Clarification on regulator free-flows

[Cthippo]

This should maybe go in the regs section, but it was a question I never got to in my OW class, so here we are...

My instructor touched briefly on free flows and we did the breathing off a free-flowing reg drill, and from her I got the impression it was a first stage phenomenon and not something that could be mitigated in the water. I have also been watching videos from Simply Scuba and Diver Ready and they discuss freeflows as a second stage phenomenon which can be easily mitigated. Is it one or the other, or both? How common are free-flows are there good ways to mitigate them?

 

[Puppeteer]

It's a 2nd stage issue predominantly, where the 2nd stage is adjusted for easy breathing effort.

Often you can stop it by giving a chop in the mouthpiece, tightening the breathing effort knob, blowing into the reg, or facing it down.

Basically a little back pressure to push the diaphragm back down to stop the free flow.

I first stage could cause free flow if it gets frozen open, but that is pretty rare and really only an issue with cold water diving.

My spare second free flowed on occasion, but I got it adjusted to increase the breathing effort slightly. No more problems and still very easy to breathe with.

My main secondary occasionally free flows if I'm on the snorkel at the surface and I didn't wind the knob back in. Easy fix.

 

[lexvil]

Both are right

 

[Centrals]

If the Intermediate pressure of the 1 stage is too high eg. seat is worn, then the 2nd stage will free flow.
If the seat of the 2nd stage is worn then same thing happens.
Any free flow has to be taken care of after the dive.

A cheap intermediate pressure gauge is extremely useful before/after a diving trip.

Compact IP Gauge (PSI and BAR)

A compact intermediate pressure (IP) gauge for SCUBA applications

www.divegearexpress.com

 

[CanadaDan]

I've had to use that skill twice on dives with frozen second stages where you could see a lump of ice that had formed inside the primary second stage. No way to solve it underwater. In both circumstances I aborted the dive and did a controlled ascent from ~15m while my buddy came with me with his octo at the ready.

Learning cold-water gear care and having equipment rated for cold water is crucial for northern divers. I could have easily avoided my incidents with proper education, care and gear choices. It's a lot to go over, I would suggest talking with a local dive shop and/or instructor, ideally ones with ice diving experience, to learn the ins and outs of it all. The shoulder seasons of diving have a lot in common with ice diving when it comes to gear handling.

Take a look though this thread for some tips...

Ice diving/Winter diving - freeze ups and free flows

We recently had an ice dive training which had multiple freeze ups and free flows mostly related to BC valves and one full face mask. Temperatures were in the 20's (F) with a slight wind. Water temps in the mid 30s. Most of the free flows happened after divers were under for a short while so...

scubaboard.com

 

[CanadaDan]

Ice Diving Tips – Scuba Regulators in Cold Water

www.intotheplanet.com

 

[Akimbo]

I can't recall having to abort a dive due to a freeflow in over 60 years of diving. Of course I have seen it happen to other divers. I do not routinely service my regulators but do check the IP before every dive trip. Outside of ice diving, nearly all the freeflows I have seen were caused by 1st stage IP creep.

 

[Subcooled]

and from her I got the impression it was a first stage phenomenon

Not always true.

A free flow can happen because of a 1st or a 2nd stage issue:

#1 either there is a small amount of water in your 1st stage (water or snow gets in while assembling the kit or there is water in the cylinder because of OOA-situations or a badly maintained compressor),

#2 or there is IP creep (do get your regs serviced),

#3 or exhaled air (which is moist of course) causes small ice crystals to form in the 2nd stage leading to a free flow of the 2nd stage. If the water is cold enough (arctic diving), this is pretty much unavoidable with most gear given enough dive time.

and not something that could be mitigated in the water.

If it's the 2nd stage that's causing the problem, then you just shut the cylinder valve and wait for the 2nd stage to melt. The problem might repeat but it's manageable if you have two breathing apparata.

I have also been watching videos from Simply Scuba and Diver Ready and they discuss freeflows as a second stage phenomenon which can be easily mitigated. Is it one or the other, or both?

It can be a 1st stage or a 2nd stage problem.

How common are free-flows are there good ways to mitigate them?

How common?
It depends: Do you dive in cold water? Do you do ice diving? Arctic ocean diving? Working hard under water in cold conditions? Have you got your gear serviced?

Ways to mitigate [in open circuit diving]?
1. Maintain your gear and keep the internals dry.
2. Two totally independent breathing apparata. Just shut the failing one and wait until ice melts (if the free flow is caused by ice).
3. Feather the cylinder valve if the problems persists.
4. Avoid exhaling into the reg above the surface if the surface temperature is below freezing (else you'll have to warm up the 2nd in the water).

 

[rick00001967]

we see free flows everytime we run an ice dive.

the comments above have covered this pretty well.

but for really cold water diving, i think the primary reason we see it so much is due to "over breathing" the reg. by that i mean divers that are not relaxed, maybe too cold, too stressed, or all three, and are breathing hard. this can cause frezzing of the parts inside the second stage and it sticks open.

almost all the free flows we see at the ice dives are solved at the surface by turning off the tank and either hanging the second stage in the water for awhile or pouring some warm water over it if that is avail.

 

[Landau]

Another way to get a free flow.

Don't rinse your gear well. Over time a large salt crystal builds up between the purge button and the diaphragm on the second stage putting pressure on the diaphragm and causing a free flow.

Solution - rinse your gear well in fresh water after each day's dives.

Don't ask me how I know