Dive Watches

Hi all,

I have just been reading an article about dive watches and especially the
techie diver ones with the helium escape valve. This advert says open the
valve on the way back up. How the hell does the helium get into the watch
if you are breathing it? Surely this is for use in a chamber if the Helium
is in side the chamber and not in breathing equipment. I have got the Omega
Seamaster with one of these valves on it and I have just left it closed but
the alarm bells went off when I read "open on the way back up". Any trimix
divers out there who want to comment on it? I just use Nitrox and hope to
go onto Trimix sometime in the near future.

Regards

Steve

On Wed, 25 Aug 2004 08:34:00 +0000 (UTC), "Steve Carmichael-Timson"
<stevect@england.earth.solarsystem.com> wrote:

>Hi all,
>
>I have just been reading an article about dive watches and especially the
>techie diver ones with the helium escape valve. This advert says open the
>valve on the way back up. How the hell does the helium get into the watch
>if you are breathing it? Surely this is for use in a chamber if the Helium
>is in side the chamber and not in breathing equipment. I have got the Omega
>Seamaster with one of these valves on it and I have just left it closed but
>the alarm bells went off when I read "open on the way back up". Any trimix
>divers out there who want to comment on it? I just use Nitrox and hope to
>go onto Trimix sometime in the near future.

The seamaster is targeted at saturation divers who work from a bell
and live in a pressurised habitat. I am not an expert on sat but I
believe that they either use Helox or high He content Trimix (I am
almost sure it is Helox). Over a period of time He will diffuse into
the air spaces in the watch due to the light nature of Helium and the
pressure differential [1]. As the habitat is slowly equalised to
surface pressure when the divers come out of sat, pressure builds
inside the watch which is subsequently release by the valve.

Of course if you are not a sat diver, it becomes a gimmick you can
show to your mates down the pub and impress the girlies with proof
that you are a macho diver as you have a technical divers watch

[1] A lot of guessing as to what actually occurs here but
fundamentally He gets into the watch somehow!

Laz

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A foolproof method for sculpting an Elephant:
First, get a huge block of marble. Then, chip away
everything that doesn't look like an Elephant.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Change "nospam" to "ntlworld" to reply.

Due to its inert nature Helium is a very small molecule, it exists naturally
as a monatomic element (it does not even bond with itself, unlike Hydrogen
H2, Oxygen O2 or Nitrogen N2); thus it will diffuse far more readily through
materials and seals that are normally non-porous even to Hydrogen.

Under the extreme pressure differentials used by saturation divers it will
pass through the waterproof / airtight seals on the watch (under the glass,
bezel, crown & back) because the diver is in a gas filled chamber, not
water.

If the pressure was not released there is the chance that the glass could
displace or 'explode' away from the watch, as the watches are designed to
withstand compressive loads as the diver descends but not expansion as the
diver ascends. This is not a problem fro normal divers as we don't
pressurise the watch (or any other device such as the computer, depth gauge
etc). in a gaseous environment, so when we ascend the watch is still loaded
with 1 BAR absolute (ambient) pressure internally, thus at the surface there
is no difference between internal and external pressure, and if there was we
can simply unscrew the crown as if we needed to adjust the hands.

"Lazarus X" <lazarusx@nospam.com> wrote in message
news:ialoi0pf600qehnbe0jifie20ovaserhg2@4ax.com...
> On Wed, 25 Aug 2004 08:34:00 +0000 (UTC), "Steve Carmichael-Timson"
> <stevect@england.earth.solarsystem.com> wrote:
>
> >Hi all,
> >
> >I have just been reading an article about dive watches and especially the
> >techie diver ones with the helium escape valve. This advert says open
the
> >valve on the way back up. How the hell does the helium get into the
watch
> >if you are breathing it? Surely this is for use in a chamber if the
Helium
> >is in side the chamber and not in breathing equipment. I have got the
Omega
> >Seamaster with one of these valves on it and I have just left it closed
but
> >the alarm bells went off when I read "open on the way back up". Any
trimix
> >divers out there who want to comment on it? I just use Nitrox and hope
to
> >go onto Trimix sometime in the near future.
>
> The seamaster is targeted at saturation divers who work from a bell
> and live in a pressurised habitat. I am not an expert on sat but I
> believe that they either use Helox or high He content Trimix (I am
> almost sure it is Helox). Over a period of time He will diffuse into
> the air spaces in the watch due to the light nature of Helium and the
> pressure differential [1]. As the habitat is slowly equalised to
> surface pressure when the divers come out of sat, pressure builds
> inside the watch which is subsequently release by the valve.
>
> Of course if you are not a sat diver, it becomes a gimmick you can
> show to your mates down the pub and impress the girlies with proof
> that you are a macho diver as you have a technical divers watch
>
> [1] A lot of guessing as to what actually occurs here but
> fundamentally He gets into the watch somehow!
>
> Laz
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> A foolproof method for sculpting an Elephant:
> First, get a huge block of marble. Then, chip away
> everything that doesn't look like an Elephant.
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Change "nospam" to "ntlworld" to reply.

"TonyH" <tony@samesamediving.com> wrote in message
news:cghu3q$2tj$1@sparta.btinternet.com...
> Due to its inert nature Helium is a very small molecule, it exists
> naturally
> as a monatomic element (it does not even bond with itself, unlike Hydrogen
> H2, Oxygen O2 or Nitrogen N2); thus it will diffuse far more readily
> through
> materials and seals that are normally non-porous even to Hydrogen.
>
> Under the extreme pressure differentials used by saturation divers it will
> pass through the waterproof / airtight seals on the watch (under the
> glass,
> bezel, crown & back) because the diver is in a gas filled chamber, not
> water.
>
> If the pressure was not released there is the chance that the glass could
> displace or 'explode' away from the watch, as the watches are designed to
> withstand compressive loads as the diver descends but not expansion as the
> diver ascends. This is not a problem fro normal divers as we don't
> pressurise the watch (or any other device such as the computer, depth
> gauge
> etc). in a gaseous environment, so when we ascend the watch is still
> loaded
> with 1 BAR absolute (ambient) pressure internally, thus at the surface
> there
> is no difference between internal and external pressure, and if there was
> we
> can simply unscrew the crown as if we needed to adjust the hands.


I assumed as much but the ad said "on the way up" and didn't mention
anything about "not on the way up whilst in the water". Ad sounds a bit
misleading as someone could really screw up a nice watch by being
misinformed.

Steve