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

[Alan James]

Hi Sean,
the wording in G.L. is.....
Section 5 C,  Hatches, doors, access ways 6.1.2
The access and exit hatches are to be provided with a closing mechanism
which makes it possible to create, even when the vehicle is surfaced, a
sufficient contact force on the hatch sealing.
In addition the closing mechanism is to be designed in a way that opening
of the hatch is only possible after pressure equalization has happened,
see also section 13,F......which reads.....measures are to be provided to
transfer in a controlled manner the higher or lower pressure eventually
built up within the pressure hull to atmospheric pressure before the access
hatches are opened.
   So this qualification is in addition to a good seal of the hatch.
On Emile's boat he has a plunger in his over pressure valve that he pushes
before opening the hatch.
Alan



________________________________
 From: Sean T. Stevenson <cast55 at telus.net>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
Sent: Thursday, December 12, 2013 4:49 AM
Subject: Re: [PSUBS-MAILIST] G.L. summary Pressure Hull
 


Is it possible that this rule is simply another way of stating that hatches need be designed to seal with pressure, such that they physically cannot be opened unless equalized (+/- a person's strength)?  Dogs in that case are just a means of providing a little bit of precompression on the O-ring in the absence of a pressure differential, and to hold the hatch against _slight_ reverse pressure, such at the 1 ATM specified by ABS.
ABS' version says that a means must be provided to equalize pressure before opening (needle valve?), that means must be provided to determine the pressure on either side, and that interlocks must be present to prevent e.g. submerging with open hatches.
I wonder if GL is really that prescriptive, or if we're misinterpreting?
Sean



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 
>
>
>
>________________________________
> 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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