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.

Anyway, my thought was to fill some already pressure resistant device
such as a pressure cooker or autoclave chamber (hello ebay!) with water
and then use shop air to increase the pressure. I don't need a viewing
window as I would basically take it up to pressure, leave it there for
a few hours, relieve the pressure and then check to see if anything
leaked.

Questions:
1) Is this concept of pressure testing sound?
2) Is there a cheaper way to do it?
3) Most importantly, is there an easier way to do this?

Thanks and please resist the urge to point out the 100's of other
failure points that I will be facing in this project such as watertight
bulkhead fittings, ballast systems, propulsion, electronics, stability
control, corrosion, battery systems, faily safe safety systems, etc,
etc...

-M

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.

Anyway, my thought was to fill some already pressure resistant device
such as a pressure cooker or autoclave chamber (hello ebay!) with water
and then use shop air to increase the pressure. I don't need a viewing
window as I would basically take it up to pressure, leave it there for
a few hours, relieve the pressure and then check to see if anything
leaked.

Questions:
1) Is this concept of pressure testing sound?
2) Is there a cheaper way to do it?
3) Most importantly, is there an easier way to do this?

Thanks and please resist the urge to point out the 100's of other
failure points that I will be facing in this project such as watertight
bulkhead fittings, ballast systems, propulsion, electronics, stability
control, corrosion, battery systems, faily safe safety systems, etc,
etc...

-M


60 psi or better seems a bit much for a pressure cooker or an autoclave. I
would think you could make one out of a 6 or 8 inch pipe nipple and a couple
caps (should be able to find one at any "industrial" plumbing supply...).
That should take at least 100 psi safely. I would be inclined, for safety
reasons, to fill it as full as possible with water and keep the volume of
air space to a minimum and not to get too cozy with it while it is under
pressure...

Jerry

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.

The actual pressure (including the 14.7 psi for surface air) will be ~ 45
psi.

You'll want to do your testing around 100 psi.


Anyway, my thought was to fill some already pressure resistant device
such as a pressure cooker or autoclave chamber (hello ebay!) with water
and then use shop air to increase the pressure. I don't need a viewing
window as I would basically take it up to pressure, leave it there for
a few hours, relieve the pressure and then check to see if anything
leaked.

You might want to consider building a test vessel from large-diameter pipe
and flat plate.

Don't forget that you'll need something that can be sealed against *more*
than your test pressure...


Questions:
1) Is this concept of pressure testing sound?

Seems so.

2) Is there a cheaper way to do it?

I don't *think* so...

3) Most importantly, is there an easier way to do this?

Not really. G

Thanks and please resist the urge to point out the 100's of other
failure points that I will be facing in this project such as watertight
bulkhead fittings, ballast systems, propulsion, electronics, stability
control, corrosion, battery systems, faily safe safety systems, etc,
etc...

-M

wrote:


Questions:
1) Is this concept of pressure testing sound?
2) Is there a cheaper way to do it?
3) Most importantly, is there an easier way to do this?


Wouldn't it be easier and cheaper to dangle the parts on a 70' wire in a
deep lake?

Gary Brady
Austin, TX

"Gary Brady" wrote in message
nk.net...
wrote:


Questions:
1) Is this concept of pressure testing sound?
2) Is there a cheaper way to do it?
3) Most importantly, is there an easier way to do this?


Wouldn't it be easier and cheaper to dangle the parts on a 70' wire in a
deep lake?

Gary Brady
Austin, TX

LOL!
The minimalist approach!

I love it.

(except that it would need to be 100-140' deep)

--
Jeff R.

Anyway, my thought was to fill some already pressure resistant device
such as a pressure cooker or autoclave chamber (hello ebay!) with water
and then use shop air to increase the pressure.

Corny kegs, formerly used by soda fountains, but now mostly used as surplus
items in the home brewing hobby, are cheap ($10 surplus), have a nice big
opening, have a 100 psi working pressure, last forever (all stainless), and
are easily resold. A homebrew hobby supplier will also have the fittings
to connect your shop air.

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.

Anyway, my thought was to fill some already pressure resistant
device
such as a pressure cooker or autoclave chamber (hello ebay!) with
water
and then use shop air to increase the pressure. I don't need a
viewing
window as I would basically take it up to pressure, leave it there
for
a few hours, relieve the pressure and then check to see if anything
leaked.

Questions:
1) Is this concept of pressure testing sound?
2) Is there a cheaper way to do it?
3) Most importantly, is there an easier way to do this?

Thanks and please resist the urge to point out the 100's of other
failure points that I will be facing in this project such as
watertight
bulkhead fittings, ballast systems, propulsion, electronics,
stability
control, corrosion, battery systems, faily safe safety systems, etc,
etc...

-M


A good, heavy duty paint or sandblaster pot should work.....

"Richard J Kinch" wrote in message
. ..
Anyway, my thought was to fill some already pressure resistant
device
such as a pressure cooker or autoclave chamber (hello ebay!) with
water
and then use shop air to increase the pressure.

Corny kegs, formerly used by soda fountains, but now mostly used as
surplus
items in the home brewing hobby, are cheap ($10 surplus), have a
nice big
opening, have a 100 psi working pressure, last forever (all
stainless), and
are easily resold. A homebrew hobby supplier will also have the
fittings
to connect your shop air.

I've got one of those in my garage, but I don't think something 6X6
will fit through the opening....

1 yes
2 Only if you already have a boat and live near the water.
3 No

But I would suggest using something more like a dead weight tester
instead of air. That is using a piston to pressurize the paint pot or
whatever. The reason is stored energy. Lots of energy with compressed
air. Very little stored energy using a piston like a master brake
cylinder to pressurize the tank. Also if you have a leak you might be
able to realize it sooner.

Dan

wrote:

Questions:
1) Is this concept of pressure testing sound?
2) Is there a cheaper way to do it?
3) Most importantly, is there an easier way to do this?



-M

Jeff R wrote:

"Gary Brady" wrote in message
nk.net...

wrote:


Questions:
1) Is this concept of pressure testing sound?
2) Is there a cheaper way to do it?
3) Most importantly, is there an easier way to do this?


Wouldn't it be easier and cheaper to dangle the parts on a 70' wire in a
deep lake?

Gary Brady
Austin, TX


LOL!
The minimalist approach!

I love it.

(except that it would need to be 100-140' deep)

--
Jeff R.


Start with a bathtub or swimming pool. Then work up to the local Dam or ocean drop-off.

Lake Tahoe would be way cool as it is very deep.

Good luck - sounds like a fun RC.

Hope you will have a camera port!

Martin

--
Martin Eastburn
@ home at Lion's Lair with our computer lionslair at consolidated dot net
NRA LOH, NRA Life
NRA Second Amendment Task Force Charter Founder

----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----

wrote:

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.

Anyway, my thought was to fill some already pressure resistant device
such as a pressure cooker or autoclave chamber (hello ebay!) with water
and then use shop air to increase the pressure. I don't need a viewing
window as I would basically take it up to pressure, leave it there for
a few hours, relieve the pressure and then check to see if anything
leaked.

Questions:
1) Is this concept of pressure testing sound?
2) Is there a cheaper way to do it?
3) Most importantly, is there an easier way to do this?

Thanks and please resist the urge to point out the 100's of other
failure points that I will be facing in this project such as watertight
bulkhead fittings, ballast systems, propulsion, electronics, stability
control, corrosion, battery systems, faily safe safety systems, etc,
etc...

-M


You could do worse than to look at the leak testers that the
watchmakers use. Mostly they test under a vacuum condition while
submerged in water. The leak tester has a clear pane or a bell jar that
allows the watch to be seen. The watch is submerged and a vacuum is
drawn, and the repairman looks for bubbles escaping. If any are seen,
they are duly noted and the watch is removed before it can absorb an
appreciable amount of water through the venting gaps. Repairs are then
made to the seals, etc.
Some testers subject the case of the watch to air pressure first, for a
period of time, then submerge them and observe for bubbles.

I like the simplicity of the long rope and a lake idea, myself, though
it makes it a bit tougher to determine the actual failure mode or point.

Cheers
Trevor Jones

"Gary Brady" wrote: Wouldn't it be easier and cheaper to dangle the parts on
a 70' wire in a deep lake?
^^^^^^^^^^^^^
Depends. Not everyone lives on the shore of a deep lake.

wrote: (clip) But I would suggest using something more
like a dead weight tester instead of air. (clip) The reason is stored
energy. Lots of energy with compressed air. (clip)
^^^^^^^^^^^^^^^^^^
If you have air available, and you know how, you can do it safely. Have a
small volume of air in contact with the water, connected to the supply
through a small orifice, or a nearly closed valve. If you get a rupture in
the test vessel, the pressure will drop, and air will only hiss from the
supply. (The danger from high pressure gas or steam exists only if there is
a substantial volume which can explode.)

Rick writes:

Anyway, my thought was to fill some already pressure resistant
device
such as a pressure cooker or autoclave chamber (hello ebay!) with
water
and then use shop air to increase the pressure.

Corny kegs, formerly used by soda fountains, but now mostly used as
surplus
items in the home brewing hobby, are cheap ($10 surplus), have a
nice big
opening, have a 100 psi working pressure, last forever (all
stainless), and
are easily resold. A homebrew hobby supplier will also have the
fittings
to connect your shop air.

I've got one of those in my garage, but I don't think something 6X6
will fit through the opening....

The opening is about a 4 x 3-1/4 inch oval. I thought the OP said the
parts were small.

On Wed, 06 Jul 2005 04:21:56 GMT, "Leo Lichtman"
wrote:


"Gary Brady" wrote: Wouldn't it be easier and cheaper to dangle the parts on
a 70' wire in a deep lake?
^^^^^^^^^^^^^
Depends. Not everyone lives on the shore of a deep lake.


Lake? Whats that?

Gunner, California High Desert


"Pax Americana is a philosophy. Hardly an empire.
Making sure other people play nice and dont kill each other (and us)
off in job lots is hardly empire building, particularly when you give
them self determination under "play nice" rules.

Think of it as having your older brother knock the **** out of you
for torturing the cat." Gunner

Gunner wrote:
On Wed, 06 Jul 2005 04:21:56 GMT, "Leo Lichtman"
wrote:


"Gary Brady" wrote: Wouldn't it be easier and cheaper to dangle the parts on
a 70' wire in a deep lake?
^^^^^^^^^^^^^
Depends. Not everyone lives on the shore of a deep lake.



Lake? Whats that?

That's that thing you think you see off in the distance..


Gunner, California High Desert


"Pax Americana is a philosophy. Hardly an empire.
Making sure other people play nice and dont kill each other (and us)
off in job lots is hardly empire building, particularly when you give
them self determination under "play nice" rules.

Think of it as having your older brother knock the **** out of you
for torturing the cat." Gunner

On Wed, 06 Jul 2005 06:56:18 -0400, the opaque JohnM
clearly wrote:

Gunner wrote:
On Wed, 06 Jul 2005 04:21:56 GMT, "Leo Lichtman"
wrote:

"Gary Brady" wrote: Wouldn't it be easier and cheaper to dangle the parts on
a 70' wire in a deep lake?
^^^^^^^^^^^^^
Depends. Not everyone lives on the shore of a deep lake.

Lake? Whats that?

That's that thing you think you see off in the distance..

That's merely a Mojave mirage. We have a river up here, but it's only
3-6' deep in most parts. That wouldn't work.


P.S: I'm about to make my annual trek to the Bay Area and even after
taking out a loan for gasoline, I won't be able to to afford to make
the extra leg down to your house to go shopping and fill up my pickup
bed, damnit. Maybe next year.


-
Better Living Through Denial
------------
http://diversify.com Dynamic Websites, PHP Apps, MySQL databases

A bit back a friend of mine used to dive, he explained that to test the
air bottles they were filled with water (pressurised)the air bottles
were placed in a tank full of water to contain any faliures.
If you want to test your enclosures this might be a way as you'd fill
the enclosure with water under pressure and see if any came out, rather
than setting up a 140' tank in your living room to see if any went in.

Just my 2cents (though, I spend pounds!)


Lee

But I would suggest using something more like a dead weight tester
instead of air. That is using a piston to pressurize the paint pot or
whatever. The reason is stored energy. Lots of energy with compressed
air. Very little stored energy using a piston like a master brake
cylinder to pressurize the tank. Also if you have a leak you might be
able to realize it sooner.

Dan


If you keep the chamber full of water, and then pressurise it with air, the
only air in the system will be that in the pipe between the chamber and the
compressor. The volume will be minimal, and as the stored energy is
porpotional the the product of the pressure and volume of the gaseous part
only , very little energy will be stored.

Tom

In article .com,
wrote:

Anyway, my thought was to fill some already pressure resistant device
such as a pressure cooker or autoclave chamber (hello ebay!) with water
and then use shop air to increase the pressure. I don't need a viewing
window as I would basically take it up to pressure, leave it there for
a few hours, relieve the pressure and then check to see if anything
leaked.

Normal pressure cookers only go to 15psi, but that is steam so there has
to be a good safety margin built in. Just be aware you are
overpressurizing the vessel and be prepared for catastrophic rupture.

--
Free men own guns, slaves don't
www.geocities.com/CapitolHill/5357/

Thanks for all the responses. It's nice to get a couple different
viewpoints and suggestions.

-M

On Wed, 06 Jul 2005 06:56:18 -0400, JohnM wrote:

Gunner wrote:
On Wed, 06 Jul 2005 04:21:56 GMT, "Leo Lichtman"
wrote:


"Gary Brady" wrote: Wouldn't it be easier and cheaper to dangle the parts on
a 70' wire in a deep lake?
^^^^^^^^^^^^^
Depends. Not everyone lives on the shore of a deep lake.



Lake? Whats that?

That's that thing you think you see off in the distance..

Hummm we call that a mirage... "witch water". Ya mean if I chase it
far enough it gets wet?

Gunner



Gunner, California High Desert


"Pax Americana is a philosophy. Hardly an empire.
Making sure other people play nice and dont kill each other (and us)
off in job lots is hardly empire building, particularly when you give
them self determination under "play nice" rules.

Think of it as having your older brother knock the **** out of you
for torturing the cat." Gunner

"Pax Americana is a philosophy. Hardly an empire.
Making sure other people play nice and dont kill each other (and us)
off in job lots is hardly empire building, particularly when you give
them self determination under "play nice" rules.

Think of it as having your older brother knock the **** out of you
for torturing the cat." Gunner

On Wed, 06 Jul 2005 04:46:57 -0700, Larry Jaques
wrote:


P.S: I'm about to make my annual trek to the Bay Area and even after
taking out a loan for gasoline, I won't be able to to afford to make
the extra leg down to your house to go shopping and fill up my pickup
bed, damnit. Maybe next year.


Damit. And I need some help in carting stuff off, as I lost the
warehouse. They are going to bulldoze it to make room for an empty
lot. Sigh..and Ive got till the first of Aug to clear out my stuff.

There is at least one fixerupper Boyer Shultz surface grinder in there
with your name on it, free of charge. (actually two or more..but Im
sure someone can make it over)


Gunner

"Pax Americana is a philosophy. Hardly an empire.
Making sure other people play nice and dont kill each other (and us)
off in job lots is hardly empire building, particularly when you give
them self determination under "play nice" rules.

Think of it as having your older brother knock the **** out of you
for torturing the cat." Gunner

In article .com,
wrote:

[...]

3) Most importantly, is there an easier way to do this?

Dunno if this is appropriate to what you're doing, but waterproof
watches are tested with vacuum. They suspend the watch in a small
container full of water then draw a vacuum and look for bubbles. Has
the benefit of keeping the innards dry if there's a failure.
Of course, that's backwards from what you're doing, and only puts out
a single atmosphere at best, but they certify watches to 100M or so
doing it.

--
B.B. --I am not a goat! thegoat4 at airmail dot net
http://web2.airmail.net/thegoat4/

On Wed, 06 Jul 2005 15:47:49 GMT, the opaque Gunner
clearly wrote:

On Wed, 06 Jul 2005 04:46:57 -0700, Larry Jaques
wrote:


P.S: I'm about to make my annual trek to the Bay Area and even after
taking out a loan for gasoline, I won't be able to to afford to make
the extra leg down to your house to go shopping and fill up my pickup
bed, damnit. Maybe next year.

Damit. And I need some help in carting stuff off, as I lost the
warehouse. They are going to bulldoze it to make room for an empty
lot. Sigh..and Ive got till the first of Aug to clear out my stuff.

Suckage, that's twice in a year.


There is at least one fixerupper Boyer Shultz surface grinder in there
with your name on it, free of charge. (actually two or more..but Im
sure someone can make it over)

I'd love some steel and other metal tidbits, and a mini mill/mini
lathe, but I don't have room for much else. My 2-car shop (well, shop
with attached home) is mostly designated for wooddorking rather than
metalheading. the table saw, carving bench, lumber rack, assembly
table, bandsaw, planer, dust collector, bench, clamp rack, air
compressor, tool box, fridge (fire safe for flammables) and belt
sander/drillpress/mortiser bench pretty much take up the space.

Since the cheaparse Chiwanese 14" cutoff saw from Ebay fried itself in
5 minutes, I could use a small metalcutting (4x6?) bandsaw, though.
And a sweet little HF TIG unit.

Some other time, I guess. Darn.


-
Better Living Through Denial
------------
http://diversify.com Dynamic Websites, PHP Apps, MySQL databases

I think the final answer is a 2-1/2 gallon pressure paint tank from
Harbor Freight because:

1) It has a good size opening
2) Can take the pressure (80psi)
3) Affordable ($80 US)
4) AND they have a store a one mile away from my house

http://www.harborfreight.com/cpi/cta...emnumber=37515

Again, thanks for the suggestions.

I work with underwater vehicles all the time (We do R&D on sonar
systems) and the way we check for leaks is to draw a vacuum inside the
vehicle and let it sit as long as possible and see if the reading
changes. The less obvious advantage of this is that we can back fill
with dry nitrogen and not have to worry about condensation when the
vehicle hits the cold water.
We do have a fancy pressure test facility that tests for structural
integrity, but most of our shells are rated for at least 1200 feet. You
might be surprised how little aluminum it takes in a properly designed
shell to be rated for 1200 feet. I would think that as long as you
design your hull to hold pressure and are just worried about the o-rings
and other seals the vacuum test might work.

-Kris

wrote:
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.

Anyway, my thought was to fill some already pressure resistant device
such as a pressure cooker or autoclave chamber (hello ebay!) with water
and then use shop air to increase the pressure. I don't need a viewing
window as I would basically take it up to pressure, leave it there for
a few hours, relieve the pressure and then check to see if anything
leaked.

Questions:
1) Is this concept of pressure testing sound?
2) Is there a cheaper way to do it?
3) Most importantly, is there an easier way to do this?

Thanks and please resist the urge to point out the 100's of other
failure points that I will be facing in this project such as watertight
bulkhead fittings, ballast systems, propulsion, electronics, stability
control, corrosion, battery systems, faily safe safety systems, etc,
etc...

-M

In article ,
Leo Lichtman wrote:

"Gary Brady" wrote: Wouldn't it be easier and cheaper to dangle the parts on
a 70' wire in a deep lake?
^^^^^^^^^^^^^
Depends. Not everyone lives on the shore of a deep lake.

So -- get 70+ feet of pipe large enough to hold your parts, and
one cap. Assemble, stand it on end, brace it form the sides, and fill
it with water. Instant small but deep lake. :-)

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

Yes I used to work with underwater gear and we used to drill and tap and
install threaded valve in main housing then pull a vacuum with a handheld
pump. Then used to leave it and watch gauge. If its air tight it will
certainly be water tight
Martin
"Kris" wrote in message
...
I work with underwater vehicles all the time (We do R&D on sonar systems)
and the way we check for leaks is to draw a vacuum inside the vehicle and
let it sit as long as possible and see if the reading changes. The less
obvious advantage of this is that we can back fill with dry nitrogen and
not have to worry about condensation when the vehicle hits the cold water.
We do have a fancy pressure test facility that tests for structural
integrity, but most of our shells are rated for at least 1200 feet. You
might be surprised how little aluminum it takes in a properly designed
shell to be rated for 1200 feet. I would think that as long as you design
your hull to hold pressure and are just worried about the o-rings and
other seals the vacuum test might work.

-Kris

wrote:
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.

Anyway, my thought was to fill some already pressure resistant device
such as a pressure cooker or autoclave chamber (hello ebay!) with water
and then use shop air to increase the pressure. I don't need a viewing
window as I would basically take it up to pressure, leave it there for
a few hours, relieve the pressure and then check to see if anything
leaked.

Questions:
1) Is this concept of pressure testing sound?
2) Is there a cheaper way to do it?
3) Most importantly, is there an easier way to do this?

Thanks and please resist the urge to point out the 100's of other
failure points that I will be facing in this project such as watertight
bulkhead fittings, ballast systems, propulsion, electronics, stability
control, corrosion, battery systems, faily safe safety systems, etc,
etc...

-M

"DoN. Nichols" wrote in message
...
Depends. Not everyone lives on the shore of a deep lake.

So -- get 70+ feet of pipe large enough to hold your parts, and
one cap. Assemble, stand it on end, brace it form the sides, and fill
it with water. Instant small but deep lake. :-)

Don't forget the 70 foot ladder. And don't step on the top! It's
dangerous.

Peter

Gunner wrote:


Lake? Whats that?

That's that thing you think you see off in the distance..


Hummm we call that a mirage... "witch water". Ya mean if I chase it
far enough it gets wet?

Gunner

Heh.. probably want to take some lunch with you though.

Interesting that it doesn't require warm weather for a mirage- I'll see
them here in the winter on real cold days, just takes a little sun on
the asphalt.

John

Keywords:
In article om, wrote:
I think the final answer is a 2-1/2 gallon pressure paint tank from
Harbor Freight because:

1) It has a good size opening
2) Can take the pressure (80psi)
3) Affordable ($80 US)
4) AND they have a store a one mile away from my house

http://www.harborfreight.com/cpi/cta...emnumber=37515

The traditional approach is to take a 16" surplus naval shell and make it
into a pressure vessel. Doc Edgerton used one to develop all the
underwater cameras for Cousteau. He got a good deal on the shells after
WWII and his company then sold them for others to use. They have an 8"
left hand threaded plug in the back end, and will handle pressures as
high as the ocean can deliver. I used his setup for my thesis work on
underwater radio.

Doug White

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!

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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