Deep dive / Free flow regulator

[Chuck J. Rylant]

I hope to get input on the risks and response to a free flow regulator during recreational deep dives.

As I expand my dive skills/knowledge, I've heard of free flow regulator dangers during deep and/or cold dives. I'm curious how significant a risk that is and what triggers it. What depths/temperatures cause those problems? The deepest I'd ever go is 130 feet and the coldest place would likely be Monterrey California. I'm not sure what the temperature is combining possible extremes of 130', in the winter, in Monterrey. If anyone knows, that would be helpful.

What is the appropriate response(s) to a free flow regulator for a recreational diver at depth? I want to take the PADI deep diver specialty but after searching here, it appears that class provides mostly deep diving experience rather than answer this question.

The reason I ask is as I expand my knowledge of recreational limits, I want to learn the most likely risks/dangers and their appropriate responses. This is not something I've heard discussed in PADI training other than breathing from a free flow regulator. Correct me if I'm wrong, but I don't think there would be time to safely ascend from 130' breathing from a free flowing regulator if you had already consumed a significant amount of gas.

 

[Scubanoobi]

Ive had 2 free flows in cold water(39 degrees) at 60 ft, both times I could still breath off of the reg normally and took between 3-5 minutes until the tank drained (freeflow started at 2500 psi). Since you have (or should have)a buddy, I wouldn't worry about it too much, jump on the octo and ascend safely. At 130 ft you should be very close to your buddy.

 

[Dhboner]

If the free flow is from your first stage (as it usually is if the water is really cold) you breathe of your buddies alternate while your buddy turns your air off at the tank valve. The buddy can then turn the air back on to see if the problem has resolved itself. Even if the free flow is resolved you thumb the dive at that point. If you have planned your dive properly your buddy will have enough back gas for a safe ascent for both of you even from 130'.

 

[decompression]

I'd recommend having a look at the unified team diving website, their rec courses are very thorough, with nitrox (rec 2) and Heliox (rec 3) for deeper diving to keep a low Equivalent Narcotic Depth (END). As one who teaches both PADI and TDI courses, the UTD curriculum does a very good job. Free flows will be addressed along with gas planning and management and situational awareness. You'll learn rock bottom gas planning and minimum deco strategy. Very useful for diving in that range.

 

[eelnoraa]

Like other said, if you reg free flow at depth, you go to your buddy's octo, turn off your tank either by your buddy or yourself, then aborb the dive. It is quite straight forward procedure wise, the key is not to panic, follow your training in OW class.

As to why a reg free flow, there can be many reasons. However, I don't think Monterey kind of temperature is the main cause if the reg was maintain and adjust properly to begin with. Also, I don't think depth has any direct affect on free flow either. But I am not a regulator tech.

 

[elan]

If you dive cold water (low 40 and below ) often you should think about having redundant gas supplies (ideally double tanks).
Going to your buddy's octo generally is not a good idea as now there is a great chance of making your buddy's reg freeflow as well (unless they have redundant gas)

Unless you have redundant air do not waste time with shutting down your gas just comeup together using up all your gas and then switch to your buddy's octo. At that point you will be shallower and likely in warmer watter.

 

[waterpirate]

This is the best argument for redundant gas that can be made. Not your buddy's. It was questions like these that led me to sling a pony bottle, get a H valve, and eventually dive doubles exclusively.

Redundant gas does not negate the buddy, but adds the luxery of time, and hopefully a reduced stress level to move on to step 2, a safe and controlled exit.

Eric

 

[Jerry_]

If you get a free flow, most important is not to panic. Take it calm and switch to the backup (provided that you have redundant equipment, which I would recommend that you have when you dive in cold water).

Alert your buddy (but she/he probably already realized), if (s)he is experienced enough start closing the bottle exit where the frozen stage is connected (some argue not to do it, because (1) it takes some time and (2) he may go wrong and close the wrong side) and imediately start your ascent calmly. If he is less experienced, start your ascent imediately.

If you run out of gas, take your buddy's backup. Again I would expect him to have two separated first stages, otherwise there is a higher risk that he also runs into a free flow. ( if the octopuss is on the same first stage as the main, the first stage will have double (and more, as you will be excited) gas getting through (see next paragraph)

Free flows occur when first or sometimes second stages freeze. They freeze as a combination of different elements (cold temperature combined with expanding gas (the gas that you breath), eventually combined with humidity already present in either of the two stages (free flow at the beginning of the dive) in winter months). The important issue is that an expanding gas is an endothermic reaction, i.e. it takes heat from the surrounding and thus cools done additionally ( basically the same process then in the clim in your car or house, or your fridge)

The type of valve/piston in the first stage influences the likelyhood of a free flow in cold water. Also some brands sell environmentally sealed regs, which also adds). Check for cold water regulators, when you buy a new one, or have your LDS confirm to what extend your regulator is suitable for cold water.

 

[DivemasterDennis]

I think this thread should also have a few "prevention" tips, even if they seem obvious. Safety discussion should always start there. First, know your regulators and the specifications for them- some have adjustable ease of breathing knobs, which can be helpful in controlling free flow, and some are designed for more extreme conditions (depth, cold). Second, have your equipment serviced regularly to assure proper operation and performance. Third, always dive with a buddy who is aware of and follows prevention steps 1 and 2.
DivemasterDernnis

 

[DA Aquamaster]

There are some threads on here that talk about good cold water technique to avoid a freeze flow in the first place, but I'll cover it here.

1. If the water temp is close to freezing (40-45F or below) do not test the reg, breathe off the reg, inflate the BC or your drysuit with the power inflator until the first stage is fully submerged. Any use at all of the first stage out of the water will result in the first stage being cooled below freezing with the result that ice can form in the ambient chamber and cause moving parts (piston or diaphragm) to stick and cause a freezeflow. If you really feel the need to test the reg, test it at home or in the dive shop where it's warm, then leave it alone at the dive site. If it worked that morning and the tank valve is open, it will work now. New divers in particular test and retest their regs and then freeze up almost immediately on the dive. It sounds counter intuitive but all that testing creates more risk than it mitigates. Keep the first stage warm by not using it until fully submerged.

2. Don't over breathe the regulator, don't make long continuous blasts on the inflator and spread the gas demands over as much time as possible - a long slow inhalation is better than a rapid one. The more gas you demand from the reg the more the reg is cooled and the more heat transfer is required to keep the first stage above freezing. As the water temp falls below about 40-45F, the temperature gradient gets small enough that heat transfer is much less efficient, so the same heat transfer takes more time.

3. Use short additions with the inflator. If you drop to the bottom like a Stuka then punch the power inflator for a long inflate, you cool the reg a lot more than if you made several small gas additions on the way down. Dropping like a rock then arresting the ascent with a long perfectly timed inflate at the bottom looks cool - unless you're in cold water and freeze flow the reg. Then you just look like a dork and you also force your buddy to abort the dive.

4. Similarly, inhaling and inflating at the same time puts a a greater cooling load on the reg - spread it out more and inflate between inhalations to allow the reg more time to transfer heat.

5. Trim boots and hose covers are nice - but they also insulate the metal portions of the reg and hose fittings from the water and reduce heat transfer. In cold water a non cold water first stage needs all the help it can get so pull the hose covers back a bit so the metal fitting is fully exposed. (If you have the really tight hose covers, cut them off and get hose covers you can pull back to rinse under - the really snug ones are corrosion magnets.)

6. Do not let the reg freeflow or allow the second stage to fall out of your mouth. Two things happen when the second stage falls out. First, it suddenly freeflows and the sudden gas flow can cause the first stage to cool enough to freeze an water touching it. On the inside of the ambient chamber, in the extreme, that means the piston or diaphragm can't return to the closed position and a freeze flow results. Second, the internal parts of the second stage are already cold (especially on the all too common craptastic plastic second stages that are very poor at heat transfer to begin with). The saving grace is that they are also more or less dry inside. However when the second stage falls out, some water enters, as the second stage parts are being chilled even further and having ice form under a lever or poppet is a possibility. That can mean the second stage will freeze (followed shortly of course by the first stage). If possible detune the flow vane in the reg so that if it falls out, it won't freeflow.

7. Ideally, if you are going to do a lot of really cold water diving, get a first stage with a sealed ambient chamber (like the Mk 17) and a second stage with either an all metal air barrel with lots of metal on the outside ends of the air barrel (like the Scubapro G250V) or even better a metal cased second stage.

8. The perfect cold water regulator looks like this:

In this case both the first and second stages are sealed from any contact with water, and the regulator has loads of surface area for superb heat transfer. With a double hose reg, about the only thing that will cause a freeze flow is really wet gas coming from the tank itself.