Author(s): Lennart Jonsson
Linked Author(s):
Keywords: Pipeline; Leak; Hydraulic transient; Wave velocity; Modulus of elasticity
Abstract: Hydraulic transients in pressurized pipelines arise due to rapid flow changes and are characterized by pressure waves propagating back and forth through the pipeline. The characteristics of the transients are affected by different properties of the pipeline and a measurement and a careful analysis of a transient make it possible to derive some information about the pipeline, i. e. a hydraulic transient might be considered as a kind of a “probe”. This paper will discuss the possibility of detecting a leak in a single pipeline by means of analyzing the transient. The basic idea is that a transient will partly be reflected at the leak and a determination of the reflection time and knowledge of the wave propagation speed will provide the basis for locating the leak. However, with a complete rupture of the pipeline the pressure oscillation time period can be used for the same purpose. Two different cases will be described, the first case referring to an experimental, 135 m long pipeline set-up with a simulated leak and one real field case referring to a long (several km) pipeline located on the bottom of a water area and with a real leak. In both cases the effect of the leak is evident and comparison between the estimated and real locations of the leaks could be performed. Some computational simulations of transients in leak cases were also done in order to show that the effect of a leak could, at least qualitatively, be obtained with a straightforward computational description of the leak. One important conclusion from the studies is, that it is of paramount importance to know the real wave velocity with a good accuracy in order to locate the leak. Preferably, the wave speed should be determined from measurements, i. e. not theoretically.
Year: 2005