Free flow at depth

[cloudflint]

I was out diving earlier today and our group had some rather strange behaviour from our regs.

Basically my regulator breathed perfectly on the surface. At about 2 meters I took a breath and my reg started to free flow slightly. I took another breath and it began to free flow even more. I turned round and went back to the surface with my buddy and I switched off my tank for a few minutes then turned it on and once again the regulator breathed fine.

We went back down and the regulator breathed fine for about 5 minutes when it happened again at about 9 meters. I swam back up to the shore and once again switched off my tank for a minute or so then switched it back on and everything was fine but we decided to call it a day.

This has me rather confused, ive been diving the reg once or twice a week for the last 9 months and its given me no trouble whatsoever. I haven't been able to check the IP but the fact that the regulator breathed fine on the surface leads me to believe that that shouldn't be the problem.

All the symptoms seem to suggest icing but the water temp was 6 degrees with air temperatures of 9 degrees so I wouldn't have thought it was cold enough to cause icing. What really makes this confusing is that one of the other guys in our group had his regulator start to free flow at 19 meters, after fiddling with it for a bit he reportedly gave his first stage a bit of a tap and it stopped free flowing. For one regulator in the group to start free flowing I could accept as some mechanical problem, but it seems weird that another guy in the group had the same thing happen when we both have fairly new regs that have been frequently used without any problems.

So, anyone got any ideas? I have my DV sitting in pieces on my table at the moment since i wont be able to trust it until i figure out why it free flowed and check everything over

 

[NJDiverMark]

6° is pretty damn cold y wouldn't it be icing? 6°c?

 

[Jimmer]

6° is pretty damn cold y wouldn't it be icing? 6°c?

Seeing as he is in Scotland, I am going to assume that he is talking 6c, and therefore it's still above freezing.

To the OP, I have seen many free flows in water above freezing, it happens. The cool air coming from the tank, plus moisture from your breath can on occasion conspire to cause a free flow. Do you breathe the regs before getting in the water? When it's getting close to freezing point, I never breathe into a reg on the surface, so I don't get moisture in the second stage.

Jim

 

[dumpsterDiver]

Until you check the IP, the discussion seems kinda silly. Sorta like ......my car stopped running... did you check if you have any gas in the tank? Well no, not yet...

 

[lowviz]

.............Basically my regulator breathed perfectly on the surface. ...........................

Don't breathe your reg on the surface even once as the air has a lot less "thermal mass" than water. Do a controlled entry with your first breath underwater. Remove your secondary and with the mouthpiece pointing down, look for a steady stream of bubbles. If bubbling, it won't get any better. Return and fix what will become a free-flow. If no bubbles, ok to go. Do not add air to wing or suit while taking a breath, spread out the load on your primary. Breathe more slowly. First from diaphram then expand chest. Slow down.

 

[Diver003]

Until you check the IP, the discussion seems kinda silly. Sorta like ......my car stopped running... did you check if you have any gas in the tank? Well no, not yet...

I don't really understand the whole intermediate pressure thing for regs still...could you do a quick run-down for me?

 

[cloudflint]

I begin to suspect it may be icing after all I dive a twin hose so I didn't expect to have problems with icing since ive dived in much colder temperatures than this without problems. We actually remarked that it was rather mild getting changed today My IP looks fine and the lever in the DV seems to be adjusted to the right height.

I seem to have a lot of moisture in the 2nd stage case however so I begin to suspect that moisture has gotten into the case and since this is the first time in a month or so that the air temp has been greater than the water temp it hasnt iced over on land giving me a false sense of security. I guess the other guys reg did the same thing since he has a piston first stage which would explain why whacking his 1st stage stopped it.

Well mystery solved at least, I really must remember that even if it feels "tropical" its still cold by normal standards!

 

[SDAnderson]

We all know that air warms as it is compressed and cools as it expands - hot fills are an example we're all familiar with. The air coming from a fully pressurized cylinder passing through the first stage will cool by 25 to 30 degrees centigrade. In ambient temps anywhere close to freezing, that cooling effect can cause real problems if the now frozen regulator is exposed to any moisture, either entrained in the gas stream or condensed in the regulator.

 

[lowviz]

...........Well mystery solved at least, I really must remember that even if it feels "tropical" its still cold by normal standards!

 

[mikecotrone]

I don't really understand the whole intermediate pressure thing for regs still...could you do a quick run-down for me?

This is how I understand IP or Intermediate Pressure. The IP (Intermediate Pressure) is the pressure level that the 1st stage is "regulating" down to between 9-10 bar (around 132psi to 147psi) from the pressure in your Cylinder (Tank). Remember your cylinder pressure can be 3000psi for an AL80 for example or 3442 for a High Pressure 130 as another example. Imagine trying to take a breath from an air stream pumping out at you with 3000psi Now we can go into great detail about balanced and non balanced first stages (which I am not experienced enough to lead), however the key takeaway for me is that a properly balanced 1st stage will be able to maintain this IP of say 140psi from the beginning of your dive with your tank at 3000psi all the way down to 500psi.

Here is a link to the Wikipedia explanation:
Diving regulator - Wikipedia, the free encyclopedia

HTH,
Mike