pUP=^ R R. R 



I o I a 



unpressurized pressurized 



Distribution of Hoop Stress 



Figure A-2. Multilayer concept of 



pressure vessel construction. 



of corrosion-resistant steel. 

 Successive layers are wrapped 

 (Figure A-2) around and the 

 longitudinal welds join the longi- 

 tudinal edges of the rolled plates 

 to form concentric cylindrical 

 shells. Shrinkage of the welds is 

 controlled so that the interior 

 layers of the shell attain a desired 

 compressive prestress. 



Desirable Features 



1. The individual layers are 

 constructed from relatively thin 

 plates which are readily available 

 and whose quality is controllable. 



2. Heavy welds are not required, 

 and the welds can be inspected as 

 each layer is added. 



3. Only a relatively thin inner shell 

 of corrosion-resistant steel is required. 

 The other layers may be of another 

 grade. 



4. Failure occurring in one layer of the vessel would not necessarily propagate 

 to other layers unless the test pressure were sufficient to cause burst of all the 

 layers. 



5. Only the inner shell is pressure-tight. The remaining layers are vented to 

 the outside so that overpressure causing rupture of the inner shell would not 

 rupture the entire tank. 



6. The fabrication experience and safety record associated with this proprietary 

 construction technique render the behavior more predictable than the behavior 

 of vessels constructed according to the separated layer concept. 



Undesirable Features 



1. Shipment of a completed 10-foot-diameter multilayer cylinder would 

 involve a 350-ton object whose external diameter of about 13 feet is close to 

 railroad size limits. 



44 



