ENGINEERING EVALUATION 



321 



A pressure-relief valve (400 psig) was installed in the low-pressure portion of the oxygen 

 system (immediately downstream of the pressure reducer). The pressure relief valve was 

 discharged overboard through the benthic wiring trunk. A flow meter was installed in the oxy- 

 gen input line to provide a visual indication of flow rates. 



Helium System — A total of 13,000 cu ft of helium was provided in the on-board supply. 

 This helium was intended for use in make-up of any losses due to leakage and absorption and 

 also to adjust the water level in the entry trunk. The helium system was installed essentially 

 as shown in Fig. 127. The helium was introduced into the blower intake of the ventilation sys- 

 tem to insure adequate mixing with the atmosphere. 



SCRUBBER- FILTER 

 EXHAUST PLENUM 



HELIUM MAKE-UP-, 



LP 0-300 PSI 

 3000 PSI H.P 



-GAS CONTROL 

 PANEL 



PO2 SENSOR 



d^ t 



GAS FLOW 



fy^ 



STUFFING TUBE 



■3^ 



-HULL (BOTTOM) 



He STORAGE, E XTERNAL , 10-1300 CU. FT. 

 BOTTLES ON MANIFOLD. 



Fig. 127. Sealab II helium system 



An additional helium system for initial charging and emergency make-up was installed as 

 shown in Fig. 128. This system was supplied from the staging vessel through the umbilical 

 cord. 



Emergency Breathing System — An emergency breathing (Bibb) system was installed to 

 provide emergency premixed breathing gases in the event that the habitat atmosphere became 

 contaminated (Fig. 129). The system would provide approximately 43 minutes' breathing time 

 for ten aquanauts. Three standard 1300-cu-ft cylinders of premixed gas were valved into a 

 regulator located in the galley area and supplied eight manifolds containing four quick- 

 connective outlets. Twelve Calypso model 1050 single hose scuba rigs, modified by removal 

 of the first- stage pressure regulator and the addition of a quick-connective fitting, were pro- 

 vided for use with the Bibb system. 



In addition to the Bibb system, twelve 38-cu-ft scuba bottles with first-stage regulators 

 (removed from Calypso rigs) and quick-connective fittings identical to those on the Bibb mani- 

 folds were provided near the entry trunk. These bottles were to be utilized by the aquanauts to 

 swim to the Personnel Transfer Capsule (PTC) in the event of emergency evacuation of the 

 habitat. 



