I have a few dive lights that I want to test, but I will not be diving anytime soon.
Is it possible to make hydrostatic chamber/pressure vessel out of, say, schedule 40 PVC pipe? Maybe a 4” diameter with end caps, and a Schrader or French valve inserted on one end? I would then fill with water, asemble with light inside, and pressurize to appropriate PSI with a high presure bike pump.
Is this possible without blowing myself up…lol :quest:
PVC can handle a few hundred psi…how deep equivalent would that be?
One light I have is supposed to be good to 50 meters.
By my calculation, that would be approximately 75 PSI. But I might be way off.
Lowes advertises their schedule 40 pipe to be at 450 PSI, so that should be more than sufficient if my numbers are correct.
Edit: It might be around 90 PSI…think I have to add about 15 PSI because that is the pressure at sea level.
Any physics pros in the house? :bigsmile:
Looks like 4” diameter schedule 40 PVC can take up to 220 psi max working pressure. Every 10m adds about 14.7 psi so it’d be the equivalent of 460 ft at max pressure.
I’m not sure how the end caps will hold at that pressure but 180 ft is about 81+14.7 psi.
That glue is pretty strong, I wouldn’t worry assuming you glued it well.
Welcome to BLF! :party:
I didn’t realize that was my first post!
Plan B
Schedule 80 pipe 630 psi vs 450
Info here
So Chazzy, what exactly is the 460 ft at max pressure from? Is that the max the schedule 40 can take?
Isn’t 50 meters the 81+14.7 number you put at the end of your post? Therefore, schedule 40 would be more than sufficient?
I think a water filled pressure tank is safe because water doesn’t expand much when the pressure is released. An air or gas filled tank would be dangerous.
Get a 25 or 50ltr air compressor, you can often pick them up at yard/garage sales pretty cheap, I got one for £10
Get a 6 inch (or bigger) removable access panel/plug from a plumbing suppliers, cut hole in end of the air tank to fit your access panel/door and seam weld it in place.
You now have what you need, and you will know it’s safe, the compressor that sits on the top will do 150 psi, the tanks always have built in safety/pressure relief valves and normally a manual pressure relief valve too
Or you can add a half inch manual leaver valve to one of the old air line tapping on the tank to release the pressure once your test is finished, before you open the access door
They normally have a pressure gauge on the tank too, so you will know how much pressure/how deep your torch is going
They also have a drain on the bottom, so it’s easy to empty the water when you done testing
Sorry, I should be more clear. 220psi is the equivalent to 460 ft.
50m is also about 88.2 psi so you’ll have no problem holding that kind of pressure with schedule 40.
So…if I fill this thing with water, seal it up, then pump air into it, I would need to pump until I reached 88.2 PSI…correct? IOW…the air pumped into the vessel would be the same PSI as the water?
try goggling “pressure pot” and one of the first few links will probably be a diving forum, that might be helpful. There was a really good thread floating around on one of the diving forums about the testing of watches(same concept), if you can find that thread.
the least amount of air is in the vessel, the safer you are, (and the less you have to pump). air compresses (stores energy), and water does not. You want it overflowing full.
Assuming the light is only submerged a couple inches under water, the gauge reading will be slightly lower than what the light is withstanding.
If there is 6” of water above the light the gauge will read 88.2 psi but the light will be facing 88.5 psi. Not a huge difference but essentially the same pressure.
Or go out to sea a ways and lower the light on a measured length of wire?
Valve stems that are replaced with tires are the answer, and easily obtained. The rest is just a plastic time capsule.
Water filled ballon and a Slide Trombone.
You will have an issue if you use a bike pump, as you pump air into your pipe/vessel full of water, as the pressure increases, the pressurised air going in will force the water back up the line into the pump
(In the same way they get oil up the drill pipe in a gas/oil rig in an offshore oil platform, when the reserve they tap stops coming up the pipe naturally, they pump some of the gas back down the pipe which forces the oil back up the pipe to the surface)
For your system to work, you will need a reserve of air of greater pressure than the final pressure you wish to achieve in your pipe/vessel
A bottle of compressed air, a diving bottle or something, or a oxygen bottle from a gas axe set would do
This is the safest way and you might bring home a fish dinner 