Complex Pipe Networks Research Articles

Reconstructing transient pressures in pipe networks from local observations by using physics-informed neural networks

Reconstructing transient states presents significant challenges, particularly within complex pipe networks. These challenges arise due to nonlinear behaviours, inherent uncertainties in the system, and limitations in data availability. This work proposed a novel approach employing Physics-Informed Neural Networks (PINN) to reconstruct transient states in pipe networks, even with limited sensor data. To integrate the complex topology of pipe network systems into neural networks, the method integrates the PINN framework with an efficient elastic water column (EWC) model which can be simply formulated across diverse pipe network configurations. The results showed the proposed PINN method can accurately reconstruct the pressure and flow variation at unmonitored locations, even provided with noisy data at a limited number of locations. One of its advantages lies in its ability to effectively capture extreme values that hold potential significance for pipe infrastructure, providing a promising avenue for pipe failure analysis and enhanced safety management. Laboratory experiments have also been conducted to validate the efficacy and reliability of this method, thus further underlining its potential for real-world applications.

Stress Classification Lines for Non-Standard Y-Tee Design in Piping System

All processes fluids in the oil and gas industry are generally transferred from one point to another via complex piping networks. The process temperature and the pressure of the fluids may vary between -21 °C to 816 °C and from atmospheric, 1.013 barg to 431 barg, respectively. Under these conditions, the entire piping networks are exposed to thermal expansion and contraction resulting in mechanical bending, potentially causing mechanical failures. The most common pipe fitting used in piping networks to divide the fluid flow into two different directions would be a standard equal tee which was designed in accordance with ASME B16.9. The equal tee, however, has distinctive flexibility characteristics compared to the pipe, which is well defined in ASME B31.3. These flexibility characteristics generate a stress intensification factor (SIF) through bending moment equations for beam-type element analysis for standard equal tee components. However, due to the limitation of SIF and flexibility characteristics for the non-standard pipe fittings, the stress evaluation could not be done using beam-type element analysis. When using finite element method (FEM) analysis, generally equivalent stresses (Von Mises or Tresca) or principal stresses would be evaluated depending on the stress categorization as explained in ASME codes and standards. In this paper, a stress evaluation method for non-standard Y-tee was developed and demonstrated against ASME VIII Div. 2 Part 5 requirement. The developed SCLs line for the non-standard Y-tee fittings provides the guides for stress assessment against design stress allowable. An optimum design for non-standard Y-tee is proposed at 45° and 60° crotch radii which resulted in lower stress value at SCL lines, hence improving the structural integrity.

Locating leakage in pipelines based on the adjoint equation of inversion modeling

This paper presents an adjoint method for locating potential leakage in a single-phase fluid pipeline based on the analytic solution of inversion modeling. By studying the mechanism of pipeline leakage pressure, the adjoint equation based on the governing equation of transient flow is established in the single-liquid phase aspect using inverse adjoint theory and sensitivity analysis method. The inverse transient adjoint equation is primarily derived from the single linear fluid pipeline in the semi-infinite domain. The Laplace method is then used to obtain an analytical solution that determines the location of pipeline leakage. The experimental results indicate that the analytic solution can quickly and accurately judge the leakage location of the pipeline. Furthermore, it presents a new approach to engineering applications, such as gas-liquid two-phase flow complex pipe networks, etc.

Frequency-based leak signature investigation using acoustic sensors in urban water distribution networks

Cities worldwide have been plagued by water pipe leaks for many decades, resulting in financial losses, public health risks, and environmental impacts. Current practice still relies heavily on periodic and localized inspection rather than long-term continuous monitoring, and since water pipelines are buried underground, leaks can often go undetected for prolonged periods. Noninvasive acoustic-based methods for continuous pipeline monitoring have gained increasing popularity the past decade thanks to the recent advances in sensing and communication technology. Previous research indicates that hydrophones, in particular, are capable of effectively detecting leak-induced acoustic waves inside a water pipe. However, most studies to date have been limited to either controlled or field test-bed settings; hence, findings might not generalize well to real-world complex pipe networks. Through rigorous leak tests conducted in a real water distribution network and an extensive analysis of the field-collected acoustic signals, the current study aims to test the applicability of low-cost, non-intrusive hydrophones attached to fire hydrants for continuous pipe monitoring and leak detection. Continuous wavelet transform, power spectrum, and band power analyses were employed to identify the leak signature and distinguish normal from leak acoustic data in various leak scenarios. Results indicate that the acoustic signals generated by the simulated leaks in this field study are characterized by a consistent increase in the power of the frequency band 150–450 Hz primarily, whereas background noise levels and conditions significantly vary depending on the location of the sensor in the network. Realistic conditions in urban water distribution networks, including background noise, complicated topology, and varying pipe size and material, are still posing significant challenges for cost-effective and widespread implementation of acoustic-based sensors to achieve continuous monitoring in water pipe networks for leak detection. Even though further research and development is required to handle the highly variable conditions of real systems, the low-cost hydrophones tested in this work demonstrated potential in detecting low-flow leaks in simple and complex pipe topologies.

Design Water Supply Network Using Epanet Software

Abstract: This study represents use of EPANET software in the design of water distribution network. EPANET software is a user friendly software. In order to ensure the availability of sufficient quantity of good quality of water to the various section of community in accordance with the demand, many computer tools were developed, out of all the tools available EPANET become most popular and convenient for the effective design of complex pipe networks. This paper highlights only the effective design and distribution of network of pipes using EPANET tool. The residual head at each and every node was found out by having the elevation as input and thereby the corresponding flow quantities were derived like residual head, velocity and nodal demand etc.

Machine learning modeling for spectral transient-based leak detection

This paper describes Machine Learning (ML)-based framework to detect leaks in pipes using transient waves. The so-called Transient-Based Leak Detection (TBLD) technology is a non-convex multi-dimensional optimization problem, usually solved by inefficient Metaheuristic Optimization algorithms (MOAs). This paper proposes an efficient ML approach to address this drawback. At the core of this methodology, an ensemble of CatBoost models was trained on >3.8 million data records for classifying the leaky sections and predicting the leak sizes. Results showed that the ML models could detect leaks with 97% accuracy and an F1-score of 0.86, implying a significant superiority compared to the MOAs. Substituting the cumbersome optimizations with an ML-based approach, this paper opens a new line of research in the TBLD, which seems more welcome for complex pipe networks.

Shockwave and dynamic pressure propagation law of methane–air explosion in full-scale pipe network

ABSTRACT Methane explosions are the main cause of coal mine disasters. Considering the scale effect involved in the process of methane explosion, small-scale methane explosion experiments can only obtain a qualitative trend of explosion parameters. It is necessary to study methane explosions in a full-size complex pipe network. In this study, the No. 501 experiment at the Lynn Lake Experimental Mine in the United States was used as the background case. GASFLOW-MPI was used to study the oscillation, attenuation, and dynamic pressure evolution laws of the explosion shockwaves in a full-size complex pipe network with consideration of the heat loss. The results showed that the numerical simulation results considering heat loss were more accurate than the adiabatic simulation results, and the average error of the peak pressure was only 4.25%. The pressure – time history curve of methane explosion shockwaves in a complex pipe network differed from that in a single pipe. The pressure peak was a bimodal curve near the explosion source, the dynamic pressure changes significantly, and both forward and reverse wind reaching 200 m/s occurred. The pressure curve far from the explosion source was a unimodal peak curve, and only the forward wind occurred. This reasonably explains the bidirectional deformation of rock bolted plates found in the US UBB accident. The results are expected to provide theoretical support for emergency mine rescue operations and mitigating the effects of methane explosions.

Failure prediction of buried pipeline by network-based geospatial-temporal solution

Corrosion is a severe threat to the integrity of buried metal pipes due to the interaction of pipe materials with the surrounding soils. A review of the published literature shows that there are serious challenges for engineers to accurately predict failures in the buried pipeline system. In this paper, a network-based geospatial-temporal solution is developed to predict the risk of pipe failures, considering the spatial dependence and temporal variability of corrosion growth. An algorithm is developed integrating theories of reliability, corrosion science, random field, stochastic process, and copula within the framework of Monte Carlo simulation. The application of the developed algorithm is demonstrated using a real complex gas pipeline network. Also, the effect of discrete intervals, temporal variability and corrosion exposure area on probability of pipe failure is investigated. It is found that the failure probability of pipe segments varies spatially and the location of pipe segment with the largest probability of failure varies with time. It is also found that the largest probability of failure of pipe network is less sensitive to the discrete intervals although a fine discretization of the random field will increase the accuracy of simulation. It can be concluded that the proposed method can predict and visualize the location, time and magnitude of risk of a complex pipe network with reasonable accuracy.

Numerical simulation of hydrodynamic performance of taper cascades in transient conditions

The hydrodynamic performance of separation cascades involves determining the distribution of pressure and flow along cascades which are important from the design and operational point of view. In this paper, numerical simulation of hydrodynamic performance of taper cascades in the transient state is presented. This mathematical modeling consisted of a set of hyperbolic partial, ordinary differential and algebraic equations of transient flow in a complex pipe network. In order to achieve this goal, a MATLAB code, named Hydrodynamic Simulation of Separation Cascades (HSSC), has been developed. This code calculates the flow and pressure distribution within the cascade components such as pipes, control valves, tanks and gas centrifuges (GC). Using this code, the results of transient hydrodynamic simulations for a taper cascade with 4 stages and 8 GCs are presented wherein the working gas is xenon, and for different operational conditions, analysis is performed on the equilibrium time and gas holdup.

Acoustics and vibrations in a complex piping network with pump startup–shutdown transients

Pump dynamic operational conditions result in extreme transient events that can enhance the response of piping networks. The predominant transients during rapid startup and shutdown are mainly studied for centrifugal pumps and are scarce for reciprocating pumps. Our study extends the conventional steady-state analysis to include the effect of reciprocating pump dynamic loading on pulsatile flow-induced acoustics and vibrations in a complex piping network. The forced response resulting from acoustical–structural coupling is assessed by utilising the one-dimensional multiphysics piping acoustic model and beam structural model. The network responses to pulsatile flows during dynamic pump loading (rapid start-up-shutdown events) are compared to the responses due to pulsatile flows during steady-state pump loading. With pump startup–shutdowns operations accompanied by pulsatile flows, the network response is the result of the combination of the transient and steady-state characteristics of plane acoustic waves and structural vibrations. The dynamic pump loading excites the fundamental, low-frequency acoustic eigenmode that causes transient loading of pipeline similar to reservoir–pipe–valve (RPV) systems.

Acoustics interaction in a complex piping network with multiple pulsatile sources

The interactions between multiple pulsatile sources and the acoustic eigenmodes are analysed to elucidate the influence of source characteristics and contrasting phase differences on the acoustic response in a liquid-filled complex piping network with multiple branches. For illustration, the interactions between two reciprocating pumps operating in a two-branched network are analysed using a one-dimensional linear model. The interactions between sources and acoustic eigenmodes lead to enhanced or suppressed acoustic responses depending on the spatial separation between the sources and their phase differences. The acoustic field measurements from the sweep of driving frequency of a mono-ethylene-glycol (MEG) pump module with two reciprocating pumps in a three-branched network are analysed. The linear model captures the approximate resonance profile of the field measurement data. The presence of plane acoustic wave attenuation in the practical case is influenced by the losses associated with pipe fittings.

Detection of soil pipe network by geophysical approach: Electromagnetic induction (EMI) and electrical resistivity tomography (ERT)

AbstractStudying soil pipes is a methodological challenge that needs improvement in detection methods in order to better recognize the role of piping erosion in land degradation and hillslope hydrology. This study explores electromagnetic induction (EMI) and electrical resistivity tomography (ERT) in order to identify soil pipes. The study was conducted in a mountainous area (the Bieszczady Mountains, SE Poland) under a temperate climate, where pipes develop in silty‐clayey soils. In the plot area, eight profiles were measured by the conductivity meter at different depths and then interpolated to present apparent electrical conductivity (ECa). Also, six ERT profiles were carried out using the Wenner‐Schlumberger electrode configuration. The ECa values measured by EMI are not very diversified, suggesting its lower sensitivity to changes in the ECa, whereas the ECa values measured by ERT are characterized by greater fluctuation, that is, better detection possibilities. ERT has revealed soil pipes as zones of higher electrical resistivity (ER >268 Ωm) than their surroundings (characterized below pipes by ER <105 Ωm) underlying the air filling of pipes (ER >427 Ωm), whereas EMI has revealed its higher sensitivity to water content. The EMI results have shown the lowering of the water table in the lower part of the slope, perhaps because of the drainage by a complex pipe network. EMI allows quick measurements of ECa providing information on water content, and thus indirectly soil pipes, but, it cannot delineate individual pipes. Only the integration of geophysical methods supported by field recognition provides an effective method to detect soil pipes.

Spatial design strategies and performance of porous pavements for reducing combined sewer overflows

The installation of Green Infrastructure (GI) is a popular strategy for reducing stormwater runoff that contributes to Combined Sewer Overflows (CSOs). However, quantifying the impact of proposed GI systems on CSO discharges is a difficult task that requires the simulation of runoff in a complex network of land parcels, drainage controls, and sewer pipes. In this study, the performance of Porous Pavement (PP) was examined, with a focus on how the spatial design of PP features affects predicted CSO volume. Numerical experiments were performed to explore how simulation-based designs can identify specific subcatchments for cost-effective PP implementation subject to budgetary constraints. Among the alternative design strategies considered, simulation–optimization was effective at finding cost-effective solutions. The experiments showed that PP can achieve substantial CSO reductions across a range of rainfalls, budgets, and CSO drainage characteristics, but the performance is sensitive to the spatial configuration of the features. Good-performing systems were also identified by generating multiple realizations via a randomized clustering strategy, with additional improvement provided by the more computationally expensive optimization process.

Hydraulic transient evaluation via fabricable impedance matrix for pipe networks

A novel analysis method is proposed to evaluate the impact of specified components in a pipe network on the severity of transient events. A new structural scheme for the impedance matrix was developed to ensure the feasibility of compartmental unsteady analyses, which can be useful for complex pipe networks with different pipeline elements. The impact of a specific pipeline element or a designated section with multiple elements on the transient response can be obtained by delineating the subtracted frequency response between a specific hydraulic impedance of the complete network and that of the missing element. A hypothetical pipe network was introduced to validate the developed method. The impacts of pipeline elements on the total transient response were perfectly matched between the subtraction of time domain responses and direct computation using the identified frequency response function. The transient relaxing impact of additional pipeline elements can be considered for the design of pipe networks.

Seismic risk assessment of supporting structures and process piping for accident prevention in chemical facilities

The seismic risk assessment of supporting structures and process piping elevated on supporting structures plays an important role in accident prevention inside process plants. Process piping is an essential yet complex network of pipes that is used inside petrochemical facilities for connecting equipment items. Even though the seismic vulnerability of process piping and supporting structures is high, as demonstrated during past accidents, the risk assessment has hitherto relied on generalized and obsolete fragility models, e.g. from HAZUS, without addressing specifically the idiosyncrasies of dynamic coupling, soil effects or source conditions. To this effect, the present study addresses the risk assessment and accident scenarios due to earthquake of a realistic process unit in a refinery. By virtue of a recent update of seismic hazard maps in the region of interest, the seismic performance of the unit should be investigated. The methodology includes five main steps that pertain to structural modelling accounting for soil effects, hazard identification, dynamic analyses and description of seismic demand – intensity relationship, fragility derivation and risk estimation as well as analysis of the accident's consequences using JRC's in house tool, ADAM. Overall, the steel structure was considerably more vulnerable than piping. Also, soil deformability and source conditions caused higher uncertainty and increased the risk. The derived fragility curves and risk estimation are tailored to a process plant that can commonly be found in modern oil refineries, and the proposed analytical framework can be easily implemented in a quantitative risk assessment for the most vulnerable equipment, at least, which is necessary for risk reduction and consequence mitigation inside chemical facilities.

Propagation characteristics of the overpressure waves and flame fronts of methane explosions in complex pipeline networks

The propagation characteristics of the overpressure waves and flame fronts of methane explosions in complex pipe networks under realistic conditions were studied. A custom-designed experimental platform was used, the propagation characteristics of overpressure wave and flame wave in complex pipe network were characterized by overpressure attenuation coefficient and flame mutation coefficient. The results showed that the overpressure wave propagation characteristics in complex pipe networks were more complicated and disordered than those in straight or simple branched pipes. The overpressure wave attenuation and superposition occurred many times in the propagation process, the explosion shock wave attenuation in the beveled branch pipe was faster. When the flame wave passed through all the branch tubes, the flame wave velocity increased significantly. When the flame wave passed through the same tube at different times, the flame wave mutation coefficient was different, the change of flame wave temperature had a certain lag compared with the change of flame velocity, resulting in the peak of flame wave temperature and flame wave velocity appearing in different branch tubes. The experimentally obtained data were fit to functional relationships using nonlinear multiple regression analysis, and good agreement between the functional relationships and the data was obtained.

Approximate approach for improving pressure attenuation accuracy during hydraulic transients

Abstract The quasi-steady friction model is generally adopted in water hammer simulation in pipe network systems, which cannot accurately reflect the attenuation of pressure, while the existing unsteady friction model is challenging to use in complex pipe network systems. In this study, a convenient method for treating the friction term is proposed based on the Moody diagram. The attenuation process of water hammer pressure can be accurately reflected by reading the relationship curve between Reynolds number and the Darcy friction factor in the pipeline transient process. Combined with the classical water hammer experiment and the long pipe valve closing experiment in our laboratory, the accuracy of this model is verified, and the influence of absolute roughness (e) and Reynolds number (Re) on the model was analyzed as well. The results show that the pressure attenuation using the Method of Characteristics (MOC) and the proposed friction model has a good agreement with the experimental data. The absolute roughness has little influence on the results in hydraulically smooth pipe, while the minimum Reynolds number has a significant influence. When selecting the minimum Reynolds number, 2% ∼ 5% of the initial flow rate is recommended for calculation.

Experimental study on the explosion characteristics of hydrogen-methane premixed gas in complex pipe networks

To explore the overpressure evolution laws and flame propagation characteristics in complex pipe networks after the addition of hydrogen to methane, we experimentally studied the explosive pressure wave and flame wave propagation laws for three different premixed gas mixtures with hydrogen-methane concentrations of 0, 10% and 20% when the equivalence ratio was 1. Experimental results indicate that the maximum explosion overpressure of the premixed gas increases with increasing distance from the explosion source, and it shows a gradually decreasing trend. In the complex pipe network, an overpressure zone is formed in the B–E–H and D–E sections of the network. The flame temperature is superimposed with the superimposition of the pressure, showing a trend of first increasing, then decreasing, then increasing, and finally decreasing in the complex pipe network. The flame arrival time increases with increasing distance, and the maximum flame speed shows a decreasing trend. The peak overpressure and maximum flame velocity of the premixed gas under a hydrogen volume fraction of 20% are 1.266 MPa and 168 m/s. The experimental research results could provide important theoretical guidelines for the prevention and control of fuel gas explosions in urban pipe networks.

Water Pipe Replacement Scheduling Based on Life Cycle Cost Assessment and Optimization Algorithm

Water distribution networks (WDNs) comprise a complex network of pipes and are crucial for providing potable water to urban communities. Therefore, WDNs must be carefully managed to avoid problems such as water contamination and service failures; however, this requires a large budget. Because WDN components have different statuses depending on their installation year, location, transmission pressure, and flow rate, it is difficult to plan the rehabilitation schedule within budgetary constraints. This study, therefore, proposes a new pipe replacement scheduling approach to smooth the investment time series based on a life cycle cost (LCC) assessment for a large-scale WDN. The proposed scheduling plan simultaneously considers both the annual budget limitation and the optimum expenditure on the useful life of pipes. A multi-objective optimization problem consisting of three decision-making objectives—minimum imposed LCC on the network, minimum standard deviation of annual investment, and minimum average age of the network—is thus solved using a nondominated sorting genetic algorithm to obtain an optimal plan. Three scenarios with different pipe replacement time spans and different annual budget constraints are considered accordingly. The results indicate that the proposed scheduling framework provides an efficient water pipe replacement scheduling plan with a smooth management budget.

Optimization of Multi-zone Cooling System of Complex Pipe Network Based on Particle Swarm and Genetic Algorithm

The cooling pipe network system of the power plant has the characteristics of multiple users, multiple working conditions, and complex topological structure. The division of water supply to the pipe network can simplify the topological structure of the pipe network, facilitate flow regulation, and adapt to the requirements of multiple working conditions. District water supply can be divided into districts according to flow, pressure and structure. The user allocation of pipe network water supply system is a typical combined optimization problem. When the system is relatively complex and the number of users is huge, conventional enumeration methods, dynamic programming and other methods are often unable to solve such problems. The combined algorithm of particle swarm algorithm and genetic algorithm can obtain approximate solutions to such problems. By using a combination of particle swarm algorithm and genetic algorithm to analyze and determine the distribution of pipe network user traffic, it is possible to avoid the waste of energy in the distribution of pipe network users based on experience. The combined algorithm proposed in this paper has high stability, can change the number of partitions to adjust user allocation according to actual needs, and has strong versatility. For the case described in this article, when the number of partitions is 2, compared to the cases where the number of partitions is 3 and 4, the flow rate and pressure drop of each partition are not much different, which can better meet the reliability and maintainability requirements