On Mon, 22 Feb 1999 16:56:51 -0800 (PST), El Bruce O wrote:

>1.  Would someone please explain "upstream" regulator design?  What is
>this?  What manufacturers DO NOT use an upstream design? 

In a second stage with an upstream valve, in the event of a first stage
failure which results in the delivery of full tank pressure to the
second stage, the second will fail in the closed position and cease
delivering air.  (HP to the second would probably rupture the hose in
this case).  Downstream valves "fail safe", in that they will free flow
rather than close when the pressure climbs, continuing to deliver air
to the diver and acting as an overpressure valve.


>2.  Isolator valve on manifold:  Si or No ?

The isolator is necessary.  In overhead environments, the possibility
exists to break off the right post knob, and if after doing so you have
a first stage failure on this post, by closing the isolator you save
half your gas (and probably your life).

>3.   Ocean diving, drysuit.  Double my alum 80's or my steel 72's
>(2650psi)?  

For open water diving, AL 80's are very streamlined and provide more
than enough gas for the bottom times you are likely to be doing in OW,
and are buoyant when empty.  For overheads, high volume low pressure
steels are the better choice, because the low pressure reduces the risk
of first stage failures, and the steels are negatively buoyant when
empty.  This is good because, in the event of a catastrophic complete
loss of gas, extricating yourself will not be further complicated by
being pinned to the ceiling.

>Thanks,
>BDG

-Sean


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