pyrotenax cables are sealed to the penetra- 

 tor body with an epoxy potting compound 

 and a soft wax overlay (Fig. 7.17d). Should 

 the epoxy material crack over periods of 

 service, then the wax under hydrostatic 

 pressure would seal the voids. The cables are 

 prevented from being axially forced into the 

 sphere by washers brazed to the cables. 

 These washers have the proper amount of 

 surface area to withstand the hydrostatic 

 pressure. The penetrator body is sealed to 

 the pressure sphere with a conical plexiglass 

 ring which is pressurized initially by a re- 

 tainer nut inside the sphere. The nut holds 

 the fitting to the hull and initially pressur- 

 izes the plexiglass material to effect a seal at 

 low pressures. The seal becomes more effec- 

 tive with depth due to high hydrostatic pres- 

 sure on the penetrator body. Similar pene- 

 trators are used on FNRS-3, ARCHIMEDE 

 and BEiV FRAISKLIN. 



The BEN FRANKLIN, during its Gulf 

 Stream Drift, used two other commercial 

 penetrators: A Viking penetrator and a Brit- 

 ish design known as the "molded gland" (Fig. 

 7.19). Additionally, a specially designed pene- 

 trator, basically a 13-mm-diameter copper 

 rod 215 mm long with a bronze machined 

 collar on the outboard end, was used to carry 

 power from the batteries into BEN FRANK- 

 LIN's hull; similar penetrators also serve for 

 battery charging and shore power. Figure 

 7.20 shows these specially designed penetra- 

 tions carrying main propulsion power 

 through the hull, and Figure 7.21 shows 

 their construction. 



The British "molded gland" penetrator has 

 been used by Royal Navy submarines for 

 several years with no reported failures (32). 

 It was originally designed for underwater 

 cables and saw its first U.S. application in 

 1969 on the BEN FRANKLIN (Fig. 7.22). A 

 paper by K. R. Haigh (33) describes the 

 molded gland and its advantages over other 

 systems. The basic principle of this gland is 

 as follows: The polythene (polyethylene)-in- 

 sulated cable core passes through the pres- 

 sure hull, which is locally deformed by a 

 protruding hollow spigot with a castellated 

 external surface. The seal is formed by mold- 

 ing polythene around the castellated spigot 

 and the cable core. On cooling, the core insu- 

 lant becomes homogeneous with the poly- 



thene, which also contracts on the castel- 

 lated surface. The application of water pres- 

 sure increases the contact pressure between 

 the polythene and the spigot, thus making 

 the gland inherently self-sealing. Pretreat- 

 ment of the spigot by the application of a 

 thin film of polythene bonded to the surface 

 ensures that the molded polythene bonds to 

 the castellated surface. If the cable is sev- 

 ered outboard at the hull, ingress of water is 

 prevented during the molding process by 

 forcing epoxy resin under pressure down the 

 interstices of the multi-strand conductors 

 thereby eliminating any voids which may be 

 present between sheath and conductor. For a 

 period of 1 year, glands of this type were 

 subjected to a water pressure of 5 tons/ 

 square inch without any evidence of penetra- 

 tion. Each gland is supplied with tails on 

 both the high and low pressure sides and 

 installation consists of screwing the gland 

 body into a prepared housing in the subma- 

 rine pressure hull. 



To join the two cable tails together, a 

 portable injection-molding machine shoots a 

 hot charge of polythene under hand pressure 

 from a gun into a transparent Perspex (plexi- 

 glass) mold clamped around the section of 

 cable core or sheath requiring reinsulation. 

 The use of Perspex, which has a relatively 

 low thermal conductivity, avoids the need for 

 heating the mold, while ensuring that the 

 injected polythene is not cooled at a rate 

 which would prevent its complete amalgama- 

 tion with the conductor insulation or sheath. 

 It also permits the operator to watch the 

 filling of the mold right up to the time when 

 reinstatement of the insulation is complete. 

 The complete joint can be tested hydrauli- 

 cally by clamping a water jacket around the 

 cable and applying any required pressure. 

 By this means, the complete external electri- 

 cal system can be tested for water-tightness 

 to full diving depth and beyond while the 

 submersible is still being built or at the dock. 



This system is described in some detail 

 because it departs radically from U.S. sys- 

 tems, in that, there is a continuous hard line 

 conductor running from the external instru- 

 ment into the hull. U.S. systems, on the 

 other hand, contain separate conductor con- 

 tact points externally at either the hull or a 

 connector, and again at the cable and the 



342 



