Re: [PSUBS-MAILIST]-pressure test/vacuum

[William Alford <walford@dbtech.net>]

At 03:12 PM 4/11/2002 -0500, you wrote:
>Wouldn't putting the sub under a vacuum work just as well?  

1 Atmosphere pressure at sea level is 14.7 PSI and this exerts great force
over a large surface area and will certainly collapse a fragile sealed
vessel if a vacuum is pulled inside, but the external hull pressure at
surface will never be more than the 14.7. The weight of seawater during a
dive is added to the existing atmospheric weight. The weight of seawater at
33 feet is around 14.7 PSI. So even if you pulled a complete vacuum
(requiring diffusion vacuum pumps like physicists use) inside the sub at
surface, you would not be able to test for external pressure for submerging
below 33 feet (that's assuming the submerged sub had 1 Atm ambient air
pressure) without applying additional external hull pressure.

William Alford
walford@dbtech.net

Tout comprendre c'est tout pardonner