PIPELINE LEAK DETECTION AND LOCALIZATION BASED ON ADVANCED SIGNAL PROCESSING AND NEGATIVE PRESSURE WAVE ANALYSIS

Pipeline monitoring and leak detection are critical for safe and economical operation as well as preventative maintenance in water and oil industry. They also provide environmental protection from crude oil emission or theft. Leak detection and localization play a key role in the overall integrity monitoring of a pipeline system especially for long residential water pipelines and midstream crude pipelines. Operational data such as fluid flow and pressure data are often utilized in many physics and computation-based leak detection and localization methods. However, noise in both flow and pressure affects recognition of actual leak pressure drop and results in false leak alarm and inaccurate leakage localization. In this paper a total variation regularized numerical differentiation (TVRegDiff) algorithm is used to estimate derivatives from noisy fluid flow and pressure data. Then possible leak events from both fluid flow data and pressure data are obtained by examining these derivatives against corresponding control limit lines. Customized parameter criteria of flow and operation activities are used to effectively filter flow and operation events from possible leak events. Therefore, earliest leak occurrence time and pressure meters can be identified. Finally, negative pressure wave (NPW) analysis is combined with the leak recognition to compute and locate leakage. Negative pressure wave methods are based on the principle that a leak will cause a sudden pressure alteration as well as a decrease in fluid flow speed which will result in an instantaneous pressure drop and speed variation along the pipeline. As the instantaneous pressure drop occurs, it generates a negative pressure wave starting at the leakage position and propagates with certain speeds towards both the upstream and downstream ends of the pipeline section. Depending on the leakage position from the two ends and actual negative pressure wave velocities towards upstream and downstream there are time sequence of the pressure wave arriving at both ends. The lapse of time arrival and negative pressure wave velocities are then used to calculate the actual leakage position within the pipeline section. A field leak case study indicates that actual leak pressure drop is correctly captured and pipeline leakage can be accurately located. The accuracy of leak localization is theoretically dependent on the pressure and flow meter frequency. With widely accepted industry standards for pressure devices used in industry applications it is proved to be a practical, efficient and accurate leak detection and localization method. This method can also be applied to not only residential water pipelines but crude oil pipelines.