沿线实时测压法用于监测大型长距离输水管爆漏

随着一些大城市建设大型长距离输水管,在沿途人口稠密区的爆管可能引发次生灾害而成为棘手问题。及时发现输水管爆漏强度和地点,迅速采取应急措施,是降低爆管灾害的重要条件。提出了沿线实时测压法监测输水管爆漏,能够在3～5 min内对1%爆漏量报警,并提供爆漏点和爆漏量等信息。利用该方法还可以分析输水管是否存在泄漏、淤塞、粗糙度增加等问题,提高了科学管理水平。     

Assessment of apparent losses in urban water systems

Apparent losses relate to water that is consumed but not paid for. Most research carried out in the last decade particularly in the United Kingdom focused mainly on leakage. Until now, there are no set procedures and guidelines for assessment of apparent losses. Much work remains to bring it to par with the available tools and methodologies for leakage management. In the absence of adequate data and proper methodology, most developed countries use default values, which tend to be lowest values for well‐managed water systems, for computation of apparent losses. These may not be appropriate for developing countries. This paper presents a methodology for the assessment of different components of apparent losses based on field audit and operational data for Kampala city's water distribution system in Uganda. Metering inaccuracies and illegal use have been found to be significant components of apparent losses. Appropriate intervention strategies have been developed based on the assessment.     

供水管网地震漏损蒙特卡洛模拟分析

为研究供水管网在不同地震烈度下的漏损情况和水力特性,基于管道地震破坏评估模型和概率分析方法,对不同地震烈度下管线的破坏概率和渗漏状态进行了计算分析,引入折减系数对管段抗震可靠度分析方法进行改进,并与传统计算方法比较,验证了其合理性。发展了Monte Carlo模拟技术在供水管网流分析方面的应用,并考虑带渗漏和爆管两种出流方式。编制程序对一大型管网进行了模拟分析,给出了震后带漏损情况下管网的漏失率和破坏情况,结果与实际地震灾害情况相符。     

Leakage detection and location in water distribution systems using a fuzzy-based methodology

Loss of water due to leakage is a common phenomenon observed practically in all water distribution systems (WDS). However, the leakage volume can be reduced significantly if the occurrence of leakage is detected within minimal time after its occurrence. This paper proposes a novel methodology to detect and diagnose leakage in WDS. In the proposed methodology, a fuzzy-based algorithm has been employed that incorporates various uncertainties into different WDS parameters such as roughness, nodal demands, and water reservoir levels. Monitored pressure in different nodes and flow in different pipes have been used to estimate the degree of membership of leakage and its severity in terms of index of leakage propensity (ILP). Based on the degrees of leakage memberships and the ILPs, the location of the nearest leaky node or leaky pipe has been identified. To demonstrate the effectiveness of the proposed methodology, a small distribution network was investigated which showed very encouraging results. The proposed methodology has a significant potential to help water utility managers to detect and locate leakage in WDS within a minimal time after its occurrence and can help to prioritise leakage management strategies.     

Estimation of the benefits yielded by pressure management in water distribution systems

The occurrence of water losses in Water Distribution Systems is inevitable. Knowing that most of the real losses take place in distribution mains and in service connections, the methodology proposed in this paper is based on several leakage-assessment approaches from literature and on water distribution network modeling. This allows assessment of the benefits that can be achieved by pressure management in Water Distribution Systems, particularly in terms of water production reduction. Moreover, this approach can be useful for cost benefit analysis to help establish the level after which there is no more economic interest in reducing water losses (Economic Level of Leakage). Finally, the results from hypothetical case studies are presented and discussed, assuming the installation of Pressure Reducing Valves at District Metered Areas entry points.     

Estimating Pipe Reticulation Losses in a Municipal Water-Supply System

Domestic water consumption in the city of Dunedin, New Zealand, is unmetered. Recently, the Council's Water Department adopted sampling methods to estimate domestic water consumption and system losses, consistent with the recent reports on managing leakage produced by the UK water industry. This paper describes the exercise (which is ongoing), including the treatment of practical issues which arise in applying the methodology. System losses were estimated to increase substantially over the initial two years of the study, leading to the investigation of an assignable cause. The data reflect the effects of the corrective action, lending considerable support to the validity of the method.     

Leakage Control in a Universally Metered Distribution System: Pinetown Water's Experience

As a result of water losses reaching a high point of 16% in 1973, combined with a relatively high and increasing retail tariff, the Pinetown Regional Water Services Corporation embarked upon a programme to reduce losses to an acceptable level of about 10%. The programme involved: (i) the establishment of district metering throughout the distribution system; (ii) the replacement of certain retail meters; and (iii) the metering of new fire connections (other than those serving sprinkler installations). Further steps were taken to improve the situation and included: (a) the monitoring of minimum night flows, (b) regular sounding of distribution mains; (c) the establishment of a full-time waste detection gang; and (d) with improved control valves becoming available, more effective pressure control of the system. The Corporation's computer was called upon to determine: (i) the monthly losses from each of the hundred or so districts; (ii) the life history, in graphical form, of retail meters under review; and (iii) a record of expenditure on leakage control. The paper describes the development of the methods used in leakage control, costing less than half a cent per cubic metre of water purchased, and outlines the practical experience gained in reducing losses from 16% to less than 5% over a period of 14 years.     

城市供水管网抗震可靠性评估的随机模拟方法

在进行管网抗震可靠性评估时,现有方法大多采用相同方式进行管道的渗漏与爆管水力模拟,这会导致管网水力模拟及可靠性评估结果的不准确。考虑到地震时管道破损具有很大的随机性,对城市供水管网抗震可靠性评估的随机模拟方法进行研究。应用蒙特卡洛模拟产生管网震损场景,用泊松随机数与均匀随机数判定管道工作状态,用正态随机数确定管道渗漏系数;利用EPANET软件中喷嘴及管道关闭功能实现管道渗漏及爆管等效模拟,提出将长管道分段并应用"分步迭代"法求解低压管网水力方程,提高震损管网水力模拟精度。以震损场景下节点流量统计平均值与正常时节点流量的比值作为可靠度指标,分别采用所提出算法及GIRAFFE软件对云南某古镇供水管网在VIII、IV烈度时抗震可靠性进行评估,评估结果证明了所提出算法的可行性。评估结果还表明,除地震烈度外,管网本身水力条件对供水可靠性影响较大,管网末端、支管服务区域及地势较高区域供水可靠性远低于干管服务区。     

Experimental evaluation of bursting capacity of corroded grey cast iron water pipeline

Cast iron was used in the water industry prior to 1970 and a large number of cast iron pipes still remain as trunk mains. These pipes have been subjected to different levels of corrosion and variety of loading conditions. This leads cast iron pipes to fail in the field without prior warning. Water utilities are seeking solutions to optimise cast iron pipe renewal and rehabilitation programs for critical water mains (diameter ≥ 300 mm). A new experimental set-up has been developed at Monash University in order to perform burst testing of large diameter cast iron pipes (diameter ≥ 300 mm). A section of cast iron pipe, extracted during maintenance in Sydney, was laser scanned to determine the remaining thickness of the pipe (minimum of 7–8 mm at the most critical patches). Although the pipe was pressurised to 3.6 MPa, catastrophic failure did not occur. Water leakage from the two critically corroded patches was observed at around 3.25–3.45 MPa internal pressure. Strain results on the outer pipe surface were greater than the strain measured during tensile testing of the same pipe material. A 3-D finite element model using the scanned pipe dimensions was able to predict the maximum pressure at pipe failure (~3.7 MPa) within the range of leaking water pressure level observed in the experiment.     

Evaluation of data driven models for pipe burst prediction in urban water distribution systems

ABSTRACT

The water distribution network is one of the most expensive parts of a water supply system. The fundamental variables of a network, material, diameter, length, age, and the hydraulic pressure of pipes are the factors that affect the pipe burst rate (PBR). Establishing a relationship among the burst rate and these factors is an important step to assess the conditions governing the network and preventing significant water leakage. Implementing the data-driven approach in PBR prediction is an effective method to find the relationship. In the present study, Grasshopper Optimization Algorithm-based Support Vector Regression (GOA-SVR), Gaussian Process Regression (GPR), and Artificial Neural Network (ANN) have been developed to predict PBR in an urban area. The results show that the GPR model outperforms other methods. Furthermore, the sensitivity analysis indicates that the pipe age has a negative effect on PBR modeling while the pipe length is the most relevant variable.     

Using the bimonthly water balance of a non-fully monitored water distribution network with seasonal water demand peaks to define its actual NRW level: the case of Kos town,Greece

Water losses in pipe networks are usually the biggest ‘water use’ due to the high leakage occurring. The need for conservative water use is today more pressing than ever due to the stressful climate change conditions, forcing water utilities to consider applying effective Non Revenue Water reduction strategies. The assessment of a network's current operating status based on the IWA water balance (WB) is a good start. Although IWA suggests the WB to be annually assessed, this is not ideal for networks experiencing seasonal demand peaks, like in Kos town, capital of Kos Island in Greece. The WB for Kos town network was assessed on a bimonthly basis, following the water billing period used by the local water utility. The results revealed that higher real loss rates occur during the lower water demand periods due to the higher operating pressures. The annual WB can not reveal water loss peak timing.     

供水管网的泄漏及压力管理

通过压力管理减少供水管网泄漏损耗是近几年在国外出现的新理念，它有效地解决了供水管网漏损这一棘手问题。对管网压力的控制可以有效地避免管网中不必要高压力的出现。减少爆管事故的发生进而降低漏损率。笔者介绍了压力管理的概念及实现方法。     

Performance-based modelling of long-term deterioration to support rehabilitation and investment decisions in drinking water distribution systems

Managing the urban drinking water system in the long term in order to maintain system performance can be challenging due to the difficulty of modelling future deterioration of the networks. This paper establishes a methodology for cohort survival models where historical (empirical) data on decommissioning ages of pipes are used to calibrate survival functions of pipe cohorts according to service level targets. The benefit of the approach is that remaining useful life of pipes, future renewal rates and investment needs can be governed by a required level of service in the network. A case study shows how the methodology can be applied to a cohort of drinking water pipes to create a ‘calibration curve’, which is a survival function calibrated with empirical data.     

Water losses investigation and evaluation in water distribution system – the case of SA city in China

Faced with the severe leakage and chaotic water management situation in developing countries, this research is committed to provide an appropriate and practical water audit calculation method for most water companies so as to guide their leakage control management. It prepares a recommended basic standard terminology for calculation of real and apparent losses, which can be consistent with practice in China. Due to more detailed subdivision of unmetered water along with water component analysis, the water consumption of SA city can be calculated more accurately. The proportion of water loss in SA is 18.02%, while unbilled authorized consumption contributes no more than 1% to the total water consumption. Meanwhile, the “Neighbourhood Metering Area (NMA)” project in SA city also suggests that metering inaccuracies and leakage on service connections up to the point of customer metering can be prioritized for active leakage control in China.     

Recent Developments in Application of 'Bursts and Background Estimates'Concepts for Leakage Management

ABSTRACT During the UK 'national leakage control initiative', which was carried out in 1991–94, Welsh Water formulated a conceptual model of leakage management which was intended for international application.
This paper explains how the concepts of 'bursts and background estimates'(BABE) have been calibrated and extended to cover financial/economic analysis and pressure management, using specialist software for practical application and following the methodologies in the recent water industry 'Managing Leakage'reports. Examples of applications of BABE software and concepts, in the UK and internationally, are also described.     

Failure of a drainage tunnel caused by an entrapped air pocket

A severe storm event occurred over the western area of Mexico City causing the rupture of a drainage tunnel, resulting in surface flooding, severe infrastructure damage and three deaths. This paper describes the methodology followed in order to validate the diagnostic of the event. The detailed investigation comprised in situ observation of the system, as well as hydraulic and structural analyses. In this case, severe pressure oscillations inside the tunnel caused by rapid filling and sudden air leakage through a large orifice (manhole) were recognized as the direct cause of the conduit burst. Further, the low strength of the concrete pipes of the tunnel, constructed without reinforced steel, and the low confinement by the dead load due to the soil above the tunnel also contributed to the rupture. The numerical results show a very unfavorable stress distribution along the tunnel stretch where the accident occurred, sufficient to cause the rupture.     

High-Pressure Water Jetting: Avoiding Damage to Sewers

High-pressure water jetting of sewers and drains is being undertaken in the UK using equipment which, under certain circumstances, can damage the pipes. Research was therefore carried out to provide information which would accurately identify the potential for causing damage and enable preventative measures to be undertaken.
This paper explains the key factors which control the potential to damage sewers and drains by pressure jetting, and provides details of a new jetting test for pipes.     

Numerical modeling of ductile crack extension in high pressure pipelines with longitudinal flaws

This study examines the applicability of a micromechanics approach based upon the computational cell methodology incorporating the Gurson-Tvergaard (GT) model and the CTOA criterion to describe ductile crack extension of longitudinal crack-like defects in high pressure pipeline steels. A central focus is to gain additional insight into the effectiveness and limitations of both approaches to describe crack growth response and to predict the burst pressure for the tested cracked pipes. A verification study conducted on burst testing of large-diameter, precracked pipe specimens with varying crack depth to thickness ratio (a/t) shows the potential predictive capability of the cell approach even though both the GT model and the CTOA criterion appear to depend on defect geometry. Overall, the results presented here lend additional support for further developments in the cell methodology as a valid engineering tool for integrity assessments of pipelines with axial defects.     

故障水井维修方法与工艺研究

在松散层中取水的深水井，使用一段时间以后，少数井孔会出现水量突然变小、漏砂、漏（成）水、出水浑浊等不正常现象。要复修这些水井，必须认真分析原因，探明井内情况。如果是滤水管部位损坏，则可用辅助滤水管，按照相应的维修方法和工艺进行维修；如果是井管损坏，则使用一种实用新型井管堵漏装置，能在很大的压力下实现有效堵漏。因此，只要选择切实可行的维修方案，使用合理的维修方法，优化维修工艺，就能快速、有效地修复故障水井，避免经济损失。     

Experimental investigation on pressure–leakage relation for high-density polyethylene pipe

ABSTRACT

Leakage control decision-making analysis needs a deep recognition of the pressure–leakage relationship. In this study, leakage behavior in High-Density Polyethylene (HDPE) pipes is investigated by a semi-industrial pilot-scale. Accordingly, some experiments were conducted on circular, longitudinal and circumferential slits for studying the effect of diameter, thickness, and material of pipes, forms, and dimensions of the leak opening, the surrounding environment, and temperature. New equations are presented to estimate the discharge coefficient for orifices and longitudinal slits in HDPE pipes. Leakage value from a longitudinal slit depends on elastic or plastic behavior of the leak area, to distinguish this, a new criterion has been introduced between elastic and plastic behaviours of the longitudinal slit. Results show that, for same leakagel area and pressure, the leakage rate of circumferential slits is generally more than orifices and less than longitudinal slits. Results of this study can be utilized for estimating the leakage rate.