Study on the integrity detection and evaluation method of damaged pipeline
To detect the integrity of damaged pipeline and accurately evaluate its damaged condition, a CCD image data guided digital automatic ultrasonic testing system was designed to realize the dynamic measurement of a pipeline damaged surface, and extract the characteristic parameter of damaged pipeline. Based on the three-dimensional discrete point set which gathered to describe the integrity of damaged pipeline, we establish a damaged pipeline entity model which is closer to the actual condition, analyze and simulate mechanical properties under the actual load by using the numerical simulation software (ABAQUS), to get the most dangerous region and the trend of stress and displacement. This method provides more reliable reference for integral safety analysis and evaluation of damaged pipeline.
Comprehensive review of structural deterioration of water mains: physically based models
Abstract This paper provides a comprehensive (although not exhaustive) overview of the physical/mechanical models that have been developed to improve the understanding of the structural performance of water mains. Several components have to be considered in modelling this structural behaviour. The residual structural capacity of water mains is affected by material deterioration due to environmental and operational conditions as well as quality of manufacturing and installation. This residual structural capacity is subjected to external and internal loads exerted by the soil pressure, traffic loading, frost loads, operational pressure and third party interference. Some models address only one or a few of the numerous components of the physical process that lead to breakage, while others attempt to take a more comprehensive approach. Initial efforts were aimed mainly towards development of deterministic models, while more recent models use a probabilistic approach to deal with uncertainties in defining the deterioration and failure processes. The physical/mechanical models were classified into two classes: deterministic and probabilistic models. The effect of temperature on pipe breakage is discussed from three angles; the first deals with temperature effects on pipe-soil interaction, the second deals with frost load effects and the third provides a brief review of various attempts to statistically quantify influence of temperature on water main failure. This paper complements the companion paper “Comprehensive review of structural deterioration of water mains: statistical models”, which reviews statistical methods that explain, quantify and predict pipe breakage or structural failures of water mains.
Thermal buckling and progressive ovalization of pipes: experiences at the TTS sodium test facility and their analysis
Abstract Two remarkable thermally induced deformation mechanisms of pipes which may have serious effects on structural integrity, thermal buckling and progressive ovalization, were observed on the horizontal piping of the sodium test facility, called TTS, with which cyclic thermal transient tests of structures had been conducted. The thermal buckling, which was caused by thermal stratification, occurred at a circumferentially welded region of the pipe where a noticeable geometrical imperfection existed. The buckling was analyzed comprehensively for this pipe, using both the finite element method and a simplified method based on Gellin's analysis results. The predictions were reasonable and gave confidence in accounting for the sodium leakage encountered at the TTS. It was also demonstrated by the finite element analyses that the progressive ovalization of the pipe cross-section from a circular to a downward triangular shape can be caused by cyclic thermal stratification under the existence of cover gas in the pipe.