The tightness behaviour of pressurised joints with and without seals

本研究计划涉及需要密封的加压接头。加压接头可分为两类：一类是有密封元件的，如螺栓法兰连接和填料箱填料；另一类是没有密封元件的，如膨胀接头。受压接头失效的主要原因是渗漏。世界范围内的调查显示，大量的逸散排放物和污染物是由这些接头产生的。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问题参数。装配程序、制造过程、设计程序和操作条件等等。尽管已经为减少逸散性排放做出了巨大的努力，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，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。拟议的持续研究项目将重点放在模拟加压接头行为和开发分析模型上，以提高其性能和开发准确的设计程序。同时，使用新开发的测试平台将允许对开发的模型进行有价值的实验验证。特别重要的是测量机械强度，泄漏，接触应力，蠕变松弛和弯曲的螺旋缠绕垫片。我们的目标是将获得的知识扩展到管与管板连接的残余应力研究中，这是我们静态和动态密封实验室最近启动的一项新的研究活动。虽然概念不同，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，特别是在不进行焊接或在焊接失败时需要第二个可靠的泄漏屏障时。最后，工作的一个重要部分将致力于对所开发的分析和数值有限元模型进行实验验证。

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.