316L不锈钢板式换热器泄漏原因

316L不锈钢板式换热器使用约半年后频繁出现泄漏事故,通过扫描电镜分析、能谱分析、金相检验、显微硬度检测和有限元模拟分析等方法对泄漏原因进行了分析.结果表明:316L不锈钢板片发生了应力腐蚀开裂,造成泄漏.板片冷加工后产生了较大的残余拉应力且环境中存在Cl-腐蚀介质,导致残余应力较大的波峰和波谷处产生裂纹和腐蚀坑,是造...     

不锈钢弯头的失效原因分析

某化工厂中变废锅出口管0Cr18Ni9不锈钢弯头发生泄漏。为查明其失效原因,对泄漏部位内外进行表面检测,发现在焊缝附近出现了大量裂纹。在该区域取样进行化学成分、硬度、金相组织、断口形貌和腐蚀产物分析,确定了弯头产生裂纹的原因是存在组织应力、焊接残余应力以及内部介质中的Cl-共同作用下,发生了沿晶型应力腐蚀开裂。     

316L奥氏体不锈钢碱液储罐开裂原因

某核电站316L奥氏体不锈钢碱液储罐发生了泄漏,采用宏观观察、化学成分分析、金相检验、硬度测试及残余应力分析等方法对该储罐开裂原因进行了分析。结果表明：储罐内壁焊缝两侧出现与焊缝平行的环向裂纹和垂直的轴向裂纹,前者主要受焊接残余拉应力作用,后者主要受冷加工残余拉应力作用,两类裂纹均为碱致应力腐蚀开裂。     

不锈钢弯头开裂原因分析

某不锈钢弯头在使用中发生泄漏。通过化学成分分析、金相检验、力学性能测试、扫描电镜和能谱分析以及晶间腐蚀试验等手段对不锈钢弯头开裂的原因进行了分析。结果表明:弯头外壁所在环境中存在腐蚀性介质,在环境介质、残余应力与工作应力的共同作用下,弯头产生了沿晶应力腐蚀开裂。     

换热器汽包封头泄漏原因分析

在检修雏护换热器汽包时发现汽包封头泄漏，在汽包封头的阀盖角焊缝处出现裂纹，裂纹平行于焊缝。采用宏观形貌分析、化学成分分析、金相检验、显微硬度测定、能谱分析以及应力分析等方法对泄漏处进行了分析。结果表明，汽包中水质含有较高浓度的碱性元素和氧、硫、氧等强腐蚀性元素，又在焊接残余应力的作用下发生应力腐蚀开裂，最后导致汽包封头产生泄漏。     

空气源热水机换热器失效分析

空气源热水机使用一段时间后其换热器换热管出现开裂泄漏,经金相、电镜分析确认为应力腐蚀。本文以降低残余应力为目的,构建换热管加工的简化理论模型和有限元模型,模拟计算模具参数的定量影响,并通过回归方程的构建取得最优参数。在参数优化后,经有限元模拟,残余应力减小25.7%,调整后制品经腐蚀性压力脉冲试验验证,耐应力腐蚀试验寿命显著提高。     

超临界机组轴封冷却器TP304不锈钢管泄漏原因分析

通过宏观检验、化学成分分析、拉伸试验、压扁试验、晶间腐蚀试验、金相检验、扫描电镜及能谱分析等方法,对某电厂汽轮机轴封冷却器TP304不锈钢管的泄漏问题进行了分析。结果表明:TP304不锈钢管在外表面残余拉应力和蒸汽中Cl-,S2-的联合作用下,经过一定时间因发生严重应力腐蚀导致管子开裂。对此,提出了消除TP304不锈钢焊管表面残余应力、严格控制汽水品质、降低有害离子含量等建议。     

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.     

WP304WX管道泄漏原因分析

不锈钢管道使用5a(年)后出现泄漏事故。采用化学成分分析、硬度测试、金相检验、晶间腐蚀与断口扫描电镜分析方法,对泄漏原因进行了分析。结果表明:焊接过程中造成的贫铬及残余应力的存在导致了管道的开裂。建议对管道所有焊缝热影响区进行探伤,查找腐蚀裂纹,对发现的裂纹进行打磨和补焊处理,并进行消除残余应力处理。     

氨水储槽泄漏原因分析

应用X射线法对氨水储槽的残余应力状态进行了检测与分析,对焊缝,热影响区、母材等部位进行了重点测试,并对热处理效果进行了检测与评价,结果表明,氨水储槽的泄漏由多种原因造成,残余应力过大是主要因素。     

乙苯/苯乙烯分离塔塔顶分布器失效分析

采用宏观及微观观察、金相检验、化学成分分析、力学性能检测等方法分析了某乙苯/苯乙烯分离塔塔顶分布器发生开裂泄漏失效的原因。结果表明:由于分离塔设备工作介质中含有Cl~-,在腐蚀介质和应力的共同作用下,最终导致了分布器侧板的应力腐蚀开裂。最后提出了相应的改进建议及防护措施。     

储气塔阀门紧固螺栓的断裂分析

储气塔运行半年即发生了阀门紧固螺栓的断裂事故。采用化学成分分析、硬度测定、金相检验以及断口的宏、微分析等方法,对螺栓断裂原因进行了分析。结果表明,由于塔内腐蚀性介质的微量渗出,导致了阀门紧固螺栓的应力腐蚀断裂。     

Failure analysis of stress corrosion cracking of 316L structured packing in a distillation tower

The present study was done to find the probable causes of AISI316L structured packings (SPs) failure in a dewatering phenol tower. In this tower, the SPs would provide a high contact surface between streams to maximize and accelerate the distillation process. Increasing vibration of discharging pump showed that there were detached pieces of SPs in pump's strainer. During plant overhaul, corrosion inspection was done and some of the broken packings were gathered for further analysis. The samples were evaluated by visual observation, optical and scanning electron microscope. Transgranular cracks in packing sheets and screws, used for restraining layers of packing together, were seen. Energy-dispersive X-ray spectroscopy (EDS) of corrosion products on packing and the fracture surface of the screw was conducted. The results showed the occurrence of chloride stress corrosion cracking. Even though the chlorine contents of tower streams were low, it seemed that process fluids have been mal-distributed leading to the local concentration of the chlorine on SPs surface. In addition to chlorine, high working temperature and applied stress provided a favorable condition for stress corrosion cracking.     

Stress corrosion failure of high-pressure gas pipeline

Incidents of failure due to corrosion/stress corrosion cracking of high-pressure gas pipelines in Pakistan have been observed to occur after about 15–20 years of service. The present paper constitutes the failure analysis of an 18-inch diameter electric resistance-welded gas pipeline. The failure was characterized, on the basis of all the available evidence and the metallurgical examination carried out on the ruptured pipe, as a stress corrosion failure that had initiated at a longitudinal ‘stress raiser’. This stress raiser, which was essentially a manufacturing defect, constituted a longitudinal ‘step’ on the pipe surface that had resulted from the faulty trimming/shaving of the weld flash. The findings of this study, thus, emphasize the need for the care that must be taken during the shaving-off of the weld flash.     

Pipeline failures in corrosive environments – A conceptual analysis of trends and effects

Pipeline corrosion is a major challenge facing many oil and gas industries today because of the enormous downtime associated with corrosion related failures. Fatigue stress initiation in pipelines has been attributed to corrosion defects whose growth is enhanced by cyclic loading caused by the operating pressure of the transported fluids. This work reviews the concept of oil and gas transmission pipeline failures in corrosive environment by highlighting the corrosion mechanisms, dominant stress corrosion cracking trends, hydrogen induced cracking and predominant models for burst pressure estimation. Fatigue stress failure trends of corroding pipelines were also explained whilst describing some pipeline manufacturing processes that increases the susceptibility to fatigue stress failure. Optimization framework for pipeline integrity assurance against corrosion fatigue failures was also shown to incorporate different steps that includes – strategic policy initiation, policy implementation, information analysis and reviews and implementation actions.     

A study on axial cracking failure of drill pipe body

Frequently happening drill pipe failure accidents in oil and gas wells not only affect drilling speed, but cause enormous economic losses and many safety issues. Most of these accidents are transverse cracking of drill pipe body and pin thread or axial cracking of box thread. Based on the axial cracking failures of drill pipe body in an ultra-deep well in China, this paper give a systematic analysis of axial cracking failure in consideration of service condition, material quality and stress corrosion mechanism. Measurement and inspection are performed on macroscopic and microscopic morphology of crack surface, corrosion products and circumferential residual stress. Then stress corrosion cracking experiments against hydrogen sulfide is conducted. Finally, the critical stress value for sulfide stress corrosion cracking of the drill pipe material is obtained, and the mechanisms of axial cracking failure and corresponding preventive measures are proposed.     

D210塔简体泄漏原因分析

采用化学成分分析、金相检验和断口分析等方法,对304L钢D210塔筒体泄漏原因进行了分析。结果表明：D210塔筒体泄漏原因是由于氯离子的存在而产生应力腐蚀开裂所致。由于敏感材料、应力腐蚀环境及应力三个条件共同存在,在一定温度下使其产生应力腐蚀裂纹,裂纹起始于筒体外壁角焊缝处,而后向内壁扩展,最终穿透筒壁,致使该塔筒体在角焊缝处产生破裂泄漏。     

Hot corrosion failure in the first stage nozzle of a gas turbine engine

First-stage nozzles of gas turbines, which are the first elements after the combustion chamber, encounter hot gases from the combustion process and have the task of directing the fluid path and increasing the velocity of combustion products. This paper reports on the incidence and failure of the first-stage nozzles of a gas turbine in September 2013 at a seaside pump-house located in the South-West of Iran. The nozzle was made of nickel-based superalloy Nimonic105. Due to nozzle failure, the turbine was damaged severely. The cause of nozzle failure was investigated. The results of visual inspection, XRD analysis of deposits on the blade airfoil, SEM images and EDAX analysis showed the characteristics of hot corrosion. Finite-element analysis (FEM) revealed that the cause of blade trailing edge failure was thermal stress leading to thermal fatigue, which accelerated nozzle blade failure in addition to the hot corrosion.     

Failure Analysis for the Welded Elbow at the Bottom of the Rectifying Tower in the Alcohol Evaporation System

Cracking was found on the welded elbow at the bottom of rectifying tower in an alcohol evaporation system. In order to determine the cause of failure, a detailed analysis was conducted. The analysis included macroscopic observation for the failed tube and optical microscopy for the morphology of cracks. The characterization of fracture was analyzed by scanning electron microscopy, and the components subjected to the cracks were analyzed using energy-dispersive x-ray spectroscopy. Results revealed that the welded elbow had suffered damage from external chloride stress corrosion cracking (ECSCC). The environmental factor responsible for ECSCC is the chloride present in the dampish insulation. The stress factor is the result of the welding residual stress induced in the material which was used to fabricate the elbow.     

昆明市南窑火毁建筑物的控制爆破拆除

介绍了地处闹市区的大面积火毁钢筋混凝土框架结构建筑物拆除爆破的设计与施工工艺 ,并对爆破方案的确定、参数的选择以及所采取的安全措施进行了论述。