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Hi Mario
I have not seen techdiver email in months even though I believe that I am
subscribed. Have you been getting techdiver email lately? If so what is
the address of the list server so that I can resubscribe. Thanks Mario.
Now on to the rebreathers.
>
>
>I saw your mail to the techdiver list (BMD bargains ?, 16 May ). I have never
>heard about the BMD rebreather nor the Seapack 1000. Do you know where I can
>get some information about them ?
For information on the BMD contact Jack Parry at the phone number I attached
to the email. Jack Parry is a sales person who has a pretty agressive
pitch. You can also contact BMD directly at
BMD Enterprises Ltd.
Phone: 604-681-9565
Fax: 604-683-3826
For information on the Seapack 1000 contact
Dick King
Bio-Marine Instruments
131 Wallace Ave, Suit 3
Downingtown P.A.
USA
19335
Phone: 610-873-7200
Fax: 610-873-1712
You might also want to look at the following URL if you have a WWW browser.
http://diver.ocean.washington.edu/rebreather.htm
>I work for the Swedish Defence Research
>Establishment, Naval medicine division and one of our fields is breathing
>equipment. I have developed a metabolic breathing simulator with
>possibilities to fully simulate human breathing. Oxygen consumption and
>carbon dioxide production can be varied as well as the breating pattern. With
>the simulator we can simulate a diver at depth at different workloads and the
>breathing equipment can be tested far beyond the limits of test divers. For
>the moment I am testing rebreathers for mine clearence divers. This means
>that I am very interested in rebreathers and I try to keep as updated as
>possible in this field. It is both of private interest as well as
>professional.
>
I would be interested in any insights you have into safety, reliability
and cost of various rebreathers.
>You mentioned almost fixed FO2 and PO2 respectively. I guess that means
>constant mass flow of the breathing mixture in the first case and some kind
>of qoutient regulator for the second case.
The Seapack 1000 is a close relative of the CCR 155 which I believe is closely
related to the US Navy MK 15/16. Howard Hall and Bob Cranston used this
rebreather to produce several popular movies and Rob Palmer used this rebreather
to explore blue holes. It is a fully closed mixed gas rebreather that
uses 3 O2 sensors and a solenoid to control the PO2 of the breathing mixture by
adding pure O2.
The BMD is a semiclosed circuit rebreather. However it does NOT use the
constant
mass flow used by the Prism or the Fieno. Instead it replaces a fixed volume
fraction on each breath. This creates completely different FO2 dynamics than
a constant mass flow rebreather. For example inspired FO2 is only weakly
related to metablic rate in a fixed volume fraction rebreather. In a constant
mass flow rebreather the inspired FO2 is strongly related to metabolic rate.
Hence with a BMD it easier to predict the final FO2 of the inspired gas.
For a more detailed analysis of these 2 types of rebreathers see
The Physiology and Medicine of Diving, Second Edition
by Bennet and Eliot.
Best Publishing.
I think this is the correct reference but I do not have it on hand. If you
cannot obtain this reference send me your snail mail address and I will mail
you a copy of the relevant chapter.
For a fixed volume fraction rebreather the inspired PO2 is roughly calculated
as follows (this is from memory and may be wrong ).
PO2 = FO2*P - 1/n*G
Where PO2 is the inspired PO2, FO2 is the supply FO2, P is the abient preasure
in atmospheres, n is the volume fraction that is replaced on each breath
and G is a physiological constant usually between 15 and 30. See the above
reference for more details on this.
Good Luck with your research.
Barrie Kovish
Vancouver, Canada
bmk@ds*.bc*.ca*
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