Assembly 



hoop loading 



be fabricated by the steel industry. 

 The end closures, again as in the 

 stacked-ring pressure vessel design, 

 can be made as a single forging, 

 if such is feasible in view of its 

 size or as a convex closure assem- 

 bled from spherical polygons 

 (pentagon shape, orange peel, etc.) 

 (Figure 10). If a yoke end-closure 

 restraint is used, the yoke and 

 bearing block are already of lami- 

 nated construction, making the 

 vessel completely modular 

 (Figure 1 1 ). 



Together with the advantages 

 enumerated in the preceding para- 

 graph, there are also disadvantages. 

 The major disadvantages of the 

 segmented-wall module design are 

 the increased weight of the struc- 

 ture over a typical stacked-ring 

 vessel design of same interior 

 dimensions and materials, and 

 considerably greater machining 

 costs of the vessel's component parts. The increased weight of the cylindrical 

 wall structure is primarily a function of a factor not encountered in the 

 monolithic, layered, or stacked-ring vessel designs. This factor, inherent in 

 segmented-wall module design, is the shear-pin linkage of individual wall 

 modules. The shear-pin linkage weakens a vessel wall by introducing shear- 

 pin holes. These shear-pin holes ( 1 ) decrease the wall's load-carrying cross 

 section at their location and (2) create stress concentrations, or stress raisers, 

 whose magnitude decreases the effective pressure capability of the vessel. 

 Besides this, the shear-pin linkage in effect reduces the pressure-carrying ability 

 of a cylinder of a given length by one-half because actually only alternate 

 layers of segment modules form a load-carrying hoop around the vessel. 



Thus, when one takes into account ( 1 ) the approximately 50% decrease 

 in pressure resistance resulting from load bearing by only alternate layers of 

 segments, (2) the presence of tensile stress raisers'^ around shear-pin holes of 

 approximately 3.5 magnitude (as compared to average stress level in segment), 

 and (3) that the shear-pin holes decrease the effective wall thickness by approx- 

 imately 25%, it would appear that the pressure-containing capability of a 



Figure 9. Engineering concept of 

 a segmented wall for 

 cylindrical pressure vessels. 



15 



