Probabilistic performance assessment of fiber optic leak detection systems

Leak Detection Systems play a major role in enhancing reliability and operability of oil and gas pipelines. They have the functional capabilities to detect, locate and quantify leaks before they can cause drastic effects to environment and operation. The performance of Leak Detection Systems is typically affected by three different failures that have severe consequences, namely, delayed detection, missed detection and false detection of a leak. These failures pose a financial burden on operating companies. Missed detection leads to oil spill and exposes operating companies to financial risk and destroyed image while false detection results in unnecessary deployment of personnel and equipment. To insure operation continuity and maintain safe environment, Leak Detection Systems should be assessed at regular basis. To fulfill this need, a probabilistic performance assessment scheme based on limit state approach for Fiber Optic Leak Detection System (LDS) has been developed. The inherent uncertainties associated with leak detection and reporting capabilities are modeled to determine the LDS detection failure probability that combines two failure events, missed detection and delayed detection. Moreover, the probability of false detection is derived in terms of the lowest detectable change, the threshold. These three parameters establish the basis for an overall assessment scheme that can be used at any time to provide an up to date assessment about the Leak Detection System. The results will serve as the basis for deciding the actions that need to be taken to upgrade, repair or replace the system components or the system as a whole. The proposed assessment scheme has been applied to a case study to demonstrate its usefulness and feasibility. Copyright © 2014 by ASME.