柱塞泵阀箱失效分析

发布时间：2018-07-14 13:23

【摘要】：压裂泵作为油气田增储上产的重要压裂设备,要求其具有性能稳定和工作可靠等特点,但压裂泵液力端阀箱破裂失效事故频发,工作寿命和利用率普遍偏低,已严重影响压裂工艺效率,成为提升压裂装备整体性能的瓶颈之一。为确定阀箱失效模式、裂纹扩展机理和查找失效原因,本论文结合了材料学、断裂力学、金相学、有限元技术和强化处理工艺等理论,对报废阀箱从实验检测到理论分析等角度出发,深入开展了阀箱的疲劳损伤机理和疲劳寿命预测研究,主要进行的研究工作如下：(1)通过广泛查阅、检索国内外文献资料,深入调研分析了现有压裂泵的性能和使用情况,全面系统地了解、掌握和研究了国内外压裂泵的技术发展动态。经过对阀箱失效模式、失效准则的研究以及综合现场失效数据分析,认为疲劳开裂是阀箱最主要和最危险的失效模式；(2)对阀箱材料进行了化学成分检验、金相观察以及硬度测试一系列理化检测试验。化学成分检验表明,阀箱材料中含有较多的耐腐蚀和耐磨损合金元素,针对阀箱易腐蚀、易磨损等恶劣服役条件,起一定的缓解作用：金相观察说明阀箱热处理工艺较合理,材料基体组织为回火索氏体和铁素体,未发现夹杂物、组织偏析、气孔等先天性缺陷；硬度测试阐明,工作介质对阀箱材料有腐蚀作用,阀箱内腔表面附近区域材料的硬度值下降明显,易形成腐蚀缺陷而诱发裂纹萌生；(3)开展了失效阀箱裂纹的断口定性分析,确定了阀箱开裂为疲劳所致。宏观形貌观察表明阀箱裂纹为非连续性生长,且直线型裂纹居多。微观形貌分析揭示,断口表面上的疲劳条纹以脆性方式扩展；(4)建立了阀箱有限元模型,引入全寿命、裂纹萌生、裂纹扩展等方法进行疲劳寿命预测,仿真结果表明：裂纹萌生预测结果与阀箱实际损伤情况吻合较好,即阀箱内腔相贯线处和阀座座孔锥面为疲劳薄弱区域,且阀箱应力集中峰值已接近疲劳极限,阀箱的高交变应力是阀箱疲劳损伤的直接原因；(5)综合探讨了自增强技术、表面强化工艺、表面加工精度以及材料选择等各种提高阀箱疲劳寿命的措施和效果,研究表明自增强和喷丸技术能有效提高阀箱疲劳寿命,建议选用强度较高且韧性良好的材料作为阀箱坯料；(6)通过阀箱材料拉伸力学性能测试、常规疲劳测试、腐蚀疲劳测试等试验,掌握了阀箱材料的基本力学性能,获得S-N曲线,以及腐蚀对疲劳寿命的影响效果。试验测试数据表明在613Mpa应力水平下,腐蚀能降低50%左右的疲劳寿命。总之,通过本论文的研究工作,确定了阀箱的失效模式、失效机理和失效原因。建立了阀箱不同疲劳寿命预测方法。从阀箱选材、结构改进和制造强化工艺方面,探讨了提高阀箱疲劳寿命的措施。为压裂泵阀箱研制提供了一些新的思路和研究方法。因此,本论文的研究工作具有一定的实际应用价值。
[Abstract]:Fracturing pump is an important fracturing equipment for increasing reservoir and production in oil and gas field. It is required to be stable in performance and reliable in work. However, the fracture failure of hydraulic end valve box of fracturing pump is frequent, and its working life and utilization ratio are generally low. It has seriously affected the efficiency of fracturing process and has become one of the bottlenecks in improving the overall performance of fracturing equipment. In order to determine the failure mode of valve box, crack growth mechanism and find out the failure reason, this paper combines the theory of material science, fracture mechanics, metallography, finite element technology and strengthening treatment technology. In this paper, the fatigue damage mechanism and fatigue life prediction of end-of-life valve box are studied from the point of view of experimental detection and theoretical analysis. The main research work is as follows: (1) through extensive reference, the domestic and foreign literature is retrieved. The performance and application of the existing fracturing pump are investigated and analyzed deeply, and the technical development of fracturing pump at home and abroad is understood, grasped and studied in a comprehensive and systematic way. Through the study of valve box failure mode, failure criterion and comprehensive field failure data analysis, it is concluded that fatigue cracking is the most important and dangerous failure mode of valve box. (2) the chemical composition of valve box material is tested. Metallographic observation and hardness test a series of physical and chemical tests. The examination of chemical composition shows that there are many corrosion resistant and wear resistant alloy elements in the valve box material, which plays a certain role in alleviating the bad service conditions such as easy corrosion and wear of the valve box. The metallographic observation shows that the heat treatment process of the valve box is more reasonable. The matrix structure of the material is tempering Soxhlet and ferrite without any inherent defects such as inclusions, tissue segregation, porosity, etc. The hardness test shows that the working medium has corrosive effect on the valve box material. The hardness of the material near the surface of the inner cavity of the valve box is obviously decreased, and the corrosion defects are easily formed and the crack initiation is induced. (3) the fracture surface of the failure valve box is analyzed qualitatively, and it is determined that the crack of the valve box is caused by fatigue. The macroscopic observation shows that the cracks in the valve box are discontinuous growth, and the linear cracks are the most. The microscopic morphology analysis revealed that the fatigue fringes on the fracture surface propagated in a brittle manner. (4) the finite element model of valve box was established to predict the fatigue life by introducing the methods of whole life, crack initiation, crack propagation, etc. The simulation results show that the prediction results of crack initiation are in good agreement with the actual damage of the valve box, that is, the intersecting line of the inner cavity of the valve box and the cone of the valve seat hole are the weak area of fatigue, and the peak value of stress concentration of the valve box is close to the fatigue limit. The high alternating stress of the valve box is the direct cause of the fatigue damage of the valve box. (5) the measures and effects to improve the fatigue life of the valve box, such as self-strengthening technology, surface machining precision and material selection, are discussed. The research shows that self-reinforcing and shot peening technology can effectively improve the fatigue life of valve box. It is suggested that the materials with high strength and good toughness should be used as the valve box blank. (6) through the testing of tensile mechanical properties of valve box material, the routine fatigue test is carried out. The basic mechanical properties of valve box material, S-N curve and the effect of corrosion on fatigue life were obtained through corrosion fatigue test and so on. The test data show that corrosion can reduce fatigue life by about 50% at 613Mpa stress level. In a word, the failure mode, failure mechanism and failure reason of valve box are determined by the research work in this paper. The prediction method of different fatigue life of valve box is established. The measures to improve the fatigue life of valve box are discussed from the aspects of valve box material selection, structure improvement and manufacturing strengthening technology. Some new ideas and research methods are provided for the development of fracturing pump valve box. Therefore, the research work of this paper has certain practical application value.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TH322

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