[PSUBS-MAILIST] Hatch Closure Mechanism

[Alan via Personal_Submersibles]

Ian, Tim,
yes I was thinking about a cam type latch dog as you described.
The automatic pressure relief valve that Emile has would automatically
reduce any pressure in the hull to the equalisers spring closure pressure,
maybe 2psi; then if you forgot to manually press this valve to fully equalise,
any internal overpressure would be released as the hatch dog incrementally
released the hatch.
I guess the only reason for this law is to prevent damage from the hatch 
opening explosively. Perhaps gas struts would be suitable to stop this!
Tim, I have a design for opening from the outside. There could be a grip
on the seaward side of the overpressure valve to equalise from outside.
I am feeling like I have some solutions now. 
Thanks, Alan.

Sent from my iPad

> On 31/12/2017, at 11:23 AM, irox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> Although it doesn't have be to the same vent/mechanism as the hatch over pressure safety.
> 
> Also, there is a requirement for opening the hatch from outside, to add more complications (if you're strictly following regulations).
> 
> -----Original Message----- 
> From: T Novak via Personal_Submersibles 
> Sent: Dec 30, 2017 1:16 PM 
> To: 'Personal Submersibles General Discussion' 
> Subject: Re: [PSUBS-MAILIST] Hatch Closure Mechanism 
> 
> Just to add a complication to the project, you will need to have the vent accessible by someone on the outside too,  in case the sub has surfaced but the operator is incapacitated.
> Tim
>  
> From: Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org] On Behalf Of Alan via Personal_Submersibles
> Sent: Saturday, December 30, 2017 12:51 PM
> To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
> Subject: Re: [PSUBS-MAILIST] Hatch Closure Mechanism
>  
> Thanks Hank,
> will have to think on this one. I want to let a novice dive my sub, so
> the system needs to be bullet proof.
> If I have some sort of lock mechanism I would need to be able to bypass
> it if I needed to escape at depth. The pressure at depth would be apposing 
> the manual operation of the overpressure valve. You could flood the sub first
> but normally the hatch is un-dogged prior to the hull equalizing.
> Cheers Alan
>  
> 
> 
> Sent from my iPad
> 
> On 31/12/2017, at 1:49 AM, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> Alan,
> You could have a lock that prevents the hatch mechanism from opening that is activated by turning the hatch vent.  I always vent before I one the hatch anyways.
> Hank
>  
> On Friday, December 29, 2017, 11:09:03 PM MST, Alan via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>  
>  
> Just doing some evening reading of the GL rules & noticed this rule about hatches....
> "the closing mechanism is to be designed in such a way that opening of
> the hatch is only possible after pressure equalisation"
> I am wondering what options there are for achieving this.
> Has anyone had experience of the hatch opening with explosive force due
> to internal over-pressure not being equalised.
> Alan
>  
> Sent from my iPad
>  
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