How was the reg tuned? Did you try the Venturi or the adjustment knob? I dive XTX50s and I usually have my necklace in - to make sure it doesn't freeflow. My primary is + and all the way out so it doesn't take a lot to make it flow, but usually flipping it so the mouthpiece faces down stops it.Following on from the soaking yesterday with the unseated QuickNeck seal, the undersuit and drysuit now dried, I tried again. Need to check the new drysuit and thick BZ400 heated undersuit and lots of diving coming up.
Went to the lake with sidemount kit as they won’t allow solo on a rebreather. Kitted up and descended down he ramp, no leaking yay!
Mooch around a bit and got to a container which is also a platform. Was preparing to enter through a window-sized hole cut into the side of it when "boom", utterly inundated with bubbles as a reg unexpectedly free-flowed.
Quite a surprise, so tried to stick a finger into the mouthpiece to no avail. Then switched regs to see if breathing it would stem the flow — of course not. Then started to shutdown the valve, loads of warnings going off about ensuring I shut down the correct valve. Stopped the flow. Waited for a few seconds and turned the valve back on again, more freeflow, so shut down again.
Now down to one cylinder, made my way to the exit and re-tried the valve and it didn’t freeflow, until I took a breath, then it freeflowed.
Damn it. Obviously my kit hates being in freshwater!
Checked the intermediate pressure when I got home, all fine. No freeflow in air either. Need to take a look inside; the XTX50s have been recently serviced along with the Mk25 first stages.
Lessons learned
- It’s the first time in my diving career that a real freeflow has happened underwater.
- Was quite a surprise and consumed a lot of gas as I should have been far quicker to do the shutdown — shallow lake, sidemount, no decompression obligation, so no real issues.
- Was surprised how violent it was, far more than being air-gunned by an instructor. Little wonder it induces panic in some people.
- As I was diving sidemount, it was easy to do the shutdown. Backmount would have been harder (although I regularly practised that when I dived backmount).
- A single tank would have meant a fast ascent to the surface (although I was diving solo, so a single with no pony would be out of the question)
Let’s hope the forthcoming sea dives are less eventful!
BTW.
If the IP is fine, does that mean that the freeflow was caused by the second stage? Are there other failure modes of the first stage that leads to second stage freeflow?