Journal of Pipeline Systems Engineering and Practice

In the most common cases, sanitation systems consist of four main phases: sewage networks, pump stations, force-main lines, and treatment plants. This research is dedicated to the systematic identification and hierarchical prioritization of crucial factors that impact the condition assessment of various stages within the sanitation system. An initial review compiled a comprehensive list of 115 factors from the literature that influence the condition assessment of the sanitation system’s distinct phases: 31 factors for sewer networks, 21 for pump stations, 18 for force-main lines, and 45 for wastewater treatment plants. By administering 88 detailed questionnaires to field experts, these factors were distilled to 59, predicated on their ascribed importance indices. Factors that achieved an importance index above the 50% threshold were considered to be significant and were retained for in-depth analysis, whereas those with an index below 50% were excluded from the prioritization process. The analytic hierarchy process (AHP) was used to compare and rank these factors. The results indicated that the two most important factors affecting the condition assessment of sewage networks are pipe material for sewers and cover and frame for manholes, respectively. The factors for pump stations are operational and maintenance procedures for pumps and protective measures for receiving wells, respectively. Pipe material, operation pressure, and corrosion of valves of mechanical pieces are the important factors for force-main lines. The age of electromechanical equipment and cavitations are the two most important factors affecting the condition assessment of wastewater treatment plants. A heuristic evaluation of three existing case studies was used to validate the model, and resulted in correlation coefficients ranging between 0.801 and 0.871. This study will support decision makers in managing sanitation system assets.

Subsea pipelines operate in harsh marine environments, and corrosion is the major cause threatening their operational safety. In this paper, the failure pressure of pipelines with multiple corrosion defects under combined loadings is investigated. A finite-element model of a pipeline with multiple corrosion defects is developed, and this model is verified with experiments. The effect of defect depth, axial, and circumferential spacings between corrosion defects on the pipeline’s residual strength is estimated. Furthermore, the failure pressure of a pipeline with multiple corrosion defects under combined loadings, such as internal pressure, axial pressure, and bending moment, is examined. This study aims to support the integrity management of subsea pipelines with multiple corrosion defects.

Abstract

The seismic resilience of water distribution networks (WDNs) as the most critical urban infrastructure is a major aspect of crisis management. Developing accurate computational models to evaluate the seismic behavior of WDNs and enhance seismic resilience remains a major research challenge. This paper introduces a novel model to evaluate the seismic vulnerability of WDNs through an artificial neural network (ANN) approach. To generate initial data to develop the seismic damage prediction model, extensive numerical modeling was performed using commercially available software to extract the strain behavior of buried pipes under seismic loading. A total of 720 numerical simulations were performed. The numerical model was validated using an experimental model. The results showed that the numerical model had an error smaller than 10% in evaluating the strain behavior of buried pipes, suggesting satisfactory model performance. This paper used a multilayer perceptron (MLP) and the Levenberg–Marquardt algorithm (LMA) because it has shown good performance in regression applications. The sensitivity of the proposed model to the number of hidden layers was analyzed, and the MLP with 15 hidden layers was found to be optimal in predicting the strain of the buried pipe under seismic loading, with a mean squared error (MSE) of 0.301 and a correlation coefficient $R=0.969$. The proposed seismic damage prediction model was executed on the WDN of Tehran, Iran, based on the initial data set under five seismic loading scenarios, calculating the numbers of breaks and leaks. The seismic resilience of the WDN was evaluated using damage, minimum water demand, and restoration time indices. Several strategies were proposed to enhance the seismic resilience of WDNs. The developed seismic resilience assessment model in this study has the capability to be applied and implemented across other WDNs.

Practical Applications

The water distribution network is critical for urban resilience, and evaluating its seismic vulnerability is essential for managing earthquake impacts, particularly in ensuring postearthquake water supply and firefighting capabilities. This study introduces a novel ANN model designed to assess seismic resilience in urban water distribution networks. The model employs advanced computational techniques to comprehensively evaluate resilience and propose enhancement strategies. A case study conducted in Tehran, Iran, validated the model’s accuracy in assessing earthquake damage and resilience strategies specific to the water distribution network. The results demonstrate the model’s effectiveness in improving urban infrastructure performance during seismic events. The seismic vulnerability prediction model and seismic resilience analysis of the water distribution network presented in this study can serve as a comprehensive tool for urban stakeholders and planners. This model is adaptable and can be applied to assess vulnerability and enhance resilience in various urban water distribution networks.

The erosion of elbows in shale gas-gathering pipelines is influenced by both internal tensile stress and solid particle erosion. However, scholarly attention to the occurrence of elbow erosion in such pipelines under stress is lacking. To address this gap, this study establishes a numerical model accounting for the two-way coupling between elbows and natural gas under internal pressure while also considering particle erosion under stress. Numerical simulations were conducted to analyze the erosion behavior of elbows under varying gathering pressures, gas flow rates, and particle sizes. The results indicate that the location of maximum stress coincides with the position of the highest erosion rate, suggesting that stress concentration renders the material highly susceptible to erosion. Additionally, an increase in collector pressure exacerbates the impact of stress on the erosion process. Gray-scale correlation analysis subsequently identifies the priority order of factors influencing the maximum erosion rate in the elbow as follows: collector pressure has the highest influence, followed by gas flow rate, and then particle size.

Multiple corrosion defects on oil and gas pipeline elbows seriously threaten the safe and smooth operation of pipelines. In this work, a three-dimensional (3D) model of circumferentially aligned corrosion defects on the external surface of the elbow subjected to mechanoelectrochemical (M-E) interaction was developed. Subsequently, the M-E interaction law of circumferentially aligned corrosion defects under internal pressure was investigated. Then the influence of the geometries of circumferentially aligned corrosion defects on the M-E interaction was studied. The critical circumferential spacings between the defects were determined. The results indicate that due to the special characteristics of the elbow structure, the nonuniform distribution of stress under the action of internal pressure leads to different failure pressures at different locations of the elbow. The variation laws of defect width are the same as that of straight pipelines, under a fixed internal pressure or a defect depth, with the increase of the defect width, the maximum stress level and corrosion rate growth slow until both barely change. In addition, this work integrates the mechanical stress field with the electrochemical corrosion field, considering the specificity of the stress distribution in the elbow. A new interaction criterion to judge the critical circumferential spacing of the interaction between adjacent defects is defined. The new interaction criterion indicates that the circumferentially aligned corrosion defects of the elbow separate when neither the mechanical stress field nor the electrochemical corrosion field mutually interact, and can be evaluated as individual corrosion defects. This work complements the integrity evaluation model for elbows containing multiple corrosion defects and provides guidance for oil and gas piping systems integrity management.