[PSUBS-MAILIST] over pressure valve

[via Personal_Submersibles]

When you are a half foot below your OP depth, the automatic  OPV knows it 
and stays shut; when you rise to a half foot above your OP depth,  the OPV 
valve knows that and opens just long enough to re-equalize the  pressure.  It 
continues to do this as you ascend.  Don't latch on to  "half foot" as a 
standard.  I only mean that as an example; it depends on  the cracking pressure 
chosen.  In reality, once the cracking differential  is reached and the 
valve opens, you'll probably be ascending faster than the OPV  is releasing 
internal pressure.  That is, since the external water pressure  is decreasing 
as you rise, the differential tends to increase unless the OPV can  keep up 
with it.
 
Hank, you're making a good point for having an adequately  sized OPV.
 
Guys, we have two different threads going on the same  topic.  Can we merge 
them?
 
Jim
 
 
In a message dated 6/19/2015 3:16:34 P.M. Central Daylight Time,  
personal_submersibles at psubs.org writes:

I don't get the "in the hands" part... its completely  automatic.

On Fri, Jun 19, 2015 at 4:09 PM, hank pronk via  Personal_Submersibles 
<_personal_submersibles at psubs.org_ (mailto:personal_submersibles at psubs.org) > 
wrote:


Agreed,
In  the hands of an experienced submarine operator an over pressure valve 
is  safe, providing it is large enough.  I have not seen an example of a  
large enough OPV.  A simple valve in the hatch will do the same job,  just need 
an umbrella :-)
The noise of a compressor is a welcome sound if  it means keeping the dome 
on the sub  :-)
Hank--------------------------------------------
On Fri, 6/19/15,  Carsten Standfuß" via Personal_Submersibles 
<_personal_submersibles at psubs.org_ (mailto:personal_submersibles at psubs.org) >  wrote:

Subject: Re: [PSUBS-MAILIST] over pressure  valve
To: "Personal Submersibles General Discussion" 
<_personal_submersibles at psubs.org_ (mailto:personal_submersibles at psubs.org) >
Received:  Friday, June 19, 2015, 2:47 PM


But a overpressure vale works
full auto. A  compressor
not.  

A OPV needs
no  energy - but a compressor did.


A OPV needs no room -  but
a compressor did.

And a
compressor  is
a noisy  solution..

vbr
Carsten



"hank
pronk  via Personal_Submersibles" <_personal_submersibles at psubs.org_ 
(mailto:personal_submersibles at psubs.org) >
schrieb:
>  Personally I think an onboard
compressor is a much safer option  than an over pressure
valve.  There are multiple safety  benefits to an onboard
compressor, over pressure being the  biggy.  With a
compressor you can get rid of the pressure  without surfacing
and trying to control a perfect ascent.   With the OPV you
have to surface a bit and let air out and wait  then surface
more and wait and so on. You can't just surface and  hope
the valve keeps up with the demand. This is more  important
for subs with large domes.
> The  next
benefit to a compressor is, if you lost all your air,  you
surface by dropping your weight.  In my case the weight  is
small and I would also drop the thruster and tail  assembly.
Still, not much sub out of the water.  With the  compressor,
I can open my vent valve in the hatch and use the  compressor
to fill the ballast tanks.
>  Hank
>
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