1. Continuous- or interrupted-thread and shear-block systems 



2. Continuous external-yoke system 



3. Tie-rod system 



Of these three end-closure restraint systems, the threaded and shear-block 

 restraint systems are the most limited in terms of internal pressure and size 

 because of the small shear surface engagement in the end flange. The contin- 

 uous yoke will operate at the highest pressure limitation, while the tie-rod 

 system occupies a middle position with respect to pressure limits. 



The three different end-closure restraint systems provide different 

 degrees of accessibility to the vessel interior via feedthroughs in the end closures. 

 The threaded and shear-block restraint systems provide maximum accessibility 

 to the end closure for installation of feedthrough, while the continuous-yoke 

 closure provides minimum or complete absence of accessibility. Here again the 

 tie-rod restraint system is midway between the two others. It provides less 

 accessibility to the end closures than the threaded and shear-block system, but 

 more than the continuous-yoke system. 



The end-closure restraint systems also vary in the ease of opening and 

 closing the vessel at the beginning and end of each test program. The continuous- 

 yoke system is here the most cumbersome and requires a very expensive and 

 elaborate opening and closing mechanism to perform a reasonably speedy open- 

 ing or closing operation. Threaded and shear-block restraint systems can be 

 easily mechanized, resulting in very fast opening and closing operations. The 

 tie-rod system is less cumbersome than the continuous yoke, but still more so 

 than the threaded and shear-block systems. It has the potential, however, of 

 resulting in an efficient system if an R&D effort is devoted to it. 



Conclusions. Tie-rod and continuous-yoke restraint systems are superior 

 to interrupted-threaded and shear-block systems for 10-foot-diameter pressure 

 vessels of 10,000-psi pressure service because the small shear surfaces of the 

 latter make them inadequate for high pressure. 



Recommendations. It is recommended that the tie-rod end-closure 

 restraint system be investigated further as there is less known about it than the 

 continuous-yoke system. It promises to be more efficient in operation than 

 the continuous-yoke system, if a successful design is found for it. 



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