[PSUBS-MAILIST] Acceptable cabin pressure swing

[Cliff Redus via Personal_Submersibles]

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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