The Overall Multi-layer Bandaging Pressure Vessel Prestress Distribution And Homogenization

Pressure vessels are widely used in the fields of production techniques, which are the necessary key equipments in various industrial departments such as chemical industry, oil refining, light industry and energy sources et al. They have two types of constructions: monolayer and multilayer. Since the multilayer construction has some advantages over the monolayer one, which not only solves the difficult probem of thick wall manufacture, but also has some special excellences in material utilization and security, multilayer vessels, especially for multilayer high pressure vessels, have widely used in various fields of process industrial productions, i.e. ammonia or urea reactors in chemical industry, hydrogenation reactor in oil refining as well as multilayered stationary hydrogen storage vessels. Along with the continual development of science and technology, pressure vessels need to be worked at the rigour conditions such as high temperature, high pressure and strong erosion, therefore, the thorough investigation of multilayer vessels is of an important significance to fit various production conditions, to meet the needs of large-scale production or function on the safe side.Since A.O.Smith Company in U.S.A put forward a type of multilayer vessel construction wrapped with steel wires in 1931, the investigations on multilayer vessel constructions have been made much progress by means of people's incessant efforts and explorations, and six types of multilayer vessel constructions have been developed, which are respectively wrapping, shrinking, plate coiling, ribbon coiling, helical plate coiling and integrated multilayer wrapping. Integrated multilayer wrapping high pressure vessel has been thought highly of in the domestic and international areas because of its security and manufacturing convenience, however, the prestressed conditions in the wrapping manufacturing process aren't clear, and haven't been utilized well up to now. This paper researched the prestress distribution and uniformization of a type of integrated multilayer wrapping high pressure vessel construction. The main contents and achievements are as follows:1. Considered the frictional force between the layers in the relative displacement of the layers, the calculation formulae in the layers or the inner shell prestressed by the wrapping force of the mechanical grips or the cooling shrinkage of longitudinal welding seams of the layers were derived by the principles of mechanics according to the actual manufacturing process and the structural characteristics of the multilayer vessel. Moreover, based on material mechanics, theoretical analyses of the prestress distribution uniformization during its manufactural process were carried out by means of some technical methods such as beating with hammer or vibration with a vibration source on the surface of the layer.2. The wrapping manufactural process of a section of the multilayer vessel of inner diameter 500mm was measured by using DH3816 Static Strain Testing Analytical System in the laboratory. The experimental results proved that, (1)the calculated values prestressed by the wrapping force of the mechanical grips well tallied with the measurement ones; (2)since the prestress distributions in the layers or the inner shell caused by the wrapping force of the mechanical grips or the cooling shrinkage of longitudinal welding seams of the layer are not uniform but regular in the manufactural process of some layer, they tended to uniformity by using some technical methods such as beating with hammer or vibration with a vibration source on the surface of the layer, therefore, the requirement of the prestress distribution uniformization could be realized.The investigation results of the prestress distribution and uniformization in a type of integrated multilayer wrapping high pressure vessel construction have a certain direct significance for the actual manufacture and insuring its manufactural quality.