Anisotropic HFI Welded Steel Pipes for Strain Based Design

2016 ◽  
Author(s):  
Oliver Hilgert ◽  
Susanne Höhler ◽  
Holger Brauer
Keyword(s):  
Full Scale ◽  
Small Scale ◽  
Steel Tubes ◽  
Line Pipe ◽  
Welded Steel ◽  
Bending Tests ◽  
Strain Capacity ◽  
Steel Pipes ◽  
Weld Material ◽  
Anisotropy Parameters

Generally isotropic behavior is assumed and demanded in line pipe specifications. Especially in strain based design, compressive and tensile strain capacity models rely on iso-tropic assumptions. On the other hand every pipe has got an anisotropic material characteristic which effects the performance in strain based design. In this contribution HFI-welded steel tubes are investigated due to their underlying material anisotropy. Depending on their basic strip weld material and production process the anisotropy differs from UOE or spiral welded pipes. Especially, in radial direction of steel pipe mechanical properties are challenging to gain. Thus two methods are suggested to characterize the anisotropic parameters in all three pipe directions. A small scale approach evaluating Lankford values and a full scale method evaluating Hill factors are applied. While Lankford method relies on strains, Hills method relies on stresses. Both methods are explained and validated by internal pressure and full scale bending tests. Using the anisotropy parameters, their effect on strain based design is analyzed — both experimentally and numerically. In the end it is shown that distinct anisotropies can provide a benefit for HFI-welded steel tubes concerning strain capacity in strain based design applications.

Girth Weld Strength Matching Effect on Tensile Strain Capacity of Grade X70 High Strain Line Pipe

2018 ◽  
Author(s):  
Hisakazu Tajika ◽  
Takahiro Sakimoto ◽  
Tsunehisa Handa ◽  
Rinsei Ikeda ◽  
Joe Kondo
Keyword(s):  
High Strain ◽  
Limit State ◽  
Full Scale ◽  
Bending Test ◽  
High Grade ◽  
Line Pipe ◽  
Bending Tests ◽  
Strain Capacity ◽  
Pipeline Project ◽  
Pipe Bending

Recently high grade pipeline project have been planned in hostile environment like landslide in mountain area, liquefaction in reclaimed land or the frost heave in Polar Regions. Geohazards bring large scale ground deformation and effect on the varied pipeline to cause large deformation. Therefore, strain capacity is important for the pipeline and strain based design is also needed to keep gas transportation project in safe. High grade steel pipe for linepipe tends to have higher yield to tensile (Y/T) ratio and it has been investigated that the lower Y/T ratio of the material improves strain capacity in buckling and tensile limit state. In onshore pipeline project, pipe usually transported in 12 or 18m each and jointed in the field. Girth weld (GW) is indispensable so strength matching of girth weld towards pipe body is important. In this study strain capacity of Grade X70 high strain pipes with size of 36″ OD and 23mm WT was investigated with two types of experiments, which are full scale pipe bending tests and curved wide plate tests. The length of the specimen of full scale bending tests were approximately 8m and girth weld was made in the middle of joint length. A fixed internal pressure was applied during the bending test. Actual pipe situation in work was simulated and both circumferential and longitudinal stress occurred in this test. Test pipes were cut and welded, GTAW in first two layer and then finished by GMAW. In one pipe, YS-TS over-matching girth weld (OVM) joint was prepared considering the pipe body grade. For the other pipe, intentionally under-matching girth weld (UDM) joint was prepared. After the girth welding, elliptical EDM notch were installed in the GW HAZ as simulated weld defect. In both pipe bending tests, the buckling occurred in the pipe body at approximately 300mm apart from the GW and after that, deformation concentrated to buckling wrinkle. Test pipe breaking locations were different in the two tests. In OVM, tensile rupture occurred in pipe body on the backside of buckling wrinkle. In UDM, tensile rupture occurred from notch in the HAZ. In CWP test, breaking location was the HAZ notch. There were significant differences in CTOD growth in HAZ notch in these tests.

Comparison of Fatigue of Girth-Welds in Full-Scale Pipes and Small-Scale Strip Specimens

2008 ◽  
Author(s):  
Stephen J. Maddox ◽  
Yan-Hui Zhang
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Initiation ◽  
Fatigue Behaviour ◽  
Initiation Site ◽  
Full Scale ◽  
Fatigue Properties ◽  
Small Scale ◽  
Welded Steel ◽  
Steel Pipes ◽  
Girth Welds

As part of a study of fatigue in girth-welded steel pipes, tests were performed under constant amplitude loading on both full-scale pipes and strip specimens cut from such pipes. Significant differences were found in their high-cycle fatigue lives, which extended to around 108 cycles, and apparent fatigue endurance limits, the small-scale strips displaying superior fatigue properties. The reasons for this were investigated considering the fatigue crack initiation site, weld geometry, type of pipe, loading conditions, residual stresses, the re-testing of unfailed specimens and size effects. Fracture mechanics fatigue crack growth calculations were also performed using a K solution specially calculated by FEA for the girth weld. Conclusions are drawn about the suitability of strip fatigue test specimens for representing the fatigue behaviour of full-scale girth welded pipes and the scope for re-testing unfailed full-scale pipes.

Effect of Thermal Aging on Strain Capacity of X80 SAW Pipes

2012 ◽  
Author(s):  
Hidenori Shitamoto ◽  
Masahiko Hamada ◽  
Nobuaki Takahashi ◽  
Yuki Nishi
Keyword(s):  
Thermal Aging ◽  
Arc Welding ◽  
Submerged Arc Welding ◽  
Full Scale ◽  
Operating Pressure ◽  
Bending Tests ◽  
Strain Capacity ◽  
Submerged Arc ◽  
Pipe Bending

Application of API X80 grade line pipes has been promoted to increase the operating pressure. It is generally known that the deformability of submerged arc welding (SAW) pipes is decreased by increasing strength of the pipes. The assessment of the strain capacity of X80 SAW pipes is required for strain-based design (SBD). In the assessment of the strain capacity, one of the important issues is the effect of thermal aging during the anti-corrosion coating on the yielding phenomenon. In this study, full-scale pipe bending tests of X80 SAW pipes produced by UOE process were performed to evaluate the effect of thermal aging on the strain capacity.

TurkStream Collapse Test Program

2018 ◽  
Author(s):  
Chris Timms ◽  
Doug Swanek ◽  
Duane DeGeer ◽  
Arjen Meijer ◽  
Ping Liu ◽  
...  
Keyword(s):  
Thermal Ageing ◽  
Full Scale ◽  
The Black Sea ◽  
Small Scale ◽  
Test Program ◽  
Line Pipe ◽  
Medium Scale ◽  
Collapse Resistance ◽  
Full Scale Tests ◽  
The Impact

The TurkStream pipeline project is designed to transport approximately 32 billion cubic meters of natural gas annually from Russia to Turkey under the Black Sea, with more than 85% of the deep-water route being deeper than 2000 m. The offshore section is intended to consist of two parallel lines, each approximately 900 km long. The preliminary stages of the front end engineering design (pre-FEED) phase was managed by INTECSEA. To support the analyses and design of the deepest portions, a full scale collapse test program was performed by C-FER Technologies (C-FER). This collapse test program, which included 62 full-scale collapse and pressure+bend tests, 54 medium-scale ring collapse tests, and hundreds of small-scale tests, was primarily aimed at measuring, quantifying and documenting the increase in pipe strength and collapse resistance resulting from the thermal induction heat treatment effect (thermal ageing) that arises during the pipe coating process. Two grades of 32-inch (813 mm) outside diameter (OD) line-pipe, SAWL450 and SAWL485 with wall thicknesses of 39.0 mm or 37.4 mm, respectively, were supplied from various mills for testing. The collapse test program objectives were as follows: • Determine the collapse resistance of line pipes originating from various pipe mills; • Determine the pressure+bend performance of line pipes originating from various pipe mills; • Measure the effect of thermal ageing on material and collapse testing results, including the impact of multiple thermal cycles; and • Evaluate the results of medium-scale ring collapse tests as compared to full-scale tests. This paper presents selected results of this work, along with some comparisons to predictive equations.

Full-Scale Reeling Tests of HFI Welded Line Pipe for Offshore Reel-Laying Installation

2014 ◽  
Author(s):  
Karl Christoph Meiwes ◽  
Susanne Höhler ◽  
Marion Erdelen-Peppler ◽  
Holger Brauer
Keyword(s):  
Mechanical Testing ◽  
Mechanical Test ◽  
Strength Properties ◽  
Full Scale ◽  
Bending Test ◽  
Small Scale ◽  
Pipe Material ◽  
Deformation Capacity ◽  
Line Pipe ◽  
Tension And Compression

During reel-laying repeated plastic strains are introduced into a pipeline which may affect strength properties and deformation capacity of the line pipe material. Conventionally the effect on the material is simulated by small-scale reeling simulation tests. For these, coupons are extracted from pipes that are loaded in tension and compression and thermally aged, if required. Afterwards, specimens for mechanical testing are machined from these coupons and tested according to the corresponding standards. Today customers often demand additional full-scale reeling simulation tests to assure that the structural pipe behavior meets the strain demands as well. Realistic deformations have to be introduced into a full-size pipe, followed by aging, sampling and mechanical testing comparable to small-scale reeling. In this report the fitness for use of a four-point-bending test rig for full-scale reeling simulation tests is demonstrated. Two high-frequency-induction (HFI) welded pipes of grade X65M (OD = 323.9 mm, WT = 15.9 mm) from Salzgitter Mannesmann Line Pipe GmbH (MLP) are bent with alternate loading. To investigate the influences of thermal aging from polymer-coating process one test pipe had been heat treated beforehand, in the same manner as if being PE-coated. After the tests mechanical test samples were machined out of the plastically strained pipes. A comparison of results from mechanical testing of material exposed to small- and full-scale reeling simulation is given. The results allow an evaluation of the pipe behavior as regards reeling ability and plastic deformation capacity.

Seamless Linepipe Response Under Small and Full Scale Reeling Simulation

2016 ◽  
Author(s):  
Israel Marines-Garcia ◽  
Jorge A. Aldana-Díaz ◽  
Philippe P. Darcis ◽  
Hector M. Quintanilla
Keyword(s):  
Lead Time ◽  
Cyclic Strain ◽  
Extensive Study ◽  
Full Scale ◽  
Small Scale ◽  
Pipe Material ◽  
Line Pipe ◽  
Offshore Pipelines ◽  
Ageing Condition ◽  
Pipe Materials

Offshore pipelines projects, installed by reel-laying operations, are gaining momentum due to the increasing worldwide capacity of Reel Lay Vessels. It is well known that reel-laying installation causes repeated plastic straining (cyclic deformation) and, as a consequence, cyclic strain and ageing test is usually required for qualifying line pipe materials for such installation method. This qualification is typically named reeling simulation. Reeling simulations can be made via full or small scale. In practice, full scale qualification lead time and full scale reeling simulation machines availability could be a constraint, thus, small scale reeling simulation is usually the best alternative. However, the similitude of small scale versus full scale simulations could be questioned. On this basis, an extensive study was carried-out considering tensile, toughness and sour testing, in order to evaluate the material response after reeling simulation, in order to clarify if the line pipe material will behave similarly regardless the straining method (small scale or full scale). Different small scale samples configuration for straining were tested, depending on the posterior mechanical or sour test, and two different full scale reeling simulation machines were used for plain pipes straining. Five seamless plain pipes, X65 line pipe were used for this study, with 3 (three) different outer diameters of 10.75″, 11.67″ & 16″ (273 mm, 296 mm & 406 mm). The current paper will present the main mechanical results of these materials after strain and ageing condition, comparing full and small scale straining methods.

Mechanical Integrity Modeling of Forge Welded Pipes for Offshore Applications

2012 ◽  
Author(s):  
Ganesan S. Marimuthu ◽  
Per Thomas Moe ◽  
Junyan Liu ◽  
Bjarne Salberg
Keyword(s):  
Weld Line ◽  
Base Material ◽  
Full Scale ◽  
Small Scale ◽  
Type Model ◽  
Model Parameters ◽  
Weld Quality ◽  
Line Pipe ◽  
Gurson Model ◽  
Mechanical Integrity

In this paper, we discuss how through-process multi-scale models can be designed and combined with properly constructed experiments in order to assess the mechanical integrity of forge welded connectors. Shielded Active Gas Forge Welding (SAG-FW) is a fully automatic solid state method for joining steel pipes and other metallic articles. After heating, welding occurs almost instantaneously when the mating surfaces of the metallic parts are brought into intimate contact at high temperature and co-deformed. The result is a metallic bond with properties similar to those of the base material. If mating surfaces have been properly prepared and are essentially free from oxides the forge weld line is completely indistinguishable even when studied under a microscope. However, improper surface finish, oxides and contaminants may contribute to reducing weld quality. The paper consists of analytical and experimental parts. First, approaches for modeling forge welding and weld integrity are assessed. Second, a Gurson-type model is studied in great detail as it appears to be the simplest and most promising concept in relation to quantitative modeling and testing of mechanical integrity of forge welds. Third, miniature notched specimens for determining parameters of a modified Gurson-model are proposed and evaluated in relation to small scale forge welding. The small scale forge welding method has been established in order to simulate full scale welding of for example line pipe and casing, but mechanical testing of small samples constitute a significant challenge. Fourth, a set of experiments is performed to further assess the concept, to the extent possible determine material parameters of the Gurson-model and to evaluate the effect of process parameter settings on the weld quality. Results from tests of welds with and without oxides are subsequently compared with results from tests of base material specimens. All tests have been performed for an API 5L X65 alloy. The results demonstrate that both capacity and ductility of the forge welds are similar to those of base material. Finally, Gurson-model parameters are assessed, and a comparison with physical observations is made. Further development of the small scale tests is needed. More extensive test programs should be performed and a comparison with full scale welding should be carried out. However, the experiments demonstrated that the proposed notched specimen designs complements conventional fracture mechanical tests (CT, SENT, SENB) or field tests proposed by various standards (Charpy, Izod, bend tests).

Full Scale Application of Thermal Ageing in Line Pipe Material Selection for Deepwater Pipelines

2014 ◽  
Author(s):  
Niels Kerstens ◽  
Ping Liu ◽  
Duane DeGeer
Keyword(s):  
Wall Thickness ◽  
Development Program ◽  
Thermal Ageing ◽  
Full Scale ◽  
Small Scale ◽  
Pipe Material ◽  
The South ◽  
Line Pipe ◽  
Material Development ◽  
South Stream

Comprising 4 pipelines over 900 km in length, with 32-in diameter and traversing water depths over 2200 m, the South Stream project requires a step-out in technology application. Following several years of preparation, the project is now approaching its implementation. In order to document the reliability of the collapse resistance for South Stream, an extensive material development program was initiated and executed, including small scale, medium scale, and full scale testing on over one hundred purposely manufactured pipe joints by world’s 5 leading mills. Testing performed included plate tests, full scale collapse tests on various combinations of plate sources, steel grades, and thermal ageing condition, pressure-bend tests, and reverse bending tests. A large number of medium and small scale tests were performed to allow the development of a suitably reliable statistical database for the probabilistic wall thickness design. In addition, programs were developed and executed for weldability tests, performing over one hundred trial welds, and for H2S resistance tests. This material development program was built on INTECSEA’s extensive experience with deep water large diameter pipelines (i.e. Oman-India, Blue Stream, Medgaz, Mardi Gras, IGI, etc.). Due to its extent and rigorous approach the South Stream material development program was able to conclusively prove the feasibility of the selected technological approach at an industrial scale. This paper provides an overview of the key design issues that were successfully addressed and the major technological advances that have been implemented as part of the linepipe material development process for deepwater pipelines in an H2S containing environment. The practical significance of this program is to optimize the wall thickness to a level that is manufacturable by the industry and hence enables the South Stream Project to proceed with its unprecedented depth and diameter combination.

The Misconception of Employing CVN Toughness as Key-Measure in Ductile Crack Arrest Prediction for Modern Line-Pipe Steels

2014 ◽  
Author(s):  
Alexander Völling ◽  
Christoph Kalwa ◽  
Marion Erdelen-Peppler
Keyword(s):  
Ductile Fracture ◽  
Data Base ◽  
Model Calibration ◽  
Crack Arrest ◽  
Full Scale ◽  
Small Scale ◽  
Material Strength ◽  
Original Material ◽  
Pipe Steels ◽  
Line Pipe

Since the late 1960s’ the Battelle Two-curve (BTC) model is the standard method applied in setting up design requirements with regard to the prevention of long-running ductile fracture in pipelines. It is a straightforward tool employing Charpy-V notch (CVN) toughness as key-measure for material resistance against crack propagation. On basis of pipe dimensions, material strength, and under consideration of decompression behavior of the transferred media, it enables to set up requirements for a minimum CVN toughness level to achieve crack arrest. Overall applicability of the BTC model is based on calibration of the underlying equations to a sound data-base, including both full-scale burst test results and small-scale laboratory testing data involving typical line-pipe grades at that period, i.e. up to grade X70 steels with below 100 J upper-shelf CVN toughness. Now over the last decades, mechanical behavior of line-pipe steels was improved significantly. Responding to market demands, higher grades were designed and also toughness levels were raised as outcome of R&D efforts within the steel industry. Unfortunately, stepping outside the original material data-base from BTC model calibration, this method did forfeit its reliability. At the beginning, mispredictions were mainly related to higher grade steels and elevated operating pressures. But more recent full-scale tests did reveal discrepancies in application of the BTC model also for so-called new vintage steels, i.e. grades actually being inside the original data base for model calibration but from current production routes. With regard to applicability/reliability of BTC model based predictions for crack arrest, the origin of uncertainty has particularly been traced back to the involved material toughness measure. Nowadays, it is common sense that the CVN upper-shelf toughness value inadequately describes the resistance against running ductile fracture. More recent thoughts coherently argue towards closer involving stress-strain response and plastic deformation capacities of the material. On basis of results for grades X65, X80 and X100, the general relation between ductility and toughness is discussed. Finally, an elastic-plastic fracture mechanics related analytical approach is introduced which enables to quantify the resistance against ductile fracture propagation. The objective is to provide a reliable procedure for crack arrest prediction in line-pipe steels.

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