activating a float valve, 

 an alarm. 



This adds air from the support vessel and sounds 



PRESSURE VESSEL- 



EXHALED O, VENT - 



TO CONTROL CONSOLE - 



II I 



-PENETRATION PLATE F-1 



HIGH PRESSURE LINE 



LOW PRESSURE LINE 



I I I II I III ITT 



-ENTRY TRUNK 

 UMBILICAL 



GAS SAMPLE TUBE 



FIGURE 5.— BREATHING GAS SUBSYSTEM SCHEMATIC 



If the breathing gas becomes contaminated, it can be purged slowly with air 

 pumped through the low pressure line or quickly by using the compressed air 

 stored on board. After air purging, nitrogen must be added to reduce the 

 oxygen partial pressure to the desired level. This may be done using nitro- 

 gen stored on board or on the surface support vessel. 



The compressed air stored on board also supplies air to the emergency BIB 

 masks for use if the minitat floods or the breathing gas becomes contaminated. 

 The compressed air can be used for charging SCUBA bottles and blowing the pon- 

 toons of the catamaran barge. The compressed air storage bottles can be re- 

 charged from the surface. 



High pressure oxygen is stored on the minitat in two cylinders that are 

 attached to the pressure vessel. These cylinders supply oxygen for decom- 

 pression. Oxygen masks have vents to dump exhaled oxygen overboard. 



The breathing gas monitoring subsystem consists of a Biomarine oxygen control- 

 ler having three galvanic O2 sensors, an MSA LIRA infrared absorbtion CO2 

 analyzer with a display and an alarm, remote O2 and CO2 indicators in the support 

 vessels, and a breathing gas sampling tube in the umbilical. The latter allows 

 an independent and more extensive assessment of the breathing gas in the pres- 

 sure vessel and wet room to be made from the support vessel. 



The minitat receives 220 volt A.C. three phase power from the surface via the 

 umbilical. Three phase 220 volt power is used by the ECS compressor and CO2 

 removal blower motors. Single phase 220 volt power is used by external 



III-6 



