Journal of Pipeline Systems Engineering and Practice

The integrity assessment of dents in liquid pipelines, as regulated by codes and standards, is based mostly on depth and threat integration, with strain analysis incorporated as a nonmandatory recommendation for gas pipelines. There have been incidents in which the current regulatory criteria have not successfully predicted imminent failures of dents, leading to operators using noncodified, more conservative approaches to maintain safety, typically resulting in poor dig efficiency. The dent assessment methods currently available in the industry do not account for the sequences of loading by which a dent may have formed. In this paper, the effects of different load sequences on the remaining life of plain dents in liquid pipelines are demonstrated using a validated finite-element analysis. A parametric study is carried out to confirm that the findings hold true for a range of pipe geometries, materials, and dent depths. The findings indicate that the severity and/or remaining life of a dent cannot be fully assessed based on its depth alone. The restraint condition, indenter shape, loading sequence, and pressure-cycling history should be considered for a reasonable assessment of the remaining life of plain dents.

Liquefaction of sandy porous soil under earthquake waves is the most important feature governing the serviceability of underground pipelines. In this study, an artificial neural network (ANN) is combined with the mesh-free local radial basis function differential quadrature (LRBF-DQ) method to estimate the effect of soil properties such as the hydraulic conductivity, unit weight, Poisson’s ratio, and deformation module on the excess pore fluid pressure and the liquefaction potential surrounding a submarine pipeline under earthquake loading. The LRBF-DQ method was used to solve the governing equations. The results obtained by the LRBF-DQ codes and ANN show that with an increase of Poisson’s ratio, the deformation module, and hydraulic conductivity of the porous seabed, the pore fluid pressure and the liquefaction potential are reduced. Moreover, the sensitivity analysis of the ANN model showed that hydraulic conductivity has a significant impact on the excess pore pressure compared with other parameters.

The performance of a water distribution networks (WDN) varies according to various factors such as physical, operational, and environmental and should be monitored to reduce and control the water losses. This study discussed the methods and tools applied to reduce, control, and monitor the leaks in a water distribution system and the results obtained after their application to a real WDS. The aim was to improve the performance of the WDS in terms of water losses and leaks monitoring and management. Denizli, a city in western Turkey, was selected as the study area. In the application area, a method with high-tech solutions for pressure management using demand modulating pressure reduction valve (PRV) controllers was applied to reduce water losses. Furthermore, data integration with an existing supervisory control and data acquisition (SCADA) system, GIS, customer information system (CIS) databases, and district metered areas (DMAs) were applied as essential for the effective water management. The results obtained by applying pressure management strategy using PRVs at the DMA scale showed that significant saving were achieved by giving less water to the system. In addition, the pressure changes and input flow rates and volumes in the DMAs were monitored in real-time by using the SCADA system to increase the performance of the WDS.

The effect of opening-bending, closing-bending, and reversed-bending loads on the ratcheting behavior of pressurized Z2CND18.12N stainless steel 90° long-radius elbow pipe was studied using finite-element (FE) analysis. Three-dimensional elastoplastic analyses with the Chen-Jiao-Kim (CJK) kinematic hardening model, implemented in the FE software ANSYS, was used to simulate the ratcheting behavior of pressurized 90° elbow pipe at flanks and intrados. The results indicated that ratcheting strain for single-step loading increased with increasing bending loading at the same internal pressure and that it increased with increasing internal pressure at the same bending loading. Multistep bending revealed that the ratcheting rate increased with increasing loading but decreased or even vanished at a lower bending level imposed after a higher bending level. Furthermore, the results generally indicated that the ratcheting strain of a 90° elbow pipe subjected to in-plane opening-bending and closing-bending loads was larger than that with a reversed-bending load.

Risk-based asset management focuses on prioritizing the most critical assets by evaluating their risk of failure. A typical way to determine the risk of failure is by assessing the asset’s likelihood of failure and its consequence of failure. The goal of this paper is to present a consequence-of-failure model using a weighted-sum multicriteria decision-making method to evaluate the economic, social, and environmental consequences of wastewater pipe failure. The model incorporates 14 factors consisting of pipe characteristics and demographic parameters arranged into a hierarchical model to determine one final consequence-of-failure score. The analytic hierarchy process (AHP) was used to determine the relative importance weights of all factors and criteria. The model was applied to a northeastern Louisiana sewer network. The results show that economic cost factors are the most important to evaluate when determining an asset’s consequence of failure. Integrating the derived model with wastewater pipe deterioration models can help utility managers prioritize critical investment needs in a more efficient manner.

This paper presents the results obtained from an experimental study investigating the effects of using expanded polystyrene (EPS) as compressible inclusion on buried high-density polyethylene (HDPE) pipe behavior. A series of full-scale tests were conducted using a laboratory testing facility to investigate the effects of using EPS on the behavior of a 300-mm-nominal-diameter lined corrugated-wall HDPE pipe buried in a poorly graded sand medium. For this purpose, five different compressible inclusion geometries were designed. EPS with $10\mathrm{kg}/{\mathrm{m}}^3$ nominal density was used as the compressible material. In order to simulate geostatic stresses imposed by shallow and high soil fills, vertical surcharge stresses up to 200 kPa were applied on surface of the burial medium. Comprehensive instrumentation was implemented in order to measure the pipe deflections, soil stresses on the pipe, and soil settlements in the pipe zone. In terms of performance and cost-efficiency, it is concluded that a single EPS panel above the pipe crown, which is as wide as one pipe outside diameter and as thick as $1/6$ of pipe nominal diameter, offers the best solution. This solution provided a reduction in vertical stress at the pipe crown up to of 76% and in horizontal stress on the pipe walls at the springline up to of 65%. Vertical and horizontal pipe deflections are reduced by 87% and 60%, respectively, under 200-kPa surcharge stress. This solution also provided near-zero pipe deflections in the 100–125 kPa surcharge stress range.

The selected route for a subsea pipeline is usually uneven and requires extensive preparation. In the case of a relatively stiff pipeline, free spans that are too long may occur even on the prepared route (causing design issues like fatigue). To solve this problem, an optimization procedure has been developed to minimize route preparation costs and to eliminate free spans. The procedure is based on the Euler-Bernoulli beam and the quartic spline used for modeling the route profile in the vertical plane. The seabed is considered to be rigid and without friction. In the procedure, the contact load between the pipeline and the seabed is constrained. A minimum limit of contact load is set to ensure that the pipeline is in contact with the seabed for its whole length so that free spans do not occur. The effectiveness of the procedure is tested in a narrow sea channel with a relatively large diameter steel pipeline for oil transportation. Optimization results are compared with the static response obtained by the nonlinear finite element method (NFEM). The comparison shows that the use of a contact load constraint leads to a significant reduction or to the elimination of free spans.

Ground deformation, which is a common consequence of surface loads, construction activities, excavation work, subterranean cavitation, soil subsidence, and so on, poses a serious threat to nearby pipelines. This work proposes a structural health monitoring (SHM) system to evaluate the safety of buried pipelines with socket joints subjected to ground deformation. Using the developed wireless microelectromechanical system (MEMS)-based inclination sensors, this system has many advantages over the traditional leveling method, including real-time monitoring, high precision, low power consumption, and economic and labor efficiency. Field tests of a 12-m buried pipe with three socket joints were carried out to observe the pipe responses under surface loading. A simplified model for finite-element (FE) analysis was then proposed to simulate the mechanical behavior of the socket joint under axial force and bending moment, which has been verified to be effective to represent the rotation responses of the joint. Using this model, numerical case studies were conducted of the buried pipeline subjected to uneven ground deformation in the general form, based on which a safety monitoring strategy was presented to achieve the three targets of detection, localization of the interference, and evaluation of its effect on pipelines.

The construction and development of a gathering and transmission pipe network in a gas field is a hard and critical task that is one of the main procedures to be performed during the gas field’s productive life. This paper reports on two mixed-integer nonlinear programming (MINLP) models including the optimization of the topological structure of the pipe network and the optimization of the pipeline routes in three-dimensional (3D) terrain to minimize the total development costs of surface production pipe networks. The models seek to define the number, location, and capacities of manifolds and central processing facility (CPF); the affiliation of wells; the points where manifolds must be installed; the interconnection between wells or manifolds; the sections or obstacles which should be bypassed; and the optimal routes of the pipelines. A new method combining the Floyd algorithm with weighted grid (FAWG) was developed to optimize the pipeline routes in 3D terrain. An increment and verification (IAV) algorithm based on the exhaustion method was developed to optimize the number and location of manifolds and CPF. Two types of connection structures from wells to manifolds and from manifolds to CPF, radial and dendritic, were applied to design the interconnection pipe structure layout between those points. Four types of pipe layouts and their corresponding costs were obtained and compared. Two different scenarios were tested in which the optimal topological structure, pipeline routes, and related design parameters of the network system in 3D terrain were obtained with minimum investments. The results were computationally feasible and innovative compared with models found in the literature.

Successful management of water distribution systems will rise in importance as more people gain access to piped water globally. While much research about the management of these systems has been completed, public concern about their safety and reliability is unabated. This paper probes whether research and policy attention has made a significant difference in the use of asset management and improved condition of distribution systems in the United States. Three streams of evidence are used: a review of research and policy reports, findings by the Asset Management Committee of the American Water Works Association, and a survey of utilities, with case studies. There are ample technologies to support asset management, but they are not employed effectively by many utilities. Well-funded utilities can implement sophisticated levels of asset management, but smaller utilities cannot take on many of these activities. The committee found a lack of commitment to asset management and that states are not promoting it aggressively. The survey reached similar conclusions and indicated that an alternative and simpler framework that uses ongoing utility activities might be accepted.

Municipalities across North America are implementing asset management programs in order to demonstrate stewardship of public assets and decrease maintenance costs. In wastewater-collection systems, sewer condition assessment is a key operation requiring extensive data collection using various methods. Closed-circuit television (CCTV) is the most commonly used method for inspection of sewers, and municipalities spend significant amounts of time and money on its execution yearly. Currently, little information is available on CCTV inspection productivity; such information would enable more efficient resource allocation, and thus the development of a CCTV average production rate is useful for municipalities and contractors. In this study, inspection data on approximately 122 km of sewer network in Edmonton, Alberta, Canada is analyzed, finding an average production rate of approximately $400\mathrm{m}/\mathrm{day}$ for sewer CCTV inspection. This paper also includes an analysis of the effects of weather conditions and temperature on CCTV inspection productivity, with monthly comparisons throughout the year, which is a critical consideration in cold regions.