Structural Integrity Of Pipes Research Articles

The structural integrity of corroded concrete sewers

The objective of the study was to analyse the relationship between the rate of corrosion and the structural integrity of old corroded concrete sewer pipes by employing different methods of calculation of the loads acting on the pipes. The article discusses factors affecting corrosion of sewer pipes and provides examples to illustrate its various rates. The four methods used in the analysis of the ring bending tensile strengths of sewer pipes differ in the assumptions concerning the determination of the size and distribution of loads acting on the pipes.The results of two case studies were used to assess how the rate of corrosion influences the structural integrity of sewer pipes. Another objective of the analysis was to check whether the prioritisation of sewers for renewal based on a method that involves determining categories of sewer failure probability due to corrosion is correct. The key conclusion is that the method based on the categories of failure probability is not always suitable to assess the structural integrity of sewer pipes and that the corrosion of the pipe walls does not always have a deteriorating effect on the structural integrity of the pipes. In some cases of tight sewer pipes around which there have been rheological transitions in the soil, the structural integrity of the pipes may improve despite the corrosion of the pipe walls.

Modal and Vibration Analysis of Filter System in Petrochemical Plant

Filter systems are widely used in petrochemical plants for removing solid impurities from hydrocarbon oils. The backwash is the cleaning process used to remove the impurities on the sieves of the filters without a need to interrupt the operation of the entire system. This paper presents a case study based on the actual project of a filter system in a petrochemical plant, to demonstrate the significant effect of vibration on the structural integrity of piping. The induced vibration had led to the structural fatigue failure of the pipes connecting the filter system. A preliminary assessment suggested that the vibrations are caused by the operation of backwashing of the filter system. A process for solving the vibration problem based on the modal analysis of the filter system using the commercial finite element software for simulation is therefore proposed. The computed natural frequencies of the system and the vibration data measured on site are assessed based on the resonance effect of the complete system including the piping connected to the filters. Several approaches are proposed to adjust the natural frequencies of the system in such a way that an optimal and a reasonable solution for solving the vibration problem is obtained.

Synthetic Aperture Focusing Technique for Detecting Transverse Cracks in Austenitic and Dissimilar Welds

The inspection of austenitic and dissimilar welds using ultrasound demands for sophisticated testing techniques. The application of reconstruction methods like the Synthetic Aperture Focusing Technique (SAFT) on the measurement results provides an appropriate approach for defect characterization and sizing. Nevertheless, the reconstruction algorithm has to consider the aniso-tropic wave propagation inside the inhomogeneous weld material. In recent years the detection of transverse cracks has become increasingly important for ensuring the structural integrity of pipes in the primary circuit of nuclear power plants or longitudinally welded, cladded pipes. However, relia-ble inspection techniques are hardly available. In this particular case, it is expected that the compar-atively long propagation path of the ultrasonic wave field inside the inhomogeneous weld material enhances the effect of anisotropy and influences the accuracy and the signal-to-noise-ratio of the reconstruction result. In this contribution we suggest an advanced ultrasonic testing technique for detecting and sizing of transversal cracks in austenitic and dissimilar welds. The method applies a SAFT reconstruction algorithm considering the anisotropy and the inhomogeneity. A V-arrangement of the transducers in pitch-catch technique is chosen to avoid a direct coupling on the weld face. The reconstruction algo-rithm is based on an extended 3-dimensional weld model and uses a ray-tracing approach for de-termining the wave propagation paths. Along with the reconstruction algorithm the transducer set-up and experimental results of different specimens with artificial transverse flaws are presented. The availability of the proposed method for crack sizing is assessed in comparison to conventional testing techniques.

원전 배관의 파손확률에 대한 검사의 영향

Pipe inspections conducted in nuclear power plants play an important role in ensuring the structural integrity of pipes. Because considerable manpower and expense is required for pipe inspections, it is very important to determine the optimum inspection period and the level of inspection. In this study, the effects of the period and the inspection quality on the failure probability of pipes are investigated using the P-PIE program, which has been developed to calculate the failure probability of pipes. The pipe data of an internal nuclear power plant is used in the study, and fatigue and stress corrosion crack growth are considered in the analysis.

Development of approach for reliability assessment of pipeline network systems

The aim of the work presented in this paper is to develop a common scientific methodology for the assessment of reliability of the pipeline network energy systems. The developed methodology is applicable for district heating, gas and oil supply networks. The reliability of all these systems depends on the degradation mechanisms and structural integrity of pipes. Structural integrity is influenced by loadings, defined by thermal–hydraulic processes. The reliability of energy network systems also depends on reliability of the installed equipment and the supply source. The reliability of pipeline networks is treated as a complex task. Consequently, the developed methodology includes three types of analyses: probabilistic mathematical, deterministic thermal–hydraulic and deterministic-probabilistic structural integrity analyses. As a pilot study, the application of the developed methodology for the analysis of Kaunas (Lithuania) district heating system was performed. The main results of this pilot study are presented in the paper. Although the original intention is to apply the developed methodology for the assessment of the reliability of the Lithuanian energy systems, in general, the methodology is applicable for any pipeline network system in any country.

Fluid effects on structural integrity of pipes with an orifice and elbows with a wall-thinned part

A wall thinning phenomenon caused by erosion, corrosion and flow accelerated corrosion is one of critical issues that should be resolved to assure the structural integrity of nuclear piping systems. The wall thinning is occasionally detected around geometry discontinuities and its excessive amount of volume loss may reach an unanticipated rupture of a piping system. In this research, fluid effects on typical piping components are investigated and a methodology to assess the structural integrity of which has a wall-thinned part is introduced. Parametric three-dimensional fluid–structure interaction and limit load analyses are carried out and, thereby, a new analytical equation reflecting the effects of assorted fluid flow and defect geometry is developed.