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Discussion Starter · #1 ·
First, let's make sure my math is right:

1 ATM = 10m = 14.4 psi, right?

I have a big air compressor in the garage. Assuming I don't need to test to depths of 200M (I just want to know if some of my homages can be worn in the pool) could I hook it up to, say, a length of pipe with a cap on each end filled with water? Shouldn't be too hard to drill and tap a hole for a brass air fitting or maybe even a Schrader valve.

Then I stick my watch case in the pipe, screw it shut, and introduce 60psi of air pressure to the pipe/chamber (gradually). Leave it for half an hour, then take the watch case out and see if any water got in. If the inside of the case is dry, then I can safely assume that the watch can take 4ATM of real pressure (not 3 "Marketing Atmospheres" of pressure that most fashion watches claim) and can probably survive a day at the pool/beach, right?

Everybody shoot holes in this until I a) am able to build a good pressure test chamber or b) say "eff it" and buy a real pressure test setup
 

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That would work.

But you could also build one that could check an assembled watch, without getting anything wet. (This would be like a professional pressure tester.)

To do this, you would need a clear container or pipe. The idea is to fill the container half way with water, and pressurize it while keeping the watch above the water. You then lower the watch into the water, while releasing the pressure from the container.

If the watch has leaks, they will allow air into the case when it's under pressure. Then, when the pressure is lowered (while the watch is under water) that air will escape from the case through those same leaks. This will appear as bubbles streaming from the case.

If you see bubbles, you can simply remove the watch from the water, and everything inside should be dry (remember, the pressure was higher inside the case, which does not allow water to leak into the the watch).

One arrangement to do this is to use a Nalgene water bottle, with a Schrader valve mounted (I found this suggestion on another forum). Here is my version:





The idea with this one would be to fill halfway with water, and hang the watch from a hook glued to the top of the bottle. After the pressure has been introduced, just invert the bottle, and look for bubbles.

Of course, anything involving high pressure has the potential to be dangerous or fatal, so proceed at your own risk. I know that people have pressurized these to over 5 ATM without incident. However, I'm chicken to put more than about 3 ATM in mine.

In fact, it makes me so nervous that I broke down and ordered a copy of the Bergeon tester (for less than $300).
 

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Discussion Starter · #3 ·
Wow that's way simpler than what I had in mind. And I don't have to worry about screwing it up when I put the guts back in the case. I guess 3ATM (about 45psi) is enough to know that I can go swimming with the watch on.
 

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If you want to try this, a couple of notes:

Go with a Nalgene bottle only...They are very substantially made, have a large mouth opening, and are the only one's that I've seen used in this manner.

Also, you will need to re-tighten the lid one or more times as you pressurize the bottle.
 

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Discussion Starter · #5 ·
I've heard stories about Nalgene bottles :D

A friend of mine works at REI and told me a story about how someone left a smoothie or something fermenting in one on top of the break room fridge for several weeks until it exploded violently, lodging the lid in an acoustic ceiling tile.

So as long as I don't pass the "explode violently" threshold, the Nalgene should be capable of containing a good amount of pressure.
 

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The Nalgene bottle is a sensational idea! I've been toying with using SCH40 PVC pipe that is readily available (should be good to - gulp - 240pis, IIRC), but it's SOOO much more fun to watch the critter squirm rather than waiting to check the results. ;-)

I especially like the process of pressurizing first and checking for bubbles vs. checking for water inside after the fact. Quality tech!

FWIW, Mythbusters did some sort of rocket test using 2L soda bottles, and put a HUGE amount of pressure in to them. They did manage to make bottles fail, and they did so in spectacular fashion, but befor they did they balooned up to probably 2x their normal size. Now this says nothing about the ability of the threads in the cap to retain said cap, so that's almost certainly the weak link in the Nalgene Pressure Tester system.

Now I've got ONE MORE THING to go spend money on... Argh!

Clair
 

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Discussion Starter · #7 ·
Maybe zip-ties would be a reasonable precaution to prevent the lid becoming a projectile in the case of a catastrophic failure...

And maybe I should be working on my final paper instead of brainstorming new toys...
 

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Discussion Starter · #11 ·
Anyone know where I can go to pick up a Nalgene bottle besides REI? The closest one to me isn't very close, and my buddy that works there is on vacation so I can't get a discount right now lol

Would a "vintage" bottle be stronger than the new BPA-free ones?

What about a jelly jar? That can probably take a lot more pressure, right? 3-5ATM is surely not enough to blow up a jelly jar...

...right?:think:
 

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You could buy two Nalgene bottles. Set one up with a valve, get behind a building or somewhere safe and pressurize it to 45psi and wait 5 minutes, then 60psi and wait 5 minutes, then 80psi and wait 5 minutes, keep going until it fails. This would be just to see what your maximum pressurization could be, not necessarily what you would ever really pressurize it to.

It's nice to have an idea where a failure could occur. However, safety is always a major concern when dealing with pressurized containers. Even a few psi can be dangerous.

But this sounds like a nice idea for exactly what your trying to find out. Please, if possible, keep a photo journal of how it goes and share with us. That would be great!

Good luck and be safe,
Mike
 

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Discussion Starter · #15 ·
You could buy two Nalgene bottles. Set one up with a valve, get behind a building or somewhere safe and pressurize it to 45psi and wait 5 minutes, then 60psi and wait 5 minutes, then 80psi and wait 5 minutes, keep going until it fails. This would be just to see what your maximum pressurization could be, not necessarily what you would ever really pressurize it to.

It's nice to have an idea where a failure could occur. However, safety is always a major concern when dealing with pressurized containers. Even a few psi can be dangerous.

But this sounds like a nice idea for exactly what your trying to find out. Please, if possible, keep a photo journal of how it goes and share with us. That would be great!

Good luck and be safe,
Mike
Yeah I guess they're cheap enough that I could test one until it blows. I just have to be really careful drilling the hole for the Schrader valve. One little crack (which is fairly easy to do when drilling plastic) and the whole thing is useless. I'd also like to have an in-line pressure gauge, which I think would be more accurate than measuring at the compressor's regulator.
 

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Is there some reason to not put the valve - and gage for that matter - in the lid of the bottle? That's where I was planning on mounting mine because (in my mind at least) the lid is the place least likely to fail from some sort of rupture. To me, the failure point on the lid is the threads pulling past the threads on the bottle, not a rupture of the lid material. My gut feeling is that that any hole drilled in the side of the bottle will be a natural failure point, but it may not be a big deal if relatively low pressure testing is the goal.

Clair
 

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<snip>

FWIW, Mythbusters did some sort of rocket test using 2L soda bottles, and put a HUGE amount of pressure in to them. They did manage to make bottles fail, and they did so in spectacular fashion, but befor they did they balooned up to probably 2x their normal size. Now this says nothing about the ability of the threads in the cap to retain said cap, so that's almost certainly the weak link in the Nalgene Pressure Tester system.

Clair
We do that every year with the Boy Scouts. The boys have a contest to see who gets the bottle to fly the highest/straightest etc. So far we haven't blown one up yet! Next launch is this coming Thursday, plus regular model rockets, it's a hoot :-!

Cheers,
Griff
 

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You could put that pressure bottle inside another 'blast containment' plastic bottle, then pump away to heart's content with very little worry. I have a Bike-E tandem that I pump the rear shock absorber up to about 200 psi: the weight of my stoker. I bet I could generate 150m pressure easily with my suspension pump. Mwa ha ha!! :-d

(One time I had changed a tube on my mountain bike, and I was happily pumping away when -=**B O O M!**=- holey smokes that made me jump.. Pinch Flat! The new tube finally tore at about 65 psi.) :oops:
 

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Just remember the difference between gauge pressure and actual pressure is 1 atm.
So 60 psi on your gauge is 60 psi above 1 atm.
Or said another way - remember we live at 1 atm, and your gauge reads 0 then.
 

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Discussion Starter · #20 ·
Is there some reason to not put the valve - and gage for that matter - in the lid of the bottle? That's where I was planning on mounting mine because (in my mind at least) the lid is the place least likely to fail from some sort of rupture. To me, the failure point on the lid is the threads pulling past the threads on the bottle, not a rupture of the lid material. My gut feeling is that that any hole drilled in the side of the bottle will be a natural failure point, but it may not be a big deal if relatively low pressure testing is the goal.

Clair
The problem with putting the valve and gauge in the lid is that once the bottle is flipped over, i have water going into the valve and gauge. I was planning on putting the gauge and valve at the halfway mark, then filling it up to not quite halfway with water, so that no matter which way i fill it, water doesn't get into the valve/gauge.
 
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