The He valve, usage in theory and practice

Archer

So couple of things...

On the crown's ability to keep pressure in or out, there is a seal as I said that is in constant contact with the case tube, even when the crown is unscrewed and fully pulled out. Because people often have the impression that when the crown is unscrewed or pulled out, that it has no water resistance, I've had to prove to people that this is simply not the case. So here's a photo of an SMP with the crown unscrewed, and fully pulled out to the time setting position:



Run through the pressure testing machine using the dive watch program, which firsts tests using a -0.7 bar vacuum, and then a +10 bar pressure - passed both tests:



So this illustrates the kind of pressure that the seal can stop, and this would be the same pressure either coming from outside the case, or inside the case. So back to your suggestion that all you would need to do is open the crown after being down 100 ft, well this is the pressure of 100 m and the seal didn't leak. So this shows you that opening the crown is not effective at releasing at least +10 bar pressure from inside the watch.

Second, you ask how much internal pressure the watch can take. Well it's not something I have photos of but I do have a video that I can explain a few things with. So when a watch fails a pressure test in the machine above, the one thing it won't tell you is the location of the leak, but there is an additional test that can be done on the machine that can prepare the watch for a water dunk test.

Once a watch fails a test in this machine, I use an additional program called simply the "leak finder" test. What this does is it takes the pressure side of the test only, in this case +10 bar, and applies this to the case for a much longer period of time than in the normal test scenario. In the normal test the watch will be under that pressure for typically 90 seconds or so. In the leak finder test, this can extend for 5 minutes or more (the time depends on exactly what the machine sees is happening). By pressurizing the leaking case, it will eventually equalize the pressure inside and outside the case at the pressure inside the test chamber - again +10 bar in this case. The machine carefully measures the deflection of the case, and tells me if the leak is small enough to submerge the case in water. I simply have a glass of water standing by, and when the case comes out, I place it in the glass, and look for where the bubbles emerge, and this tells me the leak location. Here is a video of just that on an SMP case:

So when the case was removed from the machine, the internal pressure was +10 bar, which then starts to drop slowly as the air leaks out - this is a very slow leak so the pressure would have stayed up higher for quite some time. So there is significant pressure inside this case at the moment the test chamber opens, and yet the watch does not burst apart. This tells me that at the very least the watch can hold several bars of pressure inside it without issue.
Great answer and very thorough, you sir are a font of knowledge.
Hope this helps you understand the capabilities of these watches a little better.

Cheers, Al

Archer

I can't speak to the IWC in particular, but I do know that some watches rated for high depths that do not have valves do have crystals that are installed with adhesives - Sinn is one that comes to mind.

josiahg52

I don't think so except that it is "more permanent" in that it will be more robust by design due to the higher rating. I think a watch that is rated for decompression will have a relief valve by design. This doesn't mean a watch without a relief will fail every time or at all. In fact, a 30 ATM watch probably would survive a decompression event because of it's less robust sealing systems while likely not surviving the diving event that made the decompression necessary in the first place. I just don't think that there are more than a few novel ways to seal a watch case and its crystal.

So the question is, is there a "curve" where the pressure/depth rating and the requisite methods/design/style of the seals make a relief valve redundant? Even my 1000m Oris has a relief valve.

Would the manufacturer of that 2000m rated watch tell a customer that decompression (of the watch) is not a concern?

I think to suggest that there is an intended or even direct correlation between depth/pressure rating and a watch's resistance to decompression failure is wrong. There might be an incidental or casual relationship only because those higher-rated watches have more robust sealing systems and can withstand a higher differential pressure for longer periods of time.