管网单向冲洗技术

相当比例的水介疾病是由于管网结构完整性被破坏而引起的,自来水公司必须有效地控制管网水质。单向冲洗能够维持这种控制。所谓单向冲洗技术是使水按设计方向流动,所产生的水流将管道内壁附着的杂物冲洗下来。20世纪90年代初开始应用此技术,效果良好。该文探讨了单向冲洗的关键技术因素,并对其效益和在维持管网水质中的作用进行分析。     

给水管道冲洗消毒应注意几点问题的探讨

城镇给水管道的冲洗消毒是给水工程质量管理的重要环节。给水管道在安装、试压完毕后,在正式通水投入使用前。必须进行管道的冲洗消毒工作。否则,不仅会造成给水管网的水质污染,而且还影响到管道的安全供水、阀门的正常操作使用,严重的还会引起水锤事故,带来社会和经济的负效应。本文作者对给水管道冲洗消毒中应注意的问题作了可行性探讨。     

消火栓给水系统工程设计中争议问题的讨论

根据工程实践和国内外相关文献，就当前消火栓给水系统工程设计中的室内消火栓的位置，消防电梯前室的消火栓是否计入消火栓2股水柱，SN65消火栓是否要配置水龙带，防火分区间的消火栓是否可以借用，消火栓给水系统的控制，室内消火栓给水管网阀门的设置，干式消火栓系统充水时间的确定，消火栓的间距按行走距离计算还是按消火栓保护半径计算，高压消防给水系统室外消火栓的布置，室内消防给水管网的水力计算原则和方法，消火栓给水系统分区原则等12个热点争议问题，提出了笔者的看法。     

供水管网清洗技术及其应用

周期性清洗管网对提高管网水质、恢复管道通水能力、抑制腐蚀发生、维护管网正常运行等具有重要意义，为此对管网冲洗的必要性、冲洗技术、冲洗方法以及冲洗效果评价等进行了探讨，分析了其不足之处并提出了改进建议。     

小管径金属给排水管道的不停水维修

小管径金属给排水管道的不停水维修金属给排水管道不论是架空或者是埋地铺设，常常因有砂限或年久失修、焊缝开裂等而漏水，传统维修方法是停水换管、换配件、补焊、打卡子。采取上述方法几乎都要关闭管道控制阀门或停止用水，排净系统中余水后方可施工。往往难以关闭控制...     

反冲洗过滤器的设计与应用

反冲洗过滤器主要用在水、蒸汽、油类等需要过滤的管网中．由于我国地质结构复杂具有含砂和石灰质多的特点；另外安装的管道中有不少的杂物，如焊渣、砂土等，不仅降低了水的质量，同时还影响了阀门的密封性，因此需在管路的适当位置安装过滤器．以净化水质和满足流量需求。     

阀门阀芯脱落的预防

阀门在管道中主要用来控制或调节水流量，便于检修管路时切断水流。在给水管道上用量较多的阀门为截止阀（图１）和闸阀（图２）。下面介绍这两种阀门阀芯脱落的原因及预防措施。１．截止阀阀芯脱落的预防这种阀芯的固定方法是阀杆上的孔通过铜丝与阀芯相连接，如果开关阀门时用力偏大，容易拧断铜丝。也有的铜丝已经严重腐蚀，稍微一碰或水压偏高，都会出现阀芯掉下来的现象。预防的方法是，开关阀门时用力应平稳，不能用加长杆强行关闭或开启阀门；开关时不可撞上死点，以降低脱落事故的概率。２．闸阀阀芯脱落的预防闸阀阀芯与丝杠的连接…     

城市消防给水存在问题与对策

近些年,许多城市纷纷增建了消火栓、天然水源和取水设施,并增建、扩建了给水管网,城市消防给水建设有了明显的进步。尽管如此,我国城市消防给水仍然严重不足,直接影响到城市火灾的有效扑救。归纳起来,城市消防给水主要存在以下问题： １、给水管网水量小、水压低 许多城市的给水管道铺设年代久,管道直径小,或者后期发展中铺设了较大的管道,因使用多年,陈旧失修,管道内壁结垢锈蚀,管径逐渐缩小,致使管道流量减少,水压降低,满足不了灭火所需的水量和水压。 ２、市政消火栓间距大、数量少,损坏严重,许多城市的消火栓间距都达…     

热力管网冲洗流速的探讨

本文根据流体力学的基本原理，结合《城市热力管网工程施工及验收规范》对冲洗流速的要求，从正常运行流速的角度，把管内残存杂物对管网运行的危害情况进行分类分析，探讨了正常运行流速和冲洗悬浮速度的关系，提出必须以管网各计算管段正常流速确定管道冲洗流速的观点，对热力管网冲洗流速的选择有一定借鉴价值。     

软密封阀门的橡胶密封件材料

给排水用阀门，一般介质为水，常温的中低压阀门，在管道系统中，用以控制介质的压力、流量和流向，以及用于消除停泵水锤，用于管道进排气等功能。阀门应有很好的密封性能、强度性能、调节性能、动作性能和流通性能，还要求运行安全、水质卫生、操作灵活、便于维护，寿命长。而在阀门的设计制造中，阀门的密封是第一重要的要素。     

大型集中空调水系统调试浅析——以京沪高速铁路上海虹桥站为例

总结了大型集中空调水系统调试过程中需要注意和解决的几个问题,对传统大管径空调水系统冲洗方法提出了质疑,对调试过程中的水流量分配提出了自己的观点,希望为大型集中空调水系统的调试提供一种新的思路和方法.     

Development of a convective diffusion model for lead pipe rigs operating in laminar flow

As part of achieving lower lead standards water undertakers are utilising lead pipe rigs to quantify the benefit of treatment measures. A convective diffusion model is developed for lead pipe rigs operating in laminar flow, and applied to the three operating steps of flushing, sampling and stagnation. The model is used to determine the appropriate time-scales for each stage, and the sensitivity of the measure to variations in flow-rate. In contrast to rigs operating in turbulent flow the average lead observed leaving the pipe and that in the pipe, after a period of stagnation, are substantially different. Equations are derived for both, and take into account the residual distribution of lead left in the pipe after flushing. It is shown that the lead concentration observed leaving the pipe is well approximated by a single exponential term in contrast to the concentration within the pipe. Predictions are made on the residual lead concentration that can be achieved through flushing, and its dependence on flow-rate. The relevance of the laminar flow model to that in domestic lead pipes is discussed.     

城市给水管网的水质变化规律研究

给水安全输配是保障饮用水水质的重要环节，对管网水质变化规律进行研究可为改善管网水质、建立水质模型提供基础数据。以天津市的给水管网为研究对象，沿水流路径开启消火栓放水进行测试，考察了余氯、浊度、TOC和三卤甲烷等主要水质参数在管网中的变化规律。结果表明，管道属性对水质有较大影响，并呈现出明显的规律性；为防止水质恶化，应定期排放管网末梢的死水。     

住宅小区给水管网管理

就目前住宅小区给水管网存在的跑、冒、滴、漏现象进行了阐述，主要对小区住户、小区公用设施、室外给水管网容易产生的漏水情况进行了详细的分析，并具有针对性地提出了解决的办法。对小区饮用水水质净化的必要性进行了说明，提出冲洗是水质净化的有效措施和水冲洗的具体方法。     

Comparison of engineering costs of raw freshwater, reclaimed water and seawater for toilet flushing in Hong Kong

Hong Kong is one of the very few coastal cities in the world that use ‘dual water supply systems’. Dual water supply involves two distribution systems: a freshwater system for potable use and a seawater system for toilet flushing. This study looks into the feasibility, from an engineering cost point of view, of extending seawater supply into districts where potable water is still being used for toilet flushing, including South District of Hong Kong Island, Sai Kung, Northern New Territories and Northwest New Territories. Besides seawater, raw (untreated) freshwater and reclaimed water (treated effluent from local sewage treatment works) are also considered to be used for toilet flushing for these districts. Six cases are developed for comparison by using the lowest net present value of cost criterion. The result shows that using seawater for toilet flushing in these districts has the best engineering economy.     

Rationalisation and reliability improvement of fire-fighting systems – the Novi Sad case study

Water supply systems are commonly used to supply fire-fighting water in most EU countries. To provide fast access to water, the standard practice is to install a huge number of hydrants along the entire water supply network. Pipe diameters and working pressures in the network are designed for a combination of the maximum hourly water demand and fire-fighting needs. However, in poorly managed water supply systems most of the hydrants are out of order. Although hundreds of hydrants exist in the network, the reality is that fire water tankers are usually refilled at just a few locations that are equipped with reliable hydrants maintained by the fire brigades. This paper presents a somewhat different approach for the provision of fire-fighting water. The approach discussed in the paper is based on the concept being introduced in the city of Novi Sad, Serbia, by cooperative efforts of the municipal Water Supply and Sewerage Company and the fire-fighting service. In addition to presenting the experience gained in the case study, some generic conclusions are drawn. As an alternative to having a number of unreliable and small hydrants distributed throughout the network, the new concept proposes the construction of several strategically positioned filling stations, with high-flow-rate pillar hydrants and good access roads for the manoeuvering of fire water tankers. If properly designed and distributed around the city, such filling stations would increase the reliability of fire-fighting operations. The filling stations' design methodology presented in this paper is composed of a fire-risk spatial assessment, a hydraulic check of water supply network operations and a worst-case traffic load analysis. By employing the proposed methodology, not only can the reliability of fire-fighting operations be increased, but if accepted and implemented the methodology can lead to leakage reduction and improvements in water quality and the system's energy efficiency. In the test case of Novi Sad, a large number of hydrants were replaced by 14 filling stations that have been designed and constructed. A hydraulic model of the water supply network was calibrated using pressure-drop tests and flow capacity measurements of the existing hydrants. The model was used to examine the performance of the designed filling stations during their parallel operation. The paper presents the results of the test application and recommendations for the possible implementation of the concept.     

Overnight stagnation of drinking water in household taps induces microbial growth and changes in community composition

Drinking water quality is routinely monitored in the distribution network but not inside households at the point of consumption. Fluctuating temperatures, residence times (stagnation), pipe materials and decreasing pipe diameters can promote bacterial growth in buildings. To test the influence of stagnation in households on the bacterial cell concentrations and composition, water was sampled from 10 separate households after overnight stagnation and after flushing the taps. Cell concentrations, measured by flow cytometry, increased (2-3-fold) in all water samples after stagnation. This increase was also observed in adenosine tri-phosphate (ATP) concentrations (2-18-fold) and heterotrophic plate counts (4-580-fold). An observed increase in cell biovolume and ATP-per-cell concentrations furthermore suggests that the increase in cell concentrations was due to microbial growth. After 5 min flushing of the taps, cell concentrations and water temperature decreased to the level generally found in the drinking water network. Denaturing gradient gel electrophoresis also showed a change in the microbial composition after stagnation. This study showed that water stagnation in household pipes results in considerable microbial changes. While hygienic risk was not directly assessed, it emphasizes the need for the development of good material validation methods, recommendations and spot tests for in-house water installations. However, a simple mitigation strategy would be a short flushing of taps prior to use.     

液压系统管道循环冲洗施工技术

液压系统配管的质量直接影响液压系统的可靠性,其中通过管道循环冲洗工作保证系统清洁度非常关键。详细介绍了液压系统循环冲洗的施工方法及施工要点,重点介绍了冲洗回路的连接方式。