[PSUBS-MAILIST] Over Pressure Valve

Fri Jun 19 16:18:36 EDT 2015

Jim,
For me the heat is welcome since I do most of my diving in the winter, it could be a problem for the tropical crowd.  Mind you, you would only use the compressor in an emergency.  I put my compressor in for convenience, I can recharge my tanks in 10 min or so.  Now that I have an external hp tank, it really is convenient.   I usually recharge the hp tank in the shop where it is cool and I only pump in 500 psi at a time to keep the moisture down.
I wonder if the DW's have an OPV
Hank--------------------------------------------
On Fri, 6/19/15, via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

 Subject: Re: [PSUBS-MAILIST] Over Pressure Valve
 To: personal_submersibles at psubs.org
 Received: Friday, June 19, 2015, 3:58 PM

 John, I
 hadn't given much thought lately 
 to how the Big Boys handle it.  I've planned to have a
 small, onboard 
 compressor, but its purpose is to create under-pressure to
 seal the domes prior 
 to diving.  It's not large enough to charge the
 tanks.  I'm depending 
 on a portable compressor dockside or on the support boat for
 that.  A 
 snorkel would be nice even if it extends just two feet
 above the hatch or 
 dome.  Looking forward to the update on your 65-footer at
 the 
 convention.

 Hank, that's definitely a sweet
 setup you have on Gamma.  
 The compressor recharged the tanks much more quickly than I
 expected.  I 
 don't recall how low you let them get before
 recharging.  I don't expect to 
 have room onboard, and the heat generated would be something
 of a negative in 
 semitropical conditions.

 I wish I knew what the pressure
 differential was that Captain 
 K. experienced.  Apparently it was small enough that he
 wasn't aware of it 
 and yet significant enough to convert his coming tower into
 a personnel launch 
 tube.  If the air pressure inside your sub rose to 20 psi
 or 
 about 1.33 atm, you would reach equal pressure when you got
 within 11 feet of 
 the surface.  Any depth greater than that and the outside
 pressure would 
 still be greater than the inside pressure (no OP).  The
 point being that 
 you would have to have a lot of excess interior pressure to
 experience OP at a 
 significant depth.  Wouldn't your ears tell you if you
 got as high as 20 
 psi?  Monitoring and alarm systems are a must.

 Jim

 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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 In a message dated 6/19/2015 12:35:49 P.M. Central
 Daylight Time, 
 personal_submersibles at psubs.org writes:
 Hi 
   Jim:

 On the boat if their
 was an positive pressure while submerged at 
   depth we started the air compressor and charge the air
 banks. The other option 
   was to raise the snorkel to equalize before opening the
 hatch.

 John 
   K.
 (203) 414-1000

 Sent from my iPhone

 > On Jun 19, 2015, 
   at 3:07 AM, via Personal_Submersibles
 <personal_submersibles at psubs.org> 
   wrote:
 > 
 > Jim,
 > 
 > Thanks for the
 mental diagram, 
   that helps imensely. Does any one know how the big boys,
 navy subs, deal with 
   over pressure? Has any one had their OP valve open at
 depth and if so how much 
   water came in?
 > 
 >
 Keith T
 > 
 > via 
   Personal_Submersibles
 <personal_submersibles at psubs.org> wrote:
 > 

 >> Keith,
 >>

 >> Sorry, I just got home.  I 
   was hoping Alec and some  others with more 
 >> experience than I 
   have would chime in as I see has now  happened.  There
 have 

 >> been some good discussions on OP
 valves in the  past.  
   I think some have 
 >> installed a T
 (on its side) inside the sub 
   so  the air enters the horizontal 
 >> portion, and any water 
   that comes in  goes down to a small trap or into a tube

 >> that 
   leads to a reservoir.   Others just use a rag to catch
 the small 
   amount 
 >> of water.
 >> 
 >> Alec, does
 the OP on 
   the exterior of Snoopy point downward  after it exits 
 >> at the 
   top?
 >> 
 >>
 We've also discussed having an air pressure 
   gauge or altimeter  set to zero 
 >>
 (1 atm) before diving.  
   If it indicates any pressure above  that level at 
 >> anytime 
   during your dive, you'll know you'll have an over
 pressure  situation 

 >> to deal with as you surface and
 you'll have an indication of 
   how  severe 
 >> that will be. 
 We've also discussed various 
   things that could cause  an over 
 >> pressure 
   condition.
 >> 
 >> Best regards,
 >>
 Jim
 >> 

 >> 
 >> In a
 message dated 6/18/2015 7:09:19 P.M. Central 
   Daylight Time,  
 >>
 personal_submersibles at psubs.org 
   writes:
 >> 
 >>
 If it opens when submerged, it is because air 
   is on the way out,  and that 
 >>
 prevents water from coming in. 
   Its like blowing through your nose  
 >> underwater, your nose is 
   open but if you're blowing, you don't get water
 in  your 
 >> 
   lungs.  
 >> 
 >> 
 >> Certainly
 you do get a 
   little water in if you push the valve open  manually 
 >> while 
   submerged, as a test. Or a few drops if you do so when
 surfaced  to 

 >> equalize, as the valve is all
 wet. But its nothing 
   much.
 >> 
 >>

 >> 
 >> Best,
 >> 

 >> Alec
 >>

 >> 
 >> 
 >> On Thu, 
   Jun 18, 2015 at 7:19 PM, Ken Martindale via 
 Personal_Submersibles 

 >>
 <_personal_submersibles at psubs.org_ 
   (mailto:personal_submersibles at psubs.org) 
 >>> wrote:
 >> 

 >> TEST!!!
 >>

 >> -----Original  
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 >> From:
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 >> 
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 Behalf Of via 

 >> 
   Personal_Submersib
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