Like Sg. Peppers, the R300 is a small boat. In early years I to had some pesky O2 and air leaks which I eventully sorted out. Initially I tried to control my O2 makeup valve using the measured cabin pressure with a barometer (700 to 1100 mBar). I found this quite problematic. I changed to controlling off the O2 concentration measurement rather than cabin pressure. This worked a lot better for me. When the O2 level drops below 18% the PLC opened the O2 makeup solenoid valve until the O2 concentration reaches 23% then it cuts off. It takes about 1 minute for the O2 makeup value to cycle from closed to open to closed. In additon to the automatic O2 makeup system, I have a backup manual metering needle valve with a simple direct reading medical flow rate gage. I added a cabin pressure gage that is 0-30 psia that I use to trigger overpressure alarms. I had this alarm sound on one dive
when a hair line crack developed in O2 regulator high pressure fitting. The high O2 alarm also went off. At that point I surfaced the boat. After blowing my MBTs, I began relasing my hatch latches. After releasing the first one, the other released poping the hatch open to releave the 5 psi overpressure in the boat. This sudden release of cabin air was enough to unseat my hatch o-ring. I was very nervous for about a minute until I reseated this o-ring as I could not close the hatch and my freeboard is quite small. Needles to say, my diving was over for the day and I did not dive the boat again until I found and fixed the source for the high pressure leak and installed a hull equlization valve for the hatch. I also have a high CO2 alarm which triggers when the CO2 partical pressure exceeds 5000ppm (0.5%). This happens when the CO2 absorbent becomes
saturated. Normal air has about 300 ppm of CO2. I did quite a few 4-8 hour "garage" dives to make sure the environmental controls were working and to sort out the CO2 scrubber fan size. Acturally they are a lot of fun but a bit boring. Garage dives are a great way to debug systems. The 15 alarms on the R300 are:
High Oxygen Level, > 23%
Low Oxygen Level, < 18%
High CO2 Level, > 5000ppm
Hatch Open on Dive
High Main Current, > 300 Amps
High Aux Current, >20 Amps
Low pressure in Air Tank, <750 psia
Low pressure in O2 Tank, < 550 psia
Depth Exceeds 300 ft
Low Cabin pressure , < 12 psia
High Cabin pressure , > 20 psia
Motor field winding > 248 F
Seal Barrier Fluid Outlet Temp >200 F
Low Main Battery Voltage, <110Vdc
Low Aux Battery Voltage, <22Vdc