Scubapro 109 for deep diving

[Jared0425]

The first stage did not free flow. I have not yet heard of a 17 free flow. It was the older vintage 109 that I was worried about. I got to wondering if these vintage regs were to dangerous, but then I realized that most regs would be under stress in that situation.

 

[halocline]

Case fault geometry is basically the difference in relative depth between the diaphragm and exhaust valve; if the pressure differences are enough, exhaust valve will essentially open at a pressure low enough to not allow enough pressure to stay in the reg body to keep the diaphragm from collapsing a bit and opening the lever. Since pressure differences between a set distance (about an inch in this case) are greatest at shallow depths, you'd expect this to happen shallow, but not deep. My guess is that with increased flow at greater depth, there's an increase in venturi effect and that's what causes the slight flow. That's a guess, though.

Seems the edit button is gone, so I'll correct this here. A little birdy (a pretty smart one) reminded me that although pressure difference increases proportionally, relative to the surface, greater as you get shallower, one inch of water is the same pressure differential regardless of whether it's at 1' to 1'1" or 100' to 100'1". And it's absolute pressure differential, not proportional pressure differential, that would make a reg free flow due to case fault geometry. So, the depth should make no difference for a reg's susceptibility to flowing due to case fault geometry issues.

Still, I think the reason my 109s flowed more easily at depth in certain positions (face down) was likely due to increased flow causing more venturi effect, and the birdy seemed to agree. I guess the moral is, if you're diving a 109 deep, just make sure it's set to 1" of water or thereabouts, and if it still starts to flow a bit under strong inhalation, just adjust the knob in a bit and that will stop it.

For anyone doubting the depth capacity of these 'older' 2nd stages, remember two things: 1) The 109 when upgraded with the s-wing poppet is functionally the same as a G250, and nobody doubts the depth-worthiness of that reg, and 2) Not too long ago professional divers were routinely doing extreme dives on single stage double hose regs and others that today's dive gear industry wouldn't allow in a pool.

 

[CMAN]

The 109 in question was up-graded with an s-wing poppet and balance chamber and spring. I closely inspected the reg afterward and I think that the lever was an "old style" which caused it to slightly "two step" breath. That and the diver was working it pretty hard in 37 degree water with heavy current which combinded to cause it to free-flow (I don't think it freezed flow but I can't be certain).

 

[halocline]

I would also doubt that the 2nd stage froze. The lever/poppet compatibility issue is an excellent place to start, and it does seem to be somewhat unpredictable. I've always had great results with the new curved-feet lever, so maybe try that, it's not that expensive. It's also worth looking for any IP creep, but your might have already checked that out.

 

[CMAN]

IP was (and is) good with no creep. I intend to change the lever with new style as soon as the shop gets them in. The reg has been swapped out with another 109 that has a been completely rebuilt.

 

[dumpsterDiver]

I think that is what my reg is? Works for me fine in 185, but this is not cold.

Spearfishing on a WW II Plane Wreck, SB2C, Jupiter, FL. 185 ft Depth - YouTube

[video=youtube_share;1g4Cf-7-rHQ]http://youtu.be/1g4Cf-7-rHQ[/video]