Distribution of Hoop Stress 



Figure A-1 . Stacked-ring concept of 



pressure vessel construction. 



PRESSURE VESSEL CONCEPTS 



Stacked-Ring Concept 



Discussion. The stacked-ring 

 concept (Figure A-1) consists of an 

 inner liner surrounded by reinforcing 

 rings. Since the rings are stacked 

 upon each other along the axis of 

 revolution of the vessel, they give 

 continuous radial support to the 

 liner. In this manner, the liner serves 

 prinnarily as a pressure seal while the 

 rings take the radial and circumfer- 

 ential stresses. It is felt that this 

 system is much preferable to one in 

 which a space is left between the 



reinforcing rings, since the latter method would necessitate a heavier liner in 

 order to withstand bending induced by the nonuniform support. Longitudinal 

 anchor bolts of nominal cross-sectional area would be used to hold the rings 

 together. This type of vessel requires tie rods of sufficient size to carry the 

 axial load. 



The stresses carried by the rings may be computed in the same way as 

 those in a monobloc forging, or other continuous shell. It is possible to reduce 

 the external radius by the shrink-fitting method, or the autofrettage procedure. 

 For example, calculations indicate that a suitable "ring" could be fabricated by 

 shrink-fitting a large ring onto a smaller ring. However, the increased fabrica- 

 tion costs probably outweigh any saving realized by reduction of size. 



This method of design has been used successfully in a small pressure 

 chamber.'* However, extensive changes in the tie-rod and end-closure design 

 must be made in order to (1) permit rapid access to the vessel's interior, and 

 (2) decrease the weight of the end closure, which because of its flat design 

 would result in such a thick forging for the 10-foot-diameter vessel that it 

 could not be manufactured. 



Desirable Features 



1. The individual rings are within the size and weight capabilities of fabrication 

 and transportation facilities. Final assembly would be done at the site. 



2. Since a ring would be required for the upper flange of all vessels under 

 serious consideration, the additional rings required for the body of a stacked- 

 ring vessel can be obtained without additional tooling-up costs. 



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