Page 300 - Pipelines and Risers

Residual Strength of Dented Pipes with Cracks 273

Table 15.4 Parameter studies.

Note: Distribution types used in the table include: N-Normal, LN-Log-normal, EXP-Exponential.
15.5.5 Calibration of Safety Factor

Since fracture assessment of dented pipes with cracks has not been explicitly provided in the
current codes, it is difficult to estimate implied safety level of the corresponding criterion. The
target safety level is suggested to be based on the criteria for intact pipe. This ensures that
the safety level based on new criterion is equal to or higher than that of current codes.

The relationship between reliability index and the safety factor y is shown in Figure 15.7. If
no calibration is conducted, the safety factor usually equals to ~2.0 corresponding to a target
safety level p=3.926. Based on reliability calibration and target safety level p=3.71, the new
calibrated safety factor is y=1.89. If the target safety level is changed to p=3.09, the
corresponding safety factor is ~1.617.