Is that a grappling hook on the James Bond Watch? Or maybe a second crown to actuate some grand complication? Or on the side of the Rolex Sea-Dweller and Deepsea, is it an extra button? NO! It is the Helium Escape Valve, or Helium Release Valve on some dive watches, but what does it do?
First, you will only need it if you are on a commercial dive at
great depth for a few days. I’ve never been on a dive that lasted
several days, but, hey, you never know, right? So, here is how you would
use it: get into a diving bell for several days. Gradually, the
pressure will be increased to the same as the depth where you will be
working, and you will be breathing a trimix that contains a lot of
helium or hydrogen. Sounds good so far, right? Now, at such great
pressure, the tiny molecules of helium seep past any gaskets and seals,
no matter how tight they are, and loads of helium gets inside the watch.
Now, get your bell lowered to the fantastic depth where you will be
working for a few days, and get your work done. Your watch will be fine!
Next, have your diving bell brought to the surface, keeping the
pressure the same as it was below, at your working depth. S-L-O-W-L-Y
restore the pressure to normal for the surface, and what happens to your
watch? The helium trapped inside can either cause your watch to sort of
explode (think of the crystal popping off of the watch), or you can
give it a way to escape.
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