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RE: [PSUBS-MAILIST] Flooded Stability.
Hi Jon, ABS 10-5.5 and 5.7 Pressure vessels and hx are not to be located within the pressure boundary ---------unless calcs show that inadvertent release of the contained fluid(s) will not increase the pressure inside the chamber by more than one atmosphere. 8/7.5.2 also.
The cracking pressure on some relief valves you would be lucky to have it under 2 psi. But if you had 5 psi then on a hatch with a seal on it OD of 24" would have one ton pushing it open. I am trying to do the holding down with two catches but if the hatch is supposed to take one atmosphere then there is 3 tons to contend with. If you arrive back at the surface with 1 atmosphere and given that the 15 psi is in keeping with oxygen partial pressures limitation, then that could be a fair amount of air to pass out through the relief valve. Regards, Hugh
-----Original Message-----
From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Jon Wallace
Sent: Thursday, 25 March 2010 12:29 p.m.
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Flooded Stability.
Hugh,
Do you have a reference to the ABS language? I haven't looked at them
in a couple months but I thought the relief valve was for equalizing
pressure manually similar to what we had to do with DeepWorker when we
came back to the surface, and not that there was some automatic relief
valve at a specific pressure level. While a hatch could certainly "pop"
with enough differential pressure internally/externally when it was
opened, it's hard for me to imagine how a hatch would pop on its own
upon surfacing if it is properly secured.
Jon
Hugh Fulton wrote:
>
> I was just reading the ABS rules and it says that if you have a
> cylinder of air or oxy inside that if it is totally released the
> internal pressure should not be greater than 15 psi. Also if you had
> an air leak then the internal pressure could rise so that when you hit
> the surface the hatch could pop before you vent the MBTs. You also
> have to have a relief valve with an isolating valve wired open. What
> do you set the relief valve at. Also the name plate on the vessel
> must show maximum external pressure and maximum internal pressure.
> This would also be required to determine the number of bolts holding
> the viewports in. Hugh
>
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