金属与金属接触式法兰接头在高温重整装置中的密封性能研究

发布时间：2018-07-28 12:25

【摘要】：螺栓法兰接头在化工、炼油以及电力等行业的生产装置中应用广泛。螺栓法兰接头的泄漏会造成环境污染及火灾等事故。对高温法兰接头进行保温可以节约大量能源,但保温使本就容易发生泄漏的高温法兰接头的温度进一步升高,更加剧了法兰接头的泄漏风险。如果能够兼顾节约能源、保护环境和保障安全,对高温法兰接头做保温处理将是十分有意义的。基于这一思想,对石化企业中芳烃重整装置的高温法兰接头进行了研究,以便在保证密封安全可靠性的前提下对其进行保温节能改造。为了应对高温下法兰接头发生的松弛,采用金属与金属接触式柔性石墨密封垫来替换浮动式金属缠绕垫。相比于浮动式垫片仅密封环承担螺栓载荷,金属与金属接触式垫片的密封环及外金属环均承担螺栓载荷,其中外金属环承担的螺栓载荷用于补偿法兰接头的松弛效应,因而保证了垫片密封环载荷的稳定以及法兰接头的密封可靠性。然而,针对金属与金属接触式法兰接头的研究相对较少,也没有相应成熟的法兰设计方法及螺栓装配拧紧方法。因此,需要从装配、受载及蠕变工况对金属与金属接触式法兰接头的密封可靠性进行较为全面的研究。1)分析了法兰接头温度分布的规律,为后续进行一步的热-结构耦合分析做准备。此外还分析了高温法兰接头的保温节能效益。分析结果表明法兰接头在保温后的节能效率可达94.64%,仅对12对高温大法兰进行保温改造即可节约资金85.93万元／年。2)建立了针对金属与金属接触式法兰接头密封的解析计算方法,并实现了基于泄漏率准则的法兰接头的密封性能评价。建立的解析计算方法相对简单易用且考虑载荷工况较为全面,适用于预紧、外载荷、内压、热载荷和这些载荷的组合工况,以及热紧工况。3)通过解析法及有限元法研究了金属与金属接触式法兰接头在预紧及高温工况下的行为。通过分析发现,法兰偏转角及垫片外金属环的轴向热膨胀是影响垫片载荷即法兰接头密封性能的主要因素。金属与金属接触存在时,垫片密封环的载荷会随着法兰偏转角或垫片外金属环的轴向热膨胀的增大而减小。4)对金属与金属接触式法兰接头的蠕变松弛进行了分析。高温下法兰接头的长期蠕变是影响金属与金属接触式法兰接头密封可靠性的另一关键因素,蠕变松弛会使金属与金属接触发生脱离,进而威胁法兰接头的密封可靠性。5)提出了针对金属与金属接触式法兰接头的“金属与金属接触修正”的思想来提高螺栓装配效率并保证装配效果。金属与金属接触式垫片在金属与金属接触形成前后分别对应“软垫片”状态和“硬垫片”状态,在螺栓装配过程中可以设定较大的螺栓初始预紧力使垫片由前一状态快速过渡到后一状态,硬垫片的性质会使螺栓预紧力在后续的拧紧过程中快速分布均匀并且趋近于目标值。根据这一思想设计并推荐了适用且装配效率较高的螺栓拧紧方法以供实际工程安装参考。本文的研究成果在芳烃重整装置中进行了工业化应用,并经受住了长达近2年时间连续运行的考验,证明了法兰接头保温改造工作的可靠性。
[Abstract]:Bolt flange joint is widely used in the production equipment of chemical industry, oil refining and electric power industry. The leakage of bolt flange joint will cause environmental pollution and fire accidents. The heat preservation of high temperature flange joint can save a lot of energy, but heat insulation makes the temperature of high temperature flange joint which is easy to leak and will be further increased. If it can save energy, protect the environment and protect the safety of the flange joint, it is of great significance to heat the flange joint of the high temperature flange. Based on this idea, the high temperature flange joint of the aromatics reforming unit in the petrochemical enterprise is studied in order to ensure the safety and reliability of the seal. In order to cope with the heat preservation and energy saving transformation, in order to cope with the relaxation of the flange joint at high temperature, the metal and metal contact flexible graphite seal pads are used to replace the floating metal winding pads. The bolt load of the metal ring is used to compensate the relaxation effect of the flange joint, thus ensuring the stability of the load of the gasket seal ring and the reliability of the flange joint sealing. However, the research on the contact flange joint of metal and metal is relatively less, and there is no corresponding design method of flanges and bolt assembly tightening methods. Therefore, a more comprehensive study of the sealing reliability of the metal and metal contact flange joints is needed from the assembly, loading and creep conditions. The law of the temperature distribution of the flange joint is analyzed, and the thermal structure coupling analysis of the joint is prepared for a further step. In addition, the heat preservation and energy saving benefits of the high temperature flange joint are also analyzed. The analysis of the heat preservation and energy saving benefits of the high temperature flange joint is also analyzed. The results show that the energy saving efficiency of the flange joint after heat preservation can reach 94.64%. Only 12 to the high temperature and large flange can save 859 thousand and 300 yuan / year.2). The analytical calculation method for the sealing of metal and metal contact flange joint is established, and the sealing performance evaluation of flange joint based on the leakage rate criterion is established. The analytical calculation method is relatively simple and easy to use and is more comprehensive in consideration of load conditions. It is suitable for preloading, external load, internal pressure, thermal load and the combined working condition of these loads, and the thermal tight working condition.3). The behavior of metal and metal contact flange joints under pre tightening and high temperature conditions is studied by analytical method and finite element method. The flange deflection angle and the axial thermal expansion of the outer metal ring of the gasket are the main factors affecting the gasket load, that is, the sealing performance of the flange joint. When the metal is in contact with the metal, the load of the gasket seal ring decreases with the increase of the flange deflection angle or the axial thermal expansion of the outer metal ring of the gasket to reduce.4) to the contact flange joint of metal and metal. The creep relaxation is analyzed. The long-term creep of the flange joint at high temperature is another key factor affecting the sealing reliability of the metal and metal contact flange joints. The creep relaxation will break the metal contact with the metal, and then threaten the sealing reliability of the flange joint.5). "Metal and metal contact correction" idea to improve the bolt assembly efficiency and ensure assembly effect. Metal and metal contact gasket corresponds to the "cushioned sheet" state and "hard gasket" state before and after the metal and metal contact formation. In the bolt assembly process, a larger initial bolt pretightening force can be set to make the gasket from the first one. The property of the hard gasket will make the bolt pretightening force evenly distributed evenly and close to the target value in the subsequent tightening process. According to this idea, a suitable and highly assembled bolt tightening method is recommended for practical engineering installation reference. The research results of this paper are in aromatics heavy loading. It has been industrialized and has been tested for nearly 2 years and proved the reliability of the flange joint heat preservation transformation.
【学位授予单位】：华东理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TE96

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