静密封过程中垫片的密封机理及失效分析

发布时间：2018-11-03 11:51

【摘要】：垫片密封是由螺栓、法兰和垫片组成的一种密封结构,它是石油化工设备和管道中最常用的连接形式,其中垫片是最主要的密封元件,它的性能直接影响连接系统密封的可靠性,所以,本文研究各种载荷下垫片的应力大小及分布趋势,这对垫片的使用以及对泄漏的防治具有重要的意义。首先,介绍了垫片的一般结构和种类；分析了垫片应满足的基本性能和评定垫片密封性能几个指标；对螺栓法兰连接系统进行了形状简化和受力分析,得出螺栓力和垫片反力的计算公式；应用Timosenko理论,对系统载荷与变形之间的关系进行深入分析,得出各元件间的变形协调方程,与Waters理论相比,更能真实地反映其受载情况。其次,分析了垫片的密封机理及其在加载和卸载时的密封过程,给出了垫片预紧应力的计算公式和影响因素；并用紧密性参数来衡量密封的紧密度,对紧密性等级进行了划分；研究了垫片密封失效的原因,得出了影响垫片密封失效的因素,并建立了反映垫片密封失效的模型。最后,本文选取ASMEB16.5的NPS4 Class150标准法兰为模型,用有限元参数化设计语言(APDL)建立了参数化三维有限元模型,去模拟垫片材料的非线性特性。首先研究了系统在预紧和逐渐施加内压载荷的作用下对垫片应力的影响,研究表明,此时垫片的应力分布规律基本一致,且随着内压载荷的升高,同一部位的应力强度数值相应增大,此时在法兰锥颈处出现了最大的应力强度,这与实际的情况是一致的。其次研究表明,螺栓预紧力的大小对垫片应力的大小及分布有重要影响,垫片应力随螺栓预紧力的增加而相应增大。最后研究表明,无论预紧工况还是操作工况,随着内压载荷的升高,垫片应力沿周向及径向都是不均匀分布的,垫片径向应力随预紧力的增大而增大,随内压的升高而升高,垫片外侧应力较内侧应力大,其应力的具体分布情况受各个元件的性质和具体的工况条件所影响。
[Abstract]:Gasket sealing is a sealing structure consisting of bolts, flanges and gaskets. It is the most commonly used form of connection in petrochemical equipment and pipelines, in which gaskets are the most important sealing components. Its performance directly affects the sealing reliability of the connection system. Therefore, this paper studies the stress size and distribution trend of gasket under various loads, which is of great significance to the use of gasket and the prevention of leakage. Firstly, the general structure and types of gasket are introduced, the basic performance of gasket and several indexes of evaluating gasket seal performance are analyzed. The form simplification and force analysis of bolt flange connection system are carried out, and the calculation formulas of bolt force and gasket reaction force are obtained. Based on Timosenko theory, the relationship between system load and deformation is analyzed in depth, and the deformation coordination equation among the components is obtained. Compared with Waters theory, the relationship between the system load and deformation is more truly reflected. Secondly, the sealing mechanism of gasket and its sealing process during loading and unloading are analyzed, the calculation formula and influencing factors of pretightening stress of gasket are given, the tightness degree of gasket is measured by compactness parameter, and the tightness grade is divided. The causes of gasket seal failure are studied, the factors influencing the gasket seal failure are obtained, and a model reflecting the gasket seal failure is established. Finally, the NPS4 Class150 standard flange of ASMEB16.5 is selected as the model, and the parameterized three-dimensional finite element model is established by using the finite element parameterized design language (APDL) to simulate the nonlinear characteristics of gasket material. Firstly, the influence of the system on the gasket stress under the action of pretightening and gradually applying internal pressure load is studied. The results show that the stress distribution law of the gasket is basically the same at this time, and with the increasing of the internal pressure load, the stress distribution of the gasket is basically the same. The stress intensity of the same position increases correspondingly, and the maximum stress intensity appears at the flange cone neck, which is consistent with the actual situation. Secondly, it is shown that the pre-tightening force of bolt has an important effect on the size and distribution of the gasket stress, and the gasket stress increases correspondingly with the increase of bolt pre-tightening force. The results show that the gasket stress distributes inhomogeneously along the circumference and radial direction with the increase of the internal pressure load, the radial stress of the gasket increases with the increase of the pretightening force, and increases with the increase of the internal pressure. The outer stress of gasket is larger than the inner stress, and the distribution of the stress is affected by the properties of each element and the working conditions.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：TH136

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