Fig. 8. Fiberglass cylinder segmented for 

 inspection after failure at 

 10,200 psig. 



segmented sections of fiberglass cylinders which 

 were stopped short of complete implosion. 

 Inspection of these segments have shown where 

 and how the failures occurred and where the 

 designers should give added attention in building 

 a more reliable container. 



TEMPERATURE CONTROLLED PRESSURE TEST FACILITY 



To simulate more fully the deep ocean environ- 

 ment one of NRL's pressure facilities has been 

 modified to include the capability of cooling the 

 tank and the enclosed fluid. The tank is cooled 

 by a small unit with a 3500 BTU/hour capacity. 

 The cooling coil is tightly wrapped to the out- 

 side of the pressure tank as is the thermal con- 

 trol bulb. Flexible hoses connect the cooling 

 unit (mounted on the pressure tank enclosure) 

 to the cooling coil. The cooling unit of this 

 system is capable of lowering the temperature of 

 the pressure vessel from 75°F to 32°F in about 

 1 hour and k-0 minutes. The pressure tank is 

 5 l/l6 inch ID and 6 7/8 inch 0D with an inside 

 length of 20 inches. The volume of the tank is 

 !+10 cubic inches and usually contains paraffin 

 oil. 



A tank heating unit is also incorporated to 

 bring the pressure tank temperature from its 

 cooled state to room temperature in a reasonably 

 short period of time. The heating unit is a 

 750 watt surface heating element from a domestic 

 electric range. The element is firmly in con- 

 tact with the base of the pressure tank. The 

 surface heating element can return the tempera- 

 ture of the tank from 35°F to 55°F in 2 hours 

 and 50 minutes . Both the cooling and heating 

 elements are thermally insulated from the sur- 

 rounding atmosphere. 



The temperature of the contained fluid is 

 sensed with an iron-constanan thermocouple. The 

 thermocouple junction is located on the longi- 

 tudinal axis of the pressure tank 1 inch above 

 the bottom. A thermoelectric device maintains 

 the thermocouple reference junction at 32 F. 



At present, the fluid used in the 15,000 psig 

 pressure system is paraffin oil. This oil 

 becomes sluggish near 32°F. It is desirable to 

 use an oil whose viscosity is fairly constant 

 from 32°F to 85°F. Some synthetic oils exhibit 

 this desirable trait but their coefficient of 

 compressibility is too great. The fluid which 

 embodies both of the above desirable character- 

 istics is water but some other features are not 

 so advantageous. 



DISCUSSION AND CONCLUSIONS 



With every instrument discussed at this Sym- 

 posium there is probably a common unknown; namely 

 its accuracy when operating in the real ocean 

 environment. The program at NRL is aimed at 

 testing and evaluating oceanographic sensors in 

 a simulated deep ocean environment. At this time 

 only the parameters of pressure and temperature 

 are considered. Unless there is an organized 

 and concentrated effort to design and produce 

 secondary standard instruments and test instru- 

 ments under controlled simulated parameters it 

 seems apparent that some doubt must be associated 

 with any measurements taken in situ . 



A wide range of tests have been undertaken to 

 learn more of the influence of hydrostatic pres- 

 sure on components. Many of the tests described 

 deal with areas of the utmost concern to instru- 

 ment designers — criteria for selection of elec- 

 tronic components to be used in long term submer- 

 gence and effectiveness of encapsulating materials 

 used to contain electronic circuits and seal them 

 from hydrostatic pressure. System designs could 

 be improved and production of prototypes accel- 

 erated if a clearing house for this kind of infor- 

 mation was readily available and taken advantage 

 of. This would minimize duplication of experi- 

 ments and component manufacturers could also 

 improve product design through application of this 

 knowledge . 



REFERENCES 



1. BUCHANAN, C. L. and M. FIAT0, Influence of a 

 high hydrostatic pressure environment on 

 electronic components, Marine Sciences Instru- 

 mentation , 1, Instrument Soc . Amer . , Plenum 

 Press, New York, N. Y., 1962. 



172 



