Propane bottle volume

Propane bottle volume

Post by Steve » Mon, 30 Apr 2012 00:25:45


I want to use some USED EMPTY propane bottles underwater for assisting in
airlifting, and keeping some weight off objects on the bottom.  Some will be
closed valved, and some will be drilled on the top to allow for expanding
air to just exhaust.  None will be used with valve open.

I can calculate by my math, and come pretty close, but was wondering if
anyone knew the EXACT volume of an empty 20# propane tank.  Less the tare
weight, that would be the lifting capability.

These will be used to stabilize some gold equipment, and keep the amount of
weight down at the points where it rests on the seabed.

Thanks

Steve

 
 
 

Propane bottle volume

Post by Geof » Mon, 30 Apr 2012 11:17:07



Quote:
>I want to use some USED EMPTY propane bottles underwater for assisting in
>airlifting, and keeping some weight off objects on the bottom.  Some will be
>closed valved, and some will be drilled on the top to allow for expanding
>air to just exhaust.  None will be used with valve open.

>I can calculate by my math, and come pretty close, but was wondering if
>anyone knew the EXACT volume of an empty 20# propane tank.  Less the tare
>weight, that would be the lifting capability.

>These will be used to stabilize some gold equipment, and keep the amount of
>weight down at the points where it rests on the seabed.

>Thanks

>Steve

a 20# bottle is 80% full in N.A. by law. If full it would contain 25#
of propane, at 4.2 lbs per gallon at 60F, that comes to 5.95 gallons
which is 1375 cubic inches.

 
 
 

Propane bottle volume

Post by Steve » Mon, 30 Apr 2012 12:21:04


Quote:
> a 20# bottle is 80% full in N.A. by law. If full it would contain 25#
> of propane, at 4.2 lbs per gallon at 60F, that comes to 5.95 gallons
> which is 1375 cubic inches.

So, at 62 # per cubic foot, that would have 49.33# of buoyancy less tare
weight of the tank.

I'm trying to figure out how much a tank of plain air, ambient pressure,
valve closed, would provide in lifting ability.

Subtracting 12.something for tare weight, that leaves about 37# lift.  I had
figured right around 35#, so we're close together.  And that's all I need is
to be pretty close.

Steve

 
 
 

Propane bottle volume

Post by el stroko guap » Mon, 30 Apr 2012 23:28:09

A 47.6 pound rated propane bottle was filled with 20 pounds of propane
back in the oldy days but is now filled by most vendors with 17 pounds
of propane. I don't think propane bottles are standard volume.

That said, I doubt that there are very many manufacturers and any
variance would be minimized by using bottles from the same general time
period from the same manufacturer. Like SCUBA tanks, they're stamped,
but on the top cage.

Then, you'll have to do the Archimedes thing: fill a barrel to the brim
with water, submerge the tank, and use your wife's measuring cup to
replace the displaced water. Every pint is a pound of buoyancy, minus
the tare which I'll guess at about 18.5 pounds.

esg


Quote:


>> I want to use some USED EMPTY propane bottles underwater for assisting in
>> airlifting, and keeping some weight off objects on the bottom.  Some will be
>> closed valved, and some will be drilled on the top to allow for expanding
>> air to just exhaust.  None will be used with valve open.

>> I can calculate by my math, and come pretty close, but was wondering if
>> anyone knew the EXACT volume of an empty 20# propane tank.  Less the tare
>> weight, that would be the lifting capability.

>> These will be used to stabilize some gold equipment, and keep the amount of
>> weight down at the points where it rests on the seabed.

>> Thanks

>> Steve

> a 20# bottle is 80% full in N.A. by law. If full it would contain 25#
> of propane, at 4.2 lbs per gallon at 60F, that comes to 5.95 gallons
> which is 1375 cubic inches.

 
 
 

Propane bottle volume

Post by Steve » Tue, 01 May 2012 00:15:13



Quote:
>A 47.6 pound rated propane bottle was filled with 20 pounds of propane back
>in the oldy days but is now filled by most vendors with 17 pounds of
>propane. I don't think propane bottles are standard volume.

> That said, I doubt that there are very many manufacturers and any variance
> would be minimized by using bottles from the same general time period from
> the same manufacturer. Like SCUBA tanks, they're stamped, but on the top
> cage.

> Then, you'll have to do the Archimedes thing: fill a barrel to the brim
> with water, submerge the tank, and use your wife's measuring cup to
> replace the displaced water. Every pint is a pound of buoyancy, minus the
> tare which I'll guess at about 18.5 pounds.

> esg

The thought of using these is that they will be readily available up there,
so CHEAP!  And they will hold no pressure.  They can be left open for a few
weeks, then drilled, and a fill stem/valve inserted, or welded shut.  Bad
valves can be epoxied shut.  They are just to hold air under no pressure for
buoyancy purposes underwater to help the diver take some of the weight off
the hoses and device.  Enough of them would make an airlift, but different
than airlift, these could not expand as they rise.  If one wanted to use an
actual airlift up there, they could get one.

Tares are ring stamped, and different with manufacturer.  The site I went to
had a constant 47.6 for inner volume on different manufacturers for the 20#
tank.  I'm satisfied with the 35# calculation number so far.

Steve

 
 
 

Propane bottle volume

Post by Fraser Johnsto » Tue, 01 May 2012 16:32:29


Quote:
> I want to use some USED EMPTY propane bottles underwater for assisting in
> airlifting, and keeping some weight off objects on the bottom.  Some will be
> closed valved, and some will be drilled on the top to allow for expanding
> air to just exhaust.  None will be used with valve open.

> I can calculate by my math, and come pretty close, but was wondering if
> anyone knew the EXACT volume of an empty 20# propane tank.  Less the tare
> weight, that would be the lifting capability.

> These will be used to stabilize some gold equipment, and keep the amount of
> weight down at the points where it rests on the seabed.

> Thanks

> Steve

Why not just use lift bags?

--

Fraser

 
 
 

Propane bottle volume

Post by Steve » Tue, 01 May 2012 22:27:07


Quote:

> Why not just use lift bags?

> --

> Fraser

Lack of experience by the users.  A lot of uncertified divers up there.

The potential of blowups.  Inexperienced divers are not familiar with the
rapid expansion of air between 33' and surface.  The standard volumes could
not blow up.

Wear and tear.  There probably would not be a repair facility, and if there
was, it would be expensive.

Metal will be much more durable bouncing around and rubbing on metal,
barnacles, cables, and such.

The tanks could just be left sealed, eliminating any need to figure out just
how much to use, then having that volume increase on rising, and shoot the
whole thing to the surface.

Inexperienced divers would have to use some sort of inflator for air bags,
either a hose, or taking their regulator out of their mouth.  Both have
their hazards.

Air bags have many variables, the most being that one larger than needed for
the job could be used, and a blowup happen.  The metal ones would have a
fairly constant lifting capability.

Steve

 
 
 

Propane bottle volume

Post by -hh » Wed, 02 May 2012 04:51:06



Quote:
> A 47.6 pound rated propane bottle was filled with 20 pounds of propane
> back in the oldy days but is now filled by most vendors with 17 pounds
> of propane. I don't think propane bottles are standard volume.

> That said, I doubt that there are very many manufacturers and any
> variance would be minimized by using bottles from the same general time
> period from the same manufacturer. Like SCUBA tanks, they're stamped,
> but on the top cage.

> Then, you'll have to do the Archimedes thing: fill a barrel to the brim
> with water, submerge the tank, and use your wife's measuring cup to
> replace the displaced water. Every pint is a pound of buoyancy, minus
> the tare which I'll guess at about 18.5 pounds.

> esg

One could also use a surrogate, such as rice or sand.  A different
kind of hassle - no floating issue (when submerging to measure volume)
true, but a little harder to assure  no void under the object.

-hh

- Show quoted text -

Quote:



> >> I want to use some USED EMPTY propane bottles underwater for assisting in
> >> airlifting, and keeping some weight off objects on the bottom. ?Some will be
> >> closed valved, and some will be drilled on the top to allow for expanding
> >> air to just exhaust. ?None will be used with valve open.

> >> I can calculate by my math, and come pretty close, but was wondering if
> >> anyone knew the EXACT volume of an empty 20# propane tank. ?Less the tare
> >> weight, that would be the lifting capability.

> >> These will be used to stabilize some gold equipment, and keep the amount of
> >> weight down at the points where it rests on the seabed.

> >> Thanks

> >> Steve

> > a 20# bottle is 80% full in N.A. by law. If full it would contain 25#
> > of propane, at 4.2 lbs per gallon at 60F, that comes to 5.95 gallons
> > which is 1375 cubic inches.

 
 
 

Propane bottle volume

Post by Geof » Wed, 02 May 2012 06:48:29

On Sun, 29 Apr 2012 10:28:09 -0400, el stroko guapo

Quote:

>Then, you'll have to do the Archimedes thing: fill a barrel to the brim
>with water, submerge the tank, and use your wife's measuring cup to
>replace the displaced water. Every pint is a pound of buoyancy, minus
>the tare which I'll guess at about 18.5 pounds.

If you are going to all that trouble to submerge the tank, just tie
steel or lead weights to it until it's submerged, the weight required
to submerge it is all you need to know.
 
 
 

Propane bottle volume

Post by el stroko guap » Thu, 03 May 2012 11:49:27


Quote:

> Tares are ring stamped, and different with manufacturer.  The site I went to
> had a constant 47.6 for inner volume on different manufacturers for the 20#
> tank.  I'm satisfied with the 35# calculation number so far.

> Steve

But the 47.6 is not volume, it's the weight of the liquid propane.

If you don't need to be too exact, just take it under water and measure
the buoyancy with a fish scale.

esg

 
 
 

Propane bottle volume

Post by el stroko guap » Thu, 03 May 2012 11:53:31


Quote:
> On Sun, 29 Apr 2012 10:28:09 -0400, el stroko guapo

>> Then, you'll have to do the Archimedes thing: fill a barrel to the brim
>> with water, submerge the tank, and use your wife's measuring cup to
>> replace the displaced water. Every pint is a pound of buoyancy, minus
>> the tare which I'll guess at about 18.5 pounds.

> If you are going to all that trouble to submerge the tank, just tie
> steel or lead weights to it until it's submerged, the weight required
> to submerge it is all you need to know.

But the steel weights are more buoyant than the lead weights, and to be
exact you have to compensate for the buoyancy of the weights used.

Easier to let the wife do it.

esg

 
 
 

Propane bottle volume

Post by Al Well » Fri, 04 May 2012 05:55:49

Quote:

> But the steel weights are more buoyant than the lead weights, and to be
> exact you have to compensate for the buoyancy of the weights used.

So you're saying that my aluminum travel weights won't work?
 
 
 

Propane bottle volume

Post by bullshar » Fri, 04 May 2012 22:10:09

Quote:

> I want to use some USED EMPTY propane bottles underwater for assisting in
> These will be used to stabilize some gold equipment, and keep the amount of
> weight down at the points where it rests on the seabed.

You already got the data at: http://SportToday.org/

1323 cu3 (~5.727 gallons), 47.7 lbs freshwater capacity

1323/1728 * 64 = 49 lbs sal***er displaced

less 18.5 tare gives 30.5 lbs of lift.

There is no reason to exhaust expanding air. Just shut the valves at sea level and use as-is. At the depths you mentioned earlier (2 ata or less) they should be fine with no pressurization. That way there will be no runaway or loss of lift.

If they are used in multiples they need to be kept far apart so no one gets pinched

 
 
 

Propane bottle volume

Post by Steve » Fri, 04 May 2012 23:48:04


Quote:

>> I want to use some USED EMPTY propane bottles underwater for assisting in
>> These will be used to stabilize some gold equipment, and keep the amount
>> of
>> weight down at the points where it rests on the seabed.

> You already got the data at:
> http://SportToday.org/

> 1323 cu3 (~5.727 gallons), 47.7 lbs freshwater capacity

> 1323/1728 * 64 = 49 lbs sal***er displaced

> less 18.5 tare gives 30.5 lbs of lift.

> There is no reason to exhaust expanding air. Just shut the valves at sea
> level and use as-is. At the depths you mentioned earlier (2 ata or less)
> they should be fine with no pressurization. That way there will be no
> runaway or loss of lift.

> If they are used in multiples they need to be kept far apart so no one
> gets pinched

I had thought of drilling a 2" hole in the valve end.  Or just torch a hole
and take valve and all off.  That way, with them used upside down, a diver
could put air into it if he wanted just partial inflation, and could empty
one if he wanted to exhaust air.  And then there's always the exhausting of
expanding air as it rises, but since the enclosure can't get bigger, as an
airbag sometime can, that would not be an issue.

Steve

 
 
 

Propane bottle volume

Post by Grumman-58 » Sun, 06 May 2012 01:57:45



Quote:
> I had thought of drilling a 2" hole in the valve end.  Or just torch a
> hole and take valve and all off.  That way, with them used upside
> down, a diver could put air into it if he wanted just partial
> inflation, and could empty one if he wanted to exhaust air.  And then
> there's always the exhausting of expanding air as it rises, but since
> the enclosure can't get bigger, as an airbag sometime can, that would
> not be an issue.

When new and in good shape, they're rated for 300 psi... Normally they
never see more than 175 psi even if you leave them out in the sun, IIRC...
Even 150 psi would be over 330 ft... Of course, the difference is that they
are rated for INTERNAL pressure, not EXTERNAL pressure... For what you're
talking about though, it's unlikely to be an issue, but if you are ultra
paranoid, put 50 psi in them and you can go to around 112 ft and not have
an external pressure greater than the internal pressure...