Pipeline ruptures have the potential to cause significant economic and environmental impact in a short period of time, and therefore it is critical for a pipeline operator to be able to timely detect ruptures and respond rapidly. Public stakeholder expectations are high and an evolving expectation is that the response to such an event be automated to the greatest extent possible, potentially initiating an automatic pipeline shutdown upon receipt of a system-based rupture alarm. These types of performance expectation are challenging to achieve with conventional, model-based, leak-detection systems (i.e. CPM-RTTMs) as the reliability measured in terms of the false alarm rate is typically too high to initiate automatic pipeline shutdowns.
Enbridge Pipelines Inc. (EPI) has been actively participating on an industry task force chaired by the API Cybernetics Committee, focused on the development of best practices in the area of Rupture Recognition and Response. After an industry release of the first version of a Rupture Recognition and Response guidance document, EPI has initiated development of its own internal Rupture Recognition Program (RRP) program. The RRP considers several rupture recognition approaches simultaneously, ranging from improvements to existing CPM leak detection to the development of new SCADA based rupture detection algorithms. This paper will provide an overview of the different rupture detection approaches, present some high level results and share learnings from work completed to date.
Most major liquid pipeline operators have a method of automatic leak detection monitoring and system alarming. Although those leak detection systems are able to detect ruptures the general low reliability of these systems in terms of their high frequency of false alarms (e.g. 1 or 2 false alarm a day for complicated long lines) may have played a role in some past rupture incidents. Those alarms may have caused controller desensitization and thereafter ignored or not given the appropriate attention.Some pipeline industry experts are of the opinion that in the pursuit of detecting the smallest leaks, we may have become more exposed to the ruptures.
Evaluating the effectiveness of a CPM implementation via leak testing is paramount to confirm that the performance of the CPM system is acceptable based on a pipeline company's risk profile for detecting leaks. However, leak testing of a CPM system is challenging due to the complexity of the CPM design, as well as the need to stress test the CPM over the breadth of operational scenarios to assess the robustness of the CPM, where test coverage includes steady state threshold sensitivity, transient threshold sensitivity and the threshold switching action. This paper reviews the leak testing challenges encountered during CPM implementation and evaluation, outlines its limitations, and proposes a novel approach to an API RP 1130 recommended test method that can be applied to stress test CPM sensitivity, providing an evaluation of CPM robustness over a range of varying operating scenarios. The concept of the new testing methodology, along with a feasibility study on the automation of the test process, is discussed. Extensive tests are carried out to evaluate and assess the new testing methodology, and a comparison is made with other API RP 1130 recommended leak test methodologies such as parameter manipulation tests, simulated leak tests, and fluid withdrawal tests. The results indicate that the proposed technique has far wider testing coverage compared to existing approaches to leak testing while providing similar sensitivity measurement results and appears promising for use in stress testing sensitivity of CPM systems to gain an understanding of CPM robustness, which in turn has improved the sensitivity and robustness of Enbridge's current leak detection systems.