Free Flowing Reg-How much time?

[capt. dave]

There have been many posts here concerning this topic, and as a new diver, I have read many stories (Life Lessons to name a few) about how divers handle this/these situations. Everyone here has given me a lot to think about, and at times I will close my eyes and place myself into these situations to determine what may work and what may not work (there is a psychological term for this but I won't get that deep). Irregardless of how divers handle the situation (breath through the free flowing reg., share air etc.) one thing I have not seen or read is the amount of time, on the average, depending on the tank size etc. it takes for a full tank to empty in a free flowing situation. Knowing the amount of time it takes to empty a tank in this situation, where your buddy is in reference to you, your depth and your skill level would certainly factor into this situation as far as what you would do.

So, like the tootsie roll pop, my question is how long does it take to get to the end of the air? And just for giggles, knowing how long before your empty, would you seek out your buddy or head for the surface (knowing you have adequate air to do so

 

[GrumpyOldGuy]

I think the amount of time would be grossly different for a 1st stage (frozen?) free flowing at essentially tank pressure and 2nd stage free flowing at intermediate pressure. Add to this the amount of air in the tank and size. Personally, I would not waste time figuring this out. Either I am diving with a trusted buddy close by or I have at least a bailout bottle. I should be able to get to one or the other in 10 seconds. Once I have good air, I can do a reasonable ascent.

 

[don Francisco]

When you have five bucks or so to waste, take a full tank outside, open the valve (away from your face) and time how long it takes to empty. With a free flowing reg on it'll take longer because even a free flowing reg imposes some restriction to the airflow (varies reg to reg).

So how much time? It'll vary obviously according to how much air you started with, and with other conditions, but if you did the experiment you'll see it's somewhere in the range of a minute giving you enough time to execute a backup plan, but not much time to waste thinking about it.

 

[TSandM]

Somebody -- I think it may have been Rick Murchison -- did the experiment and posted the results. HP ports take a long time to empty a tank. Freeflows, or LP port leaks, empty a tank in just over a minute.

 

[PhilEllis]

The quickest, and likely the most threatening to the successful completion of the dive, would be a complete failure of the soft HP seat. This results in cylinder pressure being delivered to the second stages. In 2002, one of our quite experienced instructors had a brand new Apeks TX-100 (first dive after testing and setup) fail in this mode about two minutes after ascent to 115 feet. Not only did the cylinder empty (HP120) in about 1 1/2 minutes, but the sheer volume of air coming from the second stages made it very difficult to manage underwater, even with a dive buddy right next to him. Both reported that the volume of air, the column of bubbles, and the general confusion, resulted in a tense situation.

After this event, we permanently changed the amount of cycling we place on a new regulator during post-sale setup, and after any rebuilds. This change has allowed us to catch probably 20 new seat failures in the past 6 years, on a variety of regulator brands.

Phil Ellis
www.divesports.com

 

[SkipperJohn]

I would think that under water and at depth the flow would slow down a bit due to pressure and water resistance.

 

[diversteve]

This may give you some idea: Scuba Diving Videos Cutting a Divers Hose Scuba Videos

 

[rstofer]

There's a video re: cutting of high and low pressure hoses here: Scuba Diving Videos Cutting a Divers Hose Scuba Videos

Richard

 

[ianr33]

This post The Deco Stop has all the information.

Worst case a full Al 80 can empty in a little over a minute.

 

[don Francisco]

I would think that under water and at depth the flow would slow down a bit due to pressure and water resistance.

The difference of a few atmospheres of ambient pressure is negligable vs the 50 or so atmospheres of a full tank. The largest meaningful variables are the capacity of the tank, and the percentage of remaining air at the start.

It should be noted that the rate of flow will decrease on a curve with dropping tank pressure, so a draining a half tank will take more than half the time that a full tank takes.