高温螺栓法兰垫片系统密封性能衰减机理及控制方法研究

The bolted flange systems are widely used in the modern process industry, and most of them are at high temperature. With the development of the society, the focus, which people care, is not only limited to the safety problem caused by the leak at the location of the bolted flange joint at high temperature, but also extended to the air pollution problem caused by the dissipation of the volatile organic compounds at the location of the bolted flange joint at high temperature. So, improving the sealing performance of bolted flange system at high temperature becomes an imperative thing. But the sealing performance of the bolted flange system will be attenuated with service time at high temperature. This project aims to study the attenuation mechanism of sealing performance and control method of bolted flange system at high temperature. Combined with theoretical analysis, numerical simulation and experimental study, the leakage mechanism of bolted flange system based on the micro-flow model at high temperature will be researched and the relation of gasket factors and leakage rate will be established to form the design rule related to leakage rate of bolted flange system at high temperature. The deformation compatibility equations and the leakage rate model related to creep time of bolted flange system at high temperature will be built up to prove the attenuation mechanism of sealing performance of bolted flange system at high temperature. The relation of the elastic interaction and leakage rate of bolted flange system at high temperature will be studied to form the attenuation control method of bolted flange system at high temperature.

在现代流程工业中，螺栓法兰连接应用十分广泛，且有相当大比例处于高温下运行。随着社会的发展，人们关注的焦点不仅仅局限于高温螺栓法兰接头处泄漏造成的安全问题，更延伸到高温螺栓法兰接头处挥发性有机物逸散造成的大气污染问题。因此，提高高温螺栓法兰垫片系统的密封性能迫在眉睫。然而，在高温下，密封性能随服役时间不断衰减。本项目旨在对高温螺栓法兰垫片系统密封性能衰减机理及控制方法进行研究。拟采用理论分析、数值模拟和试验研究等手段，以高温螺栓法兰垫片系统为对象，开展高温螺栓法兰垫片系统基于微流动的泄漏机理研究，建立垫片系数与泄漏率的关系，形成与泄漏率相关的高温螺栓法兰垫片系统结构设计方法；建立螺栓法兰垫片系统的变形协调方程以及与时间相关的泄漏率模型，探明高温螺栓法兰垫片系统密封性能衰减机理；建立高温螺栓法兰垫片系统的弹性交互作用与泄漏率的关系，形成高温螺栓法兰垫片系统密封性能衰减控制方法。

针对高温环境下长周期服役的螺栓法兰接头的密封性能衰减问题，本项目开展了高温螺栓法兰垫片系统密封性能衰减机理及控制方法研究。首先，分析了高温螺栓法兰垫片系统基于微流动的泄漏机理，基于与泄漏率相关的垫片系数，在PVRC与紧密度相关的设计方法的基础上，引进蠕变松弛系数，形成了与泄漏率相关的高温螺栓法兰垫片系统结构设计方法；其次，通过考虑螺栓、法兰和垫片各部件的蠕变因素，建立了高温螺栓法兰垫片系统的变形协调方程，进而建立了高温螺栓法兰垫片系统与时间相关的泄漏率模型，分析了不同内压和不同紧密度等级下的垫片应力和泄漏率的变化规律，探明了高温螺栓法兰垫片系统密封性能衰减机理；最后，分析了螺栓法兰垫片系统在预紧过程中的弹性交互作用，讨论了在高温长时服役过程中的螺栓载荷和泄漏率变化规律，提出了高温螺栓法兰垫片系统的螺栓再紧固时机确定方法和再紧固方法，形成了高温螺栓法兰垫片系统密封性能衰减控制方法。本项目研究成果为保证高温螺栓法兰垫片系统在长周期服役过程中的密封性能提供了理论依据，并具有较好的工程应用价值。