[PSUBS-MAILIST] Leak, pressure and life support test

James Frankland jamesf at guernseysubmarine.com
Mon Sep 2 12:29:47 EDT 2013


Hi Guys,

Sounds like the overnight vacuum test is a really good idea.  Unfortunately
i only have the standard hatch so i cant close it from outside .  I'll have
to see if i can suck it down like Hank suggests.  Got a few days to tinker.
Regards
James




On 2 September 2013 17:12, hank pronk <hanker_20032000 at yahoo.ca> wrote:

>  Hi Jim,
> I am no expert on the subject, but I do a test with as much vacuum as
> possible.  When you dive the hatch is secured tight so there is always
> pressure on the seal.  Before I converted my k350 hatch to open from both
> sides, I did the vacuum test without securing the hatch.  I does not take
> much vacuum to suck the hatch down tight.  Honestly I am not sure about a
> low vacuum test, you could be right.   I just assumed it should be more
> than less.   Before I tested my last sub in the lake, I did a vacuum test
> and I did loose vacuum overnight.  It was very minor, so I went anyways.
> Sure enough I had a leak, I took on a couple of litres of water at 200 feet
> for an hr.  I think my connection point from the acrylic cylinder to the
> hatch land was the problem.  There is no seal, it is cast in place.
> Hank
>
>   *From:* "JimToddPsub at aol.com" <JimToddPsub at aol.com>
> *To:* personal_submersibles at psubs.org
> *Sent:* Monday, September 2, 2013 8:57:18 AM
> *Subject:* Re: [PSUBS-MAILIST] Leak, pressure and life support test
>
>  Hi Hank,
>
> See if you agree with my line of thinking:  At a hatch depth of 20 feet
> you'll have about 9 psi differential on your hatch and your other
> penetrations as well.   At a hatch depth of 1 foot you have about .445 psi
> differential.
>
> For many things, the greater the pressure differential, the greater the
> chance of a leak or seepage.  However on the hatch in particular (and
> possibly on some other things), the greater the pressure forcing the hatch
> against the landing, the more tightly it will seal.  So the hatch might
> seal well at depth, but leak when barely submerged
>
> It seems it would be good to do both a high vacuum and a low vacuum test.
> If the hatch seals well at high vacuum, but leaks down at low vacuum, more
> work is needed on the latches or the mating surfaces.
>
> Best regards,
> Jim
>
>  In a message dated 9/2/2013 9:21:58 A.M. Central Daylight Time,
> hanker_20032000 at yahoo.ca writes:
>
>  Hi James,
> I always do a vacuum test before my test dives.  I use a compressor as a
> vacuum pump and draw out as much air as possible.  Then I have a valve on
> the hull and a vacuum gauge.  I let it sit for 24 hr.  If it holds the
> vacuum your set.
> Hank
>
>   *From:* James Frankland <jamesf at guernseysubmarine.com>
> *To:* personal_submersibles at psubs.org
> *Sent:* Monday, September 2, 2013 3:45:27 AM
> *Subject:* [PSUBS-MAILIST] Leak, pressure and life support test
>
>  Hi All,
>
> I did some tests at the weekend.  Very small pics attached as i havent
> updated my site yet.
>
> First i tested the battery pods and seals with old inner tubes.  Managed
> to pump them to about 5psi.  Not much but i think it was ok to indicate any
> leaks.  I couldnt see or hear anything and pressure remained steady.
>
> Then i did the very sophisticated "saucepan test" over the hatch
> viewport.  I was just a bit suspicious of this one as it has no gasket, the
> lense seats directly to the face.  No leak, but agreed, not much test
> pressure although the saucepan was full despite the spillage out the sides.
>
> Next i did a life support test.  I filled and ran the scrubber and then
> sat inside for an hour with the hatch sealed.  CO2 seemed to level out at
> about 5500ppm and i topped up O2 when it got to 19%.
>
> i also dropped half a psi of internal pressure and that seemed to hold, so
> i am hoping the boat is tight.
>
> I was going to do a leak test in a local fresh water resovoir, but as im a
> bit more confident its not going to leak now and its such a logistical
> fuss, im going to go straight in the sea.  Next week.
> Kind Regards
> James
>
>
> _______________________________________________
> 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/20130902/495d5ba0/attachment.html>


More information about the Personal_Submersibles mailing list