1 Proceedings of the ICTWS 2014 7 th International Conference on Thin-Walled Structures ICTWS2014 28 September – 2 October 2014, Busan, Korea ICTWS2014-0101 CONSIDERATIONS ON THE DESIGN OF HYPERBARIC CHAMBERS Crisan Andrei, Dubina Dan Steel Structures and Structural Mechanics department, POLITEHNICA University Timisoara, Timisoara, Romania Maurizio Pucci, Marco Bellomo Drass Group of Companies, Livorno, Italy ABSTRACT Present paper presents specific aspects of the design, operation, evaluation and maintenance of hyperbaric pressure vessels designed to operate with an internal pressure of over 30 bars. Considerations regarding the effects of cuttings for manholes, stress concentration and fatigue assessment, in the design stage, the heat affected zones, residual stress due to welding, alignment and/or planeity of manholes during the construction stage and the evaluation of fatigue induced by cyclic loading and required tests during the operation of such structures are also presented. Moreover, the final part of the paper underlines a series of proposed methods that could be used to better quantify and evaluate the life span of such structures without the need of costly and time consuming in-field tests. In addition, the proposed methods are desired to reduce the number of incursions in the plastic range in high stress concentration areas. 1. INTRODUCTION Pressure vessels (PVs) are defined as closed containers, designed to hold gases or liquids at a pressure substantially different from the ambient pressure. The difference in pressure can be dangerous and throughout the history, many fatal accidents have occurred in operation and/or manufacturing process. Their design, manufacture, and operation are regulated by engineering authorities backed up by laws. PVs are used in a variety of applications in medical, industrial, military, and the private sector. They occur in these sectors as industrial compressed air receivers and domestic hot water storage tanks. Other examples of pressure vessels are diving cylinders, recompression chambers, distillation towers, autoclaves, and many other vessels in mining or oil refineries, petrochemical plants, nuclear reactor vessels, habitats of a space ships, habitats of a submarines, pneumatic reservoirs, hydraulic reservoirs under pressure, rail vehicle airbrake reservoirs, road vehicle airbrake reservoirs and storage vessels for liquefied gases such as ammonia, chlorine, propane, butane, and liquefied petroleum gas (LPG). PVs can theoretically take any shape, but spheres, cylinders, and cones are usually employed due to ease of design and manufacture. A common shape for design is a cylinder with end caps called heads. Head shapes are frequently either hemispherical or dished (torispherical). Generally, a pressure vessel is considered to be thin-walled if its radius is larger than 5 times its wall thickness. Given this condition, the stress in the wall may be considered uniform. Thin wall pressure vessels are in fairly common use. Pressure vessels keep their shape despite the inside gas pressure, due to tensile forces within the walls of the container. The normal (tensile) stress in the walls of the container is proportional to the pressure and radius of the vessel and inversely proportional to the thickness of the walls (Ferdinand et. al. 2006). 2. GENERAL DESIGN DETAILS The term “pressure vessel” encompasses a wide range of unit heat exchangers, reactors, storage vessels, columns, separation vessels, etc. Because of the risks that would be associated with any accidental release of contents, the design,