KlausM Skrev:Man kan diskutere om de er specielt konstruerede men de er vel i bund og grund mere "utætte" mellem glas, bagkasse or kasse. Helium molekyler er mindre end vand molekyler så sålænge vand trykket ikke er for stort kan vandet holdes ude og helium trænge ud.
Dette gælder også for Rolex Sub'en og ikke kun Seiko og Orient.
Mvh
Klaus

Citat:When IWC introduced its titanium Ocean 2000 in 1982 with WR of 2,000m, the Ocean 2000 actually exceeded easily the pressure ratings of Rolex SD (1,200m WR), Omega Ploprof (600m WR) and Seiko PD (600m WR). While IWC was officially claiming 2000m WR, Ocean 2000 watches were actually tested to 3,200m WR. The very same thing happened with GST Aquatimers introduced in 1997; officially rated as 2,000m WR, but actually tested to 3,200m WR.
Every dive watch is resistant to external overpressure (WR), but often forgotten fact is that IWC’s dive watches are also resistant to internal overpressure similar way as IWC’s Pilot watches. IWC’s with 200 bar WR can withstand internal case pressure at least 60 bar. Therefore, these IWCs don’t need helium escape valves, as they can withstand internal case pressure for maximum safe saturation diving depths. IWC also mentions that if a saturation diver worries about internal case overpressure, he or she needs to unscrew the internally threaded crown in order to release any build up of helium during the rather prolonged decompression cycle.

IWC could develop an extremely deep automatic diver that would break all existing automatic diver WR records, if IWC just wanted to. There’s no doubt about it. IWC does have the knowledge, technology and capability for that. Maybe IWC does it again…who knows, only time will tell…"

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Citat:Why does the Aquatimer have no helium
valve, which the other two candidates possess?
The purpose of these valves is to allow helium,
which penetrates into a watch
during a deep dive, to escape
from its case afterwards. (During
the dive, the diver inside the
diving bell breathes an artificial
oxygen-helium atmosphere.)
Helium molecules are so small
that they can penetrate even
the tightest seal on a wellsealed
case. After helium has
entered the interior, and after
the diver returns to the surface, this gas must
be allowed to escape in order to equalize the
pressure differential between the interior of the
watch and the exterior environment. On the
Breitling and Panerai models, pressurized helium
escapes through a special valve: when the
interior pressure reaches a range of about 2.2
to 2.5 bar, this valve becomes active and opens
towards the outside. The Aquatimer was able
to do without this safety device because it’s
constructed so that its crystal can withstand an
inner pressure of up to 10 bar. A helium valve
also creates certain disadvantages. IWC’s technicians
explain: “We don’t need an additional
valve because although helium diffuses into the
watch, it also diffuses out of the watch again.
This watch can easily cope with the pressure
that’s created inside the watch during the
emergence (or “decompression”) phase,
which typically lasts several days on dives to
such extreme depths.”