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RE: Pressure Testing
A real simple and probably very good idea in regards to pressure testing would be to draw a vacuum on the hull as a first test. This could be done in any shop with very inexpensive equipment. This would simulate a depth of 30+ feet (depending on how good your vacuum pump is). By monitoring the internal pressure (vacuum) over a period of minutes or hours one could readily detect small leaks as well as test the hull to the 30' depth. This could save some time (money) and embarrassment when doing a "dunk" test at the end of a cable. At Boeing we learned that a quick way to spot a large percentage of leaks in hydraulic tubing is to do a pre-check with 100psi shop air. This uncovers the easy leaks without spilling any oil. Then when the oil is added, the pressure can be brought up slowly while looking for the small leaks which might only appear under the higher stressed conditions.
CAUTION Don't put anyone inside the sub to listen for leaks! The pressure will be too low to support life as we know it. If need be, use a video camera and lights inside and apply "Snoop" (or soapy water) to the outside for a bubble check. Here is another good reason for view ports, to look inside!
> ----------
> From: Paul Anderson[SMTP:hacker@geeky1.ebtech.net]
> Sent: Monday, February 22, 1999 12:55 PM
> To: personal_submersibles@psubs.org
> Subject: Re: Pressure Testing
>
> On Sun, 21 Feb 1999, Paul Julius wrote:
>
> >
> > At 100 feet we know that we are encountering about 50 PSI.
> > Make a block, one inch by one inch, then balance 50 pounds on top of it
> > while resting the block on random spots on the pressure hull. If the
> > hull holds up, then ok, move on.
> >
> On a real sub underwater, the pressure is applied all around the sub, not
> in one point. Though, IIRC, real subs are tested in large sealed tanks,
> if there's no air inside the tank it can be surprisingly easy to get up to
> a high pressure(same idea as doing a hydro on a boiler). TTYL!
>
>
> ---
> Paul Anderson
> hacker@geeky1.ebtech.net
> "This is Maurice, our sheep-hearding carrot."
> http://www.hpv.on.ca sys admin
> http://www.freeworldbbs.org
>