I can’t wrap my head around this.
There is water in most of the chamber. I would leave maybe 1/2” air at top. Then pump air into vessel…but after each pump, you are saying water will rise upward (float), defying gravity, through the pressurized air and into the bike pump tube?
If this is the case, my kind is blown… :Sp
Edit: Or, does some water vaporize as pressure is reduced (at the end of each pump), then vapor rises to the tube?
I was thinking of using 4” schd. 40 PVC, 1-2 ft long, with a glued cap on one end, and something like a cleanout adaptor/connection glued to the other end. That way, I could unscrew the cleanout cap to load/unload whatever I would test. It would probably need an additional 4” seal for the cap to hold pressure.
One thing I have noticed is that cleanout connections are advertised as not appropriate for pressue applications. However, 80 or so PSI doesn’t seem too high to me.
Not sure if 80psi would be adequate to ensure reliable service but if you were careful entering the water might be ok. What about using a neumatic tool quick connect instead of a schrader valve? Larger diameter threads and higher pressure rating. Common pipe thread size as well. Hit 120-130 psi no problem. Also, a plug has the threads on the outside where pressure will expand the pipe opening the threads. Better to have a cap with the threads on the inside where pressure will actually tighten the fitting.
Looks like you should go with schedule 80 PVC then
http://www.harvel.com/technical-support-center/product-specifications/pvc-pipe-schedule-80
3” chunk of sched 80 pipe (Max WP: 370 PSI)
3” end cap
3” threaded end cap
3” threaded plug
Now all you need to do is devise a way to inject compressed air into the tube w/ a pressure gauge and voila a pressure chamber
I’d still be concerned with the valve blowing out if it’s just tapped into the plastic but maybe adding to the wall thickness where it’s tapped would be sufficient.
It’s not defying gravity, but it will want to rise up the tube after each pump stroke, you would need a pump with say a 8 foot stroke so you could pressurise your tank in one stroke lol , obviously that’s not practical, that’s why you need a reserve of compressed air so you can pressurize your tank in one go as that way the constant pressurized air going in will stop the water coming back up the tube
To try and explain it a bit better, You can’t compress water , but obviously you can compress air, so as you pump the air in to your tank with your piston type pump, your pressuring the air in the tank, which is displacing the water, as the air pressure increases in your tank that water can’t compress and wants to escape, now all the while you are on the pressure stroke with your pump the pressure from your pump is greater than the air pressure in the tank and the water stays in the tank, as soon as you draw your pump back to take the next pressure stroke you have negative pressure on the pump side and the water in the tank under press, rushes back up the pipe to fill the void
That’s why you need either a constant supply of high presure air, or some sort of non return valve on your hand pump
Hope that helps, probably wasn’t the best description but hopefully it makes sense
As long as the air inlet is above the water level this won’t be a problem. Also, the inlet valve should close as soon as the pump stroke ends anyway.
That’s what we thought, and all the while we had no water in the equation it worked fine (we’d built pretty much what the op described, just using black iron pipe and fittings instead of plastic) we had it over 100 psi No problem, but as soon as we tried it with water in the water would come back up the pipe and in to the pump once we got to around 40 psi iirc
We tried a couple of different pumps and a foot pump, happened with them all?
Worked fine if we used a dive bottle to pressurise it, so the op’s build idea is sound
In the end though we built one out of an old air compressor as it was bigger and more practical and looked a bit less Heath Robinson than our first attemps
There are a number of ideas for testing watches and their water resistance. One that I’ve played with uses a 1 liter nalgene bottle but one has to be very careful about putting too much pressure in it. I must say that I am not that comfortable beyond 50 psi and I keep it out of my direct line of sight in case it blows.
Here is one using a water filter chamber:
http://www.christopherwardforum.com/viewtopic.php?f=33&t=10816
Here is a more comprehensive model:
http://www.flynwill.com/Watches/Waterproof/
Not sure if these would be large enough but it may give you some ideas.
John.
Tap it at a coupling you’ll get double wall thickness. For pressure, a propane cylinder with any amount of liquid propane in it will give you up to 190 psi. Just don’t smoke on depressurization.
Worse comes to worse, tap thru the threaded end cap on a flat end…then use a washer and nut and some RTV to seal it
Well…I went out and purchased most of the items for this sucker:
This pic has:
1 x 4” tube by approx. 16” flared piece of schedule 40 PVC pipe.
1 x 4” end cap.
1 x 4” internal fitting with threads on other end.
1 x 4” threaded screw plug.
1 x 4” rubber seal.
1 x Oatey PVC cement (I have some primer somewhere around here).
1 x Fox HP pump (already had that for shock on my MTB).
This is what it will look like open and closed, sans valves.
I have two of these Schrader valves coming which I will mount somewhere…probably on the threaded plug. One for an Ashcroft gauge I have laying around here somewhere, and the other for the HP pump.
I have lots of questions, but the most important one is…am I crazy?
That is exactly what I plan to do with the Shrader valves.
Crazy…like a fox 
Will be nice to actually see if some of the IPX8 rated lights are actually capable of handling deep pressures
I know my flashlights are water resistant enough for trotting around in the rain or maybe dropping in a puddle, but some of these dive lights were someones life might depend upon them really need ALOT more testing…
What PSI are you planning on pushing that sch40 up to?
I wonder if they have clear 4” sch40/80, you can use that for the sides, then drop a running light inside the tube and see if it goes dark, right now…you won’t be able to tell till your timer is up and you open the vessel back up
sure nuff they do
OH SNAP…they have clear everything! (but daggum it ain’t cheap!
http://www.usplastic.com/catalog/default.aspx?catid=592&clickid=popcorn
Nice find on the clear PVC. $25/ft for sched.40, and $33/ft for sched. 80…yikes! However, you wouldn’t need more than 1-2 ft.
We’ll see how this one goes together before spending that kind of dough. :money_mouth_face:
Sounds like your going to be testing lights with them switched on?
Use distilled water in your pressure vessel, that way if the light your testing let’s water in, the water won’t short out the circuitry ( obviously it may cause other damage, but at least it won’t short out the circuit boards etc)
This is mine ,made from 10 lt. dive bottle .I built to test dive flashlight up to 8 bar.
Very nice!
8 bar = approx 116 psi…right? Surely this awesome chamber can handle more than that…
Maybe that’s as high as his compressor will go but you’re right the input parts seem to be the weakest links.
The Plexiglas cover (5 mm thick) bends a bit to 8 bar, for pressures greater than what I have to use metal one.
The valve, pressure gauge and quick coupling of compressor are safe up to 20 bar.
The transparent cover is useful to see if the torch is switched off or floods, in which pressure and where water enters.
I tested up to 12 bar (as my compressor) for my use. 8)