蒸汽过热器管断裂失效分析

某奥氏体不锈钢制蒸汽过热器管在加碱煮炉过程中发生断裂。采用力学性能测定、宏微观检验及能谱分析,对该断裂管进行了分析研究。结果表明,蒸汽过热管断裂失效是由碱脆造成的。     

蒸汽状态的变化与流量计量的关系分析

流量仪表在供热管网中应用存在问题较多,主要表现在计量准确度失准,尤其是用作贸易结算时,这一问题更为突出。笔者就供热管网中蒸汽状态的改变对蒸汽流量计的影响做一分析。一、蒸汽状态的分析1．过热蒸汽变为饱和状态蒸汽由热电站输出的蒸汽一般为过热蒸汽,蒸汽在管道中经长距离输送到用户,由于管道散热,到用户后往往变成饱和状态,经过定量计算,这种状态下饱和水的体积很小,可以忽略不计。在供热管网中,上述状态的变化较为典型。2．湿饱和蒸汽变为过热蒸汽在供热管网中,当用户突然增大用汽量或蒸汽经过减压装置时,由于压力突然…     

蒸汽供热管线管损原因分析及解决方法

正一、管损原因分析1.蒸汽质量的影响在工况条件下输送过热蒸汽,蒸汽质量没有损失或损失较小,也就不存在供热管损或管损不高。但在工况条件下输送饱和蒸汽,管道散热损失会促使蒸汽汽化潜热的释放,从而产生凝结水。由于水的体积远小于蒸汽体积,蒸汽流量计计量不到,这部分无法计量的凝结水就形成供热管损。根据理论计算和有关资料介绍,当压力为0.6MPa的饱和蒸汽流经直径为100mm的具有良好保温层的管道时,在大气温度为10℃的条件下,每100m管长上每小时要凝结出约30kg凝结水。2.蒸汽状态变化给流量计带来计量误差     

蒸汽计量存在的问题及解决办法

蒸汽流量测量难度较大,因为蒸汽是比较特殊的介质,随着工况（如温度、压力）的变化,单相性质的过热蒸汽经常会转变成为饱和蒸汽,形成汽液两相流介质。目前,能准确测量汽液两相流介质的流量计量仪表几乎没有,解决两相流计量问题的办法是加强蒸汽管道的保温措施.     

湿蒸汽品质和焓的确定

如果湿蒸汽节流到大气压而仍然保持过热状态,则蒸汽的含湿量可以用节流量热计来确定。取样嘴最好安装在远离配件的蒸汽管道的垂直段。蒸汽进入量热计,通过节流孔,进入保温良好的膨胀室。可以按以下等     

多变量智能变送器在蒸汽流量计量中的应用

蒸汽是一种比较特殊的介质,随着工况（温度、压力）的变化,过热蒸汽经常会转变成为饱和蒸汽,形成汽液两相流介质。对于相流经常变化的蒸汽,使用现有的流量仪表测量其流量,肯定会存在测不准的问题。解决方法是保持蒸汽的过热度,尽量减少蒸汽的含水量（如加强蒸汽管道的保温措施,减少蒸汽的压力损失等）,以提高测量的准确度。     

高温高压过热蒸汽疏水阀消声减振研究

针对国内某公司的蒸汽疏水阀在高温高压过热蒸汽工况下产生的强振动高噪声问题,采用有限元法模拟高工况下蒸汽疏水阀内二维非定常湍流激振特性,基于时均化的流场计算和大涡模拟2种方法,模拟分析过热蒸汽疏水阀及管道产生湍流旋涡的主要因素,研究找出产生振动和噪声的流场诱因。根据频谱特性、噪声产生机理及节流降压原理,研究设计了低振动低噪声蒸汽疏水阀的节流降压消声器,并进行频谱分析,其消声量试验结果与理论分析相吻合,为设计出具有消声减振且性能优良的蒸汽疏水阀提供了可靠依据。     

油气管道失效分析与完整性管理

论述了油气管道的失效模式和失效原因,以及完整性管理的概念、流程和关键技术.对失效分析和完整性管理的关系进行了讨论,认为失效分析是油气管道完整性管理的基础;完整性管理是油气管道失效分析的延伸,是全面、科学有效的预测、预防管道失效的措施.     

输油管道改线工程风险评估应用实例

以某成品油管道改线工程为例,辨识该管道改线工程的高后果区(HCAs),确定HCAs的危险等级;选取腐蚀、第3方破坏、误操作、本体因素和管理5个一级指标构建输油管道失效可能性评估指标体系,划分3个管段,运用博弈论赋权法计算各指标权重,确定该管道失效可能性;借助CFD软件分析管道泄漏后油蒸汽扩散规律。结果表明:该管道改线工程HCAs等级整体处于Ⅱ级,管段2失效可能性较大,造成管道失效的主要因素为第3方破坏和腐蚀,随着风速增大油蒸汽的扩散范围变大但含量减小。评估结果与实际情况相符合,为管道改线工程风险评估应用研究提供了一定依据。     

蒸汽计量补偿方法不正确引起的误差分析

本文通过三组测试数据定量分析了在计量过热蒸汽时，由于采用饱和蒸汽补偿方式所引起的计量误差。     

火电厂12Cr1MoV蒸汽管爆管原因分析

通过化学成分分析、金相检验和高温拉伸试验，结合现场实际情况综合分析的方法，对某火电厂12Cr1MoV蒸汽管爆管的原因进行了分析。结果表明：管段珠光体球化评级达4．5级，高温瞬时强度和持久强度较正常工况明显降低，表明长期超温服役下材料老化是造成爆管事故的主要原因。     

某稠油井用高温蒸汽注汽管爆裂失效分析

通过对某油田稠油井发生爆裂的高温蒸汽注汽管进行宏观分析、化学成分分析、金相检验、力学性能测试以及扫描电镜断口分析,找出了该管爆裂失效的原因.结果表明:该高温蒸汽注汽管线的爆裂性质为脆性开裂,开裂起源于管表面的两处机械损伤;导致其爆裂失效的主要原因是该管在服役过程中由于水击作用发生了胀径,使注汽管壁厚不均匀;同时管表面存...     

Failure Analysis of Steam Turbine Rotor Disk

This article presents an investigation into causes of failure of rotor disk of an 8.25-MW capacity steam turbine, which failed catastrophically. Four pieces of the rotor disk detached from the tenth-stage disk of the turbine rotor during this failure. Visual inspection, chemical analysis, macro- and microscopic analysis of the failed rotor disk, analysis of the operational data, and the history of the rotor operation indicated that the failure could be attributed to stress concentrations at macropores and regions of segregation in the disk. Stress corrosion cracking (SCC) subsequently took place in the regions of stress concentration because the steam in the turbine contained chloride and potassium. The SCC produced a network of cracks associated with the macro- and microporosities. It was recommended that the disk fabrication processes ensure a high-quality microstructure and that operational monitoring of the composition of steam be initiated to ensure that the chlorides and potassium concentrations are maintained below a specified level.     

Stress Corrosion Cracking and Oil Leakage in a Control Oil Piping System

This article describes the results of an investigation concerning with the failure of a pipe which was carrying oil from the control oil unit to the steam turbine control valves servomotor. The failure was in the form of a crack, propagating horizontally along the pipe. The crack initiated on the outside of the pipe. The cause of the failure was investigated by conducting visual examination, detailed macro and microstructural examinations and determining the composition of material from the failed pipe. The composition of the pipe material was analyzed by atomic absorption spectrometer. The failure of the oil pipe was attributed to stress corrosion cracking. The pipe material is A312 TP 304L. Recommendation to minimize such failures includes coating the pipe to prevent contact with chloride from the surrounding marine environment.     

Caustic Failure of Thermal Insulated Tubing in Steam Flooding

The coupling of the pre-stressed thermal insulated tubing string broke down inside the steam flooding wells, after the tubing were used in high temperature and high pressure steam for about two years. With further check, it was found that most of the weld joints between the inner and outer tubing also cracked. The failure analysis for the accidents has been carried out by the analysis of chemical composition for the steels, microstructure observation, mechanical property tests, and the investigation of the service environment etc.. The results show that the early damage of the pre-stressed thermal insulated tubing string is mainly induced by the caustic stress corrosion, which can be strengthened by an unstable microstructure of the coupling serviced at high temperature for a long time. Moreover, the high pre-stress design on the thermal insulated pipe for the cyclic steam injection may be not suitable to the situation of steam flooding, which would result in the weld joint cracking.     

Failure analysis of TP304H tubes in the superheated steam section of a reformer furnace

The cracking failure of TP304H tubes in the superheated steam section of a reformer furnace was analyzed. Through the analysis of macro-appearance, micro-appearance of specimens with cracks, metallurgical structure of specimens from an intact pipe section and cracked pipe section, energy spectrum detection of fracture surface, residual stress measurement, and investigation of the service medium, the cracking mode was described as the stress corrosion cracking (SCC) of austenitic stainless steel. In this case, the materials in the heat affected zone were sensitized by inappropriate welding technology. This together with the higher pH value in the steam due to the failure of a gas-liquid separator led to the final cracking of the reformer furnace tube. So the inappropriate welding technology and the failure of the gas-liquid separator were the main factors in this fracture accident.     

某稠油井用热采注汽管线断裂原因分析

某油田注汽站的高温高压注汽管线在运行时发生断裂。通过化学成分分析、力学性能测试和金相检验等方法对注汽管线断裂原因进行了分析。结果表明:管线断裂起源于管表面受到的机械损伤,导致其断裂的原因是注汽管线经长期运行管壁受氧化腐蚀显著减薄,且外管壁腐蚀层下出现微裂纹及孔洞,其性能指标已不能满足技术要求,管线在两者的共同作用下发生了断裂。     

Investigation on corrosion failure of Cr–Mo P11 grade pipe in primary section of a superheated steam generation system

This paper presents failure analysis of corroded steam pipes (Cr–Mo, P11 grade) at ammonia production plant. The corrosion and deposition morphologies are characterized using scanning electron microscopy. In addition, elemental composition analysis of deposited corrosion products is carried out using energy dispersive X-ray. This study clearly indicates the sensitivity of P11 grade steel pipe to intensive oxygen corrosion in steam generation systems with improper implementation of deoxygenating processes. Furthermore, this pipe grade and oxide layer on its surface are susceptible to cracking at the presence of high-level thermal stresses.     

超临界锅炉高温过热器T91钢管爆管分析

通过化学成分、显微组织、力学性能、硬度和内壁沉积物检查等手段对某电厂超临界锅．炉高温过热器出口T91钢管爆裂的原因进行了分析。结果表明：由于该钢管内壁氧化皮脱落堆积,管内蒸汽流通面积减小,造成了钢管过热,从而引起了钢管在薄弱区域爆裂失效。