Testing computer battery hatch and O ring for security against leaks

[Altamira]

If a dive computer battery hatch cover and O ring do not leak in the pool at 15' depth, is it likely it would stay watertight at 3-4 bar? I am in the final stages of testing a privately designed, 3D printed Delrin battery hatch cover and a baked Aqualung I550 battery hatch cover that appear to now fit into my two Aeris Atmos AI computers (OEM replacements no longer available). Both hatch covers do not show any air bubble leaks while submerged in a bucket of water for 30 minutes, and wonder if it would be productive to test them in the pool before trying them on an actual dive to typical depths in fresh or saltwater? My thought is that if there is no leak at 15', it will probably be OK during a dive, but I could be way off base in my thinking. Any thoughts or comments?

 

[guruboy]

15' guarantees 15' or less. You'll want to test at higher pressure.

Search for threads about making a pressure tester at home. Essentially a PVC tube pressurized with tap water.

BTW, air volume decreases as pressure increases. So of course you didn't see any bubbles.

 

[Altamira]

15' guarantees 15' or less. You'll want to test at higher pressure.

Search for threads about making a pressure tester at home. Essentially a PVC tube pressurized with tap water.

BTW, air volume decreases as pressure increases. So of course you didn't see any bubbles.

I am not sure I understand why there would be any pressure increase/air volume increase in a bucket of water sitting at my house. I routinely test my camera housing this way before going on a dive trip, and if there is a problem with the O ring, I see bubbles escaping from the housing. Why would the computer battery hatch be any different?

 

[guruboy]

I suppose since it is always true that air will go upwards, if you had a leak from the "top" of the container, the air would come out indicating a leak.

I was thinking more of a pressurized rigid vessel containing air. Let's use a tank held with the valve at the bottom as an example.

If you opened the valve with 3000psi in it, air would expand and escape, even if it has to go out the bottom.

However, if the tank is "empty" the water pressure is greater than the air pressure inside the tank, so water would force its way in and compress the air inside, so no gas would escape even though there is a leak.

 

[guruboy]

Regarding a camera housing, that kind of test will catch obvious leaks but just because an oring will seal at low pressure differential doesn't mean it will seal at a higher pressure differential.

 

[BRT]

I use a clear house water filter housing and add pressure with an air regulator. You could also add pressure with a garden hose.

 

[Altamira]

I guess the best way to thoroughly test the seal would be to take the boat down to the lake, plug the HP hose, drop the computer in mesh bag with 100' of rope, and sink in 90' of water. But that is a PITA, so maybe I will try the water hose first because we have very high water pressure (@85 psi). I was hoping to find a testing shortcut because I have never had an O ring leak at depth if it was not leaking in a bucket of water at the surface. Perhaps I have just been very lucky in the past with O rings, and hope I don't fry one of my computers testing both of these work around battery hatch covers. I am really annoyed at Pelagic Systems for not keeping a stock of the cheap to manufacture plastic battery hatch covers that fit the Aeris computer without getting creative.

 

[BRT]

.445 psi per foot of seawater so 85 psi is 191 feet.

 

[divinh]

I've had a camera housing that was fine for 24 hrs in 1' of water, but leaked when taken to depth, 55' (test1) and 75' (test2). The problem wasn't with the o-ring, but with excess mold lines along where the o-ring sits. I found a webpage that detailed how to safely file down the mold lines and I've since taken it down to max depth 88'. 26 dives with it so far.

 

[lowlysubaruguy]

I have seen several high end watch pressure tanks selling on eBay for next to nothing. Search headings with watch repair type names. It must be common in the watch repair business to pressure test what your working on.