Ductile Fracture Control for High Strength Steel Pipelines

Author(s):  
Andrea Fonzo ◽  
Andrea Meleddu ◽  
Giuseppe Demofonti ◽  
Michele Tavassi ◽  
Brian Rothwell

The determination of the toughness values required for arresting ductile fracture propagation has been historically based on the use of models whose resulting predictions can be very unreliable when applied to new high strength linepipe materials (≥X100) and/or different operating conditions. In addition, for the modern high strength steels a methodology for determining the material fracture resistance for arresting running shear fracture starting from laboratory data is still lacking. The work here presented (developed within a PRCI sponsored project) deals with the use of CSM’s proprietary PICPRO® Finite Element code to develop methodologies for ductile fracture propagation control in high grade steel pipes. The relationships providing the maximum crack driving force which can be experienced in a pipe operated at known conditions have been determined, for different types of gas. On the other side, an empirical relationship has been found to correlate the critical Crack Tip Opening Angle (CTOA) determined by laboratory testing, to the critical CTOA on pipe (which represents the material fracture propagation resistance) with the aid of devoted simulations of past full-scale burst tests. By comparing Driving Force and Resistance Force, ductile fracture control for high strength steel pipelines can be achieved.

Author(s):  
Xian-Kui Zhu

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.


Author(s):  
Robert M. Andrews ◽  
Neil A. Millwood ◽  
A. David Batte ◽  
Barbara J. Lowesmith

The drive to reduce the installed cost of high-capacity long-distance pipelines has focused attention on increasing the strength of the pipe material, in order to reduce the tonnage of material purchased, transportation and welding costs. In parallel with developments in plate rolling and pipe fabrication, the properties and performance of prototype pipe materials and construction welds have already been extensively evaluated. While these studies have provided considerable confidence in the performance of X100 pipe, a major remaining issue in the introduction of such steels has been an understanding of the resistance to propagating fractures. The scarcity of relevant fracture propagation data and concerns about the measurement and specification of toughness in high strength steel pipes have led to doubts that the existing methods for control of ductile fracture can be extrapolated to X100 strength levels. In order to provide experimental data on which to base fracture control approaches, a Joint Industry Project has been undertaken using conditions representative of potential applications. Results are presented from two full-scale fracture propagation tests on 914mm pre-production grade X100 pipes pressurised using natural gas. The full-scale results are compared with small-scale test specimen data and also with results from other full-scale tests on high strength steel pipes. This provides a valuable insight into the fracture response of these materials. Information has also been obtained concerning the predictive capability of current gas decompression models. These results provide a contribution to the development of fracture control plans in pipelines using X100 steel linepipe.


2020 ◽  
Vol 210 ◽  
pp. 110401 ◽  
Author(s):  
Yuan-Zuo Wang ◽  
Guo-Qiang Li ◽  
Yan-Bo Wang ◽  
Yi-Fan Lyu ◽  
Heng Li

Author(s):  
D. Michael Johnson ◽  
Peter S. Cumber ◽  
Norval Horner ◽  
Lorne Carlson ◽  
Robert Eiber

A full scale fracture propagation test facility has been developed to validate the design, in terms of the ability of the material to avert a propagating fracture, of a major new pipeline to transport gas 1800 miles from British Columbia in Canada to Chicago in the USA. The pipeline, being built by Alliance Pipeline Ltd, will transport rich natural gas, i.e. gas with a higher than normal proportion of heavier hydrocarbons, at a maximum operating pressure of 12,000 kPa. This gas mixture and pressure combination imposes a more severe requirement on the pipe steel toughness than the traditional operating conditions of North American pipelines. As these conditions were outside the validated range of models, two full-scale experiments were conducted to prove the design. This paper will provide details of the construction of the 367m long experimental facility at the BG Technology Spadeadam test site along with the key data obtained from the experiments. Evaluation of this data showed that the test program had validated Alliance’s fracture control design. The decompression data obtained in the experiments will be compared against predictions from a new decompression model developed by BG Technology. The use of the experimental facility and the model to support future developments in the pipeline industry, particularly in relation to the use of high strength steels, will also be discussed.


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