亚临界机组吸收塔湍流器腐蚀泄漏原因分析

某亚临界机组运行18个月后,吸收塔湍流器发生腐蚀泄漏.通过宏观分析、材料成分分析、显微组织分析、腐蚀产物成分及断口形貌分析等方法探究了腐蚀泄漏的原因.结果 表明:该吸收塔湍流器分别发生了两种腐蚀,在TP304不锈钢部分发生缝隙腐蚀,在TP316L不锈钢部分的焊缝部位发生应力腐蚀,并提出了应对措施以避免此类事故的发生.     

汽油滤清器泄漏原因分析

汽油滤清器在整车进行24个循环试验后发生泄漏。利用宏观分析、金相检验和扫描电镜及能谱分析等手段对汽油滤清器泄漏原因进行了分析。结果表明,缝隙腐蚀和电偶腐蚀是造成汽油滤清器罐体早期泄漏的主要原因。汽油滤清器罐体与支架在最初阶段由于接触区域存在缝隙,发生了缝隙腐蚀,致使汽油滤清器罐体铝发生点蚀、支架镀层局部脱落;镀层脱落后,滤清器罐体铝与支架基体由于电极电位的不同进而发生了电偶腐蚀,加速了滤清器罐体腐蚀的进程,导致汽油滤清器发生泄漏。     

某冷凝器换热铜管腐蚀穿孔分析

针对某冷凝器中换热铜管发生腐蚀穿孔泄漏,进行宏观检查、化学成分分析、扫描电子显微镜检查以及腐蚀产物能谱分析,认为HSn70-l铜管在海水环境中发生脱锌选择性腐蚀是腐蚀导致铜管穿孔泄漏的主要原因,并给出防止HSn70-l铜管脱锌腐蚀的建议。     

蒸汽管线三通管的泄漏原因分析

催化装置的蒸汽管线上有多个三通管均在焊缝处发生蒸汽泄漏。采用化学成分分析、硬度测试、宏观和微观分析等方法对泄漏的三通管进行了分析。结果表明,由于在焊接时,接口处未焊透留下了缝隙,在工作介质和焊接应力的长期作用下产生了缝隙腐蚀和应力腐蚀,最终导致泄漏。     

冷凝器铜管断裂原因分析及防护措施

某电厂300MW机组汽轮机冷凝器投产几年来,铜管多次发生泄漏,为了分析冷凝器铜管泄漏原因,抽取已断裂的铜管试样,采用化学元素分析、机械性能、金相、扫描电镜、能谱分析等试验研究方法对断裂等新管进行了分析,结果表明：铜管断裂由于应力腐蚀、应力腐蚀裂纹开裂于外壁,黄铜管内壁存在脱锌腐蚀现象。并提出了降低拉应力、改善水质和工况、进行阴极保护、定期清洗等防护措施。     

黄铜冷凝管硫酸亚铁膜的性能研究

由于冷却水的作用,热电厂冷凝器黄铜管常发生不同程度的腐蚀,导致黄铜管泄漏甚至破裂.这不仅大大缩短了黄铜管的使用寿命,造成了经济损失;更为严重的是因为冷凝器泄漏而污染了锅炉水质,直至整个发电机组停止运行.因此,采取有效的措施阻止黄铜管的腐蚀,保证设备的安全运行,是发电厂金属腐蚀与防护工作中的一个重要课题. 目前,国内外电厂均采用冷却水中添加硫酸亚铁处理,使铜管表面生成一层水合氧化铁(γ-FeOOH)的保护膜层,从而可降低黄铜管的腐蚀速度,延长其使用寿命.国内在七十年代对成膜的各种条件如溶液中Fe~(++)浓度、溶液的pH值、温度、流速等进行了大量研究工作,并相继在现场使用     

核电站用离心式冷水机组换热器铜管腐蚀泄漏分析

某核电站用离心式冷水机组蒸发器/冷凝器铜管在投运前发生制冷剂泄漏,通过对泄漏点进行微观分析,并从设备制造工艺过程排查产生问题的原因,确认换热器铜管在出厂前内壁残留了少量的空压机润滑油.残留的润滑油在一定潮湿空气中长期暴露而水解酸化形成铜管敏感的羧基酸根介质,进而在铜管表面产生电化学反应形成蚁巢腐蚀,最终造成泄漏.     

舰船冷凝器用B30铜合金传热管标准体系

综述了舰船冷凝器用B30铜合金传热管标准的国内外现状,在对比分析B30铜合金传热管的化学成分、室温拉伸性能、工艺性能、无损检测等主要技术内容的基础上,结合舰船冷凝器用B30传热管的腐蚀泄漏问题,提出了B30传热管标准技术内容的增加建议。      

冷凝器传热管腐蚀失效分析

针对船用冷凝器B30换热管的腐蚀泄漏问题,通过对管材理化分析、腐蚀形貌观察、金相分析和腐蚀产物分析等探讨了其腐蚀失效的原因,结果表明:B30换热管成分满足设计要求,内外表面金相组织分布不均;失效主要由内表面的腐蚀引起,表现为富Ni相优先腐蚀,导致其包围的富Cu相脱落,宏观上表现为点蚀坑的不断加深与扩大,最终导致B30换热管腐蚀穿孔失效。     

印刷电路板缝隙腐蚀行为研究

采用模拟印刷电路板缝隙腐蚀装置,发展阵列电极方法测试缝隙内电路板表面铜在NaCl溶液中的腐蚀电位,研究了多种因素对其缝隙腐蚀行为的影响.结果表明,缝隙宽度为20～30μm时,印刷电路板容易发生缝隙腐蚀;在浸泡初期,缝隙内铜的腐蚀电位随浸泡时间延长负移,但浸泡48 h后,变化趋势较小;溶液中NaCl浓度达到1 mol/L时,对促进电路板的缝隙腐蚀作用较为明显;酸性范围内,缝隙内电路板腐蚀电位随缝隙大小、浸泡时间、NaCl溶液浓度、溶液的pH值降低而负移;温度低于45℃后,缝隙内铜的腐蚀电位随温度的升高而降低.     

埋地管道漏损检测的声传播特性研究

地下管道漏损的准确定位问题一直是困扰世界范围内供水系统和市政建设的难题。管道漏损不仅会浪费大量的资源,而且还会造成严重的事故以及环境污染。针对埋地管道这样一个典型的土-管-液三相耦合问题,将管道周围土壤做弹性体考虑,对弹性介质中充液管道的声传播特性进行了解析研究。推导了低频域周向波数n=0的轴对称管道振动耦合方程,通过数值方法分别得到了流体波(s=1)和壳体压缩波(s=2)的复波数解。结果显示,管外土介质会使管道流体波波数减少(也即加快波的传播速度),而对壳体压缩波的传播影响较小。由于管-土作用产生的能量辐射,在整个研究频段s=1波和s=2波都有较大的衰减。研究结果可为埋地管道漏损的精确检测提供理论支持     

A PROCEDURE FOR ANALYSIS OF LEAK BEFORE BREAK IN PIPES SUBJECTED TO FATIGUE OR IGSCC ACCOUNTING FOR COMPLEX CRACK SHAPES

Abstract A procedure is described which predicts the growth of an initial circumferential surface crack through a pipe wall and further on to final failure of the pipe. The crack growth mechanism can either be fatigue or stress corrosion. Consideration is taken to complex crack shapes, since especially the last growth mechanism often results in a substantially longer crack length on the inside of the pipe than on the outside for the initial leaking crack due to the distribution of weld residual stresses. The procedure has been implemented in a computer program that in an integrated fashion calculates crack sizes and mass leak rates as a function of time and also predicts when leakage and final failure occur. The information obtained makes it possible to judge if the concept of leak before break is fulfilled.     

供水管道泄漏声信号及其传播特性

相关仪利用供水管道泄漏时产生的泄漏声波对漏点定位。泄漏信号验证为高斯分布,泄漏声波主要是在管道里的水中传播,与管壁发生流固耦合作用,引起管壁振动。用FIR滤波器对管道系统建模,采用最小均方误差(LMS)自适应系统辨识方法得到管道的冲激响应函数,与线性相位FIR滤波器的冲激响应相比较,表明泄漏声波在传播过程中存在频散。泄漏声信号受各种噪声干扰,根据互谱相位谱信息估计泄漏信号的频带范围,对信号滤波后作时延估计,结果表明,提高了泄漏定位的置信度。     

Modeling Acoustic Emission Signals Caused by Leakage in Pressurized Gas Pipe

Leakage in high pressure pipes creates stress waves which transmitted through the pipe wall. These waves can be recorded by using acoustic sensor or accelerometer installed on the pipe wall. Knowing how these waves vibrate pipe is very important in continuous leak source locating process. In this paper the pipe radial displacement caused by acoustic emission due to leakage is modeled analytically. The standard form of Donnell’s nonlinear cylindrical shell theory is used to derive the motion equation of the pipe for simply supported boundary condition. Using Galerkin method, the motion equation has been solved and a system of nonlinear equations with 7 degrees of freedom is obtained. A MATLAB code according to Runge-Kutta numerical method is generated to solve these equations and derive the pipe radial displacement. To check the theoretical results, acoustic emission testing with continuous leak source and linear array of two sensors positioned on two sides of the leakage source were carried out. The major noise of recorded signals was removed through the wavelet transform and filtering technique. For better analysis, fast Fourier transform (FFT) was taken from theoretical and de-noised experimental results. Comparing the results showed that the frequency which carried the most amount of energy is the same that expresses excellent agreement between the theoretical and experimental results validating the analytical model.     

XFEM fracture analysis of cracked pipeline with and without FRP composite repairs

Abstract

The effect of fiber reinforced polymer composite (FRPC) repair on crack propagation in thin-walled steel pipes is examined. The extended finite element method is used in this study to simulate a pressurized cylindrical pipe with longitudinal crack in two conditions: the original cracked pipe and the pipe repaired with a composite patch. Carbon/epoxy or E-glass/epoxy FRP in two different fiber orientations are assumed for cracked pipe repair. Performance of four types of FRP repair systems are investigated by CTOA, COD and COA fracture criteria for both the pipe integrity assessment and the potential age of leak before break criterion.     

金属压扁型正压漏孔不同压力下的漏率研究

在不同入口和出口压力条件下,正压漏孔的漏率值会发生变化,在使用时需要对正压漏孔的校准值进行修正。对2支金属压扁型正压漏孔在多种压力条件下进行漏率测量,给出了测量结果,然后根据管道流导理论推导出正压漏孔漏率随压力变化的修正公式,并对修正结果与实验测量数据进行了研究分析。     

4333M4超高压反应管的断裂韧度

通过非标准拱形三点弯曲试样的试验,采用柔度法标定,测定了进口4333M4低合金超高强度钢管材的临界应力强度因子KIC,并对该超高压反应管进行了先漏后破分析。结果表明:该钢材有较高的断裂韧度,符合SFAC 98—01Rev.2《超高压用无缝合金钢管技术条件》的要求,且管材符合先漏后破标准。     

Failure characteristics of glass-reinforced plastic pipe and pipe assembly

In the examination of glass-reinforced plastic (GRP) pipes and components after failure the fracture is often so catastrophic that much of the evidence is destroyed or hidden. When a leak failure occurred during a hydraulic pressure test on a GRP pipe bend the opportunity was taken to examine the bend wall in detail at a number of localities. They included, not only the region where the leak was apparent but also at areas where strain and displacement measurements had indicated the possibility of failure arising. The 250 mm diameter pipe specimen tested consisted of a right-angled pipe bend with flanged, straight lengths each attached by a butt joint. The resin matrix was polyester and the reinforcement was E-glass in the form of chopped strand mat of four layers weighing 2·4 kg/m².

Although the failure pressure was entirely satisfactory from a design point of view, three important areas of weakness were discovered. They were associated with procedures for butt jointing and for moulding of the bend unit. The resulting micrographs were of sufficient quality to act as comparators for examination of possible service failures.     

R290分体式空调器室内泄漏安全性实验研究

采用实验研究的方法,模拟出房间空调器使用中可能出现的各种制冷剂泄漏的情况,对0.5 mm和4 mm两种泄漏孔径、260 g和350 g两种充灌量以及在室内外机连接管上加装电磁阀开关等不同情况下R290制冷剂在空调房间内的分布规律进行了实验研究。实验结果表明房间空调器内制冷剂充灌量和泄漏口径的大小对房间安全性有着很大的影响,而在室内外机连接管上加装电磁阀可以有效地减缓R290的泄漏速率,提高R290分体式空调器的安全性。