Re: [Paddlewise] Inflatable PFD's

From: Dave Kruger <dkruger_at_pacifier.com>
Date: Fri, 03 Sep 1999 16:45:27 -0700
Gary Pewitt wrote:
> 
> Since your lungs can only produce about 3 1/2 psi, filling the pfd
> by mouth will make very little difference in the final inflation
> pressure when you trigger the high pressure CO2 bottle.
> In other words "it don't ammount to a fart in a wirlwind".

I believe this is misleading.  Though mouth inflation is done at relatively
low pressure, it is possible to fill the inflatable PFD by mouth.  The *very
small* (in volume) CO2 cylinder has to have an *initially* very high pressure
so that it can contain the necessary number of air molecules to fully inflate
the PFD.  When exhausted, the CO2 cylinder does not exert its full initial
pressure.

Consequently, if you inflate the PFD to fullness with your mouth, *and then*
the CO2 cylinder is triggered, it will endavor to *add* its molecules to the
ones your mouth put there -- possibly causing the pressure to rise to
(roughly) twice what the CO2 cylinder could achieve alone.  This might exceed
the ability of the PFD to hold air -- in other words, it might pop.

My guess is that mfrs anticipate someone doing this and build in a safety
factor of two or three so it probably would not leak.  Anybody tried this?

-- 
Dave Kruger
Astoria, OR
chemist


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Received on Fri Sep 03 1999 - 22:25:26 PDT

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