Diving the Closed Circuit FGGIII

Test dives have been going quite well and have been conducted in Sydney Harbour, on a wreck in 68 metres off the North coast of NSW, and in the Pearse Resurgence freshwater cave in New Zealand down to 75 metres. This photo shows the HUD displaying High PPO2!

I can hear you saying "I thought CCR diving meant no bubbles". The bubbles you can see in the pictures are from a leaking Air2 which is slowly draining my oxygen cylinder. Even with this leak, the unit still managed an 80 minute dive to 68 metres and used less than a single 20 cubic foot pony bottle of oxygen!

On a recent dive, while ascending through 55 metres, I noticed one of my sensor readings jumping all over the place. This was only a mild concern, as the electronics were still operating the unit perfectly with the other two sensors. I kept a ready eye on the readout while still ascending, and when at 50m, a second sensor started playing up so I had to do something about it. I immediately went to open circuit bailout while I decided what to do. First was a diluent flush, so I swapped back to the breather and filled the unit with trimix 12/44. This brought the overall PPO2 down and one sensor came good, giving me two good sensors and normal operation. However, as I continued to breath and watch the display, the second sensor went bad again. I once again switched to open circuit so I was breathing a known gas as I wanted to keep my ascent going after spending a couple of extra minutes while trying to sort out the problem. When at the 40m stop, a look at the display indicated things had settled down, so I went back on the breather but after a minute or so the sensors became erratic again. That was it I thought, I'd complete the dive on open circuit. When arriving at the 6m stop I thought to myself, 'Well, you don't need the electronics to run in fully closed 100% oxygen mode, so I'll switch to the breather and finish the deco. As I took my first breath, all I got was a mouthful of horrible tasting water, the unit had a total loop flood.

The brains trust at work. From left we see Phil, Pete, me (squatting), Steve, and Barry. All these guys are regular rebreather divers and between them own 3 Inspirations, 3 Draegers, and 1 Mk15. You can see the pile of soggy Divesorb in the lid of the FGG. After removal, someone suggested we put the flooded Divesorb in the oven to dry it out. After an hour it was back to its original consistency, but I wasn't feeling lucky (stupid) enough to dive with it. It went in the garbage.

When we got back on dry land I performed a positive pressure test, and the unit was airtight, filled with water, but airtight! A strip down showed that the scrubber was completely filled with water, as was the exhalation counterlung. The inhalation bag was dry. It would seem that the total flood was probably caused by me, I must have left the mouthpiece open the last time I did a swap. I'll NEVER do that again! The sensors in the scrubber were flooded, as were the electronics in a separate enclosure which is vented to the scrubber. These were given a thorough washing in fresh water and allowed to dry. The electronics board needed a few of the joints resoldered as well. This done, the unit was reassembled and did the same dive again the next day with absolutely no problems.

Photo's by Mad Max