石化极端工况下法兰连接的可靠性研究

发布时间：2018-06-10 02:08

本文选题：螺栓法兰连接 + 蠕变　；参考：《华东理工大学》2015年硕士论文

【摘要】：本文以螺栓法兰连接为对象,研究其在预紧、承压等基本工况以及高温、蠕变、骤停等极端工况下的完整性和密封性。研究突然停车再开车、降温速率以及垫片形式对法兰连接应力及密封性能的影响。利用有限元软件ANSYS对法兰连接建模并进行模拟,由于周期对称性仅建立法兰连接的1/28模型。计算过程中综合考虑了垫片压缩回弹特性、材料非线性、法兰和螺母接触等高度非线性行为。热-机械耦合结果表明温度载荷对法兰连接影响较大,应力大幅增加。考虑螺栓、法兰材料蠕变后,螺栓应力不断下降并重新分配。骤然停车再开车后法兰位移、应力、偏转角都变大,反复停开车操作将使法兰偏转更严重,泄漏趋势增大,强度也将无法满足要求。不同形式的垫片对法兰连接密封性能的影响不同,需根据具体情况决定是否需要热紧操作以防止泄漏。高温、蠕变及骤然停车再开车等极端工况对法兰的完整性和密封性影响深远,使法兰连接处于复杂应力及应力波动状态,增大垫片的泄漏趋势,应尽量避免。实际使用时应根据具体要求选择合适的降温速率及垫片类型,以减少泄漏的发生。上述研究结果对石化装置中法兰连接的选型以及开停车过程控制具有重要的工程指导意义。
[Abstract]:In this paper, the integrity and sealing of bolted flange connections under the basic conditions of preload and pressure, as well as under extreme conditions such as high temperature, creep and sudden arrest are studied. The effects of sudden stopping and restarting, cooling rate and gasket form on flange connection stress and sealing performance were studied. The finite element software ANSYS is used to model and simulate the flange connection. Because of the periodic symmetry, only the 1 / 28 model of the flange connection is established. The high nonlinear behavior of gasket compression springback, material nonlinearity, flange and nut contact are considered. The results of thermal-mechanical coupling show that the temperature load has a great influence on the flange connection, and the stress is increased greatly. Considering bolt, flange material creep, bolt stress decreases and redistribution. The flange displacement, stress and deflection angle are all increased after the sudden stop and start up. The flange deflection will become more serious after repeated stopping operation, the leakage trend will increase, and the strength will not meet the requirements. Different types of gaskets have different effects on the sealing performance of flange connections. It is necessary to determine whether hot tightening operation is required to prevent leakage according to the specific conditions. Extreme conditions such as high temperature, creep and sudden stopping and restarting have a profound influence on the integrity and sealing of flange, which makes the flange connection in complex stress and stress fluctuation state, increases the leakage tendency of gasket, and should be avoided as far as possible. In practical use, appropriate cooling rate and gasket type should be selected according to specific requirements to reduce leakage. The above results are of great significance to the selection of flange connection and the control of on-off process in petrochemical plant.
【学位授予单位】：华东理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ055.81

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