How fast do you lose a tank of air after blowing gauges off

From a previous thread of mine re OOA situations I recounted my instructor
losing his gauges at depth which we treated as an OOA situation. Many people
pointed out that while this is a high pressure situation it is low flow so
not really out of air. However I am sure I remember the hose stopping
flowing well before we hit the 3m SS but it was 30 odd years and numerous
bottles of home brew ago . Anybody got the actual figures on how quickly a
88 aluminium would drain after losing the gauges, is it dependent on depth
and/or how the gauges came off

dechucka wrote:
> From a previous thread of mine re OOA situations I recounted my instructor
> losing his gauges at depth which we treated as an OOA situation. Many people
> pointed out that while this is a high pressure situation it is low flow so
> not really out of air. However I am sure I remember the hose stopping
> flowing well before we hit the 3m SS but it was 30 odd years and numerous
> bottles of home brew ago . Anybody got the actual figures on how quickly a
> 88 aluminium would drain after losing the gauges, is it dependent on depth
> and/or how the gauges came off
>
>
>
If ya read the thread, the numbers are there from, as I remember, Al
Wells and Scott.

On the high pressure side, there is no need for volume so both the first
stage and hp hose have pinhole passages. Regardless of where the failure
is, the air escapes at high pressure but low flow. Did Al say 22 minutes
to empty a full tank? It would be about the same whether the Bourdon
tube burst or the hose burst.

On the low pressure side, the regulator is built to flow a large volume,
and the tank will drain considerably faster than it will in the case of
a hp failure. A second stage free flow may occur with the demand valve
wide open or less than wide open. With the valve wide open, the tank
would drain about as fast as a ruptured lp hose or loss of the hose from
the first stage. 8 - 10 minutes to drain a full tank is my guess, but
someone will correct me.

O-ring failure (extrusion of a large chunk of the o-ring) will drain the
tank about as quickly as a lp failure because the gap between the 1st
stage and the tank valve is still pretty small.

Scott gave burst disk numbers which are a pretty fast drain rate,
because that's what the burst disk is designed to do - dump pressure fast.

None of these are depth dependent until the tank gets down to the
ambient pressure, i.e. about 60# at about 100', then flow will stop.

esg

El Stroko Guapo wrote:
> dechucka wrote:
>
>> From a previous thread of mine re OOA situations I recounted my
>> instructor losing his gauges at depth which we treated as an OOA
>> situation. Many people pointed out that while this is a high pressure
>> situation it is low flow so not really out of air. However I am sure I
>> remember the hose stopping flowing well before we hit the 3m SS but
>> it was 30 odd years and numerous bottles of home brew ago . Anybody
>> got the actual figures on how quickly a 88 aluminium would drain after
>> losing the gauges, is it dependent on depth and/or how the gauges came
>> off
>>
>>
> If ya read the thread, the numbers are there from, as I remember, Al
> Wells and Scott.
>
> On the high pressure side, there is no need for volume so both the first
> stage and hp hose have pinhole passages. Regardless of where the failure
> is, the air escapes at high pressure but low flow. Did Al say 22 minutes
> to empty a full tank? It would be about the same whether the Bourdon
> tube burst or the hose burst.
>
> On the low pressure side, the regulator is built to flow a large volume,
> and the tank will drain considerably faster than it will in the case of
> a hp failure. A second stage free flow may occur with the demand valve
> wide open or less than wide open. With the valve wide open, the tank
> would drain about as fast as a ruptured lp hose or loss of the hose from
> the first stage. 8 - 10 minutes to drain a full tank is my guess, but
> someone will correct me.
>
> O-ring failure (extrusion of a large chunk of the o-ring) will drain the
> tank about as quickly as a lp failure because the gap between the 1st
> stage and the tank valve is still pretty small.
>
> Scott gave burst disk numbers which are a pretty fast drain rate,
> because that's what the burst disk is designed to do - dump pressure fast.
>
> None of these are depth dependent until the tank gets down to the
> ambient pressure, i.e. about 60# at about 100', then flow will stop.
>
> esg
>
>
I am going to agree with Mike on this one. Here is Al's link.
http://tinyurl.com/3e2wr9

If your SPG fails (as in lets gas escape), then worst case scenario is
the same as a HP hose failure. About 22 minutes at any depth with a
full Al80.

"nitespark" <nitespark@cox.net> wrote in message
news:nj_Aj.21364$yk5.15384@newsfe18.lga...
> El Stroko Guapo wrote:
>> dechucka wrote:
>>
>>> From a previous thread of mine re OOA situations I recounted my
>>> instructor losing his gauges at depth which we treated as an OOA
>>> situation. Many people pointed out that while this is a high pressure
>>> situation it is low flow so not really out of air. However I am sure I
>>> remember the hose stopping flowing well before we hit the 3m SS but it
>>> was 30 odd years and numerous bottles of home brew ago . Anybody got the
>>> actual figures on how quickly a 88 aluminium would drain after losing
>>> the gauges, is it dependent on depth and/or how the gauges came off
>>>
>>>
>> If ya read the thread, the numbers are there from, as I remember, Al
>> Wells and Scott.
>>
>> On the high pressure side, there is no need for volume so both the first
>> stage and hp hose have pinhole passages. Regardless of where the failure
>> is, the air escapes at high pressure but low flow. Did Al say 22 minutes
>> to empty a full tank? It would be about the same whether the Bourdon tube
>> burst or the hose burst.
>>
>> On the low pressure side, the regulator is built to flow a large volume,
>> and the tank will drain considerably faster than it will in the case of a
>> hp failure. A second stage free flow may occur with the demand valve wide
>> open or less than wide open. With the valve wide open, the tank would
>> drain about as fast as a ruptured lp hose or loss of the hose from the
>> first stage. 8 - 10 minutes to drain a full tank is my guess, but someone
>> will correct me.
>>
>> O-ring failure (extrusion of a large chunk of the o-ring) will drain the
>> tank about as quickly as a lp failure because the gap between the 1st
>> stage and the tank valve is still pretty small.
>>
>> Scott gave burst disk numbers which are a pretty fast drain rate, because
>> that's what the burst disk is designed to do - dump pressure fast.
>>
>> None of these are depth dependent until the tank gets down to the ambient
>> pressure, i.e. about 60# at about 100', then flow will stop.
>>
>> esg
>>
>>
> I am going to agree with Mike on this one. Here is Al's link.
> http://tinyurl.com/3e2wr9
>
> If your SPG fails (as in lets gas escape), then worst case scenario is the
> same as a HP hose failure. About 22 minutes at any depth with a full
> Al80.

Thanks for the link must of missed that post. I will have to go back to my
log book to see exactly what happened. Probably find we were only at 6m it
was a free flow and he didn't use my air and I have embellished the story
over the years

On Sun, 09 Mar 2008 19:22:59 -0400, nitespark <nitespark@cox.net>
wrote:

>I am going to agree with Mike on this one. Here is Al's link.
>http://tinyurl.com/3e2wr9
>
>If your SPG fails (as in lets gas escape), then worst case scenario is
>the same as a HP hose failure. About 22 minutes at any depth with a
>full Al80.

22 minutes? HP hose failure? I don't think so, Tim. That looks like a
typo to me. How about 2 minutes? Why does he choose to use minutes
there instead of seconds as in all the other scenarios?

How can a free flowing HPR drain a system faster than a "failed" HP
hose? Are we talking full end cut off or just a minor cut? This would
be more informative if all the units were seconds and all the values
specified instead of "same within..." otherwise these estimates are
totally useless. I suppose the uselessness of these data support the
conclusion that any equipment failure should lead to an OOA abort.

Quote:
I completed the test on the surface (0 feet) with 4 aluminum 80’s and
a Zeagle D50 regulator.

Here are the results

1. Failed Burst Disk = 72 seconds
2. Failed HP Hose = 22 minutes
3. Failed LP Hose = 83 seconds
4. Free Flow High Performance Regulator = 255 seconds

I then repeated the test at 4 atm’s / 99ft

1. Failed Burst Disk = Same within a second or 2
2. Failed HP Hose = Same within a minute
3. Failed LP Hose = Same within a second or 2
4. Free Flow High Performance Regulator = 155 seconds

I then repeated the test at 8 atm’s / 231ft

1. Failed Burst Disk = Same within a second or 2
2. Failed HP Hose = did not complete due to time restraints but would
assume it would be with a minute difference
3. Failed LP Hose = Same within a second or 2
4. Free Flow High Performance Regulator = 91 seconds

On Mon, 10 Mar 2008 09:21:16 +1100, dechucka wrote:

> From a previous thread of mine re OOA situations I recounted my
> instructor losing his gauges at depth which we treated as an OOA
> situation. Many people pointed out that while this is a high pressure
> situation it is low flow so not really out of air. However I am sure I
> remember the hose stopping flowing well before we hit the 3m SS but it
> was 30 odd years and numerous bottles of home brew ago . Anybody got the
> actual figures on how quickly a 88 aluminium would drain after losing
> the gauges, is it dependent on depth and/or how the gauges came off

For the depths that we dive, it is quite unlikely that we would notice any
difference in the time that it took to empty a tank with a blown HP hose
or gauge...

Although it might take a bit of time for a full tank to empty, you need to
look at it in the worst case of when you are already down to 500 psi or so
and getting ready to ascend... If you assume 22 minutes for a full 3000
psi AL80 and a linear flow rate (bad assumption, I suspect), you are
losing 136 psi per minute which gives you less than 4 minutes before you
are truly out of air... If you start up immediately, you'll probably be
OK, but if you try to spend some time trying to fix the problem (and you
fail), you might be out of air by the time you make it to the surface...

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On Sun, 09 Mar 2008 18:38:50 -0700, Geoff wrote:
> 22 minutes? HP hose failure? I don't think so, Tim. That looks like a
> typo to me. How about 2 minutes?

I dunno about the actual numbers, but I'm quite certain that an HP hose
failure (as in full cut, or just leaving the hose off the 1st stage)
will take closer to 22 minutes than 2 minutes to empty an AL80.

The 1st stage has a restriction in the HP port (look inside the port) to
limit the flow through the port.

--
Art Greenberg
artg at eclipse dot net

On Sun, 09 Mar 2008 18:57:45 -0400, Dan Bracuk wrote:

> I don't think it's dependant on depth. I think it's a function of how
> much air is there to start with and how wide open the valve is.

Then try it at 6735 ft and see how quickly it stops bubbling...
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On Sun, 09 Mar 2008 18:38:50 -0700, Geoff wrote:

> How can a free flowing HPR drain a system faster than a "failed" HP hose?
> Are we talking full end cut off or just a minor cut? This would be more
> informative if all the units were seconds and all the values specified
> instead of "same within..." otherwise these estimates are totally useless.
> I suppose the uselessness of these data support the conclusion that any
> equipment failure should lead to an OOA abort.

The HP hoses tend to have rather small orifices in the fittings on the
ends, unlike the LP hoses... I believe that many of the regulators also
have small diameter orifices for the same reason...

Assuming that it takes 22 minutes to empty an AL80 through a burst HP
hose, one could probably get away with making a cheap set of doubles by
hooking a short HP hose between two 1st stages... You would still want a
2nd stage on each 1st stage, but for shallower depths, you could probably
get away with not having to switch 2nd stages periodically... One of these
days, I'm going to have to give that a try...

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On Sun, 09 Mar 2008 22:56:30 -0400, Dan Bracuk wrote:

> If that's above sea level, maybe. If it's below, I'll take your word for
> it.
>
> Maybe.

Nope, not above sea level, I'm talking about depth... Run the numbers and
calculate the pressure at that depth and you'll see what I'm talking about...

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