I don't think that air would work well. The gas should probably be dry
nitrogen to prevent fogging of lenses and condensation on internal parts.

The cases of fish sonars and other equipment is often purged with nitrogen
to eliminate the air moisture.

WB
..................

"RogerN" wrote in message
hlink.net...

wrote in message
oups.com...
Hi,
I'm building a small underwater tethered / robot / submarine /
doo-hickey and I need a cheap way to pressure test the individual
components to make sure they don't leak. Max diving depth will be 70'
which is around 32psi and each component will be no larger than 6"x6".
I know each component should be tested to 1.5X to 2X its expected
range.


Sorry for the delayed reply but I haven't kept up with the newsgroups
lately. I had some thoughts of building a tethered or radio control
submarine camera setup. The thought I had was to fill the submarine with
air pressure equal to or greater than the water pressure. One way would
be
to build it to handle pressure (PVC pipe?) and air it up to a little more
pressure than it needs, perhaps 35 - 50 psi in your case. Another idea
would be to have an air tank inside and a pressure sensor. If the
external
water pressure was greater than the inside pressure, crack a valve to let
some air pressure inside the submarine.
Good luck!






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