Quantification of multilayer and multiwall layer gaps
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Large size and high pressure and temperature requirement for the pressure vessel in the process industry requires high thickness of the shell. These high thicknesses lead to manufacturing problems during rolling, handling, forming etc. To overcome this problem, different construction techniques have been developed like Multilayer & Multiwall. Multiwall construction is a shrink fit technology where we thermally expanding the layers to fit over the other layer. In Multilayer technique, sector of shell layers are mounted over inner shell and welded till the required thickness is achieved. Layer gap in both the techniques is a common manufacturing limitation. In this research, we used three layers for both Multiwall and Multilayer cases. A Parametric model was developed using Matlab to vary the gap size and the configuration was analyzed using finite element method to understand the effect of layer gap size. High tangential localized stress zones were observed at the start and end of gap. Stress distributions were plotted along the thickness. Stresses were calculated on the inner layer with gap. Gradual decrease in the localized tangential stresses was plotted by varying the gap arc length. The system was analyzed by increasing the gap height and variation of tangential stresses was plotted along the thickness. The motive is to understand how individually layers behave after the expansion of the layers with gap under pressure. If the size of these gaps is large, it may lead to a situation when layers (one or more) may bear the load separately and hence may lead to failure of the equipment.