Freeflowing regs

I was wondering about the mechanics of a freeflowing regulator, and should this happen, how to overcome it.

Does the freeflow happen at the 1st or 2nd stages, or both, simultaneously? Is there any way to tell the difference when it happens?

If it's the primary reg diaphram that is stuck open, can't you switch to your octo and ascend?

I've read that free flows happen more in colder water. Is this true?

If it's your 1st stage, do both your primary and octo free flow? What then? I know there is a way to breathe off a freeflowing reg, but I'd like some insight into how, etc.

This has not happened to me yet, and I get my reg serviced yearly. But just in case......

Thanks in advance,
Lisa

A free flow can be caused by either the 1st, or 2nd stages. The first stage of the regulator takes that 3,000 psi air right out of the tank, and reduces the pressure. I think it is reduced to about 150 psi.

In a balanced regulator the 2nd stage reduces the air pressure to the pressure of the ambient water.

If the 1st stage pressure is too high the 2nd stage can not compensate, and the reg will free flow. This may, or may not cause both your primary & your secondary to free flow. Most secondaries are adjusted to be harder to breath to prevent easy free flows.

If a 2nd stage is adjusted to be too easy to breath then it will easily free flow.

If the primary is free flowing, and not the secondary, I would recommend staying with the primary (if at all possible). It is going to be discharging air no matter what, so you might as well breath off of it. If you switch to a non-free flowing secondary then you are breating air that is above and beyound the air coming out of the primary. This may make a safety difference in the time you have to safely ascend.

fisheyeview:

A free flow can be caused by either the 1st, or 2nd stages. The first stage of the regulator takes that 3,000 psi air right out of the tank, and reduces the pressure. I think it is reduced to about 150 psi.

In a balanced regulator the 2nd stage reduces the air pressure to the pressure of the ambient water.

If the 1st stage pressure is too high the 2nd stage can not compensate, and the reg will free flow. This may, or may not cause both your primary & your secondary to free flow. Most secondaries are adjusted to be harder to breath to prevent easy free flows.

If a 2nd stage is adjusted to be too easy to breath then it will easily free flow.

If the primary is free flowing, and not the secondary, I would recommend staying with the primary (if at all possible). It is going to be discharging air no matter what, so you might as well breath off of it. If you switch to a non-free flowing secondary then you are breating air that is above and beyound the air coming out of the primary. This may make a safety difference in the time you have to safely ascend.

Click to expand...

Yes, and keep in mind that a free-flowing reg will drain a tank in about a minute. And that's only if it's completely full at 3000 psi. To be prepared for a freeflow, you need a close buddy or a redundant air source, such as a pony bottle (not a Spare Air).

Always wondered why they don't put a shut-off valve where the hose goes into the second stage so you can shut it off if it free-flows.

apexs makes a device.......

Apeks Products

M

fisheyeview:

A free flow can be caused by either the 1st, or 2nd stages. The first stage of the regulator takes that 3,000 psi air right out of the tank, and reduces the pressure. I think it is reduced to about 150 psi.

In a balanced regulator the 2nd stage reduces the air pressure to the pressure of the ambient water.

If the 1st stage pressure is too high the 2nd stage can not compensate, and the reg will free flow. This may, or may not cause both your primary & your secondary to free flow. Most secondaries are adjusted to be harder to breath to prevent easy free flows.

If a 2nd stage is adjusted to be too easy to breath then it will easily free flow.

If the primary is free flowing, and not the secondary, I would recommend staying with the primary (if at all possible). It is going to be discharging air no matter what, so you might as well breath off of it. If you switch to a non-free flowing secondary then you are breating air that is above and beyound the air coming out of the primary. This may make a safety difference in the time you have to safely ascend.

Click to expand...

It's a good bit more complicated.
A free flow can be cause by a failure of either the first or second stage OR it may be perfectly normal, modern high performance regs should free flow under certain conditions.

Lets look at failures first. The job of a first stage is to reduce the tank pressure to an intermediate pressure (know as IP) which is in the range of 135 to150 psi. If the first stage starts leaking- not holding the IP at the proper value the pressure in the LP (second stage) hoses will build until something gives. Modern second stages will start to leak or free flow once pressure exceeds the pressure where the second stage parts can deal with the pressure. Balanced second stages will tolerate more excessive IP than non balanced second stages but they will start to leak once the pressure builds to more than they can handle. This is an important safety feature, much better for the second stage to vent gas than to have the hose explode. It is common for slight first stage leaks to only open one or the other second stages due to different setup of the stages or on being balance and the other not.
Second stages can also be responsible for free flows, depending on the severity of the free flow it could be from broken or worn parts or if the free flow is slight, simple adjustment issues.

There are also times when a free flow is normal and lack of them indicates a second stage problem. Modern high performance second stages incorporate a venturi effect to improve their performance. This venturi produces a slight vacuum inside the second stage when air flow exceeds a given point. This vacuum assist the diver by making the reg breath easier, however like most everything else there is a price. The second stage relies on a slight amount of back pressure to be developed in the divers mouth to control the venturi effect. If the reg does not get this back pressure the venturi effect will feed on itself until it has the second stage held wide open and it will continue to violently free flow until sufficient back pressure is created to cancel the vacuum created by the venturi. Most HP regs have adjustments to vary the amount of vacuum created by the venturi. If the venturi on a modern reg is set to max and the purge button is pressed, the reg should free flow violently, grabbing the mouthpiece provides enough back pressure to interrupt the process and stop the free flow.

Breathing off a free flowing reg is a noisy affair but fairly easy to do. You should have been shown how to do it in your OW class. If not, I would suggest you contact an instructor and have them teach you how to perform the procedure. In a real free flow, it's best to stick with the free flowing reg, you are losing gas fast and every bit you can recover from the escaping gas the more you have to work with. In addition the octo will likely breath very badly due to the reduced IP- the first stage can only flow so much.

Airleron:

I've read that free flows happen more in colder water. Is this true?

If it's your 1st stage, do both your primary and octo free flow? What then? I know there is a way to breathe off a freeflowing reg, but I'd like some insight into how, etc.

Click to expand...

In very cold water, ice can form in the 1st stage and cause it to freeze open, this causes a freeflow. Since it's the expansion of air that cools the reg to below freezing, once it starts it's unlikely to stop until you get to warmer water. Other than freezing, regs won't freeflow more in cold water, but freezing is a serious issue for cold water divers. That's why cold water divers prefer sealed 1st stages that don't allow any water to come in contact with the working part of the reg. Cold water is generally anything below 40F, but temps in the low-mid 40s can also be problematic.

There's a high pressure valve in 1st stages, and if it totally fails, the stage will send much higher pressure to the 2nd stages and LP inflator hose than they are capable of handling. This can result in simultaneous freeflow of both primary and octo, and the LP inflator. That's especially daunting at depth, because it results in the immediate uncontrolled inflation of your BC. You have to think fast and disconnect the LP inflator hose, dump air quickly, and hope that you're not already on the surface before you figure it out.

Luckily, that kind of total HP valve failure is very rare. More comon would be a slight leak at the valve seat which sends creeping higher pressure until one of the 2nd stages starts to flow. The really old school divers used a non balanced octo specifically because it would start to freeflow in the presence of this creeping pressure (called IP creep) before a balanced 2nd stage.

You can breathe off of a freeflowing 2nd stage; you can sip the air with one lug of the mouthpiece in your mouth if it's really bad. If it's only a small or moderate freeflow, you can keep the reg in your mouth and block the mouthpiece opening with your tongue. The excess air will simply escape out the exhaust valve. The only problem with this is if it's a really violent freeflow you'll feel the reg trying to push air into your lungs, and you probably want to avoid that. I've had a few freeflows and never had one that was so bad I couldn't keep the reg in my mouth.

BTW, someone posted something about balanced 2nds reducing IP to ambient pressure. That's not entirely accurate in that all 2nd stages do that, and it has nothing to do with balancing. Balanced 2nds simply take some of the pressure from the 1st stage and divert it so that it helps to keep the 2nd stage closed. This allow the use of a much lighter spring in the 2nd stage and theoretically better breathing. In truth there are other issues, and one of the best breathing regs I've ever used is an unbalanced metal case SP 109, about 30 years old.

Garrobo:

Always wondered why they don't put a shut-off valve where the hose goes into the second stage so you can shut it off if it free-flows.

Click to expand...

One reason might be that if the FF is being caused by the 1st stage, then shutting off the primary will simply move the freeflow to the alternate.

The simple answer is learn to breath off a freeflowing reg.

Garrobo:

Always wondered why they don't put a shut-off valve where the hose goes into the second stage so you can shut it off if it free-flows.

Click to expand...

The problem with a shutoff is that when you have a first stage freeflow the IP (intermediate pressure) which should be about 150psi over ambient pressure will just keep climbing until it finds an outlet. This normally happens when the IP exceeds the spring strength on the second stage and the second stage freeflows. If you put a shutoff on the primary hose then the backup will freeflow, if you add a shutoff to the backup then you will either get an inflator freeflow or a burst hose.

From our (my buddy and mine) past experiences, as I'm still new and researching if anything is inaccurate please correct me.

Airleron:

I was wondering about the mechanics of a freeflowing regulator, and should this happen, how to overcome it. Does the freeflow happen at the 1st or 2nd stages, or both, simultaneously? Is there any way to tell the difference when it happens?

Click to expand...

Both can free flow. We got both stages flowing during our last 10 dives. The mechanic is that the moisture inside the stage forms ice crystals and the mechanical parts get stuck. The valve cannot close so the air goes out.
As of my understanding if it's only the second stage flowing and you start breathing octo it should not flow. But the flowing stage may cause the 1st stage freefow.

We had a second stage flow when we wend deeper 70' the second stage started leaking. After closing it with thumb it stopped. Then again started. After moving up 20 feed it has not locked up anymore. Later we discovered that it was too easy even on the hardest user setting and had it adjusted. We still have to see if it does that again.

If it's the primary reg diaphram that is stuck open, can't you switch to your octo and ascend?

Click to expand...

You can switch to it but it will not help you. you octo will start flowing as well.

I've read that free flows happen more in colder water. Is this true?

Click to expand...

Yes the coder the water the more chances you will get it. The gas expending cools down the stage and the temperature gets below water freezing point. In many cases when you dive cold especially low 30 as of my understanding the 1 st stage will be colder than 0c but if you do not get moisture inside nothing bad happens. If you get any moisture inside you get the lock.

If it's your 1st stage, do both your primary and octo free flow? What then? I know there is a way to breathe off a free flowing reg, but I'd like some insight into how, etc.

Click to expand...

If IP raises to some point the valve of the second stage will open and the air will start escaping. The stage with easiest spring will open first. Generally the octos have harder settings so they will not start flowing first. but if you breath out of it it will start flowing.

Yes you can breath from the reg. I posted a topic in incidents about our free flow. It was our first time and it was weird though we managed it well mostly due to the fact that my buddy has been practicing breathing from free flowing reg before. He was breathing from it for a minute until we put our brains back in hand and switched him to my reg. It was on 85 feet in 38F water. You just need to let the excess air let out bu opening your lips if you hold it with your teeth. Or if you have one hand free just take it out of the mouth or put just half way through and breath. You have have some water getting in but moving your tungue up you can prevent it from getting inside. If you do not do that you can have air get into your stomach and it's really uncomfortable.

One scenario that we were working after was in the case of flowing - switch to the redundant source then shutdown the valve self or buddy, wait for a couple of mins then open and see if it's still flowing. Then depending on the situation surface or continue the dive.

One SB member also suggested another scenario such as modulating the breathing with the valve to reduce the air lose.

This has not happened to me yet, and I get my reg serviced yearly. But just in case......
Thanks in advance,
Lisa

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This has nothing to do with servicing your regs annually. It's about cold temperature and water in the reg. Though malfunctioning reg will more likely have different problems.