PRESSURE VESSEL 



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MANUAL VALVE 

 (HUMIDITY CONTROL) 



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FIGURE 4.— THERMAL CONTROL SUBSYSTEM SCHEMATIC 



A CO2 scrubber containing baralyme granules is attached to the inlet of the 

 thermal control subsystem heat exchanger assembly. An electrically powered 

 blower pulls air through the canister and then through the heat exchangers. 

 The canister is designed to hold the C0„ partial pressure below 0.5% atmos- 

 pheric (3.8 mm Hg) for 60 man hours per canister filling. A second blower 

 is provided for operation of the scrubber on battery power if the primary 

 blower fails . 



The breathing gas subsystem consists of the gas storage and handling equip- 

 ment for making up, sustaining, and purging the minitat breathing gas, 

 supplying the built-in-breathing (BIB) masks, and charging SCUBA bottles. 

 It also provides compressed air for emptying the catamaran pontoons . Figure 

 5 is a schematic diagram of the breathing gas subsystem. 



The minitat breathing gas is a mixture of oxygen and nitrogen having a par- 

 tial pressure of oxygen in air at one atmosphere. The initital breathing 

 gas is provided by pressurizing the pressure vessel with air to the appro- 

 priate calculated pressure and then pressurizing it to full depth pressure 

 with nitrogen. After the minitat is emplaced, the hatch is opened and the 

 wet room is blown dry using air to force the water level down to a refer- 

 ence mark on the inside wall of the wet room and then nitrogen to empty the 

 wet room. These gasses are pumped through the low pressure gas line and 

 controlled by a flow control console aboard the support vessel. 



Metabolic oxygen is supplied by adding a small amount of compressed air 

 through the low pressure line. An oxygen controller automatically admits 

 air to the minitat to maintain the desired oxygen concentration. Excess 

 nitrogen escapes through the entry trunk. Any loss in pressure as might 

 be caused by a leak will be detected by water rising in the entry trunk and 



III-5 



