and present submersibles; Figure 5.16 pre- 

 sents a design recommended for habitats as 

 well as for submersibles where long-term 

 creep loading introduces more stringent re- 

 quirements. 



All the current and proposed designs call 

 for a retaining ring and either an "O" ring or 

 gasket for low pressure seals. The high pres- 

 sure seal is effected by making a lapped-joint 

 seal between the viewport and insert. An 80- 

 to 90-percent contact is achieved by surface 

 finishing in the 8- to 32-rms range. Snoey 

 and Katona (26) provide a step-by-step deri- 

 vation of the formulas and curves related to 

 conical viewport design and include test pro- 

 cedures which preceded these data. 



Piping: 



Submersible piping systems serve several 

 functions: 



Ballasting: Carrying compressed air from 

 storage to ballast tanks for blowing. 



Trim: Transporting trim fluids fore or aft 

 to their respective reservoirs. 



Hydraulics: Transporting fluid to activate 

 a device such as a manipulator or weight 

 dropper. 



Breathing Gasses: Supplying air or mixed 

 gas from external reservoirs into the pres- 

 sure hull or within the pressure hull itself. 



Four types of materials have been used to 

 perform these functions: Cupro-nickel, mo- 

 nel, stainless steel and flexible wire-braided 

 plastic hose. 



Cupro-nickel (7030) is a universally ac- 

 cepted piping material for the transfer of 

 salt water. It is very corrosion resistant but 

 costly. 



Monel has the same advantages as cupro- 

 nickel and has been used primarily for oxy- 

 gen systems. Its disadvantages are not only 

 cost, it is difficult to obtain by virtue of its 

 wide use and demand in military subma- 

 rines. Strangely, according to Purcell and 

 Kriedt (27), it is not clear why monel is the 

 preferred material for oxygen systems in 

 U.S. military submarines; indeed, after a 

 thorough investigation into the advantages 

 and disadvantages of other materials, they 

 conclude that other materials would serve as 

 well. 



Stainless steel piping finds wide applica- 

 tion in submersibles of the private sector. 

 Though not as corrosion resistant as cupro- 

 nickel and monel, it is far less expensive and 

 easily obtained. Standard aircraft ^/s-inch 

 stainless steel is the most commonly used 

 variety. 



0.226 



0-RING 



NOTE - 



PARKER 2 -457, N-183-9 

 NITRILE (BUNA N) 

 90DUROIV1ETER 



AFTER MACHINING, ANNEAL AT 

 175°F FOR 22 HOURS; COOL AT 

 5°F PER HOUR 



Fig. 5.16 Recommended viewport seal design. (From Ref. (26)] 



262 



