The tightness behaviour of pressurised joints with and without seals

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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.