Session: 03-03-04 Feature Assessment Case Studies Session 2 - Cracking - Part II

Paper Number: 87340

87340 - Recoating Scc on Gas Pipelines Without Grinding 

Considering both safety and cost-effectiveness in repairing SCC colonies, TC Energy and Blade Energy Partners conducted an engineering assessment to determine whether SCC colonies with depths of 20%wt, 30%wt and 40%wt in base material and DSAW pipe can be left in a gas pipeline without grinding out (depending on material fracture toughness and associated length) provided the features are recoated properly with a high-performance coating system. The operator would choose the safety level for recoating/grinding based on a fitness for service assessment.

The assessment findings suggest the following conclusions can be drawn:

·         1, Theoretically, SCC colonies and crack-like flaws with lengths and depths that are assessed by integrity assessment as fit-for-service can be left in gas pipelines without grinding out as long as the potent environment is isolated from the pipe surface by recoating.

·        2, Experimentally, both Australia Pipeline Associate (APIA) and the current study of the full-scale tests showed the amount of fatigue crack extension in air is small depending on depth and length after pressure cycling (Dp = 0.1 MAOP) for a number of cycles that replicate 50–year life of gas pipelines.

·         3, Review of available fatigue crack growth data in literature, and small- and full-scale fatigue testing by the current project indicated that the API 579 Paris Equation recommended by API 579‑1/ASME FFS‑1-2016 is an upper bound for fatigue crack growth. Therefore, the API 579 equation can be used to establish the limit crack size for SCC recoating.

·         4, Limiting crack dimensions for recoating without grinding were estimated using two different methodologies: API 579 FAD Level 2 method and CorLAS method. The effectiveness and appropriate conservatism of the analysis was demonstrated with the full-scale testing and validated by manual calculations.Each conclusion will be discussed in the presentation and demonstrated with examples.

          5. The field coating specification and procedures are consistent with  all the requirements in the Canadian Standard and INGAA Best Practices as well as the MQAP for the liquid coatings. 

Each conclusion will be discussed in the presentation and demonstrated with examples

Presenting Author: Ryan Milligan Blade Energy Partners

Presenting Author Biography: Ryan Milligan is a senior engineer at Blade Energy Partners and lab manager for Blade Energy Laboratories and has acquired over eight years of experience in the oil and gas industry. Ryan’s expertise includes materials, small- and full-scale testing, and finite element analysis. He has conducted research and failure analyses for upstream and midstream operations. He received his master’s degree in Civil Engineering from Texas A&M University in 2013.