Why a time component in IPX standards?

[Glock27]

Why would there be a time component in IPX standards? I would think that an O-ring would seal to a certain pressure regardless of how long it was at that pressure.

G27

 

[kramer5150]

A lot of water seals need time exposure before they fully leak, like a slow leak in the "U" catch under a sink.
Dive watch water resistance standards have always had a time exposure element.

 

[gcbryan]

I don't get the time component either. I just take it to mean that it's not really waterproof but will handle submersion for short periods of time as in a light dropped in a puddle or stream.

I've never seen any such limits on my dive lights or dive computers. I've found dive lights underwater that have obviously been there awhile that work upon putting new batteries in them.

If it's really waterproof there should be no time limit. I've only seen that with the IP 7 or 8 (whatever it is) standard of 1 meter for 30 minutes. That's just one step better than water resistant.

 

[kramer5150]

A lot of water seals need time exposure before they fully leak, like a slow leak in the "U" catch under a sink.
Dive watch water resistance standards have always had a time exposure element.

... specifically ISO6425 compliant dive watches.
http://en.wikipedia.org/wiki/Water_Resistant_mark

 

[Bigmac_79]

I can't say for sure, but my guess is that many lights would be waterproof indefinitely, but the IPX standard only requires them to be underwater a certain amount of time. Thus, two lights could qualify as "waterproof for 30 minutes at 1 meter" even if one light was about to get flooded and another could have sate there for weeks.

As for why the IPX standard should be light that, my guess is that most lights measured by IPX standard aren't meant to be dive lights, and thus don't need to survive underwater indefinitely. For the average flashlight, or even some sort of professional/tactical/it's gotta work 100% light, the user is not going to be underwater (or at least not for long), so the light won't spend much time underwater.

In most cases, a light won't spend much more time underwater than it's user, unless the light is dropped on accident. If you drop your light in the water, and don't find it after 1/2 an hour, you've probably lost it, and it won't matter if it breaks or not.

Sure, it would be useful for a light to be able to handle being underwater indefinitely, but when setting a standard, we just need to qualify it for standard use.

 

[Th232]

From a biomedical engineering perspective, nothing is ever 100% leak proof, even when we weld things together. In medical implants hermeticity is defined as x number of helium atoms getting into the device over y days/months/years rather than "nothing will ever get through".

While flashlights and implants are different fields, I suspect it's a similar situation here, personally I've never viewed rubber as a material that's completely impermeable to water. Just a material that will block a lot of it.

Fun fact of the day: If you take a thin sheet of silicone, fill it with water and leave it, you can come back to find water on the other side of the sheet. You can also do this with a thicker sheet, but evaporation may hide any evidence of water leaking.

 

[Glock27]

O-rings don't dissolve. I would expect a properly greased one would fill any microscopic imperfections in the 2 surfaces that have contact. You would think that it would take a long, long time for a good grease to dissolve in water.
My SC60 has far exceeded the IPX8 standard it is rated. Mine has spent hours at 4 feet of depth at the bottom of our above ground pool. Having only 1 O-ring that is subject to failure cuts down the odds of flooding a great deal.

G27

 

[Th232]

Just curious, where was dissolving mentioned? It's not a problem of the O-ring dissolving, it's more about it not being 100% impermeable to various substances. A lot of things are like sponges on a microscopic/atomic level. Question then is just how much will get through in a given timeframe. For a properly designed system the timeframe should definitely exceed a reasonable stint underwater, but that doesn't mean it'll stay like that forever, as per what Kramer also said.

 

[Glock27]

I would think that it is that water is eventually traveling Around and Not Through the O-ring.

G27

 

[jh333233]

I would think that it is that water is eventually traveling Around and Not Through the O-ring.

G27

Depends on the tightness of the junction, if the oring is fat enough, it will provides a better water resistance
Imagine the rubber strips on windows

 

[tam17]

Most O-rings are made from NBR rubber, so they may be permeable for some gasses (small molecules) over the longer period of time (days/months), but water passing through them is not an issue at all.

Cheers,

Tam

 

[jh333233]

Just a metaphor, the tighter the junction is, provides better resistance since a larger pressure is required to "breakthrough" it

 

[Haesslich]

I'd also suggest the time component is to also keep idiots from saying a device that can resist a splash is waterproof, due to the time component.... which also certifies the seal won't go in five minutes.

 

[jh333233]

Most O-rings are made from NBR rubber, so they may be permeable for some gasses (small molecules) over the longer period of time (days/months), but water passing through them is not an issue at all.

Cheers,

Tam

Repulsion btwn polar and non-polar molecule?

 

[Size15's]

Madness to even suggest this of course but product testing takes time.
Testing equipment is expensive and testing lab time is expensive.

Given that it is likely rather difficult to determine whether a product has leaked under test during the test (unless the testing rig is sensitive enough to detect ingress which I doubt), if the test took too long then it would take ages to put a product through testing if the goal was to balance water-proofness with other characteristics such as ease of threaded component rotation, performance under a range of temperatures etc.

 

[tam17]

Repulsion btwn polar and non-polar molecule?

😕

Gas permeability resistance of NBR is 2 out of 5 (5 being excellent) and water permeability resistance 5 out of 5, so in real life permeability shouldn't be a problem (however microscopic surface irregularities, o-ring wear and chemical damage should).

Try googling "dynamic sealing o-ring", lots of resources come up 🙂

Cheers,

Tam

 

[Ian2381]

I tested my MiNi AA in a swimming pool for a few hours and definitely it is waterproof and no water penetrated the light but the problem is moist, moist was inside the light affecting the electronics and made my light flicker but after drying the light works perfectly.

 

[gcbryan]

I think size15.s is right. The limit is a testing limit. It doesn't mean it's going to leak after 30 minutes but since these aren't dive lights there has to be a limit to the test.

Dive lights would have testing limits as well but in reality time isn't much of a factor. With dive lights it's depth (or rather pressure that equates to depth).

 

[jh333233]

Madness to even suggest this of course but product testing takes time.
Testing equipment is expensive and testing lab time is expensive.

Given that it is likely rather difficult to determine whether a product has leaked under test during the test (unless the testing rig is sensitive enough to detect ingress which I doubt), if the test took too long then it would take ages to put a product through testing if the goal was to balance water-proofness with other characteristics such as ease of threaded component rotation, performance under a range of temperatures etc.

Theres some method, this is 1 of them
Assume the product is dry inside
put some anhydrous cobalt(2) chloride paper inside (pink)
if it did leaked after, that thing turns blue