[PSUBS-MAILIST] Hatch interlock

Wed Mar 2 16:53:19 EST 2016

I will have one transducer per hatch, so that I can track the interlock status and seal integrity per hatch. Each transducer is therefore exposed to whatever pressure exists at the flange between orings, which in the case of the lockout hatches must necessarily include the pressure at full lockout depth, because those flanges are exposed to full pressure when the lockout is operated.  This means that in order for this conceptual design to work, I must accept a larger range, lesser resolution measurement for those hatches, but it occurs to me now that in every case, I would need to accommodate the maximum anticipated pressure on either side of each hatch, if I expect to be able to track progressive seal leakage without damaging a transducer. Ergo, only the 1 atm spaces could make use of 0 - 15 psia transducers. The rest would have to be 0 - 250 psia or whatever, and I may require higher resolution signal conditioning (24 bit?) to effectively measure the range below 1 ata.

Sean

On March 2, 2016 1:19:54 PM MST, Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>Sean,why not leave the transducer in the 1 atm compartment & just
>attach itto the pipe from the compressor that would run through the
>wall to the variouscompartments & sealing flanges. There are of course
>other complications withreleasing the vacuum pressure on the individual
>hatches.Alan
>
>
>From: Sean T. Stevenson via Personal_Submersibles
><personal_submersibles at psubs.org>
>To: Personal Submersibles General Discussion
><personal_submersibles at psubs.org> 
> Sent: Thursday, March 3, 2016 8:35 AM
> Subject: Re: [PSUBS-MAILIST] Hatch interlock
>   
>It is not the personnel transfer hatch that presents the problem, but
>rather the egress hatches in the lockout chamber, as those flanges will
>see the lockout pressure in normal operation.  I can get away with a
>larger range pressure transducer for those hatches, but then I lose
>measurement resolution.Sean
>
>
>On March 2, 2016 9:32:49 AM MST, Alan James via Personal_Submersibles
><personal_submersibles at psubs.org> wrote:
>Sean,that sounds a good idea. Nuytco set the o-ring on the deep worker
>hatch externally with a vacuumpump, but with your twin seal idea you
>could do this from within the sub without decreasing the hull
>pressure.  If the transducers are just monitoring the vacuum between
>the o-rings can't the transducer bem! ountedon the 1atm side of the
>diver lockout hatch & not be exposed to diver lockout pressure?Alan
>
>
>From: Sean T. Stevenson via Personal_Submersibles
><personal_submersibles at psubs.org>
>To: "personal_submersibles at psubs.org" <personal_submersibles at psubs.org>
>
> Sent: Thursday, March 3, 2016 1:41 AM
> Subject: [PSUBS-MAILIST] Hatch interlock
>   
>Doing some further design on my lockout submersible project, I came up
>with a novel way to implement hatch interlocks, which doubles as a seal
>condition monitor, and a means of establishing a preliminary seal in
>the absence of a pressure differential without relying on the hatch
>dogs to p! rovidethe initial o-ring squeeze.My design entails two
>o-rings per hatch (vessel has six hatches: cabin loading / escape,
>outer lockout loading / escape, inner lockout loading / escape, inner
>lockout egress , outer lockout egress, and transfer). These o-rings are
>concentric face seals, each residing within a half dovetail groove for
>positive retention of each o-ring when the hatch is opened or
>manipulated. The grooves are oriented such that the flat face of each
>half dovetail faces the intermediate space between the two rings. This
>intermediate volume is not isolated, but rather connected (on the
>sealing flange side) to a vacuum transducer, and piped through
>appropriate valving to a vacuum pump. When the hatch is closed, this
>intermediate space is pulled to vacuum (as strongly as the pump
>allows), then locked off, and the strength of this vacuum is measured
>by the transducer and continuously monitored. The interlock is clear as
>long as the vacuum holds, a! ndactivates the moment the seal is rele!
>ased,instead of relying on some arbitrary movement of the hatch to
>indicate that it is open.Apart from the obvious expense, I see a
>potential problem with exposing those vacuum transducers in the lockout
>hatches to high pressure, necessitating either a less sensitive
>transducer that will withstand the pressure, or some means of isolating
>the transducer when the pressure approaches the limit of its range -
>I'm still working this out in my head, but I thought I would share
>anyway.Sean
>
>_______________________________________________
>Personal_Submersibles mailing list
>Personal_Submersibles at psubs.org
>http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>
>
>   
>Personal_Submersibles mailing list
>Personal_Submersibles at psubs.org
>http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>
>
>_______________________________________________
>Personal_Submersibles mailing list
>Personal_Submersibles at psubs.org
>http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>
>
>
>
>------------------------------------------------------------------------
>
>_______________________________________________
>Personal_Submersibles mailing list
>Personal_Submersibles at psubs.org
>http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.whoweb.com/pipermail/personal_submersibles/attachments/20160302/68a3e73a/attachment-0001.html>