The tightness behaviour of pressurised joints with and without seals

本研究提案涉及需要密封的加压接头。压力接头可分为两种类型：具有密封元件的接头，如螺栓法兰连接和填料函填料，以及不具有密封元件的接头，如膨胀接头。众所周知，压力接头失效的主要原因是泄漏。世界范围内的调查表明，大量的散逸性排放和污染物是从这些接缝中产生的。密封元件，如垫圈，压缩填料和机械密封及其安装的结构组件并不是唯一的参数。组装程序、制造过程、设计程序和操作条件仅举几例。尽管为减少散逸性排放作出了巨大努力，但防止泄漏仍然是最具挑战性的任务之一。通过以前的资助，已经对加压接头的一般行为及其泄漏控制参数有了基本的了解。拟议的继续研究项目的重点是模拟承压接头行为和开发分析模型，以提高其性能和开发准确的设计程序。与此同时，使用新开发的测试台将允许开发的模型进行有价值的实验验证。特别重要的是测量螺旋缠绕垫片的机械强度、泄漏、接触应力、蠕变松弛和屈曲。我们的目标是将所获得的知识扩展到管与管接头的残余应力研究中，这是我们的静态和动态密封实验室最近推出的一项新的研究活动。尽管概念不同，但膨胀接头需要紧密，以避免热交换器和蒸汽发生器中的流体混合，特别是当不进行焊接或在焊接失效的情况下需要第二个可靠的泄漏屏障时。最后，工作的一个重要组成部分将致力于开发的分析和数值有限元模型的实验验证。

This research proposal deals with pressurised joints that require to seal. Pressurised joints can be categorized into two types: those that have a sealing element such as bolted flange connections and stuffing box packings and those that do not have a sealing element such as expanded joints. It is well established that the major cause of failure of pressurised joints is leakage. Worldwide surveys show that an important amount of fugitive emissions and contamination are produced from these joints. The sealing elements such as gaskets, compression packings and mechanical seals together with their structural assembly in which they are mounted are not the only parameters to blame. Assembly procedures, fabrication processes, design procedures and operating conditions are just to name a few. Even though a substantial effort has been put towards reducing fugitive emissions, preventing leakage remains one of the most challenging tasks. A fundamental understanding of the general behaviour of pressurised joints and their leakage controlling parameters has been gained through previous funding. The proposed continuing research project put emphasis towards simulating pressurized joint behaviour and developing analytical models for the purpose of improving their performance and developing accurate design procedures. In parallel, the use of newly developed test rigs will allow a valuable experimental validation of the developed models. Of particular importance are measurements of mechanical strength, leakage, contact stresses, creep-relaxation and buckling of spiral wound gaskets. It is our goal to extend the gained knowledge to the study of the residual stresses in tube-to-tubesheet joints, a new research activity that has recently been launched in our Static and Dynamic Sealing Laboratory. Although different in concept, expanded joints need to be tight to avoid mixture of fluids in heat exchangers and steam generators and in particular when welding is not performed or a second reliable leakage barrier is required in case of weld failure. Finally an important part of the work will be devoted towards experimental validation of the developed analytical and numerical FEM models.