供水管网中灰口铸铁管的管垢特性与管段力学性状初探

发布时间：2018-02-21 12:52

本文关键词： 灰口铸铁管腐蚀结垢三维扫描数值模拟应力计算　出处：《浙江大学》2013年硕士论文　论文类型：学位论文

【摘要】：灰口铸铁管曾作为城市给水系统中的主要管材被大量使用于我国的城镇给水管网中,虽然截至2012年,灰口铸铁管已经被禁止使用于给水系统中,但是据不完全统计我国现仍有51%灰口铸铁管在给水管网中服役。由于灰口铸铁管本身的材质原因,在使用一段时间后,灰口铸铁管内壁会发生腐蚀,形成腐蚀坑；同时腐蚀产物沉淀、粘结于管道内壁形成管垢。管道的腐蚀会使管壁变薄降低管道强度、腐蚀产物的溶解污染了管内饮用水、管壁结垢导致管道内过水断面面积减小减弱了管道的输水能力。灰口铸铁管腐蚀结垢所带来的水质污染问题、管网安全问题及供水保障问题已经严重威胁到了每一个用水者的切身利益。针对现阶段我国供水系统中由灰口铸铁管所引起的各类问题较为频繁这一实际情况出发,本文中以杭州市供水管网中的一段管龄为15年的灰口铸铁管管段作为研究对象,采用化学分析的方法对灰口铸铁管内壁腐蚀结垢瘤进行浅析；借助三维扫描建模技术,将灰口铸铁管内壁形态进行了数字化还原；通过对模型中腐蚀坑洞的测量统计,得到了管道内壁腐蚀瘤(坑)的分布情况与形态大小；最后采用计算机数值模拟的方法在不考虑土体荷载与约束的情况下对灰口铸铁管管内流态情况、管道内受力等情况进行了模拟研究；结合腐蚀管道剩余强度理论,采用数值计算的方法得出腐蚀后灰口铸铁管的剩余强度值；以灰口铸铁管的剩余强度值和模拟研究的结果作为基础,判断了管段是否安全。研究结果表明：灰口铸铁管内壁的腐蚀结垢起始于金属的电化学腐蚀,管垢的主要成分是：铁、氧、铝、硅、硫、碳。其中铁和氧的成分比例占到了管垢的90%。管内水垢主要是由腐蚀沉积物组成,形态以凸起的瘤状为主,腐蚀瘤尺寸差异较大,在管内无规则分布；这些形态各异的腐蚀沉积物的不规则分布,导致了管道内流体的流态紊乱、管内压力和流速分布不均,对供水管网造成水头损失增加、供水不足及能源浪费；管道在腐蚀破坏后,管道仅在内压的作用下极易在腐蚀坑洞处形成应力集中,应力集中点的Mises应力大小甚至能达到管道内压的数倍,同时腐蚀破坏带来的管道的剩余强度衰减也降低了管道使用过程中的安全系数。本论文得到了水体污染控制与治理科技重大专项课题：“典型城市饮用水安全保障共性技术研究与示范(编号：2008ZX07424)".'‘潮汐影响地区饮用水安全保障技术集成与示范”(编号：2008ZX07424-001)和“山地丘陵城市饮用水安全保障共性技术研究与示范”(编号：2008ZX07424-004)的资助。
[Abstract]:Gray cast iron pipes have been widely used in urban water supply networks in China, although as of 2012, gray cast iron pipes have been banned from being used in water supply systems. However, according to incomplete statistics, there are still 51% gray cast iron pipes in service in water supply pipe network in China. Due to the material reason of gray cast iron pipe itself, the inner wall of gray cast iron pipe will be corroded and corrosion pit will be formed after using for a period of time. At the same time, corrosion products precipitate and form pipe scale by sticking to the inner wall of the pipe. The corrosion of the pipe will make the pipe wall thinning and reduce the strength of the pipe, and the dissolution of the corrosion product will pollute the drinking water in the pipe. The fouling of the pipe wall leads to the reduction of the cross section area of the pipeline, which weakens the water delivery capacity of the pipeline. The water pollution caused by the corrosion and scaling of the gray cast iron pipe, The problem of pipe network safety and water supply security has seriously threatened the vital interests of every water user. In view of the fact that all kinds of problems caused by gray cast iron pipe are more frequent in the water supply system of our country at present, this paper takes a section of gray cast iron pipe in Hangzhou water supply network as the research object. Chemical analysis method is used to analyze the corrosion and scaling of the inner wall of gray cast iron pipe; with the help of 3D scanning modeling technology, the shape of inner wall of gray cast iron pipe is digitally reduced. The distribution and shape of corrosion nodule (pit) in the inner wall of pipeline are obtained. Finally, the internal flow state of gray cast iron pipe is simulated by computer numerical simulation method without considering the soil load and constraint. Based on the theory of residual strength of corroded pipeline, the residual strength of corroded gray cast iron pipe is obtained by numerical calculation. Based on the residual strength of gray cast iron pipe and the result of simulation study, the safety of pipe section is judged. The results show that the corrosion and scaling of the inner wall of gray cast iron pipe begin with the electrochemical corrosion of metal. The main components of the scale are: iron, oxygen, aluminum, silicon, sulfur, etc. Carbon. The proportion of iron and oxygen is 90% of the scale in the tube. The scale in the tube is mainly composed of corroded sediment, which is mainly shaped by bulge, and the size of the corrosion tumor varies greatly, and it is not distributed regularly in the tube. The irregular distribution of these corrosion sediments in different shapes leads to the fluid flow disorder in the pipeline, the uneven distribution of pressure and velocity in the pipe, the increase of water head loss, the shortage of water supply and the waste of energy. After the pipeline is corroded and destroyed, it is easy to form stress concentration in the corrosion pit under the action of only internal pressure. The Mises stress at the stress concentration point can even reach several times of the internal pressure of the pipeline. At the same time, the residual strength attenuation of pipeline caused by corrosion damage also reduces the safety factor in the process of pipeline operation. In this paper, a major scientific and technological project on water pollution control and control has been obtained: "study and demonstration of common technologies for drinking water safety assurance in typical cities (No.: 2008ZX0742424)" .integration and demonstration of drinking water security technology in tidal affected areas (. Number: 2008ZX07424-001) and "Research and demonstration of common technologies for the safety of drinking water in hilly cities" (No.: 2008ZX07424-004).
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU991.33

【参考文献】