Engineering Critical Assessment (ECA)

Location: Online (via Zoom Meeting) or on site if requested (additional travel and accommodation costs will apply)
Dates: September 01-02, 2021
Start Time: 09:00 am CST – 2 days (5 hours/day)
Min no. of participants: 5

Course Content

• Background: Pipelines may contain flaws in the form of crack-like defects, either present after manufacture or developed during service. ECA is the methodology used to estimate the critical loads at which such flaws propagate.
• Basic Concepts: The basic concepts used to define and measure material toughness and crack driving force will be reviewed. Current methods for stress-based design to establish critical conditions, including the CTOD (crack-tip opening displacement) design curve, FAD (Failure Assessment Diagram), and tearing instability will be discussed.
• Recent Developments: Recent developments in strain-based design, introduced primarily for pipelines crossing unstable terrain or subjected to plastic strain during pipe laying, will be discussed.

Summary of Key Points

• Methodology of ECA: Standard techniques to perform ECA based on fracture mechanics principles are available in a number of pipeline standards, including CSA Z662 (the Canadian pipeline code). For stress-based design, ECA may be done using the Crack Opening Displacement COD design curve (CSA) or Failure Assessment Diagram FAD.
• Toughness Property Measurement: For assessment of girth weld imperfections, initiation toughness and resistance curves may be measured using ASTM or BSI standards, for crack tip locations specified in CSA Z662. However, these standards specify highly constrained specimens to provide a lower-bound toughness; the actual toughness can be significantly higher because of the lower constraint in a pipe (i.e. shallow defect, tension loading).
• Current Developments: To support strain-based design, a toughness testing method using a single-edge-notched tension-loaded SE(T) (or SENT) specimen is nearing standardization.