Free flow at depth

[wardric]

OP says freeflow at depth.

been there long ago. 130+
Got my buddy's attention
switched to his octo
he closed my tank
we started ascending
at 60' opened the valve, still freeflow
close the valve
at 40' opened the valve, no freeflow
I switch to my main, buddy goes to my octo (he was getting mighty low)
we go at 15'
buddy switch to his main
we empty our tanks there and ascend

It worked

(but many lessons were learned that day )

 

[Dirkadiver]

Consider diving w/ a bailout bottle. When I dive single tanks I always carry a 30 cu. ft. bailout. It may be a little more trouble getting geared up, but it will pay dividends in the event of a freeflow & absent buddy.

 

[DA Aquamaster]

Large and violent freeflows are most often caused by one of three things:

1. A frozen first stage (the # 1 cause in water colder than 50 Degrees F) and

2. Ice forming in the second stage where it blocks the lever. (much less common even in very cold water but something that was totally unheard of with all metal second stages, so it is a possibility with a plastic second stage)

3. A foreign object blocking the lever in the second stage.

My thoughts are that shutting the tank valve after you switch to your buddy's second stage or your own bail out bottle will allow # 1 and #2 to resolve themselves after a couple minutes when the offending ice thaws. The less time it freeflows the less ice will form and the faster it will thaw.

On a deep dive I think it is prudent to preserve what ever tank you have left in the tank to give you as many options as possible for a normal ascent. You can re-crack the valve and see what happens in a minute or two and if you again have a functioning reg, you have access to a lot more air.

That said in cold water unless you have a really bullet proof cold water reg, a large pony is a good idea. For deep diving I'd regard 19 cu ft as the minimum and a 30 is better.

3# may be resolved by jarring what ever is blocking the lever loose. This can only be done with the reg out of your mouth so you just as well switch to your octo. Doing it soon is also a good idea as the freeflow caused by #3 can lead to #1 or #2 in water colder than 60 degrees as the high freeflow puts an enormous adibatic cooling load on the first and second stages. Again shutting the tank valve can help resovle the situation if you can switch to your buddy's octo. (or better yet your buddy's long hose primary).

Slight freeflows are caused by one of two things.

1. A leaking high pressure seat in the first stage. This causes excessive intermediate pressure and (for everyone but Poseiden owners) the freeflowing second stage results as means to safely vent excess pressure. In slight leak situations the freeflow will not start for several seconds to even several minutes after the last purge or inhalation.

The very small "minutes" variety HP seat leak may be discovered on the surface before your dive when your regs starts softly hissing/freeflowing after being set up and turned on a few minutes. The much leakier several seconds variety becomes apparent on the surface but also in the water between breaths. Small leaks inevitably turn into large leaks as HP seats never get better. The wildcard is how fast they get bad. It may occur over the course of severla dives or it may occur in the space of one dive, so finding even a slow HP seat leak in a pre dive inspection is cause to abort the dive unless you can borrow another reg.

2. A leak in the soft seat in the second stage. These differ from first stage leaks causing excess intermediate pressure in that they leak immediately upon pressurizing the reg. The intermediate pressure does not matter as the seat cannot seal against the orifice anyway.

With an adjustable second stage, more spring pressure may help (and some lightly adjusted regs will leak slightly in the all the way out position normally anyway) but if the amount you have to screw the knob in to stop the leak is excessive or near all the way in, it is a good idea to get the reg serviced before you dive it as again these leaks can get worse very quickly. You may find after a few dives on a recently serviced reg that you have to turn the knob in slightly farther than you did on dive #1. That is ok and is just a sign that a normal seating groove has formed. But a big or rapid change inhow far in the knob needs to be is a symptom of a potential problem.

With a non adjustable second stage you are pretty much stuck and will need to take it in for adjustment or replacement of the seat. A slight leak may occur because the tech, in their efforts to produce the best possible inhalation performance, adjusted the valve assembly slightly to lightly so that when the seating groove forms, a leak occurs. In this case a 2 minute adjustment willl solve the problem. If not, seat replacement will be required.

In any case diagnosing any freeflow should always start at the first stage so be sure you tech checks the intermediate pressure to ensure that there is not a first stage issue on top of a second stage issue.

 

[wardric]

Consider diving w/ a bailout bottle. When I dive single tanks I always carry a 30 cu. ft. bailout. It may be a little more trouble getting geared up, but it will pay dividends in the event of a freeflow & absent buddy.

That was one of these lessons

 

[netwayne]

Thanks for all the good info shared! Looks like there are multiple ways to deal with the free flow. It's great to have options and I guess the key is staying calm enough to realize those different options.

 

[Ed Palma]

Dumb question, from someone not an expert in regulators: how often is a free flow due to a first stage, versus a second stage, malfunction? Is first stage failure very common, e.g., from freezing?

No problem with freezing where I dive (The Philippines...)

However, there are instances where the 1st stage was clearly the cause of a free flow. One failure I once encountered in a first stage was the rupture of the o ring between the HP side and LP side. It occurred at depth and produced a staccato free flow - sorta like a machine gun being fired as the IP shot above the 200 PSI (over ambient) limit of the 2nd stage. Replaced o-ring and checked other components, and it was okay again.

On another reg that I worked on, there was an ever so slight IP creep (probably 5 PSI per minute). Theoretically, it wouldn't have induced free flows (unless you're the type who can hold your breath for 12 minutes). But at any rate, upon disassembly and inspection, I noted that the HP seat was a little cut up and that a "thread" of nylon was causing the minor leak. I cleaned up the seat a bit (just short of refacing it) and now the creep has resolved.

 

[Rick Inman]

I just disagree with feathering the valve, shutting down and trying to clean the reg, switching regs, etc. On a single, a freeflow = mandatory thumb.

When my buddy and I had cheap regs (years ago), in the winter in our 40 degree water, free-flows were a regular part of the dive. If I had a FF, I'd just go on my buddies alt for a bit, turn mine off, give it a couple of mins to un-freeze, turn it back on and then continue the dive. Sometimes it would take a couple of tries, and our rule was, if it didn't stop after three tries, or if the buddies reg started FF-ing while sharing gas, we'd call the dive.

It was really no big deal. Recreational dives, of course.

Now we all dive good regs, so it's not an issue. I've have had to feather a stage on a malfunctioning FF-ing reg, which was also no big deal.

 

[keyshunter]

No problem with freezing where I dive (The Philippines...)



On another reg that I worked on, there was an ever so slight IP creep (probably 5 PSI per minute). Theoretically, it wouldn't have induced free flows (unless you're the type who can hold your breath for 12 minutes). But at any rate, upon disassembly and inspection, I noted that the HP seat was a little cut up and that a "thread" of nylon was causing the minor leak. I cleaned up the seat a bit (just short of refacing it) and now the creep has resolved.

Interesting that this is still done. In days of yore, many regs used simple puck hp seats (think Sherwood, SP MK 2, etc.). When the seat had already been flipped, and no new one was available, one carefully sanded the old seat to remove part of the seating groove. Usually it worked at least until a new seat could be obtained.

 

[Ed Palma]

Interesting that this is still done. In days of yore, many regs used simple puck hp seats (think Sherwood, SP MK 2, etc.). When the seat had already been flipped, and no new one was available, one carefully sanded the old seat to remove part of the seating groove. Usually it worked at least until a new seat could be obtained.

Its a trick I heard from the vintage double hose divers (Thanks Luis H and Captain! ).

I had trouble sourcing parts for this reg (a beuchat VX10), so my options were rather limited. Anyway, good to know that this old technique still works.