Session: 03-03-07 Feature Assessment Case Studies Cracking I

Paper Number: 134079

134079 - Development of a SCC Crack Growth Rate Calculator 

Abstract: 

Stress corrosion cracking (SCC) integrity management of pipelines faces a particular challenge in that it is very difficult to estimate a representative crack growth rate (CGR) once SCC is confirmed to be affecting a particular asset.

Published SCC rates can be unreliable, as most assume a range of time periods for when cracks initiated (having a very large effect on resultant rates, especially for older pipelines) and give very little detail to help assess whether the published rate is applicable to a particular asset or operational conditions. Further complicating matters is that laboratory testing tends to be under Stage II growth conditions (crack initiation) where the crack growth rates are known to be much higher than compared to Stage III conditions (steady state growth of deeper cracks where the pipeline asset is currently operating). As a result, maximum crack growth rates can vary greatly from approximately 5 mm/yr (for laboratory testing) to 0.8 mm/yr from field reports (where conditions that resulted in this high rate are not known). Although these values are known to be in the upper end of the range, a “rule of thumb” sometimes used by operators can be around 0.3 mm/yr. But even this value can be considered to be conservatively aggressive when compared to some instances of reliable rates of approximately 0.15 mm/yr.

 

To help provide a starting point for operators, a SCC Crack Growth Rate Calculator has been developed that brings together the different parameters that are known to affect SCC crack growth rates (both for high-pH SCC and for near-neutral-pH SCC) from published scientific laboratory data in order to estimate what crack growth rate is possible for a particular asset, until more reliable data (such as from established laboratory fractographic methods) is available. This paper describes the development of this calculator and highlights the importance of obtaining reliable data.

Presenting Author: Erwin Gamboa ROSEN

Presenting Author Biography: Dr Erwin (Erk) Gamboa is a mechanical engineer who completed his PhD in Stress Corrosion Cracking from The University of Queensland, Australia in 2003. The following 13 years were spent in Australia as a University lecturer, industrial failure investigator and as a researcher for the gas pipeline industry in Australia, publishing more than 50 scientific articles in the areas of welding, coatings, fatigue and SCC in pipelines. Dr Gamboa changed continent to start working for TransCanada Pipelines (Calgary, Canada) in 2016 in the area of Risk, supporting threat management teams to manage 97,000 kms of gas transmission pipelines for the threats of SCC (axial and circumferential), manufacturing, hard spot and thermal expansion. In 2021, Dr Gamboa moved to Newcastle (UK) and joined ROSEN's Crack Management Group, helping pipeline operators around the world inspect and manage the integrity of their assets, in particular against cracking threats. Missing the snow and the mountains, Dr Gamboa and his family returned to Calgary 2023, still working for ROSEN.

Authors:

Erwin Gamboa ROSEN
Andrew Wynne ROSEN Group