[PSUBS-MAILIST] Acceptable cabin pressure swing

[Alan via Personal_Submersibles]

Brian,
either Carsten or Emile designed & built there own check valve.
They posted the design on Psubs. Very easy to make & you can
plunge it to equalize the pressure before opening the hatch.
i think I have a pic of it on my other computer. can try & find it
( when I get up) if you are interested.
Cheers Alan

Sent from my iPad

> On 28/02/2016, at 4:07 am, Cliff Redus via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> Brian, see McMaster Carr part number 4620K41.  This has a 1 psi cracking pressure, not 0.5 psi that I mentioned earlier.
> 
> Cliff
> 
>> On Thursday, February 25, 2016, Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:e a picture of it 
>> Cliff,          Where did you find that 1/2 psi relief valve?
>>  
>> Brian Cox
>> 
>> --- personal_submersibles at psubs.org wrote:
>> 
>> From: Cliff Redus via Personal_Submersibles <personal_submersibles at psubs.org>
>> To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
>> Subject: Re: [PSUBS-MAILIST] Acceptable cabin pressure swing
>> Date: Thu, 25 Feb 2016 19:05:00 -0600
>> 
>> Jon for my boat, I have a pressure relief valve with a 1/2 psi cracking pressure to vent pressure while on the surface.  I have a high cabin pressure  alarm that triggers at 20 psia (5.3 psig) and a cabin lower pressure alarm set at 12 psia (-2.7 psig).   In the PLC I also record and display the cabin pressure at the time the hatch is closed and log all alarm states every second.  
>> 
>> I have never had either a high or low cabin pressure alarm while diving.  I have had elevated cabin pressure caused by accidently having the backup manual O2 value open and a leak in an air fitting on anther occasion.
>> 
>> Cliff
>> 
>> On Wed, Feb 24, 2016 at 1:12 PM, Jon Wallace via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>> 
>> I think this is somewhat subjective but what is general consensus on maximum cabin pressure swing (higher/lower) relative to hatch closing at the start of a dive before setting off alarms?  My thought is that an alarm should sound well before any point of emergency.  I'm considering sounding a warning at 2psi +/- and an alarm at 4psi +/-  but I'm not sure if this is too strict.
>> 
>> Jon
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