Fracture Control Testing and Acceptance Criteria for Line Pipe

1981 ◽  
Vol 33 (03) ◽  
pp. 527-534 ◽  
Author(s):  
D.A. Hansen
Keyword(s):  
Acceptance Criteria ◽  
Line Pipe ◽  
Fracture Control

The Specifications Dilemma Posed by Ultra High Toughness Line Pipe Steels

2016 ◽  
Author(s):  
B. N. Leis ◽  
J. M. Gray ◽  
F. J. Barbaro
Keyword(s):  
Critical Element ◽  
Line Pipe ◽  
Control Plan ◽  
Full Size ◽  
Manufacturing Procedure ◽  
High Vapor ◽  
Qualification Testing ◽  
Fracture Control ◽  
Shear Failures ◽  
Propagating Shear

Pipelines transporting compressible hydrocarbons like methane or high-vapor-pressure liquids under supercritical conditions are uniquely susceptible to long-propagating failures in the event that initiation triggers this process. The unplanned release of hydrocarbons from such pipelines poses the risk for significant pollution and/or the horrific potential of explosion and a very large fire, depending on the transported product. Accordingly, the manufacturing procedure specification (MPS) developed to ensure the design requirements are met by the steel and pipe-making process is a critical element of the fracture control plan, whose broad purpose is to protect the environment and ensure public safety, and preserve the operator’s investment in the asset. This paper considers steel specification to avoid long-propagating shear failures in advanced-design larger-diameter higher-pressure pipelines made of thinner-wall higher-grade steels. Assuming that the arrest requirements can be reliably predicted it remains to specify the steel design, and ensure fracture control can be affected through the MPS and manufacturing procedure qualification testing (MPQT). While standards exist for use in MPQTs to establish that the MPS requirements have been met, very often CVN specimens remain unbroken, while DWTT specimens exhibit features that are inconsistent with the historic response and assumptions that underlie many standards. In addition, sub-width specimens are often used, whereas there is no standardized means to scale those results consistent with the full-width response required by some standards. Finally, empirical models such as the Battelle two curve model (BTCM) widely used to predict required arrest resistance have their roots in sub-width specimens, yet their outcome is widely expressed in a full-size context. This paper reviews results for sub-width specimens developed for steels in the era that the BTCM was calibrated to establish scaling rules to facilitate prediction in a full-size setting. Thereafter, issues associated with the use of sub-width specimens are reviewed and criteria are developed to scale results from such testing for use in the MPS, and MPQT, which is presented as a function of toughness. Finally, issues associated with the acceptance of data from unbroken CVN specimens are reviewed, as are known issues in the interpretation of DWTT fracture surfaces.

Fracture Control for the Alliance Pipeline

2000 ◽  
Author(s):  
Bob Eiber ◽  
Lorne Carlson ◽  
Brian Leis
Keyword(s):  
Natural Gas ◽  
New Technology ◽  
Fracture Initiation ◽  
Line Pipe ◽  
Control Plan ◽  
High Toughness ◽  
Pipe Burst ◽  
Fracture Control ◽  
Pipe Fittings ◽  
Fracture Arrest

This paper reviews the fracture control plan for the Alliance Pipeline, which is planned for operation in 2000. This natural-gas pipeline is 2627 km (1858 miles) long, running from British Columbia, Canada to Illinois, USA. Interest in the fracture control for this pipeline results from its design, which is based on transporting a rich natural gas (up to 15% ethane, 3% propane) at a relatively high pressure 12,000 kPa (1740 psi). This break from traditional pressures and lean gases, which frequently are constrained by incremental expansion, is more efficient and more economical than previous natural gas pipelines. Use of higher pressures and rich gas requires adequate fracture control for the line pipe, fittings, and valves. This fracture control has been achieved for the Alliance Pipeline by specifying high-toughness steels, in terms of both fracture-initiation and fracture-propagation resistance for the line pipe, fittings and heavy wall components. While beneficial from an economics viewpoint, the need for higher toughnesses raised concern over the validity of the fracture control plan, which was based on existing and new technology. The concern focused on fracture arrest using high toughness steels. The concern was associated with characterizing fracture arrest resistance using Charpy V-notch impact toughness, the most commonly used method to measure fracture arrest resistance. Developments were undertaken to address problems associated with the use of higher-toughness steel and these were validated with full-scale pipe burst tests to demonstrate the viability of the fracture control plan. The solution involved extending existing methods to address much higher toughness steels, which provided a significantly improved correlation between fracture arrest predictions and experimental results. In the burst tests, data was collected to validate the Alliance design and also to extend the database of fracture arrest data to assist future pipelines. Data such as the pressure between the pipe and soil as the gas escapes from the pipe, the sound levels in the atmosphere, the movement and strains in the pipe ahead of the running fracture were instrumented in the test and the available results are presented.

How New Vintage Line-Pipe Steel Fracture Properties Differ From Old Vintage Line-Pipe Steels

2012 ◽  
Author(s):  
G. Wilkowski ◽  
D.-J. Shim ◽  
Y. Hioe ◽  
S. Kalyanam ◽  
F. Brust
Keyword(s):  
Brittle Fracture ◽  
Fracture Behavior ◽  
Pipe Steel ◽  
Full Scale ◽  
Actual Behavior ◽  
Correction Factors ◽  
Pipe Steels ◽  
Line Pipe ◽  
Line Pipe Steel ◽  
Fracture Control

Newer vintage line-pipe steels, even for lower grades (i.e., X60 to X70) have much different fracture behavior than older line-pipe steels. These differences significantly affect the fracture control aspects for both brittle fracture and ductile fracture of new pipelines. Perhaps one of the most significant effects is with brittle fracture control for new line-pipe steels. From past work brittle fracture control was achieved through the specification of the drop-weight-tear test (DWTT) in API 5L3. With the very high Charpy energy materials that are being made today, brittle fracture will not easily initiate from the pressed notch of the standard DWTT specimen, whereas for older line-pipe steels that was the normal behavior. This behavior is now referred to as “Abnormal Fracture Appearance” (AFA). More recent work shows a more disturbing trend that one can get 100-percent shear area in the standard pressed-notch DWTT specimen, but the material is really susceptible to brittle fracture. This is a related phenomenon due to the high fracture initiation energy in the standard DWTT specimen that we call “Abnormal Fracture Behavior” (AFB). This paper discusses modified DWTT procedures and some full-scale results. The differences in the actual behavior versus the standard DWTT can be significant. Modifications to the API 5L3 test procedure are needed. The second aspect deals with empirical fracture control for unstable ductile fractures based on older line-pipe steel tests initially from tests 30-years ago. As higher-grade line-pipe steels have been developed, a few additional full-scale burst tests have shown that correction factors on the Charpy energy values are needed as the grade increases. Those correction factors from the newer burst tests were subsequently found to be related to relationship of the Charpy energy values to the DWTT energy values, where the DWTT has better similitude than the Charpy test for fracture behavior (other than the transition temperature issue noted above). Once on the upper-shelf, recent data suggest that what was once thought to be a grade correction factor may really be due to steel manufacturing process changes with time that affect even new low-grade steels. Correction factors comparable to that for X100 steels have been indicated to be needed for even X65 grade steels. Hence the past empirical equations in Codes and Standards like B31.8 will significantly under-predict the actual values needed for most new line-pipe steels.

Fracture Control in Carbon Dioxide Pipelines: The Effect of Impurities

2008 ◽  
Author(s):  
Andrew Cosham ◽  
Robert J. Eiber
Keyword(s):  
Carbon Dioxide ◽  
Saturation Pressure ◽  
Transportation Infrastructure ◽  
Low Carbon ◽  
Long Distance ◽  
Intergovernmental Panel ◽  
Line Pipe ◽  
Low Carbon Economy ◽  
Effect Of Impurities ◽  
Fracture Control

The fourth report from the Intergovernmental Panel on Climate Change states that “Warming of the climate system is unequivocal...” It further states that there is a “very high confidence that the global average net effect of human activities since 1750 has been one of warming.” One of the proposed technologies that may play a role in the transition to a low-carbon economy is carbon dioxide capture and storage (CCS). The widespread adoption of CCS will require the transportation of the CO2 from where it is captured to where it is to be stored. Pipelines can be expected to play a significant role in the required transportation infrastructure. The transportation of CO2 by long-distance transmission pipeline is established technology; there are examples of CO2 pipelines in USA, Europe and Africa. The required infrastructure for CCS may involve new pipelines and/or the change-of-use of existing pipelines from their current service to CO2 service. Fracture control is concerned with designing a pipeline with a high tolerance to defects introduced during manufacturing, construction and service; and preventing, or minimising the length of, long running fractures. The decompression characteristics of CO2 mean that CO2 pipelines may be more susceptible to long running fractures than hydrocarbon gas pipelines. Long running fractures in CO2 pipelines may be preventable by specifying a line pipe steel toughness that ensures that the ‘arrest pressure’ is greater than the ‘saturation pressure’ or by using mechanical crack arrestors. The preferred choice is control through steel toughness because it assures shorter fracture lengths. The ‘saturation pressure’ depends upon the operating temperature and pressure, and the composition of the fluid. ‘Captured’ CO2 may contain different types or proportions of impurities to ‘reservoir’ CO2. Impurities, such as hydrogen or methane, have a significant effect on the decompression characteristics of CO2, increasing the ‘saturation pressure’. The implication is that the presence of impurities means that a higher toughness is required for fracture arrest compared to that for pure CO2. The effect of impurities on the decompression characteristics of CO2 are investigated through the use of the BWRS equation of state. The results are compared with experimental data in the published literature. The implications for the development of a CCS transportation infrastructure are discussed.

Tandem Flux-Cored Arc Welding for High Strength Line Pipe

2014 ◽  
Author(s):  
Christopher J. Penniston ◽  
Robert M. Huntley
Keyword(s):  
Arc Welding ◽  
Short Circuit ◽  
High Strength ◽  
Fine Tuning ◽  
Crack Tip Opening Displacement ◽  
Acceptance Criteria ◽  
Line Pipe ◽  
Power Sources ◽  
Flux Cored Arc Welding ◽  
Mechanized Welding

The benefits of mechanized welding for pipeline construction are well known, as reflected by the high industrial acceptance and usage of its variations. However, the engineering and qualification costs associated with the preparation of alternative acceptance criteria for typical pulsed and short-circuit MIG (GMAW-P and GMAW-S) girth welds can make the implementation of mechanization too costly and/or time consuming for small projects. A multi-wire welding technology, employing a high-deposition consumable that possesses excellent positional capability, along with paired digitally controlled asynchronous inverter power sources, is presented. Trials were performed on CSA Z245.1 914 mm (NPS 36) OD × 20.4 mm WT Grade 483 heavy wall high strength line pipe. One variant used an 8-head internal welding machine for the root pass, and a conventional single torch short-circuit GMAW hot pass in a compound narrow-groove configuration. A second variant utilized an externally applied controlled short-circuit GMAW-S process for the root pass in a factory-style pipe bevel configuration. Both variants employed fill and cap passes using tandem pulsed gas-shielded flux-cored arc welding (T-FCAW-G/P), using rutile consumables, with the “bug and band” MOW II mechanized welding system. Basic mechanical testing was performed on the first weld variant, along with single-edge notched bend (SENB) crack tip opening displacement (CTOD) tests, and results are presented. A productivity comparison is then shown, using weld data from the second weld variant against alternative processes, showing considerably lower fill and cap pass arc time using the T-FCAW-G/P process. Given the process’s low tendency for the formation of planar discontinuities, the process is appealing for the use of “workmanship” acceptance criteria. With further procedure development and fine-tuning of the process, tandem flux-cored arc welding may prove viable, particularly for “short” pipelines, where the costs of comprehensive engineering critical assessment/fitness-for-purpose weld procedure qualification and associated engineering work aren’t justified; as a higher productivity alternative to single wire flux-cored arc welding for mechanized tie-in welding; as a much higher productivity alternative to SMAW for tie-ins; or with a narrow groove design, mainline applications for longer-distance projects.

Fracture Control — Offshore Pipelines: Probabilistic Fracture Assessment of Surface Cracked Ductile Pipelines Using Analytical Equations

2005 ◽  
Author(s):  
Andreas Sandvik ◽  
Erling O̸stby ◽  
Arvid Naess ◽  
Gudfinnur Sigurdsson ◽  
Christian Thaulow
Keyword(s):  
Fracture Behaviour ◽  
Crack Growth Resistance ◽  
Bending Moments ◽  
Line Pipe ◽  
Offshore Pipelines ◽  
Crack Driving Force ◽  
Ductile Tearing ◽  
Fracture Assessment ◽  
Fracture Control ◽  
Probability Of Fracture

Since modern pipelines usually display ductile fracture behaviour, fracture assessments accounting for ductile tearing should be used. In this work we use a simplified strain-based fracture mechanics equation in the probabilistic fracture assessments. Furthermore, we use the traditional tangency criterion between the crack driving force and the crack growth resistance, in calculation of the onset of critical ductile tearing. Additionally, two types of external load on the line-pipe are considered, namely strains due to external bending moments and internal pressure. We establish the probability of fracture for line-pipes with relevant diameter to thickness ratios, and thicknesses, for J-laid or S-laid offshore pipelines. The distinction between system effects, in which all defects are likely to be subject to the same loading, and cases where only a small part of the pipeline will experience high loading, is also discussed.

Integrity Implications of Unintentionally Expanded Line Pipe

2014 ◽  
Author(s):  
M. J. Rosenfeld
Keyword(s):  
Construction Projects ◽  
High Strength ◽  
Line Pipe ◽  
The Us ◽  
Test Pressure ◽  
Fracture Control ◽  
External Loads ◽  
Pipe Manufacturing ◽  
Diameter Change

Pipeline construction projects underway in the US during the 2005 to 2010 timeframe encountered occurrences of unintended diameter expansion during hydrostatic testing of high-strength line pipe. Causes of expansion were in some cases attributed to inadequate pipe manufacturing and procurement practices or in other cases to high external loads present concurrently during pressure testing. This paper considers the implications to long-term pipeline integrity arising with pipe that underwent unintended diameter change with associated strain accumulation. The paper presents a relationship between test pressure and diameter expansion, estimation of the reserve strain capacity, effects on fracture control, and effects on integrity reassessment intervals. The conclusions are that the integrity issues associated with limited magnitudes of diameter change can be readily managed.

Probabilistic Fracture Analysis of Pipelines

2002 ◽  
Author(s):  
Shahani Kariyawasam ◽  
Mark Stephens ◽  
Wytze Sloterdijk
Keyword(s):  
Fracture Initiation ◽  
Crack Arrest ◽  
Small Samples ◽  
Mixed Mode Fracture ◽  
Line Pipe ◽  
Initiation And Propagation ◽  
Probabilistic Characterization ◽  
Fracture Control ◽  
Added Uncertainty

Many pipelines were built before the industry developed material specifications for fracture control. For these older pipelines an essential first step in fracture control is to estimate the existing likelihood of fracture initiation and propagation. It is also desirable for operators to know the size of defects the pipeline can tolerate without causing pipeline fracture. This paper describes a methodology developed for the probabilistic characterization of the fracture initiation and propagation susceptibility of older pipeline segments, made from line pipe exhibiting (by today’s standards) low to moderate strength and low notch toughness. It is applicable to ductile, brittle and mixed-mode fracture behaviour. A probabilistic analysis approach is ideally suited to the problem since it offers a way to quantitatively address both the inherent variability in the mechanical properties of line pipe and the uncertainties associated with the various models currently available to determine the conditions necessary to cause crack initiation or to force crack arrest. The method described addresses both of these forms of uncertainty, and also reflects the added uncertainty inherent in trying to estimate material properties for existing lines from small samples of data.

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