Pressure Pot to Test DIVE LIGHTS!

[josb]

so some of you take lights down below 130+ feet of water (60 psi paint pot for instance) ?
I can hardly imagine.
Would minimizing the quantity of gas space inside of a light or other container make it more resistant?
Say for instance if the same seal is only protecting a cc of compressible gas instead of 2 cc?

The answer on your first question is YES.
The answer on your second one is NO.

Explanation 1, yes we go sometimes deeper then the 130 feet (± 40m) but that's not only the reason to test dive lights to a bigger depth then this, you would also like to have some safety ( I like a 100% safety and I test my lights up (down) to 10 bar (100m).

Explanation 2, it doesn't matter how much air is behind your seal, 1 cc will only be faster filled then 10 cc when it starts leaking.
It's the seal that should be OK regardless of the amount of air behind it.

 

[wquiles]

Thank you guys. It seems the unit from HF would indeed be a good first test platform (obviously not to 10 bar!). I think I am going to get one to start playing with this stuff. I will report back when I get it

Will

 

[350xfire]

Will:
Yes, I brought it up before. I do think that it would be a nice simple solution to manufacturing one from scratch. For $80 you can't go wrong.

 

[Codiak]

Joshb,
The only thing that's 100% with water and leaks, is that the water will leak in sometime.
If I was selling a light i only guarantee it to 50% of the psi I tested it at... But for DIY test, when it leaks I'll fix it for the next dives and switch to my backup.

 

[josb]

Joshb,
The only thing that's 100% with water and leaks, is that the water will leak in sometime.

Yes, but depends on your maintenance.

If I was selling a light i only guarantee it to 50% of the psi I tested it at... But for DIY test, when it leaks I'll fix it for the next dives and switch to my backup.

OK, I would do the same when I would sell my lights, advertising with a 50% safety (and knowing that there is still an extra safety) but I wasn't talking about selling.
By the way of course you can buy what I build

When it leaks at your first dive OK you have to switch to your backup but ...... you did a bad job.
Once I take one of my lights down on a dive I know its OK and not leaking (exept for that one time I finished a light just a couple of days before the holiday, it was OK in the pressure pot but the sealing cap on the toggle switch started to leak after a couple of dives, now I never use toggle anymore)

 

[wquiles]

I am curious and wanting to learn more about testing, now that I have the HF pot on its way to me. How long do you guys leave the light in the pressurized pot before you check for leaks? 24, 48 hours? Longer?

Will

 

[josb]

I am curious and wanting to learn more about testing, now that I have the HF pot on its way to me. How long do you guys leave the light in the pressurized pot before you check for leaks? 24, 48 hours? Longer?

Will

If it doesn't leak in the first couple of minutes why would it start to leak after 24 hours?
I usually put it in for 30 minutes to 1 hour or so.
When I want to test a switch (for instance a piezo) I go more rapid up and down in pressure to see if I get unexpected switching happening.

 

[350xfire]

I do 2 hours. I recently developed a small leak on mine so I will leave it in longer and let the compressor cycle a few times.

 

[eh4]

Are you guys using a color changing test paper like you'll find inside of a cell phone? Seems like with all the trouble of pressure testing you wouldn't want to simply count on a visual inspection, too easy to miss a bead of water in a seam or something. Or is it the case that once you have any leak at great pressure, that it'll inevitably become a substantial leak?

 

[warscout2]

How much did you guys pay to have a shop build a pot? I don't have access to equipment that would be able to handle this.

 

[lucca brassi]

Point is into rapid decompression , of equipment survive that , it will survive everything .Those you have metal light headed or tank it will be good to test equipment also on low temperature.

Otherwise good and caculated design don't need such testing it is just an certificate for good work .

 

[wquiles]

Otherwise good and caculated design don't need such testing it is just an certificate for good work .

Good points. I am designing the light to be dive-rated from day one, but like you said I do want to actually test it and make 100% sure my paper design hold up under pressure (pun to myself intended!) :devil:

 

[wquiles]

How much did you guys pay to have a shop build a pot? I don't have access to equipment that would be able to handle this.

I just ordered the unit from Harbor Freight to do testing up to an equivalent of 120-130 feet or so. On special right now for $80 or so - not too bad to get started with pressure testing, before moving to a more formal setup like others have shown in this thread

Will

 

[DIWdiver]

How much did you guys pay to have a shop build a pot? I don't have access to equipment that would be able to handle this.

Most of us built our own, didn't pay a shop. What you need to pay a shop depends heavily on what you want them to do...

What are you looking for? Maybe someone can help you out.

 

[lucca brassi]

I am designing the light to be dive-rated from day one, but like you said I do want to actually test it and make 100% sure my paper design hold up under pressure (pun to myself intended!) :devil:

That's point IMO ;

- using thin front glass , using combined or laminated glass , wrong glass types or some plastic that might crack ( temperature load, saltwater
corrosion )
- moding lights that are designed for ''water resistant use '' (like maglite BTW ) ,
- sealing too big air gaps for switches ,
- correcting poor fittings .....using materials that are not designed for compression presure (from outside) - like plastic tubes for plumbing (works in expansion)
- using wrong type of O-rings on wrong designed type of sealing (dynamic/static)
- if you use additional sealing of threads with some sealing compound
- electric fittings , switches (designed for water or not)

all together gives us some uncertainty , which is unknown and rises with all possible failures mentioned above.
and many things in ''divelight library '' are not put there because of collecting some web pages , but because of warning of possible failure in design.
I work with enviromental and electrical testing on our products , I have a lot of years some aquariums till I start diving ;-))

 

[wquiles]

I got the HF pot. Man, it is heavy!!!. Thick walls and (seems) like a good gasket. Max. rating is 80 psi.

I will clean it, set it up, pressurize to 80 psi, and see if it can maintain pressure (no leaks, etc.). I will report back later

Will

 

[350xfire]

Cool, good luck! I think it will work. Pressure it up to 120 and lets see...

 

[wquiles]

Cool, good luck! I think it will work. Pressure it up to 120 and lets see...

The container itself can easily do more, but I would likely have to re-inforce and/or replace the stock holding hardware before I go higher then the "rated" 80 PSI

 

[350xfire]

Ah, don;t be scared! Pressure it up and lets see how much it can take.. The Chinese are known for super high quality products built to many times their rated capacity.... lol!

 

[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.

Just an FYI to anyone silly enough to do this. I had the bottom end of this pipe (not shown in image) fail last night during a pressure test. It had a flat end cap glued to the end of the pipe. The bottom cap used to dome out a bit under pressure, so I assume it finally gave out.

The resulting failure was less than dangerous though, a bit of a bang and lots of water in the back yard. I plan to cut the end of the pipe off an glue on another end cap, as for $3.50 and 6 months service it's a good investment in my book.