[PSUBS-MAILIST] Hatch interlock

[Sean T. Stevenson via Personal_Submersibles]

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 bemounted on 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 provide the 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, and activates 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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.whoweb.com/pipermail/personal_submersibles/attachments/20160302/f1f6bfbc/attachment.html>