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Hi!

Here is some info about high pressure bottles. The information is a short
transcript from a phonecall to Onno Verberne at Raufoss A/S.

The current bottles in production, or about to enter production, are
bottles in 1l 700bar, 2l (1.8l) 700 bar, 20l 250bar and 200l 250(?)bar.

All bottles are made with the same technology, an inner liner (a sort of
gasket)
and on this "bottle" there is spun a fiber. This can be compared to
construction
of modern grp (glass fiber reinforced plastic) hulls in small boats. There is
also possible to change the fiber to get other caracteristica for the bottle.
I gess this is basicly higher pressure.

Heat buildup during normal filling, does not harm the bottle. If the bottle
reach abnormal temperatures (>120 degrees Celsius, can be extended) the resin
can be destroyed but not the fiber. The bottle should still be resonable
safe.

A 20l bottle is expected to have a weight of 12kg, but they have reason to
belive the actual production weight are 10kg. The bottle is *not* for diving
but "diving is a very interesting market".

Safty with this bottles is exelent, with a guaranted burst pressure 3x rated
pressure. For the 20l it is 750bar guaranted but actual burstpressure is
closer
to 800bar. The 1l 700bar bottle burst at about 2.3-2.4kbar. A question about
how the bottle takes a free fall onto a sharp point was answared "exelent,
but
if the issue is of great consern we can try it". Further it was stated that
the
bottle should be stronger in this respect than a steelbottle.

The pricetag is about 1.5-2x higher than a steel bottle.

I discussed the possibility of using oxygen in this bottles and I was told
that
there is possible to use different liners for different gasses. For oxygen
they
use steel liners (?), but other options may give lighter bottles. That is 
plastic liners, but there is some consern about the bottle leaking gas. For a

diver filling the bottle immediate before a dive with normal air this is
not of great consern.

Today the 20l is made with an aluminium liner.

The technology are a defence product that is been comersialized from the
production of rocket motors.

Is this an interesting consept for divers? I think lighter bottles is of no
use
with the current pressure of 200-300bar, as a diver must add more artificial
weight. For someone doing cavediving it may be interesting as he may carry
his 
bottle inside long tunnels. If the pressure is increased there is a point
where
the bottle no longer have serious lift and you do not need to add extra
weight.

After the conversation I have the impression the firm will be very
interesting
in contact with person(s) with ideas of how to use this product. One idea is
to
reduce the high saftyfactor (my idea) to increase the working pressure, for
the
1.8l bottle this can be set to approx 1.2kbar, to contradict the lift from
todays large bottles. If I do a gross oversimplification this should
approximate
700bar of ideal gas, or 6.3l at 200bar. There seems to be possible to further
increase the pressure to get even more air but the cost will increase. That
is
a change to carbon fibre.

The simplest interface between such a bottle and scuba equipment is with the
use of a zero-stage to lower the pressure to 100-200 bar before it enters the
scuba equipment.

One creasy idea, what about an underwater scooter with the 200l bottle? Or
what
about a stage bottle to be used in emergency to fill youre own bottles from,
but
how shall you connect underwater? 

John

I do not work for Raufoss.

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