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.

The Practical Application of Fracture Control to Natural Gas Pipelines

2008 ◽  
Author(s):  
K. A. Widenmaier ◽  
A. B. Rothwell
Keyword(s):  
Natural Gas ◽  
Large Scale ◽  
High Strength ◽  
Fracture Initiation ◽  
Opening Angle ◽  
Pipe Material ◽  
Design Factor ◽  
Line Pipe ◽  
Natural Gas Pipelines ◽  
Crack Tip Opening

The use of high strength, high design-factor pipe to transport natural gas requires the careful design and selection of pipeline materials. A primary material concern is the characterization and control of ductile fracture initiation and arrest. Impact toughness in the form of Charpy V-notch energies or drop-weight tear tests is usually specified in the design and purchase of line pipe in order to prevent large-scale fracture. While minimum values are prescribed in various codes, they may not offer sufficient protection in pipelines with high pressure, cold temperature, rich gas designs. The implications of the crack driving force arising from the gas decompression versus the resisting force of the pipe material and backfill are examined. The use and limitations of the Battelle two-curve method as the standard model are compared with new developments utilizing crack-tip opening angle and other techniques. The methodology and reasoning used to specify the material properties for line pipe are described and the inherent limits and risks are discussed. The applicability of Charpy energy to predict ductile arrest in high strength pipes (X80 and above) is examined.

Brittle Fracture Arrest in High Charpy Energy Steels: Comparisons With Some Existing Data

2014 ◽  
Author(s):  
G. Wilkowski ◽  
D-J. Shim ◽  
Y. Hioe ◽  
S. Kalyanam ◽  
M. Uddin
Keyword(s):  
Brittle Fracture ◽  
Pipe Steels ◽  
Shelf Energy ◽  
Line Pipe ◽  
Pipe Burst ◽  
Sensitivity Studies ◽  
Shear Area ◽  
Fracture Arrest ◽  
Pipeline Design ◽  
Very High

Current line-pipe steels have significantly higher Charpy upper-shelf energy than older steels. Many newer line-pipe steels have Charpy upper-shelf energy in the 300 to 500J range, while older line-pipe steels (pre-1970) had values between 30 and 60J. With this increased Charpy energy comes two different and important aspects of how to predict the brittle fracture arrestability for these new line-pipe steels. The first aspect of concern is that the very high Charpy energy in modern line-pipe steels frequently produces invalid results in the standard pressed-notch DWTT specimen. Various modified DWTT specimens have been used in an attempt to address the deficiencies seen in the PN-DWTT procedure. In examining fracture surfaces of various modified DWTT samples, it has been found that using the steady-state fracture regions with similitude to pipe burst test (regions with constant shear lips) rather than the entire API fracture area, results collapse to one shear area versus temperature curve for all the various DWTT specimens tested. Results for several different materials will be shown. The difficulty with this fracture surface evaluation is that frequently the standard pressed-notch DWTT only gives valid transitional fracture data up to about 20-percent shear area, and then suddenly goes to 100-percent shear area. The second aspect is that with the much higher Charpy energy, the pipe does not need as much shear area to arrest a brittle fracture. Some analyses of past pipe burst tests have been recently shown and some additional cases will be presented. This new brittle fracture arrest criterion means that one does not necessarily have to specify 85-percent shear area in the DWTT all the time, but the shear area needed for brittle fracture arrest depends on the pipeline design conditions (diameter, hoop stress) and the Charpy upper-shelf energy of the steel. Sensitivity studies and examples will be shown.

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.

scholarly journals Design, Development and Confirmation of a High Toughness Gas Line Pipe for Alliance Pipeline at Camrose Pipe Company

2000 ◽  
Author(s):  
Alex J. Afaganis ◽  
James R. Mitchell ◽  
Lorne Carlson ◽  
Alan Gilroy-Scott
Keyword(s):  
Design Development ◽  
Line Pipe ◽  
High Toughness ◽  
Assessment Tests ◽  
Chevron Notch ◽  
Energy Measure ◽  
Drop Weight Tear Test ◽  
Fracture Assessment ◽  
Fracture Arrest ◽  
Pipe Manufacturing

Through 1999, Camrose Pipe Company manufactured ∼152 km (∼45 000 tonnes) of 1067 × 11.4mm pipe for Alliance Pipeline Partnership Ltd. This section of Alliance’s pipeline was manufactured to a design whose pipe fracture toughness requirements was significantly beyond those historically manufactured in Canada and initiated a major leap in plate/pipe manufacturing toughness capability. The development of line pipe toughness in Canada culminating in this order will be profiled. Further, this high toughness design is at the far reaches of the traditional fracture arrest models. Besides the traditional Charpy energy measure, and to confirm Alliance’s confidence in their fracture arrest design, another two sets of fracture assessment tests were used on a trial and production basis: the API chevron notch drop weight tear test (CN DWTT) energy and the energy of a similar test using an Alliance notch modification. The results of these tests will be reviewed and compared.

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.

Review of Fracture Control Technology for Gas Transmission Pipelines

2014 ◽  
Author(s):  
Xian-Kui Zhu
Keyword(s):  
Ductile Fracture ◽  
Fracture Propagation ◽  
High Strength ◽  
Fracture Initiation ◽  
Alternative Methods ◽  
Opening Angle ◽  
Pipeline Steels ◽  
Control Plan ◽  
Fracture Control ◽  
Arrest Toughness

A fracture control plan is often required for a gas transmission pipeline in the structural design and safe operation. Fracture control involves technologies to control brittle and ductile fracture initiation, as well as brittle and ductile fracture propagation for gas pipelines, as reviewed in this paper. The approaches developed forty years ago for the fracture initiation controls remain in use today, with limited improvements. In contrast, the approaches developed for the ductile fracture propagation control has not worked for today’s pipeline steels. Extensive efforts have been made to this topic, but new technology still needs to be developed for modern high-strength pipeline steels. Thus, this is the central to be reviewed. In order to control ductile fracture propagation, Battelle in the 1970s developed a two-curve model (BTCM) to determine arrest toughness for gas pipeline steels in terms of Charpy vee-notched (CVN) impact energy. Practice showed that the BTCM is viable for pipeline grades X65 and below, but issues emerged for higher grades. Thus, different corrections to improve the BTCM and alternative methods have been proposed over the years. This includes the CVN energy-based corrections, the drop-weight tear test (DWTT) energy-based correlations, the crack-tip opening angle (CTOA) criteria, and finite element methods. These approaches are reviewed and discussed in this paper, as well as the newest technology developed to determine fracture arrest toughness for high-strength pipeline steels.

Drop Weight Tear Testing of High Toughness Pipeline Material

2004 ◽  
Author(s):  
Kjell Olav Halsen ◽  
Espen Heier
Keyword(s):  
Fracture Initiation ◽  
Test Method ◽  
Side Impact ◽  
Battelle Memorial Institute ◽  
Line Pipe ◽  
Pipeline Steels ◽  
High Toughness ◽  
Drop Weight ◽  
Drop Weight Tear Test ◽  
Impact Side

Drop Weight Tear Testing is a common test method for determining a material’s ability to arrest a propagating crack. This testing method was developed by Battelle Memorial Institute, and is conducted in accordance with standards as API RP 5L3 ‘Recommended Practice for Conducting Drop Weight Tear testing on Line Pipe’ and EN 10274 ‘Metallic Materials - Drop Weight Tear Test’. One problem that has been encountered when performing Drop Weight Tear Testing of high toughness TMCP materials is that the pre-deformed material in the pressed notch is not sufficiently embrittled to ensure initiation of a brittle fracture. According to prevailing standards a brittle initiation is necessary for a valid test result. The material opposite the notched side (impact side) will deform quite considerably and is due to strain hardening expected to loose toughness prior to the actual fracture initiation takes place. Consequently high toughness material may give poor test results. In that respect, DNV initiated a Joint Industry Project called ‘Drop Weight Tear Testing of High Toughness Pipeline Material’, where the main objective was to obtain a better understanding on how the results from the DWTT should be interpreted for high toughness pipeline steels. During the project an extensive amount of Drop Weight Tear tests (DWTT) were performed on relevant modern pipeline steels. The resulting shear ratios were determined according to conventional fracture surface evaluation methods as well as newly developed methods as presented in the literature. The appearance of energy curves for both regular DWTT specimens and specimens with varying back gouge depths was also considered in the investigation and the consistency between the estimated shear ratios and the corresponding measured absorbed energies were thoroughly evaluated. This paper summarizes the results and recommendations obtained in the performed investigations.

Decompression Wave Speed in Rich Gas Mixtures at High Pressures (37 MPa) and Implications on Fracture Control Toughness Requirements in Pipeline Design

2010 ◽  
Author(s):  
K. K. Botros ◽  
J. Geerligs ◽  
R. J. Eiber
Keyword(s):  
High Pressure ◽  
Natural Gas ◽  
Wave Speed ◽  
Equations Of State ◽  
Gas Mixtures ◽  
Internal Diameter ◽  
Decompression Wave ◽  
Fracture Control ◽  
Predicted Values ◽  
Fracture Arrest

Measurements of decompression wave speed in conventional and rich natural gas mixtures following rupture of a high-pressure pipe have been conducted. A high pressure stainless steel rupture tube (internal diameter = 38.1 mm, and 42 m long), has been constructed and instrumented with 16 high frequency-response pressure transducers mounted very close to the rupture end and along the length of the tube to capture the pressure-time traces of the decompression wave. Tests were conducted for initial pressures of 33–37 MPa-a and a temperature range of 21 to 68 °C. The experimentally determined decompression wave speeds were compared to both GASDECOM and PIPEDECOM predictions with and without non-equilibrium condensation delays at phase crossing. The interception points of the isentropes representing the decompression process with the corresponding phase envelope of each mixture were correlated to the respective plateaus observed in the decompression wave speed profiles. Additionally, speeds of sound in the undisturbed gas mixtures at the initial pressures and temperatures were compared to predictions by five equations of state, namely BWRS, AGA-8, Peng-Robinson, Soave-Redlich-Kwong, and GERG. The measured gas decompression curves were used to predict the fracture arrest toughness needed to assure fracture control in natural gas pipelines. The rupture tube test results have shown that the Charpy fracture arrest values predicted using GASEDCOM are within +7 (conservative) and −11% (non-conservative) of the rupture tube predicted values. Similarly, PIPEDECOM with no temperature delay provides fracture arrest values that are within +13 and −20% of the rupture tube predicted values, while PIPEDECOM with a 1 °C temperature delay provides fracture arrest values that are within 0 and −20% of the rupture tube predicted values. Ideally, it would be better if the predicted values by the equations of state were above the rupture tube predicted values to make the predictions conservative but that was not always the case.

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.

Sign in / Sign up

Export Citation Format

Share Document