Assessment of Corrosion Defects in Old, Low Toughness Pipelines

2006 ◽  
Author(s):  
Michael Martin ◽  
Robert (Bob) Andrews ◽  
Vinod Chauhan
Keyword(s):  
Transition Temperature ◽  
Transition Region ◽  
Assessment Methods ◽  
Transition Curve ◽  
Metal Loss ◽  
Pipe Material ◽  
Regulatory Requirements ◽  
Line Pipe ◽  
Corrosion Defects ◽  
Dependent Failure

Corrosion metal loss in one of the major damage mechanisms to transmission pipelines worldwide. The remaining strength of corroded pipe subjected to internal pressure loading has been extensively researched and guidelines for assessing corrosion are well defined. Methods including ASME B31G, RSTRENG and LPC have been developed, validated and matured to the extent that they are now incorporated in standards and regulatory requirements. However, these methods are based on the assumption that the pipe fails via a ductile mechanism, i.e., the line pipe material has sufficient toughness to prevent a toughness dependent failure. This limits the application of the existing methods to materials that have sufficient toughness. It is possible that some older pipelines operate with the material in the ductile / brittle transition region of the Charpy transition curve, or even on the lower shelf. It is also possible that under fault conditions, a pipeline normally operating on the upper shelf could be temporarily in the transition region. In these circumstances, existing assessment criteria may be non-conservative. At present there are no rigorous criteria available for assessing corrosion defects in low toughness pipe. This paper presents an approach for removing the uncertainty in the use of existing methods for assessing corrosion defects in older, low toughness pipelines based on the Beremin approach to brittle cleavage fracture. Comparison of the Beremin results with existing assessment methods allows an ‘effective transition temperature’ to be defined as the temperature at which the existing method is no longer conservative. The results suggest that, for the corrosion defects investigated, the effective transition temperature is sufficiently low that existing assessment methods will remain conservative.

Assessment Methods and Technical Challenges of Remaining Strength for Corrosion Defects in Pipelines

2018 ◽  
Author(s):  
Xian-Kui Zhu
Keyword(s):  
Prediction Models ◽  
High Strength ◽  
Failure Criteria ◽  
Assessment Methods ◽  
Metal Loss ◽  
Strength Assessment ◽  
Corrosion Defects ◽  
Technical Challenges ◽  
Experimental Validations ◽  
Constraint Effects

This paper presents a technical review of remaining strength assessment methods, major technical challenges and on-going progress for line pipes containing metal loss defects. A brief review is first given to burst prediction models for defect-free pipes, including the strength solutions and flow solutions of burst pressure and their experimental validations. Followed are more detailed review and evaluation of existing corrosion assessment methods, including three-generation models developed for low to high strength pipeline steels. Major challenges to improve the corrosion models are then discussed in regard to full-scale testing, numerical modeling, material failure criteria, constraint effects, and applications to real corrosion defects. Finally, on-going progress is presented for developing improved assessment models to predict more accurate remaining strength of corroded pipelines.

When Old Line Pipes Initiates Fracture in a Ductile Manner

2006 ◽  
Author(s):  
G. Wilkowski ◽  
D. Rudland ◽  
D. Rider ◽  
P. Mincer ◽  
W. Sloterdijk
Keyword(s):  
Transition Temperature ◽  
Ductile Fracture ◽  
Static Loading ◽  
Crack Depth ◽  
Temperature Shift ◽  
Charpy Impact ◽  
Pipe Material ◽  
Line Pipe ◽  
Strain Rate Effects ◽  
Constraint Effects

This paper presents a procedure to determine the lowest temperature that a ductile fracture will initiate in old (or new) pipe that behaves in a brittle manner (by Charpy testing). Over the last decade, much work has been done to assess constraint effects on the crack-driving force for specimens and cracks in pipes. The material’s transition temperature where the fracture process changes from ductile tearing to cleavage fracture at crack initiation is affected by the constraint conditions, but is a material property that cannot be determined analytically. This paper presents a methodology to account for constraint effects to predict the lowest temperature where ductile fracture initiation occurs and relates that temperature back to Charpy impact data for X60 and lower grades, particularly for older vintage linepipe materials. The method involves a series of transition temperature shifts to account for thickness effects, strain-rate effects, and constraint effects to give a master curve of transition temperatures from Charpy data to through-wall-cracked or surface-cracked pipes (with various surface-crack depth values) under quasi-static loading. These transition temperature shifts were based on hundreds of pipe tests and thousands of specimen tests over several decades of work by numerous investigators. Conducting tests on 1927 and 1948 vintage line-pipe steels subsequently validated this method. In addition, data were developed on the 1927 vintage pipe material to assess the effect of the bluntness of a corrosion flaw on the lowest temperature where ductile fracture will still occur under quasi-static loading. An addition transition temperature shift occurs as a function of the bluntness of the flaw.

Predicting the Fracture Initiation Transition Temperature in High Toughness, Low Transition Temperature Line Pipe With the COD Test

1974 ◽  
Vol 96 (4) ◽  
pp. 330-334 ◽  
Author(s):  
R. J. Podlasek ◽  
R. J. Eiber
Keyword(s):  
Transition Temperature ◽  
Static Loading ◽  
Crack Opening ◽  
Fracture Initiation ◽  
Full Scale ◽  
Pipe Material ◽  
Opening Displacement ◽  
Line Pipe ◽  
High Toughness ◽  
Critical Flaw

This paper describes the use of the crack opening displacement (COD) test to predict the fracture initiation transition temperature of high toughness, low-transition temperature in line pipe. A series of COD tests using t × t and t × 2t specimens made from this line pipe material. The COD test was conducted over a range of temperatures and the point where the upper shelf COD values began to decrease with decreasing temperature was defined. To verify the full-scale significance of this temperature, a series of three experiments was conducted on 48-in. (1.22m) dia line pipe to bracket the transition temperature defined in the COD Test. The results suggest that the COD transition temperature can ve used to define the fracture initiation temperature for static loading in pipe. In addition, in the transition temperature region, the full-scale results, while limited in number, suggest that the COD values could possibly be used to predict the critical flaw sizes in the pipe material.

Crack in Corrosion Defect Assessment in Transmission Pipelines

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
A. Hosseini ◽  
D. Cronin ◽  
A. Plumtree
Keyword(s):  
Crack Depth ◽  
Evaluation Criteria ◽  
Average Error ◽  
Failure Behavior ◽  
Pipe Material ◽  
Line Pipe ◽  
Collapse Pressure ◽  
Defect Assessment ◽  
Level 3 ◽  
Corrosion Defects

Cracks may occur coincident with corrosion representing a new hybrid defect in gas and oil pipelines known as crack in corrosion (CIC) that is not directly addressed in the current codes or assessment methods. Hence, there is a need to provide an assessment of CIC and evaluate the line integrity, as well as identify the requirements for defect repair or line hydrotest. An experimental investigation was undertaken to evaluate the collapse pressures of lines containing corrosion, cracks, or (CIC) defects in a typical line pipe (API 5L Grade X52, 508 mm diameter, 5.7 mm wall thickness). The mechanical properties of the pipe were measured using tensile, Charpy, and J-testing for use in applying evaluation criteria. Rupture tests were undertaken on end-capped sections containing uniform depth, finite length corrosion, cracks, or CIC defects. Failure occurred by plastic collapse and ductile tearing for the corrosion defects, cracks, and CIC geometries tested. For the corrosion defects, the corroded pipe strength (CPS) method provided the most accurate results (13% conservative on average). The API 579 (level 3 failure assessment diagram (FAD), method D) provided the least conservative collapse pressure predictions for the cracks with an average error of 20%. The CIC collapse pressures were bounded by those of a long corrosion groove (upper bound) and a long crack (lower bound), with collapse dominated by the crack when the crack depth was significant. Application of API 579 to the CIC provided collapse pressure predictions that were 18% conservative. Sixteen rupture tests were successfully completed investigating the failure behavior of longitudinally oriented corrosion, crack, and CIC. The pipe material was characterized and these properties were used to predict the collapse pressure of the defects using current methods. Existing methods for corrosion (CPS) and cracks (API 579, level 3, method D) gave conservative collapse pressure predictions. The collapse pressures for the CIC were bounded by those of a long corrosion groove and a long crack, with collapse dominated by the crack when the crack depth was significant. CIC failure behavior was determined by the crack to corrosion depth ratio, total defect depth and its profile. The results showed that the failure pressures for CIC were reduced when their equivalent depths were similar to those of corrosion and using crack evaluation techniques provided an approximate collapse pressure.

Smart PIG “Fingerprint” Inspections Can Lead to Fitness for Purpose Assessments and Contractual Disputes

2002 ◽  
Author(s):  
Roland Palmer-Jones ◽  
Phil Hopkins ◽  
Popi Nafis ◽  
Gordon Wintle
Keyword(s):  
High Sensitivity ◽  
Baseline Survey ◽  
Metal Loss ◽  
Safe Operation ◽  
Line Pipe ◽  
Fit For Purpose ◽  
The Subject ◽  
Corrosion Defects ◽  
And Storage ◽  
Pipeline Corrosion

A recent ‘fingerprint’ smart pigging inspection recorded over 40,000 metal loss (corrosion) features in a 57km 42” diameter, dry gas pipeline supplying a major LNG facility in Indonesia. The pipeline had been in operation for less than 6 months. Assessment of these results by the inspection company identified 10 sections of pipe that required repair according to ASME B31.G, indicating that the pipeline was not ‘fit for purpose’. The pipeline operator immediately cut out these 10 sections to ensure the continued safe operation of the new pipeline. A detailed pipeline corrosion study subsequently identified the features as corrosion that had occurred during transport and storage of the line pipe. In addition, the corrosion was found to be less severe than initially thought and the same work assessed the remaining defects and, calculations using DNV Guideline RP F101, showed that the features were all acceptable. It was concluded that the high sensitivity of the smart pigging tool, combined with the failure to identify the cause of the features and the simple initial feature assessment overestimated the significance of the corrosion defects. This demonstrates the need for good care and inspection of line pipe during transport storage and construction. It also highlights the need to conduct engineering assessments to determine the inspection philosophy and to quantify the ‘workmanship’ level of metal loss features acceptable on a fingerprint run, before the run takes place. Otherwise new pipelines containing ‘custom and practice’ defects could be the subject of lengthy and costly disputes between operator and constructor. This paper proposes a method for assessing baseline survey data that provides an acceptance level for pre-existing defects. This methodology will assist operators in assessing smart pigging data from new pipelines.

scholarly journals Buckling and vibration analysis of shape memory laminated composite beams under axially heterogeneous in-plane loads in the glass transition temperature region

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Nilesh Tiwari ◽  
A. A. Shaikh
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Boundary Conditions ◽  
Shape Memory ◽  
Transition Region ◽  
Shape Memory Polymer ◽  
Shear Deformation Theory ◽  
Effect Of Temperature ◽  
Glass Transition Region

AbstractBuckling and vibration study of the shape memory polymer composites (SMPC) across the glass transition temperature under heterogeneous loading conditions are presented. Finite element analysis based on C° continuity equation through the higher order shear deformation theory (HSDT) is employed considering non linear Von Karman approach to estimate critical buckling and vibration for the temperature span from 273 to 373 K. Extensive numerical investigations are presented to understand the effect of temperature, boundary conditions, aspect ratio, fiber orientations, laminate stacking and modes of phenomenon on the buckling and vibration behavior of SMPC beam along with the validation and convergence study. Effect of thermal conditions, particularly in the glass transition region of the shape memory polymer, is considerable and presents cohesive relation between dynamic modulus properties with magnitude of critical buckling and vibration. Moreover, it has also been inferred that type of axial loading condition along with the corresponding boundary conditions significantly affect the buckling and vibration load across the glass transition region.

Development of X90 and X100 Steel Grades for Seamless Linepipe Products

2014 ◽  
Author(s):  
Diana Toma ◽  
Silke Harksen ◽  
Dorothee Niklasch ◽  
Denise Mahn ◽  
Ashraf Koka
Keyword(s):  
Wall Thickness ◽  
Deep Water ◽  
High Strength ◽  
Oil And Gas Industry ◽  
Pipe Material ◽  
Line Pipe ◽  
Materials Development ◽  
Additional Tool ◽  
Technical Requirements ◽  
Steel Grades

The general trend in oil and gas industry gives a clear direction towards the need for high strength grades up to X100. The exploration in extreme regions and under severe conditions, e.g. in ultra deep water regions also considering High Temperature/High Pressure Fields or arctic areas, becomes more and more important with respect to the still growing demand of the world for natural resources. Further, the application of high strength materials enables the possibility of structure weight reduction which benefits to materials and cost reduction and increase of efficiency in the pipe line installation process. To address these topics, the development of such high strength steel grades with optimum combination of high tensile properties, excellent toughness properties and sour service resistivity for seamless quenched and tempered pipes are in the focus of the materials development and improvement of Vallourec. This paper will present the efforts put into the materials development for line pipe applications up to grade X100 for seamless pipes manufactured by Pilger Mill. The steel concept developed by Vallourec over the last years [1,2] was modified and adapted according to the technical requirements of the Pilger rolling process. Pipes with OD≥20″ and wall thickness up to 30 mm were rolled and subsequent quenched and tempered. The supportive application of thermodynamic and kinetic simulation techniques as additional tool for the material development was used. Results of mechanical characterization by tensile and toughness testing, as well as microstructure examination by light-optical microscopy will be shown. Advanced investigation techniques as scanning electron microcopy and electron backscatter diffraction are applied to characterize the pipe material up to the crystallographic level. The presented results will demonstrate not only the effect of a well-balanced alloying concept appointing micro-alloying, but also the high sophisticated and precise thermal treatment of these pipe products. The presented alloying concept enables the production grade X90 to X100 with wall thickness up to 30 mm and is further extending the product portfolio of Vallourec for riser systems for deepwater and ultra-deep water application [1, 3, 4].

Probabilistic Assessment of Minor Mechanical Damage

2006 ◽  
Author(s):  
Patrick H. Vieth ◽  
Clifford J. Maier ◽  
William V. Harper ◽  
Elden Johnson ◽  
Bhaskar Neogi ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Mechanical Damage ◽  
Residual Deformation ◽  
Evaluation Process ◽  
Assessment Methods ◽  
Metal Loss ◽  
Probabilistic Assessment ◽  
Pipeline System ◽  
Pressure Cycle ◽  
Important Field

In-line inspection (ILI) of the Trans Alaska Pipeline System (TAPS) using high resolution metal loss tools indicated 77 locations with suspected minor mechanical damage features (MDF). The tools used are able to detect the presence of a suspected feature, and measure indented dimensions, but are insufficient to detect the presence of cracks or gouges needed to reliably assess feature severity based solely on the ILI data. Excavations of 42 sites deemed most severe provided important field data characterizing residual deformation dimensions, the occurrence of gouges or cracks, and allowing a reliable field assessment of defect severity. Upon completion of the excavations, 35 possible MDF locations remained unexcavated. An engineering evaluation was undertaken to assess whether or not these remaining minor MDF pose a threat that is significant enough to warrant excavation. Multiple assessment methods were utilized including deterministic, probabilistic, and risk assessment methods. The probabilistic assessment of 35 unexcavated MDFs was performed using PCFStat; or Pressure Cycle Fatigue Statistical Assessment, which uses Monte Carlo simulation to estimate remaining fatigue life. PCFStat performs 1,000’s of simulations for each case where the input parameters are randomly selected from expected distributions. Of particular importance is the fatigue environment of the location. The results of the probabilistic assessment were used to estimate the potential for failure of remaining MDFs. The results suggest that 25 of 35 unexpected damage features had a POF of less than 10−4 over the remaining expected pipeline life cycle and thus are unlikely to fail. Alyeska considered a combination of probabilistic, deterministic and risk assessment results to decide on the actual locations to be examined. The results of probabilistic analysis also were found to support the outcome of the operator’s risk-based evaluation process.

Predicting the Brittle-to-Ductile Transition Temperatures for Surface Cracks in Pipeline Girth Welds: It’s Better Than You Thought

2008 ◽  
Author(s):  
Gery Wilkowski ◽  
David Rudland ◽  
Do-Jun Shim ◽  
David Horsley
Keyword(s):  
Transition Temperature ◽  
Surface Crack ◽  
Master Curve ◽  
Crack Depth ◽  
Temperature Shift ◽  
Transition Temperatures ◽  
Surface Cracks ◽  
Line Pipe ◽  
Brittle To Ductile Transition ◽  
Girth Welds

A methodology to predict the brittle-to-ductile transition temperature for sharp or blunt surface-breaking defects in base metals was developed and presented at IPC 2006. The method involved applying a series of transition temperature shifts due to loading rate, thickness, and constraint differences between bending versus tension loading, as well as a function of surface-crack depth. The result was a master curve of transition temperatures that could predict dynamic or static transition temperatures of through-wall cracks or surface cracks in pipes. The surface-crack brittle-to-ductile transition temperature could be predicted from either Charpy or CTOD bend-bar specimen transition temperature information. The surface crack in the pipe has much lower crack-tip constraint, and therefore a much lower brittle-to-ductile transition temperature than either the Charpy or CTOD bend-bar specimen transition temperature. This paper extends the prior work by presenting past and recent data on cracks in line-pipe girth welds. The data developed for one X100 weld metal shows that the same base-metal master curve for transition temperatures works well for line-pipe girth welds. The experimental results show that the transition temperature shift for the surface-crack constraint condition in the weld was about 30C lower than the transition temperature from standard CTOD bend-bar tests, and that transition temperature difference was predicted well. Hence surface cracks in girth welds may exhibit higher fracture resistance in full-scale behavior than might be predicted from CTOD bend-bar specimen testing. These limited tests show that with additional validation efforts the FITT Master Curve is appropriate for implementation to codes and standards for girth-weld defect stress-based criteria. For strain-based criteria or leak-before-break behavior, the pipeline would have to operate at some additional temperature above the FITT of the surface crack to ensure sufficient ductile fracture behavior.

scholarly journals Fractographic Analysis Of Selected Boron Steels Subjected To Impact Testing

2015 ◽  
Vol 60 (3) ◽  
pp. 2373-2378 ◽  
Author(s):  
W. Dudziński ◽  
Ł. Konat ◽  
B. Białobrzeska
Keyword(s):  
Transition Temperature ◽  
Impact Testing ◽  
Transition Curve ◽  
Brittle Transition ◽  
Significant Difference ◽  
Brittle Transition Temperature ◽  
Ductile To Brittle Transition ◽  
Character Of Fracture ◽  
The Impact ◽  
Boron Steels

Abstract In this paper dynamic properties of low-alloy boron steels – Hardox 500, B27 and HTK 900H in delivered state (after hardening and tempering) are considered. Charpy V-notch (CVN) test results in connection with fractography in the ductile-to-brittle transition temperature region were analyzed. Obtained from CVN test the impact transition curve, not always predicts properly a behavior of materials in conditions of dynamic loading. So an analyze of character of fracture helps to evaluate the real behavior of materials. Tested samples were cut out longitudinally in relation to cold work direction. The results of CVN test for selected steels, in temperatures: −40°C, −20°C, 0°C and +20°C are presented. Regarding ductile-to-brittle transition temperature, there is a significant difference taking into account values of Charpy V energy absorbed and a character of fracture.

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