锅炉水冷壁管爆管原因分析

采用宏观检验、力学性能检测、金相检验、扫描电镜检查和X射线衍射分析等方法对某锅炉水冷壁管发生爆管的原因进行了分析。结果表明：水冷壁管爆裂是由于酸泄漏事故引起的,泄漏导致接触烟气侧的管内壁存在较多细小的微裂纹,使材料的拉伸强度和屈服强度大幅降低,加上锅炉水系统漏入酸溶液引起了氢腐蚀,最终导致水冷壁管在工作应力下发生氢脆断裂。     

某热电厂600 MW锅炉水冷壁管开裂原因

某热电厂600 MW锅炉水冷壁管在水压试验时出现开裂.采用宏观分析、化学成分分析、金相检验、力学性能试验等方法对开裂原因进行了分析.结果表明:水冷壁管原始管材边角部位存在夹渣缺陷,使得母材形成不连续缺陷,在水压试验升压时,裂纹扩展最终导致管子开裂失效.     

电站锅炉水冷壁管失效分析

某钢铁公司电站锅炉仅服役15000h就发生水冷壁管破裂事故。采用化学成分分析、金相检验及水垢结构X射线衍射分析等方法对失效水冷壁管进行分析,并结合锅炉运行状况进行调查。结果表明：水冷壁管破裂是管壁内侧水垢阻碍热传导所致。水垢则是锅炉运行过程中注入未经软化水造成的。     

Failure Analysis of Carbon Steel Tubes in a Reformed Gas Boiler Feed Water Preheater

Journal of Failure Analysis and Prevention - This study involves the failure analysis of carbon steel tubes in a reformed gas boiler feed water preheater unit operating at an ammonia plant. It was...     

锅炉过热器管爆裂原因分析

针对某热电厂4号锅炉12CrlMoV钢过热器管的爆裂破坏,进行了宏观形貌、化学成分、金相组织、扫描电镜等的分析。结果表明,炉管爆裂的原因是炉内局部温度过高,该处炉管长期过热,管壁组织珠光体球化达到5级．晶界出现蠕变裂纹,导致炉管强度降低所致。     

Investigations on the Failure of Economizer Tubes in a High-Pressure Boiler

This article describes the results of an investigation concerning the failure of economizer tubes of a high-pressure boiler in a dual-purpose power/water cogeneration plant. The failure was observed in the form of rupturing of one tube and a macrohole or pinhole in another tube. The boiler had an operating period of 116,123 h since its inception. For approximately the first 100,000 h, the fuel for the boiler was crude oil, which was replaced by Bunker C oil. The boiler tube is fabricated from carbon steel SA 210A1. The location of the failure was determined by on-site visual inspection of the boiler. Detailed macro- and microexaminations of inner and outer scales on the tube were begun to determine the cause of the rupture. The composition of the fire- and waterside scale and ash deposited on the outer surface of the tubes was analyzed by energy-dispersive x-ray (EDX) technique. The reduction percentage of wall thickness of the tube facing inside and outside the furnace was calculated. The cause of the failure of the economizer tube appears to be H₂SO₄ dew-point corrosion. The relatively low temperature of feedwater lowered the tube metal temperature and promoted the condensation of H₂SO₄. The external deposits on the tubes, as a result of bunker oil firing, further helped to lower the tube metal temperature, thus promoting H₂SO₄ condensation over the deposit and subsequent corrosion of the tube wall. Recommendations are given to prevent/minimize such failures.     

Evaluation of a Failed Water Wall Boiler Tube

A metallurgical evaluation was performed to investigate a crack in a lateral water wall boiler tube. The 2.5-in. diameter, carbon-steel tube was removed from a 125 MW coal-fired boiler used for base load electric power generation. Visual examination, microstructure characterization, and SEM/EDS analysis were used to determine that hydrogen damage was the primary failure mechanism.     

Stress Assisted Corrosion of Waterwall Tubes in Recovery Boiler Tubes: Failure Analysis

Waterside cracking of carbon-steel boiler tubes is one of the major safety and efficiency concerns in kraft recovery boilers in the pulp and paper industry, because any water leak into the furnace could cause a smelt-water explosion in the boiler. Failed carbon-steel boiler tubes from different kraft recovery boilers were examined to understand the role of carbon-steel microstructure on crack initiation and crack morphology. A number of carbon-steel tubes showed a deep decarburized layer on the inner surface (water-touched) and also an unusually large grain size at the inner tube surface. In some boiler tubes, cracks were found to initiate in areas with large-grained-decarburized microstructure. However, tubes without such microstructure were also found to have stress assisted corrosion (SAC) cracks. It was found that the decarburization and large grained microstructure may facilitate initiation and growth, but it is not necessary for SAC of carbon-steel boiler tubes.     

锅炉顶棚过热器管开裂原因分析

对某热电厂3号锅炉的无损探伤检查,发现该炉部分顶棚过热器管的背火面上存在裂纹。通过对过热器管的裂纹形貌、化学成分、金相组织和断口等的分析,确认3号锅炉顶棚过热器管的开裂失效性质属于热疲劳破坏。     

某自备电厂锅炉水冷壁管穿孔原因

某工业园区自备电厂锅炉水冷壁管在运行期间多次发生穿孔事故,通过内壁垢样分析和金相检验等方法,结合现场工况,对水冷壁管的穿孔原因进行了分析.结果表明:锅炉内水的电导率和SiO 2含量偏高,且现场缺少在线仪表监测,造成内壁结垢,继而引发了垢下局部碱腐蚀,造成管壁减薄至无法承受工作应力而穿孔爆裂.     

Fatigue Failure of 321 Stainless Steel Superheater Tubes from a Thermal Incinerator

Several boiler superheater tubes showed circumferential cracking at weld seams after 2 years in noncontinuous service (several shutdowns). On-site inspection revealed that several tubes were cracked and leaked; while many others were cracked, however, the severity was less pronounced. Two types of superheater tubes samples were collected: one with butt-welded tubes and the other with fillet-welded sleeve. The latter was found to be out of the boiler fireplace, and the sleeve was used as tubing support to the boiler shell. Detailed investigation showed that the butt-welded tubes contained circumferential fatigue cracks that initiated from the internal surface. The cracks initiated in the heat-affected zone and propagated as a result of tube vibration. The variations in the tube internal diameter and tube wall thickness are expected to play a role in tube fatigue failure. On the other hand, tubes with fillet-weld sleeve showed circumferential cracking as a result of fatigue crack initiation from weld defects on the tube external surface. The high vibration during several unscheduled shutdowns in addition to several other factors such as variations in tube inside diameter, wall thickness, and weld defects resulted in the initiation and propagation of fatigue cracks and premature failure. White deposits, similar to those observed when boiler tubes failed by caustic exposure, were seen in the vicinity of the tube cracks. Therefore, it was difficult to confirm whether the boiler tubes failed because of the fatigue cracks or because of the caustic salts (pH control chemical).     

电站锅炉末级再热器管泄漏失效分析

采用化学元素分析、力学性能试验、金相分析及断口扫描电镜观察等方法对某电站锅炉末级再热器管泄漏失效的原因进行了分析.结果表明,焊接质量不良,存在未熔合焊接缺陷,在退刀槽应力集中处萌生裂纹,进而扩展,是导致泄漏的原因.     

Failure Analysis of T12 Boiler Re-Heater Tubes During Short-Term Service

The failure of T12 re-heater tubes that had been in service only for 3000 h was investigated. The wall thickness of the tubes was visibly reduced by heavy oxidation corrosion on the outer and inner walls. The original pearlite substrate completely decomposed. Uniform oxide scale appearance on the inner wall shows obvious vapor oxidation corrosion characteristics. Corrosion originated in the grain boundary, and selective oxidation occurred due to ion diffusion in the substrate. The layered oxide scale formed on the inner wall is related to the different diffusion rates for different cations. Exposure to high temperature corrosive flux accelerated the corrosion on the outer wall. The microstructure degradation and corrosion characteristics of the tubes indicate that the tubes failed primarily because of overheating, as evidenced by calculations.     

Caustic Corrosion Failure of Back Wall Riser Tube in a High-Pressure Boiler

This article describes the results of an investigation concerning the failure of the back wall riser tube of a high pressure boiler in a SWCC dual purpose power/water cogeneration plant. The failure occurred in one tube (facing furnace) which contained eight ruptured openings covering a length of approximately 1.8 m. The tube material was carbon steel (SA 210A1). The cause of the failure was determined by on-site visual inspection of the boiler and detailed macro and micro examinations of inner and outer scales on the tube. The in situ non-destructive testing of selected boiler riser tubes was carried out using boroscope and ultrasonic test (UT). The composition of the tube material and fire and water-side scale deposits were analyzed by energy dispersive x-ray (EDX) and inductively coupled plasma (ICP) techniques. The cause of the failure of the riser boiler tube appears to be caustic attack. The inside brown scale that developed during service resulted in overheating, wall thinning due to caustic corrosion, and the associated ruptures of the tube in areas of high stress. The escaping steam eroded the outer surface of the tube resulting in heavy loss of metal around the rupture points (punch). Recommendations are given to prevent/minimize such failures.     

Investigation of Premature Failure of a Coal-Fired Boiler Superheater Tube

Journal of Failure Analysis and Prevention - A metallurgical investigation has been carried out to ascertain the cause of premature failure of boiler superheater tube. The tube material was...     

An Investigation on the Causes of Failure in A210 Carbon Steel Boiler Tubes in an Oil Refinery

As boilers are subjected to corrosive streams and harsh operating conditions, their tubes are susceptible to corrosion and failure by different damage mechanisms. In the current study, the causes of cracking and failure of connection tubes of a boiler header are studied. These tubes were connected between the primary and secondary headers of the boiler and according to the design information were constructed of ASTM A210-A1 carbon steel. There were two cracked tubes wherein one of them had a crack in a weld HAZ region and another had a crack in the base material. To investigate the failure, different microscopical and analytical techniques such as SEM and mechanical tests were used. The results of analysis showed that the material of construction was in accordance with the design specification. Considering the cracks dagger-shaped appearance, it was concluded that thermal fatigue due to the operation conditions and utilization of water spray cooling technique was the main cause of the failure.     

Investigation into the Probable Cause of Failure of Economizer Tube of a Thermal Power Plant

In this investigation, we examined the probable cause of failure of a welded joint of a economizer tube of a 210 MW thermal power plant. X-ray radiography and chemical analysis along with detailed optical and scanning electron microscopic (SEM) examination of the economizer tube were carried out. It was concluded that severe blowholes, pipings, and porosity along with brittle fracture were responsible for the failure.     

Failure Analysis and Fatigue Investigation on Titanium Tubes in a Condenser

This paper presents an analysis of condenser titanium tube leakage in nuclear power plants. Chemical compositions, mechanical properties, metallographic structures, and microscopic morphologies were analyzed. The results show that the titanium tube leakage was mainly caused by fatigue failure on the basis of the fatigue fracture features. Fatigue tests had been carried out in both air and steam environments, and the fatigue resistance of titanium tubes decreased distinctly in a steam environment. Based on the investigations, proper recommendations have been proposed to enhance the prevention of fatigue fracture of titanium tubes in condensers.     

锅炉水冷壁管开裂分析

通过宏观检验、尺寸测量、金相检验和断口分析等方法,对锅炉吹灰器附近水冷壁管开裂的原因进行了分析。结果表明:吹灰器附近水冷壁管与密封板之间的温度偏差及与正常部位水冷壁管之间的温度偏差导致密封板割缝根部产生了较高的峰值热应力,此应力随着锅炉的启停和吹灰过程而循环交替,再加上吹灰器附件水冷壁管弯折处割缝根部本身就存在应力集中,使得吹灰器附件水冷壁管弯折处密封板割缝根部发生了低周疲劳开裂。     

680t／h电站锅炉高温过热器爆管原因分析及预防措施

某台680t／h电站锅炉高温过热器最近发生两起爆管事故，通过对爆管样管进行宏观检验、化学成分分析和金相检验判断爆管的根本原因。结果表明：由于长时间超温运行导致管子早期蠕变引起爆管，并采取了有效的预防措施。