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高温下工作的炉管因蠕变裂纹的扩展导致了炉管的失效.本文采用C形试样进蠕变裂纹扩展试验,并用弹性应力强度因子K,净截面应力σ_(net)以及蠕变条件下的能量积分C~*,对获得的不同温度和不同载荷下的裂纹扩展数据进行处理,结果表明:C~*能够较好地描述蠕变裂纹扩展的整个过程.把材料的蠕变性能与裂纹扩展性能联系在一起,进一步讨论了温度的影响.对炉管受力情况进行简化,把断裂力学的方法应用到炉管的残余寿命估计中去,获得了初步的结果. 相似文献
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<正> 转化炉管裂纹小型超声检测装置是大连理工大学研制的一项科技成果,包括硬件部分——高温厚壁管件内壁裂纹超声检测装置和软件部分——炉管检测技术与级别评定、寿命预测、影响因素分析等技术。该装置用于测定合成氨装置、甲醇装置的转化炉管,乙烯装置的裂解炉管和炼油装置的制氢炉管的使用寿命。检测的材质为HK和HP。被测炉管的范围为直径100—152mm,壁厚10—25mm。辽河化肥厂用该装置测定一段转化炉,预先割除应更 相似文献
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作者根据剖析已服役43000小时HK—40炉管所获的资料,本文讨论了炉管的宏观组织及炉管不同高度和焊接接头各部位的显微组织、裂纹形态及分布状况,并分析了它们同炉管材质、工作温度、内外壁温差、应力状况的关系。对炉管的σ相问题及用持久强度、蠕变孔洞来推断炉管残余寿命等问题进行了探讨。认为用高温断裂力学的方法来研究服役条件下裂缝的扩展速率及找出其破裂的临界状况,是估算残余寿命的较好方法。所剖析的炉管取自以天热气为原料的30万吨含成氨装置的一段转化炉,管子中装有触煤,通过反应CH_4 H_2O→3H_2 CO—Q来制取氢。美国凯洛格型一段炉中,每42根φ113×20.90mm、长近10米的HK—40炉管为一排,下端焊在同一根800合金集气管上,形成竖琴管排。一共九排,合计炉管378根。通常,每根炉管都是由3~5节素管对接焊而成,上部伸出炉项外的是碳钼耐热钢,因而有一个异种钢焊接接头。原料气由每根炉管上部输入。根据设计条件,入口气温度510℃,出口气为823℃,管壁平均温度899℃,内压30~35kgf/mm~2,入口气水碳化(H_2O:C)为3.5:1.0左右。原料中≯0.5ppm。设计寿命10~5小时。然而由于工况的恶劣和复杂。世界各国的炉子一般都达不到设计寿命。 相似文献
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本文采用C形试样进行蠕变疲劳裂纹扩展试验,探讨开停车对炉管的影响.试验表明:在蠕变疲劳交互作用下与纯蠕变相比,其断裂时间明显降低,裂纹扩展速率增加. 通过三个力学参数(K_I,σ_(ref)、C~*)分别与裂纹纹扩展速率(da/dt)在广泛范围内的关联,发现用参数C~*描述蠕变疲劳裂纹扩展的规律最适合.由此提出了一种以参数C~*控制的寿命外推方法. 另外,作者设计了一台适合于RD_2——3型试验机的蠕变-疲劳控制装置;并讨论了C形试样极限载荷P_L的计算公式. 相似文献
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刘丽丽 《中国石油和化工标准与质量》2021,(11):23-24
锅炉是石油化工生产的重要设备,预测锅炉炉管的剩余寿命,能确保锅炉的高效、稳定、安全运作,提升石油化工生产综合效益.本文在阐述锅炉炉管剩余寿命预测基本观点的基础上,就当前石油化工行业用锅炉炉管剩余生命预测问题展开分析,并构建石油化工行业用锅炉炉管剩余寿命预测模型,估算炉管剩余寿命,期望能进一步提升锅炉炉管剩余寿命的预测精... 相似文献
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裂解炉辐射炉管的设计寿命一般达10万小时,但决定其使用寿命的因素很多,实际的炉管更换周期与设计寿命可能存在较大差距。在使用过程中,很难对裂解炉炉管的剩余寿命进行准确的评估。为能准确掌握使用中裂解炉炉管的状态,采用化学成分分析和常温、高温力学性能试验等多种分析手段及Larson—Miller参数法进行使用状态评估和剩余寿命预测,从而达到合理操作处于寿命末期的辐射炉管、科学安排炉管更换时间的目的。 相似文献
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通过对BA-101乙烯裂解炉炉管进行金相、显微硬度及力学性能等试验研究,分析了该炉辐射段炉管损伤的原因,基于金相分析结果和Larson-Miller曲线评估与该炉管相同服役条件下其他炉管的剩余寿命。结果表明:BA-101乙烯裂解炉炉管运行30 660h后晶界出现蠕变孔洞,且内表面发生一定程度的渗碳,炉管渗碳部分与非渗碳部分之间膨胀系数不同,造成材料内应力增加,该应力与其他应力共同作用使炉管在停炉过程中发生较大损害。BA-101乙烯裂解炉炉管在管壁正常操作温度(1 000℃)时,剩余寿命约为17 000h。 相似文献
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针对典型的制氢装置转化炉炉管,阐述了转化炉炉管的腐蚀介质及原因,提出了高温蠕变、高温氧化、应力腐蚀、渗碳和脱碳以及氯离子腐蚀是造成转化炉炉管开裂的主要原因.控制原料气中氯离子含量,选择适宜的过渡段炉管材质以及严格控制转化炉运行参数,可使腐蚀得到控制. 相似文献
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The strength of a commericially available hot isostatically pressed silicon nitride was measured as a function of temperature. To evaluate long-term mechanical reliability of this material, the tensile creep and fatigue behavior was measured at 1150°, 1260°, and 1370°C. The stress and temperature sensitivities of the secondary (or minimum) creep strain rate were used to estimate the stress exponent and activation energy associated with the dominant creep mechanism. The fatigue characteristics were evaluated by allowing individual creep tests to continue until specimen failure. The applicability of the four-point load geometry to the study of strength and creep behavior was also determined by conducting a limited number of flexural creep tests. The tensile fatigue data revealed two distinct failure mechanisms. At 1150°C, failure was controlled by a slow crack growth mechanism. At 1260° and 1370°C, the accumulation of creep damage in the form of grain boundary cavities and cracks dominated the fatigue behavior. In this temperature regime, the fatigue life was controlled by the secondary (or minimum) creep strain rate in accordance with the Monkman–Grant relation. 相似文献
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介绍一段炉下集气管的基本情况及其焊缝破裂的宏观形象。通过金相分析,确定焊缝发生失效的原因是下集气管内壁焊缝存在未焊透缺陷及手工电弧焊中产生的液化裂纹,提出防止产生焊缝失效的建议和措施。 相似文献
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二段转化炉烘炉工艺过程 总被引:1,自引:0,他引:1
UHDE型二段转化炉由于空气分布器的局部损坏,导致二段炉锥体耐火衬里的冲蚀.通过采用国内耐火材料修复后,进行了耐火衬里的烘炉,烘炉质量的好坏直接影响到炉体的寿命.通过进一步实践,取得很好的效果.本文主要对二段转化炉(局部)耐火衬里的烘炉原理进行探讨,并阐述烘炉工艺过程. 相似文献
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David S. Wilkinson Carlos H. Cáceres A. Gordon Robertson 《Journal of the American Ceramic Society》1991,74(5):922-933
The mechanisms responsible for creep damage accumulation and fracture have been examined in two commercial hot-pressed aluminas. Differences between the two materials can be ascribed to minor compositional variations. Three damage regimes have been identified, depending on stress. However, in all three regimes, failure is controlled by crack propagation. At high stress, a single crack, nucleated at a processing flaw, controls failure. These cracks grow in a linear elastic stress field. At intermediate stresses, crack tip stresses relax, and many microcracks are nucleated. They grow and link under strain control. The details of this process differ under tension and bending, thus invalidating the flexure test as a means of establishing creep life, even in simple, single-phase materials. At the lowest stress, extensive cavitation, with relatively little microcrack development, is observed. However, failure continues to be dominated by the growth of cracks. The material is damage tolerant and can be thought of as superplastic. We find that processing flaws (primarily large grains) control the creep life at all stresses. These should therefore be carefully controlled in materials aimed at high-temperature structural applications. 相似文献
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乌石化化肥厂第二套合成氨装置的二段转化炉拱顶自投运以来,拱顶砖经多次检修,仍出现裂纹和破碎现象,使用寿命过短。针对该问题论证改进二段转化炉拱顶结构的可行性,提出改变拱角和增加耐火砖强度的方案。 相似文献
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An interesting phenomena of crack restoration and increasing strength of concrete under biaxial compression creep were described in this paper. A small loading apparatus was prepared and a long work distance optical microscope with variable focus was used for studying the cracks. It was found from the micrographs that these cracks diminished under biaxial compression creep. There were increases in the strength of the creep specimens under the sustained biaxial compression load compared with the free companion ones. Multiaxial compression caused by the early temperature rise inside the mass concrete may strengthen the concrete and reduce the tensile cracks during and after temperature drop. 相似文献