Validation of Assessment Methods for Production Scale Girth Welding of High Strength Steel Pipelines with Multiple Pipe Sources

Details

• Creators:
  Swankie, Troy
• Corporate Creators:
  GL Noble Denton
• Contributors:
  Kieba, Max
• Corporate Contributors:
  United States. Dept. of Transportation. Pipeline and Hazardous Materials Safety Administration
• Subject/TRT Terms:
  • Defects
  • Evaluation and assessment
  • Flaw detection
  • Gas metal arc welding
  • High strength steel
  • Mechanical properties
  • Pipe
  • Pipelines
  • Validation
  • Welds
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• Publication/ Report Number:
  Report Number: 10361
• Resource Type:
  Tech Report
• Geographical Coverage:
  United States;United Kingdom
• TRIS Online Accession Number:
  01643615
• Edition:
  Issue: 1.0
• Corporate Publisher:
  GL Noble Denton
• Abstract:
  There is an increasing need to deliver energy from sources in remote areas to demand centers. For ; example, in North America, the delivery of gas from Alaska to demand centers in the lower 48 states is of ; major economic and strategic interest. This will require the design and construction of large diameter, long ; distance pipelines through adverse environments. The economics of these pipelines are dependent on the ; use of high strength steels to reduce the tonnage of steel required and on high productivity girth welding ; processes to shorten the construction period. ; Robust inspection methods are required to reliably detect and size any defects which may occur during ; welding, and an equally robust method is required to assess the impact of those defects on the safe ; operation of the pipeline. ; There are a number of methods that are commonly used for the assessment of a girth weld containing a ; ‘fabrication’ defect. These range from the more generic workmanship (or weld quality) defect acceptance ; limits to the more complex pipeline specific engineering critical assessment (ECA) methodologies where ; defect limits are derived based on the pipe size, material properties and pipeline loading conditions. ; The ECA approach is widely used to derive girth weld defect acceptance limits that are specific to a ; pipeline. They are based on either semi-analytical methods or on the results of large-scale tests on pipeline ; girth welds. There is no one standardized method. ; The guidance produced by the European Pipeline Research Group (EPRG) is an example of an established ; methodology based on the results of large-scale tests, while commonly used pipeline specific analytical ; assessment methods include API 1104a ; and CSA Z662a ; . Other commonly used semi-analytical methods, ; which are more generic in application, include API 579-1/ASME FFS-1a ; and BS 7910a ; . ; The application of any of these methods has certain limitations. For example, there is no ‘upper limit’ to line ; pipe strength specified for use of the ECA methodology presented in API 1104, although there are ; limitations to some of the equations used within the procedure which limit their range of applicability up to ; grade X80 line pipe. Similarly, the EPRG guidelines are limited to pipelines constructed from grade X70 line ; pipe; although much work has been undertaken to demonstrate the applicability of the guidelines to ; pipelines constructed from grade X80 line pipe, an updated guidance document has yet to be published. ; The objective of this project was to investigate the applicability of these ‘established’ methods for defining ; girth weld defect acceptance criteria for pipelines constructed from grade X100 line pipe. ; BP provided the project with ten girth welds following completion of their full-scale X100 operational trial at ; GL Noble Denton’s Spadeadam test facility located in Cumbria, England. This BP project involved the ; construction of two sections of 48in diameter pipeline. The construction process replicated full-scale ; practice, where the pipeline was welded above ground and then lowered into the ditch and backfilled. The ; pipeline test sections were then pressure cycled at a frequency to simulate 40 years of operation over a two ; year period. The project team selected the most appropriate girth welds that they considered would enable ; the effects of material variability between abutting pipes, different heats, and different pipe manufacturers to ; be investigated. ; A materials test program was developed to fully characterize the performance of each girth weld. In total, ; 217 tensile tests, 108 Charpy impact tests and 54 fracture mechanics tests were undertaken, in addition to ; weld macro sections and hardness surveys. The test program concluded with 30 curved wide plate (CWP) ‘mid-scale’ tests, of which 19 specimens contained machined surface breaking defects of specified depth ; and length dimensions. The remaining CWP specimens contained either natural welding defects (e.g., lack ; of penetration, lack of side wall fusion or porosity), deliberate defects that were introduced during welding, ; or combinations of natural and deliberate defects. ; Each CWP test was assessed using the procedures given in API 1104 (Option 2), EPRG, CSA Z662, ; BS 7910 and API 579-1/ASME FFS-1. The results of the small-scale test program for each weld were used ; as input into each assessment. The results of the assessments were compared with the results from the ; CWP tests to assess the limitations of each assessment method. ; In general, each assessment method performed well, giving a conservative prediction of failure stress. ; However, the accuracy of the prediction was found to vary significantly.
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• Format:
  PDF
• Funding:
  DTPH56-07-T-000006 WP #275
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/34644/dot_34644_DS1.pdf
• File Type:
  [PDF - 16.04 MB]
• Collection(s):
  PHMSA Collection ; US Transportation Collection
• Main Document Checksum:
  urn:sha256:eb450cd0aef37399f1adbcb7fdf9fd2dcea0b29fbde6702ff286bda7cd2ae208