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John,
In a message dated 98-04-21 01:17:52 EDT, you write:
<< Okay, I know there is a huge amount of hype over "Oxygen clean and
compatible." I knwo that if you are getting partial-pressure blends, it is
a good idea to have your tanks O2 serviced. My question now is about
regulators. For EAN that is 40% or less, what should I REALLY be doing?
Do I need new o-rings in all of my lines? Do my 1st and 2nd stage need to
be serviced?
I seem to get a different answer from everyone I talk to, ranging from
"Our equipment should never be used with EAN, best get our new green-body,
dedicated Nitrox regulator that is good up to 21% Oxygen"
to
"I use whatever regulator I want for my 100% O2."
For basic Nitrox work, what should I do? I was looking to buy a new reg
soon, either a Sherwood Oasis or one of the Scubapro G-series. Are either
of these going to be a problem? Thanks,
John Norman
arclight@ex*.co* >>
===================================
I don't think there is any need to worry about or modify any regulator for
mixes up to 40%. If it still makes you nervous just put the regulator on a
tank of air shortly after you have used it for nitrox and run some air through
it so that it will only have been exposed to 40% O2 for the duration of the
dive.
At these percentages the primary concern is cumulative deterioration of non
compatible materials and a checkup every year with "moderate" use should cover
you OK. You might want to simply have it O2 cleaned and fitted the first time
you have it serviced - it should not cost much more than a regular check up
and you can stop worrying about it.
NOW ! When you start getting over 50% combustion begins to be a concern as
well because the plumbing of the regulator is technically no different from
that of a fill station. If you keep deco mixes turned off during a dive till
needed, as you should, then it is easy to open the valve fast enough to
produce a nice pressure front and sudden quick flow in parts of the regulator.
BTW this ability to open the valve slowly should be a consideration when
choosing valves for tanks that will carry high O2 mixes - the old Sherwoods
are a favorite in this respect - Thermos are marginal - don't know about any
others.
For mixes above 50% I would go with O2 clean and compatible if for no
other reason than to reduce deterioration of seals and seats and then don't
use it for any other applications.
I personally think the Sherwood Magnum is an excellent compromise between
quality and price as a deco gas regulator. It is simple, reliable, cheap and
easy to repair and O2 clean. (this is assuming that the new one is as good as
the older model with the round second stage) There are many other makes
and models just as good for this application and you don't need anything fancy
for deco bottles (many divers use a Sherwood Brute for this).
If you are using the regulator for primary back gas on nitrox dives and
want just a tinsy bit more quality I think the Oasis is a good choice for the
same reasons - I have used it to 260 feet (on trimix) with no problems and you
can buy two of them for the price of a G250. My guess is that you have a
Sherwood / Scubapro dealer convenient to you.
The company reps have a card issued by their lawyers that they read their
response to any technical questions from. Can't blame them really - the
public is a legally treacherous bunch to deal with.
The Green & yellow regs look great and do make for quick ID. IF IF IF
they are really O2 cleaned and compatible, rather than just painted green and
yellow, they should be good for any mix at all. The little extra you pay for
them is about what you would pay to have a straight regulator O2 cleaned so
there is nothing wrong or stupid about buying one of these unless the dealer
is tacking on an additional "wow appeal" factor to the price.
Now pay attention ! Since you can use any uncleaned regulator for up to
40% nitrox there is no real need to make a regulator ACTUALLY O2 clean and
compatible
for such applications from a legal standpoint. This means that a company can
extrude a few green and yellow parts to put on these regulators and say that
they are specifically for nitrox up to 40% only because they are identifiable
by color code when there is no internal difference between them and the plain
old black and chrome models. If you buy one of these "nitrox dedicated
regulators" make sure the company will proudly announce that they are suitable
for 100% O2 applications - otherwise they are not really O2 compatible.
You are right about the tanks and partial pressure fills - get them
cleaned and be careful where you have them filled so that they will stay that
way !
Hope this helps,
Chuck Boone
--
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