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Hi Renaldo and others
 
 In view of my previous fights with Draeger, let me say at the outset that I am
not a Draeger technician, or authorised service agent, and have not been on any
Draeger courses. 
 
OK, first thing: The Draeger is a balanced second stage, and I mean fully
balanced. As you should be aware, a downstream second stage acts as its own
safety valve in the event of a pressure surge. The Draeger requires (and is
fitted with) a separate overpressure relief valve. I prefer to use downstream
second stages only.
 
Second, the Draeger has a fancy "pressure amplifier" built into the first stage
design. Normally, interstage pressure is a constant above ambient pressure. On
the Draeger, the difference increases by 0.5 bar for every 10m depth. So if
your interstage is 10 bar at surface, it is 12.5 bar above ambient at 50m. If
you mix another make downstream second stage with the Draeger first stage, you
risk the other make freeflowing at depth as the interstage pressure rises
relative to ambient. For this reason Draeger insist on only using the Shark
with their second stages.

Thirdly, because the interstage pressure rises (relative to ambient pressure)
with depth, a certain depth will be reached where the overpressure valve will
open. In other words, this regulator has a definite maximum depth. 

Finally, I'll let you figure out the effect of this one: Imagine using this DV
as the secondary (ie normally unused) DV on your rig. As you descend, the
interstage pressure rises, both because of the increasing depth and because of
the pressure amplifier. Now ascend again. Ambient pressure drops. Where does
the excess interstage pressure go?

Go speak to Draeger themselves. They will probably tell you that this regulator
should not be used for deep or technical diving under any circumstances.

In short, this doesn't appear to be a regulator compatible with Hogarthian
philosophies.

Safe diving

Mike


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