[PSUBS-MAILIST] G.L. summary Pressure Hull

[Douglas Suhr]

I have to admit this one really befuddles me. What if you were to have two
(independent) pressure sensors/gauges, one for cabin pressure and one for
ambient pressure, but the gauges were linked at the needles with a one-way
gate. This way, the gauges would both be free to move independently, but
the gate would only open (and unlock the hatch lock-out via a switch) when
both needles were lined up in tandem indicating equal pressure, be it at
the surface or underwater. I think actually designing and building such a
device would prove very difficult.

Is this what they are talking about, or am I confused?

Because if so, I'm not sure I would ever want to implement such a device on
my vessel. If a malfunction of this system were to occur during an
emergency egress, how much more time would it take to bypass the hatch
lock-out? 3 seconds is a long time when you are dying!

With pressure gauges alone I will have a pretty good idea of where I stand
in terms of equalization.




On Wed, Dec 11, 2013 at 9:53 AM, Joe Perkel <josephperkel at yahoo.com> wrote:

> Alan
>
> No definitive answer but we can postulate that both sensing and actuation
> are involved.
>
> On sensing, differential pressure on either side of the hatch is
> translated to a impulse to actuation.
>
> On actuation, a method of locking out the operator from physically
> un-dogging the hatch, is the only way to meet the standard as per your O.P.
>
> Joe
>
> Sent from Yahoo Mail for iPad <http://overview.mail.yahoo.com?.src=iOS>
>
>  ------------------------------
> * From: * hank pronk <hanker_20032000 at yahoo.ca>;
> * To: * Personal Submersibles General Discussion <
> personal_submersibles at psubs.org>;
> * Subject: * Re: [PSUBS-MAILIST] G.L. summary Pressure Hull
> * Sent: * Wed, Dec 11, 2013 2:36:26 PM
>
>   Alan,
> Is this equalization from overpressure inside the hull? or external
> pressure.
> Hank
>
>
>   On Wednesday, December 11, 2013 1:23:21 AM, Alan <
> alanlindsayjames at yahoo.com> wrote:
>  Can anyone enlighten me on what sought of mechanism
> is used that renders the opening of the hatch possible only after
> equalisation, as per G.L. Requirements?
> Thanks
> Alan
>
> Sent from my iPad
>
> On 11/12/2013, at 3:01 PM, Alan James <alanlindsayjames at yahoo.com> wrote:
>
> Hi,
> I'm not covering much in this section because if I started on construction
> regulations, I would just be duplicating what was printed.
> G.L. wants you to have manufacturer certificates for every non structural
> screw.
> Any company you contract to do your welding has to have their facilities,
> personal
> & supervision approved by G.L..
> Some points of interest are.... hatches need to be opened from both sides,
> they need
> to be able to be secured open, they need to be designed in a way that
> opening of the
> hatch is only possible after equalization. Two measures are required to
> guarantee that
> the hatches are closed & secured before diving; one measure is to be
> visibly noticeable.
> Mechanical measures for stopping a banging of the hatch is required.
> Any external through hulls are to be protected against damage by
> appendages or covers.
> If you are doing calculations on a computer you have to prove that the
> program is suitable.
> Alan
>
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