Mailing List Archive Mailing List Archive
Well I've now got the OK to put this posting up onto techdiver. Seems like
with
the Biomarine $5k unit, this one for $3k and the Cochran/Prism unit for $5k,
the
affordable closed circuit rebreather market is finally becoming a reality.
I've got some pictures of the 'Inspiration' rebreather, taken at the UK IANTD
weekend. I'll scan them in over the next 2 days & send them to Eric Lundquist
<ericl@oc*.wa*.ed*> to put up onto his web page
(http://diver.ocean.washington.edu/rebreather.html)
Hassle Eric, not me, if you don't get to see them next week or so (sorry
Eric..!)
*****************************************************************************
Launch of A.P.Valves "Inspiration" Closed Circuit Rebreather
The IANTD annual conference in Swindon, UK saw the launch of a new closed
circuit mixed gas rebreather that is expected to retail for two thousand pounds
(ie approx $3000).
The rebreather has been developed by Dave Thompson, Pheonix Diving Ltd in
conjunction with A.P.Valves over the past 3 years and is planned to be
available
to suitably trained divers by November 1996. A.P.Valves are the British
company well known for their manufacture of the "Buddy" range of buoyancy
compensators.
All training will only be conducted under IANTD guidelines. A sequence of 3
courses, totalling around 10-12 days in total are needed before the unit can be
used for mixed gas decompression diving. The courses are :
IANTD Rebreather Module I - No stop Nitrox rebreather diving
Prerequisite = IANTD Advanced Nitrox Diver.
Course = 3 to 4 days
IANTD Rebreather Module II - Decompression Nitrox rebreather diving
Prerequisite = IANTD Technical Nitrox Diver.
Course = 3 days
IANTD Rebreather Module III - Decompression Trimix rebreather diving
Prerequisite = IANTD Trimix Diver
Course = 4 to 5 days
I would expect that the total cost of all 3 courses would amount to just under
1000 pounds ($1500).
The unit itself comprises a harness and back plate + cover, housing two 3 litre
cylinders and a cylindrical scrubber unit. Wrapping over the shoulders and
extending around the front is a split inhalation/exhalation counterlung. The
rebreather as seen at Swindon had an integrated A.P.Valves 'wings' buoyancy
compensator that I understand is not to be included in the price of the system.
However, any Dive-Rite or OMS wings already owned by the prospective purchaser
will bolt directly onto the rebreather.
The rebreather is a fully closed unit capable of being used with Nitrox or
Trimix as a diluent and has a maximum expected operating depth of around 100
metres. I guess the max depth limit will depend upon things like warmth,
open circuit bailout, acceptable deco time & so on, rather than any function of
the operation of the rebreather itself.
Although the rebreather contains electronics and processing capability
to control the partial pressure of the breathing mix, there is at present no
decompression capability. All decompression must be worked out in advance and
tabulated using the "Proplanner" decompression software or any other software
capable of handing constant ppO2.
Alternatively, for nitrox use a standard constant FO2 nitrox computer can be
used. This is done by setting the nitrox mix on the computer for a ppO2 of 1.3
for the maximum intended depth. At any shallower depth the actual mix in the
counterlung will be more oxygen-rich than the dive computer thinks it is,
giving
an additional factor of safety. The deco using a dive computer in this way may
end up being either longer or shorter than using square profile tables, but it
does give a greater underwater flexibility. Clearly, this option is not
presently available for trimix...no one yet sells a trimix open cicuit dive
computer.
The unit displayed and demonstrated at Swindon held two gas cylinders - one for
oxygen and one for the diluent, either air or Trimix. If advantage is to be
taken of the counter-diffusion benefits of using Nitrox for decompression
following a Trimix dive then it would be a relatively simple matter to manifold
an addition diluent cylinder to enable this gas switch. This facility wasn't
actually on the unit I saw at Swindon, so I'm limiting my description to what I
actually saw rather than what might be done on some future unit.
At present the "Inspiration" rebreather has an automatic injection of oxygen,
controlled by 3 oxygen sensors and a 'voting logic' system. Diluent is
manually
injected by the diver as the counterlung collapses with increasing depth. The
oxygen partial pressure set-point is selected by the diver at either 0.75 or
1.3. It is intended that a set point of 0.75 would be used at the start of the
dive until the diver has reached the bottom. The set-point would then be
switched to 1.3 for the remainder of the dive, until the diver came back up to
3
metres, when it would be switched back to 0.75 to prevent unnecessary injection
& waste of oxygen. A 1 hour dive typically used about 20 bar of both oxygen
and
diluent. Both cylinders can be filled to 232 bar.
Both the inhalation and exhalation hoses pass over the shoulders to the
mouthpiece via water traps that will discharge any water accidentally entering
the hoses into the counterlungs, where it can be vented back out of the system.
The mouthpiece has a simple open-close facility by rotating the body of the
mouthpiece against the gumshield.
The carbon dioxide scrubber stack is mounted between the two cylinders and
holds
sufficient sodium hydroxide ("Sofnolime") for 6 hours of diving. The
accumulated diving hours between scrubber renewal is logged automatically by
the
control unit and a warning is given when the scrubber needs renewing. A
hydrophobic membrane is used to repel any water that manages to get past the
water traps and enters the scrubber unit.
I had a brief opportunity to try the "Inspiration" rebreather in the hotel pool
at the Swindon weekend. My initial impressions were very favourable. The unit
is very comfortable to wear and fits on with conventional adjustable shoulder
straps, a cummerbund waist strap and a chest cross strap Mechanical contents
pressure gauges for both cylinders were located comfortably around the waist
region , alongside the primary partial pressure display unit. The entire
rebreather weighed less than my lightweight steel twin 12 litre cylinders. The
mouthpiece feels less cumbersome than it looks and the buoyancy of the inlet
and
exhaust hoses is counterbalanced by two brass rings. Breathing underwater is
predictably easy, but unlike some other rebreathers I have tried, the breathing
resistance does not vary with diver orientation. I tried lying on my back,
standing inverted and swimming on both sides. The light breathing resistance
remained constant.
Initially, I was too buoyant. Exhaling through my nose to dump some gas
resulted in my having insufficient gas in the counterlung to breath
comfortably.
The addition of two leadshot weightbags to special compartments built into the
unit solved this problem and the rest of the trial experience was a pleasure.
So...when can we all buy one ?? Well the last hurdle to be overcome is to
get
EEC certification for life support systems, which involves assessment by an
independent authority. This is not expected to be a real hurdle. The unit has
to conform in breathing resistance at the intended depth and also has to exceed
certain scrubber breakthrough criterea. On both counts the unit exceeds the
performance of the Drager Atlantis rebreather, which passed both tests easily.
Assuming all goes well then an initial batch of 50 units are to be manufactured
and are expected to be available by November 1996.
At present A.P.Valves are NOT interested in taking deposits or names and
addresses until they have a rebreather to sell. Please don't waste your time
and theirs by hassling them and pleading that you are a special case !! Wait
until November 1996 and THEN contact them and get your name & deposit down. We
all know the bad press that companies like Biomarine & Cis-Lunar are getting
for
not answering mail from prospective or actual customers. I wouldn't like the
same word to be spread around from a responsible UK company like A.P.Valves.
So
don't, I repeat *DON'T* hassle them until November. After all the time we have
been waiting for a sensible and affordable rebreather to come...November isn't
so long to wait, is it ?
Regards, Steve M.
**************************************************************************
* * *
* Dr. S. G. Millard, * E-Mail : ec96@li*.ac*.uk* *
* Senior Lecturer, * *
* Department of Civil Engineering * Tel : 0151 794 5224 (UK) *
* University of Liverpool, * 44 151 794 5224 *
* PO Box 147, * (International) *
* Liverpool L69 3BX, * *
* UK. * Fax : 0151 794 5218 (UK) *
* * 44 151 794 5218 *
* * (International) *
* * *
**************************************************************************
Navigate by Author:
[Previous]
[Next]
[Author Search Index]
Navigate by Subject:
[Previous]
[Next]
[Subject Search Index]
[Send Reply] [Send Message with New Topic]
[Search Selection] [Mailing List Home] [Home]