Vulnerability of water distribution networks with real-life pipe failure statistics

Reasons for occasional, random pipe bursts in water distribution networks (WDNs) might come from numerous factors (e.g. pH value of the soil, the pipeline material). Still, the isolation of the damaged section is inevitable. While the corresponding area is segregated by closing the isolation valves, there is a shortfall in drinking water service. This paper analyses the vulnerability of segments of WDNs from the viewpoint of the consumers that is the product of the failure rate and the relative demand loss. Real pipe failure database, pipe material and pipe age data are used to increase the accuracy of the failure rate estimation for 27 real-life WDNs from Hungary. The vulnerability analysis revealed the highly exposed nature of the local vulnerabilities; the distribution of local vulnerability values follows a power-law distribution. This phenomenon is also found by investigating the artificial WDNs from the literature using N rule in terms of isolation valve layout, namely the ky networks, with similar results.

Segment-based resilience response and intervention evaluation of water distribution systems

The consideration of isolation valves and segments is essential for evaluating the water service and resilience of water distribution systems when shutdowns are required under pipe failure. However, little work has been done on assessing the resilience response and intervention based on segments. This study investigates the impact of intervention (valve density and protection of critical segment) and response (recovery time and recovery sequence) on system resilience taking valve layout into consideration. An algorithm to identify segments based on the graph theory is proposed. Resilience is quantified using the satisfactory rate of the water supply demand. Critical segments are ranked based on resilience analysis. The resilience evaluation method is applied to a case study network. It is found that valve optimization can significantly reduce the number of valves without considerably decreasing the resilience performance. Valve density and the protection of critical segment can reduce the severity of pipe failure, while efficient recovery response can reduce the severity and shorten the duration of pipe failure simultaneously. The criticality of segments depends on the segment location and hydraulic interdependency among segments.

Rehabilitation of an Industrial Water Main Using Multicriteria Decision Analysis

This paper demonstrates the application of multicriteria decision analysis (MCDA) methodology in a real case study aiming to choose the best rehabilitation intervention of an industrial water main. This methodology is composed of three main stages: problem identification, structuring, and evaluation. Problem structuring, a crucial stage for the outcomes, includes identifying objectives, selecting scenarios within the analysis period, defining problem alternatives, and defining the problematic type. Problem evaluation includes the selection of assessment metrics, selection of the aggregation method, application of the method, and a sensitivity and robustness analysis. Two scenarios, nine assessment metrics, and seven alternatives are established, and two ranking methods (the additive model and ELECTRE III method) are used to compare the alternatives. The results show that the best solution corresponds to building a new pipe and deactivating the existing one, as it significantly reduces the pipe failure risk and O&M costs, whereas the worst solution is always the status quo case, since it is the only alternative that does not improve the system performance, independently of the ranking method and the analyzed scenario.

Corrosion Behavior of Thermal Seamless Carbon Steel Boiler Pipes

The current study was absorbed on corrosion of ASTM A106 grade B -02 seamless carbon steel boiler pipes. Beyond corrosion experiments in corrosive medium with varying pH values, the weight lost in addition to corrosion rate (m.p.y) values were computed. The weight loss of boiler tube specimens exposed to corrosive liquid was shown to rise as the exposure period of the specimens increased. The results of the microstructure imaging showed that a de-carburized film of 240 µm thickness was shaped on the fireside of the pipe boiler, with ferrite and a few phases of pearlite. On the water lateral side, it was revealed that boiler pipe failure begins with small rust particles that expand to greater sizes and form scales that are displaced from the boiler pipe's surface. On the surfaces of the boiler pipe water side, several pits with crevice corrosion were observed. The corrosion amounts were discovered to decrease when the specimens' exposure time to corrosive environments and hydrogen ion concentration contents increased (pH). The findings of mechanical characteristic values such as hardness, yield strength, and tensile strength revealed that the waterside had higher values than the fireside, while the middle of the pipe had reasonable values. The findings also demonstrated that at low pH values, a tiny size of rust was created on the boiler tube specimen surface. However, at high pH values of corrosive medium, big sizes of corrosion rust were observed on the specimen surfaces.

Simulation of Deformation Transfer Coefficient of Pipe Bend Buried Based on Shaking Table Test and Goodman Contact Element

Due to the large difference of stiffness between pipe and soil, the movement of the two can not be coordinated under seismic. Therefore, the deformation transfer between pipe and soil is a very important research content in the study of pipe failure. At present, scholars have done less research on the pipe-soil deformation transfer of elbow. In this paper, the fitting formula of deformation transfer coefficient of buried elbow under seismic action was obtained by scale shaking table test of pipe bend and 3D finite element model based on Goodman contact element. Then, the test results are compared with the calculation results of the fitting formula and the simulation results of the finite element method to verify the rationality of the fitting formula and analyze the change law of the deformation transfer coefficient at the elbow of the pipe, including the influence of different pipe diameters, buried depth, wall thickness, soil properties, and elbow angles. It is confirmed that these factors have a great influence on the deformation transfer between the pipe and soil, which indicates that the fitting formula of the deformation transfer coefficient at the elbow is of huge significance to the earthquake resisting design of pipe.

The Problem of Freezing of Copper Water Heat Pipes

To cool electronic components of spacecraft, engineers are considering the use of heat pipes, which are sealed copper pipes containing an annular copper wick saturated with water. Water vapor from the hot end travels to the cold end, where it condenses in the wick and flows back to the hot end. In space, the cold end can freeze the water inside, which can cause two modes of pipe failure. First, if water accumulates in the cold end, then freezes, it can burst the pipe wall. Second, with the repeated expansion of the freezing water, pores in the copper wick can enlarge, reducing the speed of transport and hence the heat pipe's effectiveness. In this work we will examine both types of failures, with an eye toward establishing tolerances below which we expect the wick to remain functional.

Thermophysical Properties of Mixtures of Thorium and Uranium Nitride

The miscibility, lattice parameter, and thermophysical properties of (Th0.2U0.8)N and (Th0.5U0.5)N have been investigated. It is shown that additions of thorium nitride (ThN) to uranium nitride (UN) increases the thermophysical performance of the mixed nitride fuel form in comparison to reference UN. In the more dilute limit, additions of ThN serve as a burnable neutronic poison and reduces the change in keff over the lifecycle of the fuel. At higher concentrations, additions of ThN serve as a significant fertile source of 233U. Where appropriate, comparisons to previous work on UN + PuN mixtures are made, as this is a comparable fuel form for potential fast reactor concepts, and a suitable point of contrast in the possible design space afforded by mixed (ThxU1 − x)N fuel forms. The data from this work are the input parameters for finite element modeling of the temperature distribution in a compact reactor. The results of modeling and simulation of this core design are shown for the case of steady-state operation and during double, adjacent heat pipe failure.