Predictive crack growth models for pipeline integrity and risk management - phase II

近中性pH应力腐蚀开裂(NNpHSCC)对加拿大管道公司和加拿大消费者来说都是一笔巨大的成本。从完整性管理的角度来看，NNPHSCC是通过对石油管道的在线检测或对天然气管道的水压试验来控制的。这两种技术中的任何一种都可以提供多年的服务故障保护，然后必须重复这一过程。对于天然气管道来说，测试周期特别麻烦，因为水压测试技术只能检测到在水压应力下失效的相当大的缺陷。这些程序也非常昂贵。复查间隔或复测间隔目前是基于经验模型确定的，这是相当不精确的。艾伯塔大学的长期研究发现，管线钢在NNpH环境中的裂纹扩展行为与腐蚀-疲劳行为是一致的，并且裂纹扩展速率可以与一个包含所有可能的与裂纹扩展相关的可测量变量的项相关联。

Near-neutral pH Stress Corrosion Cracking (NNpHSCC) represents a substantial cost to Canadian pipeline companies and hence to Canadian consumers. NNpHSCC is controlled from an integrity management point of view by in-line inspection for oil pipelines or by hydrostatic testing for gas pipelines. Either of these techniques provides protection from in-service failures for a number of years and then the process has to be repeated. The testing cycle is particularly troublesome for gas pipelines since only quite large flaws that fail at hydrotest stress are detected by the hydrostatic testing technique. These procedures are also enormously expensive. The re-inspection interval or re-test interval is currently determined based on empirical models, which are rather imprecise. Long term investigation at the University of Alberta has found that the crack growth behavior of pipeline steels in NNpH environments is consistent with that of corrosion-fatigue, and crack growth rate can be correlated with a single term that is incorporated with all possible measurable variables pertinent to crack growth.