Full-Scale Tests of Cold Bend Pipes

2004 ◽  
Author(s):  
M. Sen ◽  
J. J. R. Cheng ◽  
D. W. Murray ◽  
J. Zhou ◽  
K. Adams ◽  
...  
Keyword(s):  
Compressive Strain ◽  
Local Buckling ◽  
Full Scale ◽  
Combined Loading ◽  
Experimental Program ◽  
Test Procedures ◽  
Buckling Behavior ◽  
Residual Strains ◽  
Full Scale Tests ◽  
Bend Angles

An experimental program sponsored jointly by SNAM Rete Gas, Tokyo Gas Co., Ltd. and TransCanada Pipelines Ltd. was conducted on cold bend pipes under combined loading. These tests were designed to study the local buckling behavior and to develop the critical compressive strain criteria for cold bend pipes under combined loading. The test program includes eight full-scale specimens of NPS24 and NPS30 pipes with pipe thickness up to 14.3 mm. The test parameters include different D/t ratios (44, 69, and 93), material grades (X60, X65, and X80), bend angles (1.0 to 1.5 degree/diameter), and operation pressures (0%, 40%, 60%, and 80% of SMYS). In addition to full-scale tests, initial imperfections and residual strains due to cold bend processes were also measured. This paper describes the test specimens, test setup, instrumentation, and test procedures used in the program. A brief discussion of the test results is also covered in the paper.

HPHT Subsea Connector Verification and Validation Using an API 17TR8 Methodology

2021 ◽  
Author(s):  
Barry Stewart ◽  
Sam Kwok Lun Lee
Keyword(s):  
Failure Modes ◽  
Production Systems ◽  
Three Dimensional ◽  
Full Scale ◽  
Verification And Validation ◽  
Combined Loading ◽  
Load Path ◽  
Capacity Curves ◽  
Industry Standards ◽  
Full Scale Tests

Abstract Wellhead connectors form a critical part of subsea tree production systems. Their location in the riser load path means that they are subjected to high levels of bending and tension loading in addition to internal pressure and cyclic loading. As more fields continue to be discovered and developed that are defined as High Pressure and/or High Temperature (HPHT) these loading conditions become even more arduous. In order to ensure the integrity of HPHT components, industry requirements for components are setout in API 17TR8. This technical report provides a design verification methodology for HPHT products and some requirements for validation testing. The methodology provides detail on the assessment of static structural and cyclic capacities but less detail on how to assess the functional and serviceability criteria for wellhead connectors. Similarly, API 17TR8 does not include prescriptive validation requirements for wellhead connectors and refers back to historical methods. This paper describes a practical application of the API 17TR8 methodology to the development of a 20k HPHT connector and how it was implemented to verify and validate the connector design through full scale tests to failure. A methodology was developed to meet the requirements of the relevant industry standards and applied to the connector to develop capacity charts for static combined loading. Verification was carried out on three dimensional 180° FEA models to ensure all non axi-symmetric loading is accurately captured. Connector capacities are defined based on API 17TR8 criteria with elastic plastic analysis (i.e. collapse load, local failure and ratcheting), functionality/serviceability criteria defined through a FMECA review and also including API STD 17G criteria including failure modes such as lock/unlock functionality, fracture based failure, mechanical disengagement, leakage and preload exceedance. These capacities are validated through full scale testing based on the requirements of API 17TR7 and API STD 17G with combined loading applied to the Normal, Extreme and Survival capacity curves (as defined by "as-built" FEA using actual material properties). Various test parameters such as strain gauge data, hub separation data, displacements, etc. were recorded and correlated to FEA prediction to prove the validity of the methodology. Further validation was carried out by applying a combined load up to the FEA predicted failure to confirm the design margins of the connector. Post-test review was carried out to review the suitability of the requirements set out in API 17TR8 and API STD 17G for the verification and validation of subsea connectors. The results build on previous test results to validate the effectiveness of the API 17TR8 code for verification and validation of connectors. The results show that real margins between failure of the connector and rated loads are higher than those defined in API 17TR8 and show that the methodology can be conservative.

The Initial Post-buckling Behavior of Face-Sheet Delaminations in Sandwich Composites

2003 ◽  
Vol 70 (2) ◽  
pp. 191-199 ◽  
Author(s):  
G. A. Kardomateas ◽  
H. Huang
Keyword(s):  
Interface Crack ◽  
Transverse Shear ◽  
Compressive Strain ◽  
Sandwich Beam ◽  
Local Buckling ◽  
Face Sheet ◽  
Material System ◽  
Buckling Behavior ◽  
Post Buckling ◽  
Composite Face

Should an interface crack between the layers of the composite face-sheet or between the core and the composite face-sheet of a sandwich beam/plate exists, local buckling and possible subsequent growth of this interface crack (delamination) may occur under compression. In this study, the buckling, and initial post-buckling behavior is studied through a perturbation procedure that is based on the nonlinear beam equations with transverse shear included. Closed-form solutions for the load and midpoint delamination deflection versus applied compressive strain during the initial postbuckling phase are derived. Illustrative results are presented for several sandwich construction configurations, in particular with regard to the effect of material system and transverse shear.

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.

Assessment of Dents Under High Longitudinal Strain

2018 ◽  
Author(s):  
Bo Wang ◽  
Yong-Yi Wang ◽  
Brent Ayton ◽  
Mark Stephens ◽  
Steve Nanney
Keyword(s):  
Longitudinal Strain ◽  
Scale Validation ◽  
Compressive Strain ◽  
Full Scale ◽  
Ground Movement ◽  
Strain Capacity ◽  
Parametric Analyses ◽  
Full Scale Tests ◽  
Assessment Procedures ◽  
The Impact

Pipeline construction activities and in-service interference events can frequently result in dents on the pipe. The pipelines can also experience high longitudinal strain in areas of ground movement and seismic activity. Current assessment procedures for dents were developed and validated under the assumption that the predominant loading is internal pressure and that the level of longitudinal strain is low. The behavior of dents under high longitudinal strain is not known. This paper discusses work funded by US DOT PHMSA on the assessment of dents under high longitudinal strain. Parametric numerical analyses were conducted to identify and examine key parameters and mechanisms controlling the compressive strain capacity (CSC) of pipes with dents. Selected full-scale tests were also conducted to experimentally examine the impact of dents on CSC. The focus of this work was on CSC because tensile strain capacity is known not to be significantly affected by the presence of dents. Through the parametric analyses and full-scale validation tests, guidelines on the CSC assessment of dented pipes under high longitudinal strain were developed.

Local Buckling Assessments for the Medgaz Pipeline

2007 ◽  
Author(s):  
D. DeGeer ◽  
C. Timms ◽  
J. Wolodko ◽  
M. Yarmuch ◽  
R. Preston ◽  
...  
Keyword(s):  
Finite Element ◽  
Gas Flow ◽  
Local Buckling ◽  
External Pressure ◽  
Full Scale ◽  
Regression Equations ◽  
Finite Element Analyses ◽  
Bending Strain ◽  
Primary Focus ◽  
Full Scale Tests

Medgaz is a consortium of leading international energy companies, with the aim of designing, building and operating an Algerian-European gas pipeline via Spain. The offshore section of this pipeline will be 210 km long, traversing the Mediterranean Sea floor at a maximum depth of 2160 metres. The 24-inch diameter, grade X70 line will provide up to 8 billion cubic metres of natural gas per year, with first gas flow expected in 2009. To support the technical issues surrounding such an ultra-deepwater pipelay, a number of full scale local buckling tests and detailed finite element analyses were undertaken at the C-FER facility in Edmonton, Canada. Local buckling conditions of concern included buckling of the pipe section at the pipe-buckle arrestor interface and collapse of the plain pipe under high external pressure. These conditions may arise during various phases of pipeline installation and operation, but the primary focus was to evaluate the local buckling integrity of the pipe during installation using the S-lay method. These conditions were assessed for both as-fabricated pipe and pipe that was heat treated to simulate a pipe coating process. This paper describes the Medgaz pipeline, its current state of development, the installation challenges that necessitated the buckling assessments, and some of the work performed throughout the study, including full scale tests, finite element analyses, and regression analyses. Collapse and critical bending strain predictive equations were developed and are also presented, and are compared to other well known collapse and critical bending strain equations. The results of these assessments have suggested that, for the local buckling conditions presented herein, the S-lay method can be successfully employed for ultra-deep water pipelay. The results demonstrated that the proposed pipe-buckle arrestor connection design will not cause premature buckling as the pipe traverses along the stinger during installation. In addition, potentially high bending strains in the overbend will not significantly influence the collapse strength of the pipe. The regression equations presented in this paper have also been shown to provide an accurate means of predicting pipe local buckling and collapse.

Steady State Techniques in Creep Force Estimation: Results From Full Scale Tests of the SOAC Vehicle on a Roller Rig

1989 ◽  
Vol 111 (1) ◽  
pp. 61-68
Author(s):  
Imtiaz-ul-Haque ◽  
E. Harry Law
Keyword(s):  
Steady State ◽  
Forced Response ◽  
Full Scale ◽  
Force Estimation ◽  
Test Procedures ◽  
Creep Force ◽  
Roller Rig ◽  
Full Scale Tests ◽  
The U.S

Steady state forced response tests of the SOAC vehicle were conducted on the roller rig (Roll Dynamics Unit) at the U.S. DOT/Transportation Test Center. This paper presents the test procedures, the results of the tests, and the analysis procedures developed for the estimation of the creep coefficients. Results of the estimates are compared with theory and possible reasons for discrepancies are discussed.

scholarly journals Laboratory Study of Local Buckling, Wrinkle Development, and Strains for NPS12 Linepipe

2000 ◽  
Author(s):  
Sreekanta Das ◽  
J. J. Roger Cheng ◽  
David W. Murray ◽  
S. A. Wilkie ◽  
Z. Joe Zhou
Keyword(s):  
Fluid Pressure ◽  
Local Buckling ◽  
Pipe Material ◽  
Axial Loads ◽  
Buried Pipelines ◽  
Test Procedures ◽  
Complex Load ◽  
University Of Alberta ◽  
Full Scale Tests ◽  
Internal Pressures

Buried pipelines are subjected to fluid pressure (oil/gas/water), axial loads, moments, and complex load combination histories. As a result, they may develop large compressive strains and curvatures leading to formation of localized buckles or wrinkles in the pipe shell. Recently, full-scale tests on 12.75″ diameter (NPS12) energy pipes have been carried out at the University of Alberta to study the behavior of wrinkle development and the ultimate limiting strains at the wrinkle locations. Different internal pressures, and axial loads were applied to produce a wrinkle, followed by load variations intended to produce fracture that could develop in buried pipelines in the field. Three different axially loaded tests are reported. Two different internal pressures were applied, namely, (i) 0.8py and (ii) 0.4py, where py is the required internal pressure to cause the yield stress of the pipe material to be developed in the circumferential direction. Also, two different specimen lengths were adopted. They are: (i) 406 mm (16 inch) and (ii) 736 mm (29 inch). All specimens were loaded axially until the wrinkle formed. It was observed that the pipes are highly ductile and very large compressive strains can be developed without fracture or leakage in the pipe wall. Because the pipe specimens of the first two tests did not fail (i.e. fracture) under monotonically increasing displacements and strains, the third wrinkled specimen was subjected to load histories involving strain reversals. This load history resulted in a low cycle failure after a very few cycles. The paper addresses test procedures, buckling and post-buckling behavior of NPS12 energy pipelines and relates them to three different types of strain measures, namely, material strain, wrinkle strain and overall strain as observed from these tests.

Comparison of Compressive Strain Limit Equations

2014 ◽  
Author(s):  
Nader Yoosef-Ghodsi ◽  
Istemi Ozkan ◽  
Qishi Chen
Keyword(s):  
Compressive Strain ◽  
Local Buckling ◽  
Strain Curve ◽  
Full Scale ◽  
Structural Testing ◽  
Slope Instability ◽  
Ground Movement ◽  
Movement Experience ◽  
Strain Limit ◽  
Key Variables

Buried pipelines subjected to non-continuous ground movement such as frost heave, thaw settlement, slope instability and seismic movement experience high compressive strains that can cause local buckling (or wrinkling). In the context of strain-based design, excessive local buckling deformation that may cause loss of serviceability, or even pressure containment in some cases, is managed by limiting the strain demand below the strain limit. The determination of compressive strain limit is typically performed by full-scale structural testing or nonlinear finite element analysis that takes into account material and geometric non-linearity associated with the inelastic buckling of cylindrical shells. Before performing testing and numerical analysis (or when such options do not exist), empirical equations are used to estimate the strain limit. In this paper a number of representative equations were evaluated by comparing strain limit predictions to full-scale test results. Work prior to this study has identified the importance of key variables that have the greatest impact on the local buckling behaviour. Examples of these variables include the diameter-to-thickness ratio (D/t), internal pressure and shape of the stress strain curve. The evaluation presented here focused on how existing equations address these key variables, and the performance of the equations with respect to key variables and in different ranges.

Local Buckling Behavior of 48″, X80 High-Strain Line Pipes

2010 ◽  
Author(s):  
Nobuhisa Suzuki ◽  
Hisakazu Tajika ◽  
Satoshi Igi ◽  
Mitsuru Okatsu ◽  
Joe Kondo ◽  
...  
Keyword(s):  
High Strain ◽  
Compressive Strain ◽  
Local Buckling ◽  
Bending Test ◽  
Test Results ◽  
Geometric Properties ◽  
Pipe Surface ◽  
Bending Tests ◽  
Buckling Behavior ◽  
Post Buckling

Two bending tests of X80-grade, 48″ high-strain line pipes pressurized to 60% SMYS were conducted to investigate local buckling behavior. The thickness and D/t ratio of the line pipes were 22.0 mm and 55.4, respectively. The mean Y/T ratio of the high-strain pipes was 0.82. A full-scale bending test apparatus was constructed to conduct the bending tests. The bending test results clarified that the pipes have the 2D average critical compressive strain of 1.51 and 1.67%, which satisfy the strain demand of 1.35%. Validation of FEA is conducted taking into account geometric properties of the pipes in terms of outside diameter and thickness and longitudinal flatness. The FEA results coincide with the test results with respect to peak load, critical displacement, critical rotation and critical compressive strain. The FEA results about the load and displacement relationship also show good agreement with the test results during post-buckling deformation. One developed wrinkle and some small wrinkles were observed on the pipe surface during post-buckling deformation, whose cross sections were fairly captured considering the geometric properties.

Behavior of wrinkled steel pipelines subjected to cyclic axial loadings

2007 ◽  
Vol 34 (5) ◽  
pp. 598-607 ◽  
Author(s):  
Sreekanta Das ◽  
J.J Roger Cheng ◽  
David W Murray
Keyword(s):  
Failure Strain ◽  
Axial Loading ◽  
Cyclic Strain ◽  
Full Scale ◽  
Axial Loads ◽  
Test Procedures ◽  
University Of Alberta ◽  
Ductile Behavior ◽  
Full Scale Tests ◽  
The University

Full-scale laboratory tests were carried out at the University of Alberta to investigate the post-wrinkling ultimate behavior of steel pipelines. The pipe specimens exhibited extreme ductile behavior and did not fail in fracture under monotonically increasing axisymmetric compressive axial loads and displacements. Fractures developed at the wrinkled region, however, when a wrinkled pipe specimen was subjected to cyclic strain reversals due to unloading and loading of primary loads. This paper presents test procedures, complete post-wrinkling behavior, fracture limit strain values, and fracture configurations obtained from full-scale tests on wrinkled pipe specimens under cyclic and monotonic axial loadings. Key words: steel pipeline, laboratory testing, cyclic axial loading, wrinkling, post-wrinkling behavior, accordion failure, strain reversals, fracture.

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