Re: [PSUBS-MAILIST] Diver Lockout.... serious question here!!

["Sean T. Stevenson" <cast55@telus.net>]

Where the volume of the lockout chamber is insignificant in comparison to the 
volume of the rest of the sub, then the lockout may be vented into the sub.  
This will result in a pressure increase over 1 atm, but this may be 
acceptable if the difference is slight and/or the exposure time is low before 
an opportunity to vent the sub to atmosphere arises.  If this is not the 
case, then the lockout chamber gas needs to be compressed to reduce the 
pressure.  This compressed gas may be vented to sea, or reclaimed into 
storage bottles.  In the case of deep lockout operations, and depending on 
the volume of the lockout, reclaiming the gas may be more cost effective.

It is certainly dangerous to reduce the lockout pressure too fast when persons 
are inside.  A good lockout design might incorporate small diameter through 
hull gas fittings to the compressor system, such that in the event of a valve 
or piping failure, the pressure reduction in the lockout would not exceed the 
maximum permissable ascent rate under normal operating conditions, until the 
failure could be isolated.  You still run the risk of exceeding the 
decompression ceiling in the event of a failure, but provided you notice and 
respond to it quickly, this would reduce the risk of barotrauma events.

-Sean


On July 28, 2007 21:29:06 Lil Brother LLC wrote:
> I've got into some pretty serious questions lately......and I've done a
> little reading about diver lockout (archives), but the archives raised a
> question.
>
> If you have a 1 atm sub, with a diver lockout........how do you lock a
> diver back in?
>
> Are there any 1 atm subs with a lockout?
>
> If there are......if the lockout has been pressurized to the outside
> pressure........what method is used to depressurize it back to 1 atm?
> (these questions are redundant I know)
>
> And  the last....the important one.....is this on the dangerous side? If
> you depressurize to fast......the bends.
>
> I was reading about the nice sub.....(the Krata I think.....please don't
> quote me ....I've had a very long two days)......but I didn't notice if it
> was 1 atm or not.
>
> Some one learn me on this.   :-)
>
> (Hey....at least I know what a VBT is for now.)
>
> James Long
> Owner/Designer
> Lil Brother LLC (Instrument Division)
>
>
>
>
>
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