PDH装置外网料腿膨胀节失效原因及措施

通过对丙烷脱氢装置外网料腿膨胀节失效样品的化学成分,断口能谱,扫描电镜,金相及运行工况进行分析,得出波纹管膨胀节失效的主要原因是晶间腐蚀和应力腐蚀联合作用的结果。针对PDH装置含硫,含氯的运行工况,检修期间要避免连多硫酸腐蚀,定期更滑膨胀节,材料升级等预防和处理措施,可以防止因膨胀节失效导致装置非计划停车造成经济损失。     

金属波纹膨胀节开裂失效原因分析

采用宏观检查、扫描电镜、X射线能谱、金相分析及化学分析等方法,对金属波纹膨胀节开裂的原因进行了分析。结果表明应力腐蚀是造成金属波纹膨胀节开裂失效的根本原因,并据此提出了改进建议。     

城市热网不锈钢波纹管膨胀节失效分析

对某316L不锈钢波纹管膨胀节的开裂原因进行了分析。该膨胀节在热网蒸汽管线中服役了约4年。该管线运行压力1.1 MPa,运行温度230℃,管线介质为过热蒸汽。通过金相检查、断口分析等方法可知,该膨胀节的失效原因为碱性介质聚集所引起的碱应力腐蚀开裂。     

高温烟气膨胀节波纹管开裂失效分析

为查明重油催化生产装置中的一套高温烟气膨胀节波纹管的泄漏原因,针对波纹管进行了检测分析。结果表明,波纹管开裂失效是高温烟气中的硫化物造成的应力腐蚀。根据失效机理以及现场情况,采取了波纹管更换材料、降低连接附加载荷以及停工时热空气吹扫等技术措施,使得膨胀节的使用寿命延长。     

耐腐蚀波纹管膨胀节新材料试验研究

Ｂ－３１５钢波纹管膨胀节，是结合我国炼油厂的实际需要，开发出来的一种新型高温、耐腐蚀的膨胀节。它具有良好的焊接性能和优良的抗点蚀、晶间腐蚀有应力腐蚀能力，可用于含有氯离子、连多硫酸、硫化氢等腐蚀的环境中。     

减压塔挥发线上膨胀节破裂问题的探讨

我厂减压塔上U型膨胀节(d_0822)在运行服役期间,发生了非正常性失效,出现了数条穿透性裂纹和大量的非穿透性裂纹,产重影响了生产的正常进行。本文分析了膨胀节破裂部位材料的裂纹形貌、化学成分及金相组织,作者认为:该膨胀节的破裂行为,系穿晶型应力腐蚀破裂。本文进一步对膨胀节破裂部位进行了应力分析、计算和评定,分析了腐蚀性工作介质对膨脓节破裂的影响,讨论指出:膨胀节的应力腐蚀破裂,是由高水平的拉应力和较高含量的氯离子的联合作用所致。据此,本文提出了防护对策:①改膨胀节的拼焊成型为卷焊简体的液压成型。②蒋膨胀节的波数由4增至5。③合理选用膨胀节的材质。     

减压塔出口膨胀节泄漏失效分析及修复

对某石化公司二蒸馏装置减压塔馏出口管线上的覫Ф1100 mm膨胀节在蒸汽吹扫时的泄漏失效进行了分析。结果表明,由氯离子引起的应力腐蚀以及电化学腐蚀的共同作用是导致膨胀节泄漏的根本原因。另外,膨胀节不锈钢材料与碳钢之间的电位差加速了电化学腐蚀的速度。修复后跟踪观察表明,对整个焊口使用"贝尔佐纳"技术屏蔽隔离以避免氯离子的结聚是解决膨胀节泄漏的有效方法。     

催化裂化装置用膨胀节失效案例分析及壁温对其寿命的影响

在查阅文献基础上 ,整理了国内主要催化裂化装置膨胀节的失效案例 ,并分析了产生失效的主要原因。首次用远红外测温仪对装置中的膨胀节进行了温度分布测量 ,发现垂直安装的膨胀节温度分布比较均匀 ,而水平安装和倾斜安装的膨胀节最低点的温度最低 ,最高点温度最高。分析认为 ,产生这种温度分布的原因是催化剂粉尘在最低点不断沉积导致膨胀节最低点壁温逐渐降低。并认为水平安装和倾斜安装的膨胀节容易失效也是由于催化剂粉尘不断沉积导致壁温低于露点温度从而引起应力腐蚀开裂。并提出了避免最低点温度降低的措施 ,以提高膨胀节的寿命。     

30万t/a催化裂化装置烟机入口膨胀节波纹管开裂分析

分析了催化裂化装置烟机入口膨胀节使用不到一年即发生开裂失效的情况,得出该膨胀节失效原因是内壁发生晶间腐蚀和低周腐蚀疲劳。     

膨胀节补偿及支架脱空失效的原因分析

分析某余热发电项目SP锅炉入口烟风管道运行时,波纹膨胀节补偿失效及支架脱空失效原因,认为管系中膨胀节各项参数的确定及支架类型的选用至关重要。通过管系应力分析,对膨胀节部分参数及支架的类型等进行了调整并取得成功。     

Internal stress analysis of epoxy adhesively-boned joints based on their thermomechanical properties at cryogenic temperature

Internal stress analysis is essential to structural design of materials applied in cryogenic engineering. In this contribution, thermomechanical properties including dynamic thermomechanical properties and thermal expansion behavior of four epoxy resins, namely the polyurethane modified epoxy resin (PUE), diglycidyl ether of bisphenol A (DGEBA), tetraglycidyl-4,4′-diaminodiphenylmethane (TGDDM) and triglycidyl-p-aminophenol (TGPAP) were studied by dynamic thermomechanical analysis. Internal stress of the epoxy layer in the bonded joint was calculated based on the thermomechanical properties. Meanwhile, the structure-cryogenic property relationship of epoxy resins were investigated. Results demonstrate that internal stress in the four epoxies bonded joints is 6 ~ 21 MPa at −150°C, and is positively correlated with the average thermal expansion coefficient (CTE) of epoxy resins. TGDDM and TGPAP showed higher retention of lap shear strength both at −196°C and after temperature cycling due to their lower CTE. Morphology of the fractured surface of bonded joints demonstrated that internal stress is responsible for the severe interface failure at −196°C. It reveals that selection of epoxy resins with low CTE is beneficial for designing high-performance epoxy adhesive systems served at cryogenic temperature.     

Mechanical behavior of polyurethane adhesive bonded joints as a function of temperature and humidity

The temperature and humidity were found to be the most effective parameters in the behavior of polyurethane flexible adhesive bonded aluminum joints. In order to obtain the effect of environment on bond strength, toughness, failure displacement, joints stiffness and failure model, in this work, aluminum single-lap joints were tested under various temperatures (25, 40, 60 and 80 °C) and relative humidity (RH, 55, 65, 75, 85, 95 and 99%) using an environmental chamber. The results showed that as the humidity increased from 55 to 99%, bond strength decreased as linear function. As the temperature increased from 25 to 80 °C, the bond strength decreased as exponential function. The joints stiffness reduced gradually with the increase of temperature and humidity. The analysis of the failure section of the ageing joints showed that the humidity caused the transition of the failure model, and the increase of the temperature promoted the change of the failure model. Besides, at low humidity (55 and 65%), failure displacement decreased gradually with the increase of temperature, and at high humidity (95 and 99%), failure displacement increased. This study will help engineers design a reliable, safe and effective bonding structure. And it is conducive to solve the problem of joint strength degradation in the hygrothermal environment.     

Failure prediction of adhesively bonded CFRP-Aluminum alloy joints using cohesive zone model with consideration of temperature effect

To predict the failure of adhesively bonded CFRP (Carbon Fiber Reinforced Plastics)-aluminum alloy joints applied to High Speed EMU (Electric Multiple Units) more accurately with consideration of temperature influence, a combined experimental-numerical approach is developed in this study. Bulk specimens and adhesive joints, including thick-adherend shear joints(TSJ), scarf joints(SJ) with scarf angle 30°(SJ30°), 45°(SJ45°), and 60°(SJ60°), as well as butt joints(BJ), were manufactured and tested at 23°C (room temperature, RT), 80°C (high temperature, HT) and ?40°C (low temperature, LT). Quadratic stress criteria built at different temperatures were introduced in the cohesive zone mode (CZM) to conduct a simulation analysis. Test results suggest that the effects of HT on mechanical properties of adhesive are more obvious than the effects of LT. It is also found that TSJ show the greatest improvements in failure strengths at LT due to the occurrence of cohesive failure, while SJ and BJ tend to develop fiber tears due to the presence of normal stress. Stress distributions of adhesive layer are found to be symmetrical except for the normal stress of SJ. This simulation analysis shows that the prediction accuracy is related to quadratic stress criteria applied, and that the relative errors of prediction results are less than 7.5% for engineering applications.     

温度变化对复合材料双面搭接接头拉伸强度的影响分析

介绍了复合材料三种连接方式之一——胶接。对双面搭接接头进行了有限元建模,在不同的高温环境下进行拉伸试验,运用相关的失效准则,分析判断复合材料胶接接头的破坏形式,确定温度对破坏形式的影响。通过试验,验证了分析的正确性,对复合材料胶接接头的强度校核及设计改进有重要的指导作用。     

Hydrothermal effects on mechanically fastened glass/polypropylene composite joints

This study deals with the hydrothermal effects on mechanically fastened glass fiber mat/polypropylene composite joints with different joint geometry. Three kinds of joint geometries were adopted; hole diameter was 6 mm, the length from top edge to the hole center was 18 mm (3e) and the specimen width was 12 (2 w), 18 (3w), and 30 mm (5w). The joints were immersed in hot water at 60 and 80°C. The effect of water temperature on the failure load appeared clearly in 2w3e joints. The higher water temperature induced more strength reduction. The dominant failure mode changed from the net-tension to the bearing for the original dry joints for wider specimens. The failure mode changed from multiple to net-tension only for 3w3e joints, because of a remarkable tensile strength reduction. The failure strength and the failure mode were predicted by the macroscopic failure criterion, and the characteristic experimental curves, and the FEM analysis. The predicted results agreed with experiment.     

Theoretical and experimental studies for the failure criterion of adhesively bonded joints

The objective of this work was to develop a criterion for predicting the failure strength of joints bonded by ductile adhesives. To obtain the criterion, first, fracture tests were carried out on T-peel joints and single-lap joints with various joint geometries, adhesives, and adherend materials. Then using the fracture loads obtained in the tests, a finite element analysis was performed by which the stresses in the adhesive joints were calculated. It is concluded that the failure of an adhesively bonded joint occurs when the maximum of the ratio of the mean to effective stresses exceeds a certain value, which can be considered a new material constant of a ductile adhesive.     

Advanced pressurelessly prepared adhesive composites based on modified preceramic polymer for the joining of amorphous SiBON ceramics

A series of polysilazane (PSZ)-based adhesives, which could be employed for high temperature environment in aerospace industry, were prepared to bind amorphous SiBON ceramics. It was found that the addition of dopants had a significant influence on the binding strength of samples, and physicochemical properties of adhesives were also closely correlated to their kinds and quantities. The fracture mechanism and phase transformation in joints were characterized. New phases including C₃N₄, Si₃N₄, SiC, BN, Si, ZrB₂ and amorphous SiCN, were formed with the increase of treatment temperature, influencing the binding strengths of samples. The maximum binding strength of joints could reach 16 MPa after heating at 1100 °C in N₂. The macroscopic and microscopic images of the fractured surface of joints and finite element analysis of the joint indicated that the failure of the joint occurred not only at the binding layer but also at the ceramic substrate. This work can serve as a guide for binding amorphous ceramic for high temperature environment.     

Effect of the temperature on the strength of adhesively bonded single lap and T joints for the automotive industry

Adhesively bonded lap and T joints are used extensively in the manufacture of automotive structures. In order to determine the effect of using a structural adhesive instead of spot-welding, a detailed series of tests, supported by finite element analyses, was conducted using a range of loadings. The adhesive was a toughened epoxy and the adherend was a grade of mild steel typical of that used in the manufacture of car bodyshells. The lap joints were tested in tension (which creates shear across the bondline) and three point bending. Previous studies at room temperature have shown that joint failure is dictated by adherend yielding and adhesive strain to failure. In the present study, to asses the effect of temperature that an automotive joint might experience in service, tests were carried out at ?40 and +90 °C. It is shown that the failure criterion proposed at room temperature is still valid at low and high temperatures, the failure envelope moving up and down as the temperature increases or decreases, respectively.     

Progressive failure and experimental study of adhesively bonded composite single-lap joints subjected to axial tensile loads

Experimental tests and finite element method (FEM) simulation were implemented to investigate T700/TDE86 composite laminate single-lap joints with different adhesive overlap areas and adherend laminate thickness. Three-dimensional finite element models of the joints having various overlap experimental parameters have been established. The damage initiation and progressive evolution of the laminates were predicted based on Hashin criterion and continuum damage mechanics. The delamination of the laminates and the failure of the adhesive were simulated by cohesive zone model. The simulation results agree well with the experimental results, proving the applicability of FEM. Damage contours and stress distribution analysis of the joints show that the failure modes of single-lap joints are related to various adhesive areas and adherend thickness. The minimum strength of the lap with defective adhesive layer was obtained, but the influence of the adhesive with defect zone on lap strength was not decisive. Moreover, the adhesive with spew-fillets can enhance the lap strength of joint. The shear and normal stress concentrations are severe at the ends of single-lap joints, and are the initiation of the failure. Analysis of the stress distribution of SL-2-0.2-P/D/S joints indicates that the maximum normal and shear stresses of the adhesive layer emerge on the overlap ends along the adhesive length. However, for the SL-2-0.2-D joint, the maximum normal stress emerges at the adjacent middle position of the defect zone along the adhesive width; for the SL-2-0.2-S joint, the maximum normal stress and shear stress emerge on both edges along the adhesive width.     

基于X射线衍射法的不锈钢波纹管膨胀节残余应力测试

不锈钢波纹管膨胀节是城市燃气管道的重要组成部分.近年来由于应力腐蚀破裂引起的事故频繁发生,因此对其失效机理的研究具有较高的实用意义.文章基于X射线衍射法对膨胀节的残余应力进行了测试,并观察了固溶处理对残余应力的影响.结果表明:未经固溶处理时,波纹管波峰和波谷处均存在残余应力,且分布不均匀,在波峰径向存在残余拉应力,径向...