State-of-the-Art in Leak Detection and Localisation

Abstract

Many fluids transported by pipelines are hazardous. It is therefore often necessary to install leak detection (and localization) systems (LDS), particularly due to legal regulations such as - the Code for Federal Regulations (CFR) Title 49 Part 195 [1], API 1130 2nd Ed. [2], both for the USA, or - the Technische Regel fur Fernleitungen (TRFL) (Technical Rule for Pipelines) in Germany [5]. This article gives an overview of methodologies, methods and techniques for leak detection and localization; [6] and [7] are two other interesting sources giving an overview. Some remarks concerning (legal) regulations both for the USA and for Germany will be shown in section 1. Section 2 summarizes the requirements on LDS concerning (1) reliability, (2) sensitivity, (3) accuracy, and (4)robustness. These terms had been defined with respect to LDS within API 1155 [3], and will be explained in some detail within this section 2. External based LDS (according to API 1130 2nd Ed.) use local leak sensors to generate a leak alarm. Acoustic emission detectors, fibre optical sensing cable, vapour sensing cable, and liquid sensing cable based systems are shortly presented in section 3. Internal based LDS (also according to API 1130 2nd Ed.) use normal field sensors (e. g. flowmeters) for leak detection and sometimes leak localization. A significant part of the paper (section 4) deals with these internal systems such as - balancing systems (line balance, volume balance, compensated mass balance, etc.) - Real Time Transient Model LDS (RTTM-LDS) - pressure/flow monitoring, and - statistical analysis LDS. Different methods for leak localization (gradient intersection method, wave propagation analysis etc.) will be shown in section 5. The presentation of an Extended RTTM approach (E-RTTM) combining advantages of conventional RTTM LDS and statistical systems follows in section 6, together with the demonstration of applicability by means of two examples, - a liquid multi-batch pipeline, and - a gas pipeline. The University of Applied Sciences in Gelsenkirchen and KROHNE Oil & Gas from the Netherlands work closely together in the field of leak detection. The outstanding properties of the E-RTTM technology therefore motivated them to choose E-RTTM for PipePatrol, the KROHNE Oil & Gas leak detection and localization System.