Pressure Pot to Test DIVE LIGHTS!

[Doc Ed]

My more circuitous method for calculation is converting PSI to ATM (14.7 PSI = 1 ATM) then correlating every ATM of change to 10 meters change in depth (1 ATM of change = 33 feet). Another on-the-fly calculation is converting meters to feet... these conversions are something familiar to most divers who have to deal with gauges in either imperial or metric values.

 

[gcbryan]

100fsw (feet salt water) = 44 psi.

That's not correct. You forgot surface pressure. 100fsw is 4 ATA or 4 * 14.7 psi so 58.8 psi.

 

[Doc Ed]

New to this and this is all fantastic and radical, I love that you all are using ingenuity and self reliance to create the toys that are way overpriced.
Sorry if I missed it, but how do you correlate PSI to depth ? Is there a calculation?
Thanx AV

Oh, there's something that you should be careful about when referring to correlations between pressure and depth - be sure to specify if its in absolute pressure (as GC is referring to) or PSIg (gauge pressure). On the surface at sea level, we're all at an absolute pressure 0f 14.7 PSI (or 1ATM), but since the gauges we use are zeroed out at sea level, at 33 ft, it would be 14.7 PSIg (but with an absolute pressure of 29.4), at 66ft, 29.4PSIg (or 44.1 psi absolute), and at 100ft, it would be 44.1 PSIg (and 58.8 PSI absolute).

 

[Racket]

That's not correct. You forgot surface pressure. 100fsw is 4 ATA or 4 * 14.7 psi so 58.8 psi.

I think you should add the word "entirely".

44.1 psi would be the Δ between the surface and 100FSW correct?

 

[gcbryan]

I think you should add the word "entirely".

44.1 psi would be the Δ between the surface and 100FSW correct?

That is correct. However when you are at 100 fsw you and your light are experiencing 58.8 psi and that's what you should be testing for. Actually you should probably be testing for a static pressure equivalent to 300 fsw if you want a serious dive light.

 

[Racket]

That is correct. However when you are at 100 fsw you and your light are experiencing 58.8 psi and that's what you should be testing for. Actually you should probably be testing for a static pressure equivalent to 300 fsw if you want a serious dive light.

No you test for 44.1 psi because the the 14.7 psi = zero on a pressure gauge. Regardless you should always have a safety factor that is 20% of your max depth, so this conversation is somewhat moot.

 

[DIWdiver]

Don't forget to test at shallow depth as well. Some leaks show up at 15 ft, then seal when you go to 60 ft. What you are testing for at max depth is catastrophic failure, not leaks, except in rare designs where the case can distort enough to cause a leak, yet not implode.

 

[SmokedCPU]

thats true than many light that leaked, leak in shallow water, and some of these that leaked shallow, even dont flood at all when put down to abyss fast like hell !

Btw feeling a dx 1.5mm glass mag lens imploding at 78ft is cool. it sound like a gun shoot, and was the only nice thing in this boring dive at this time i did not have a test pot

 

[gcbryan]

thats true than many light that leaked, leak in shallow water, and some of these that leaked shallow, even dont flood at all when put down to abyss fast like hell !

Btw feeling a dx 1.5mm glass mag lens imploding at 78ft is cool. it sound like a gun shoot, and was the only nice thing in this boring dive at this time i did not have a test pot

Nothing like the real thing anyway (ocean testing that is)!

What was the diameter of the 1.5mm lens? 52mm?

 

[350xfire]

Put your dive computer in the pressure pot and you'll know exactly where you went!

 

[lucca brassi]

Put your dive computer in the pressure pot and you'll know exactly where you went!​

that is what friend did for our diving newspaper when put GALILEO SOL to 220 bar

http://translate.google.si/translate?sl=sl&tl=en&js=n&prev=_t&hl=sl&ie=UTF-8&layout=2&eotf=1&u=http%3A%2F%2Fwww.slodiver.net%2Fpreizkus%2Fgalileo_sol.prn.asp

 

[dusty2]

According to my calculations Pressure at 300 fsw is 150psi or 10 bar but that is adding the 33.3 for pressure at the surface. If you go by the concept that the gage is calibrated at surface pressure then you would remove one atm then it would com to somthing like 132 psi for 300 feet = 9.009009 atm X 33.3 = 299.9999997 pretty close I think. but then I am NOT related to Einstein even distantly:shakehead

 

[DimitrisV]

I made mine one week ago. I cut the cylinder on lathe machine
All the other job is done by me.

I tested yesterday to 2bar. I have to find a better pump or another way to push the air inside (the tank is almost full of water)

 

[350xfire]

You cut that big old tank without any support?

 

[DIWdiver]

Very nice work!

You could use a BC inflator hose and a scuba tank for an air supply. I bought an air tool regulator at the home store and put a BC fitting on the input, so I can power my air tools from a pony bottle. Much more convenient to use than a compressor, if your tool doesn't need high air volume. Then you could use the regulator to control the pot pressure. Make sure you add a bleed valve, because the regulator probably won't let the pressure back down.

As long as there's very little airspace in the system, the explosion hazard is small.

 

[Packhorse]

How much pressure do you think those 4 latches can hold back?

 

[betti154]

Nice setups.

My solution to the pressure pot problem is somewhat more simple. 6" pressure pipe with garden hose fitting. I fill it with water, drop in my housings and connect to garden hose to it. Dive computer confirms depth equivalent to 50-60m depending on mains pressure. Serious depth rating aside, my theory is if it's going to leak it'll do so in the first few metres.

The ends do bow out a little and the main oring springs a little leak now and then, but it takes only seconds to setup and costs less than $15.

 

[SmokedCPU]

How much pressure do you think those 4 latches can hold back?

I agree, when i calculated my pot to use it around 300PSI the numbers became impressive with a 6'' pipe. It was calculated as a safety, in fact i only go half way, but i wont get the lid in the head

Dont push these latches too mush or get back from the lid when pumping ...

 

[DIWdiver]

... Serious depth rating aside, my theory is if it's going to leak it'll do so in the first few metres.

I agree. Any o-ring in good condition can handle pressures far in excess of anything we see in diving. And higher pressures tend to push the o-ring into a BETTER seal, not a worse one. The seal is most likely to leak during your 10 foot (I'm American - sue me) safety or deco stop, unless the pressure at depth causes the housing to deform to the point where the seal fails.

I feel strongly that the most important pressure tests are at 10 feet and max depth. The first checks the seal, the second checks the housing. Leaving out either is doing half the job.

 

[DIWdiver]

Nice setups.

My solution to the pressure pot problem is somewhat more simple. 6" pressure pipe with garden hose fitting. I fill it with water, drop in my housings and connect to garden hose to it. Dive computer confirms depth equivalent to 50-60m depending on mains pressure. Serious depth rating aside, my theory is if it's going to leak it'll do so in the first few metres.

The ends do bow out a little and the main oring springs a little leak now and then, but it takes only seconds to setup and costs less than $15.

That's a pretty quick and easy setup. Actually a very nice build. If I didn't already have a test vessel, I'd seriously consider this design.

But in the US, 40-60 psi water pressure (3-4 bar) is common, and would simulate 120 ft/40m depth or less. 6 bar/60m equivalent pressure is considered high and on the verge of requiring regulation to prevent damage to household plumbing fixtures. If regulation is required, it is usually set at 40-60 psi.

While 60psi/120ft/40m should satisfy most recreational divers, I like to test below, within, and beyond the expected envelope to ensure good behavior and good reliability across the expected envelope.