compression test were conducted according to the seismic design code of the Japan Gas Association (JGA). Based on these full-scale tests, the safety performance of high quality HFW linepipe when applied to seismic regions is discussed in comparison with the mechanical properties obtained in small-scale tests, such as the tensile and compression properties of the base material and weld seam, focusing especially on the compressive and tensile strain capacity of HFW linepipes from the viewpoints of full-scale performance and geometrical imperfections. The results of the bending test under internal pressure and the uniaxial compression test without internal pressure complied with the JGA seismic design code for permanent ground deformation induced by lateral spreading and surface faults. In addition, a full-pipe tension test was also conducted in order to investigate the tensile strain capacity of HFW linepipes for axial deformation.

Tensile Properties of Cold Bends for Line Pipes

2007 ◽  
Vol 129 (3) ◽  
pp. 229-235 ◽  
Author(s):  
Naoki Fukuda ◽  
Hiroshi Yatabe ◽  
Tomoki Masuda ◽  
Masao Toyoda
Keyword(s):  
Tensile Properties ◽  
Tensile Tests ◽  
Full Scale ◽  
Small Scale ◽  
Fe Model ◽  
Cold Bending ◽  
Bending Process ◽  
Residual Strains ◽  
Cold Bends ◽  
The Relationship

To comprehensively investigate the tensile properties of cold bends, full-scale cold bending experiments, tensile tests using prestrained small-scale specimens, and finite element (FE) analyses of the cold bending processes were conducted on API 5L X60 and X80 grade line pipes. The tensile tests revealed that the tensile properties of the cold bends were comparable to the uniaxially prestrained specimens machined from the straight part of the pipes. A FE model simulating the cold bending process was verified with the full-scale experimental results in terms of the distributions of residual strains. These results supported a procedure for estimating the tensile properties of the cold bends with a combination of the FE model and the tensile tests using the prestrained specimens; the residual strains obtained from the FE model are transformed into the tensile properties based on the relationship between the residual strains and the tensile properties. This study clarified that the tensile properties come close to being uniformly distributed by reducing the distance between the bending locations; the distance between the bending locations has a significant influence on the overlap of adjacent deformed areas, which governs the distribution of the tensile properties of the cold bends.

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