Re: Which reg?

[Alex Towns <Alex.Towns@xxxxxxxxxxxxxxxxx>]

> >>There are a number of reasons first is the pressure relief valve in
> >>the hose assembly, agreed this does help a freeflow problem, but
> >>it's curing something that is not a problem, its the old unseen demons
> >>again.

That depends on who you talk to - It certainly was a major problem for a 
good friend of mine - double independants inside a cave & both his TX50's 
simultaneously freeflowed ~10min into the dive, emptying both tanks in less 
than a minute - thankfully he managed to get out. Analysing afterwards, it 
was difficult to conclusively say what could have been done better, bar 
possibly side mounting for better access to the tank valves - he said it 
was all over so fast. Freeflows arn't unseen demons in cold fresh water!

> The pressure relief in the hose assy is not there to prevent freeflow
> problems - it's to prevent overpressurisation of the hose as the 2nd 
> stage is an upstream valve.

No that isn't what Andy meant - In the event of a 1st stage freeflow, the 
gas does not gush out of the mouthpiece & down your throat, instead it 
escapes from the release valve allowing you to breath as normal from the 
2nd stage for the precious few seconds of gas remaining. It also means the 
rush of bubbles is to the side of your face instead of right in front and 
may help the diver deal with the problem with an unrestricted view.

> >>You cannot get at the diaphragm to fix any seating problems. 

Still thinking about this one! The only diaphram in a Jet is the exhaust 
which is protected by an endcap held in place with 4 screws. The wet 
breathes I've had (and yes it is a problem) is from rust/sea lice getting 
trapped under the diaphram. One idea is to modify the screws so that they 
can be removed by hand - possibly a T bar welded to the top! These screws 
do not need to be tight, just able to secure the endcap. Once removed, the 
diaphram is easily cleared/replaced and the endcap reattached. A bit of a 
mare of a proceedure u/w but possible!

One other idea to prevent crude getting inside the 2nd stage, is to stretch 
some tights over the opening before placing on the mouthpiece, which will 
act as a sieve and help prevent nasties sneaking inside!


The hoses
> >>are non-standard so you cannot easily swap a second stage with a buddy
> >>unless they are using Jetstream as well. 

This goes for the Cyclon as well. Personaly I carry a spare 2nd stage with 
hose on the boat. How do you change a hose u/w - do you take a spanner down 
or just leave the nut loose? Jet's don't have a nut just a bit to grab with 
your hand, where as most other standard hoses are done up with a nut! I've 
seen one guy loose his 2nd stage just as he got on the boat - popped of the 
end of the hose hit someone on the head then plopped into the water - then 
we just had to catch the swirling LP hose - fun! 


If you do flood the firststage
> >>the water has a tendency to blow the needle valve within the hose.

Do you have any references about this senario? To me it seems that water 
forced through the 2nd stage at high pressure would not be too kind, but 
I'd like to get an official view (for what it's worth) on the consequences 
of such an action!


Once I've got a successfull mod for accessing the exhaust the main issue is 
what happens to the working bits if you find yourself having to change 2nd 
stages/regs underwater! If it indeed does damage the internals than that is 
a problem - water being forced through the 'condom' inside the barrel could 
possibly cause more problems than the needle valve!

However with minimal moving parts inside the 2nd stage, with the exception 
of needing to replace regs I can't think of a good reason to open up the 
2nd stage whist underwater. If access is possible to clear the exhaust, 
which can be done with 2nd stage insitu. I don't think changing regs would 
allow sufficiant water to enter, to cause the same problems as say 
stripping down the 2nd stage.

With the exception of wishing to be able to clear the exhaust diaphram I've 
had very few problems with my Jet's for the many years I've used them and 
it'll take alot of persuading to make me change from these hediously 
'stroky' regs which don't half work well at depth!

Love 'em or hate 'em ;o)
Alex