Pipeline corrosion management
The reliability-based approach has been gaining popularity in the industry as a tool for planning transmission pipeline corrosion management programs.
Compared to the typical experience-based deterministic safety factors prescribed in standards, the traditional reliability-based approach has the following advantages and disadvantages:
| Traditional Reliability-Based Approach | Experience-Based Deterministic Safety Factors |
|---|---|
| + produces a consistent risk level after repairs | – produces unknown risk level after repairs |
| + reduces unnecessary excavations by targeting high-risk pipeline sections | – does not target high-risk locations |
| – uses computationally challenging probabilistic calculations | + uses simple deterministic calculations |
C-FER has developed a simplified reliability-based approach that eliminates the computational effort required for of the traditional reliability-based approach. This approach, called the Limit State Design (LSD) approach, uses a set of deterministic safety factors that have been calibrated to produce a similar risk level to the reliability-based approach. Since the safety factors are deterministic, their application does not require probabilistic calculations.
A comparison of the number of repairs required by the LSD approach, an operator full reliability-based approach, and the CSA Z662 (Clause 10.10.2) deterministic approach on real pipeline cases to determine corrosion repairs has been published in the paper, Implementation of Reliability-Based Criteria for Corrosion Assessment, covering almost 1200 km of pipeline and over half of millions of corrosion features.
The results are show in the figures below:
These figures demonstrate that the LSD approach in realizes the benefits of the traditional full reliability-based approach in optimizing repairs to achieve consistent safety levels, eliminating unnecessary conservatism, while being easy to use due to its deterministic format.
