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Greg writes:
> >
> > Other divers in the club have been using them for a while and I've seen
> > a few free flow problems. Last Winter at least one became unusable when
> > the 1st stage froze after a free flow.
> 
> Stage bottle regulator reliability is a crucial issue for some divers, such
> as those using TRIMIX. Decompression gas carried in stage bottles is the one 
> area where there generally is no backup or redundancy (Mix divers here do
> not use support divers and most of the schedules only have provisions for a
> loss of the shallow decompression gas - O2). Loss of decompression gas is a 
> serious problem, so selecting a reliable regulator is important. Although
> sherwood regs are very economical to purchase and service I use them because 
> I find them to be very reliable. I've never had a freeflow. I wouldn't have 
> the same confidence in a cyclon 300 or a Thor (same first stage).
> 
> On the other hand, if I was doing a shallow no-stop air dive in relatively
> warm waters I'd take the cyclon 300 every time.

I think I should put my comment in perspective. The free flow happened
as the diver was entering the water and was standing waist deep. She
pressed the purge button and it free flowed. She spent a minute or so
trying to stop it and then called some other divers over. As they came
over they were telling her to get the 1st stage under the water, which
she didn't do. The air temp was around 3oC, the water temp was a few
degrees higher. By the time the others reached her and got the cylinder
turned off there was ice all over the 1st stage. In the end she decided
not to dive.

I don't know what temperatures John dives in but I would doubt they
get much more extreme than 3oC unless he is ice diving. Even in the
circumstances above the problem could have been dealt with by simply
dropping the pillar valve underwater as soon as the reg free-flowed.

I have never seen a cyclon 300 free flow underwater. If it was fine
when I entered the water then I would not worry about it. I am quite
happy to use one on a stage bottle. Although I won't for much longer
as the guy who owns it asked for it back last night. He also asked
for my own regs as well so that he could dive with the trimix boys
- see below.

> (Mix divers here do not use support divers and most of the schedules
> only have provisions for a loss of the shallow decompression gas - O2).

I thought I'd just comment on how it's done here - not as any form of
criticism of how you do it. There are very few "sport" trimix divers
in my area - 7 to be exact. They have formed a syndicate and organise
expeditions together. At least one of them must volunteer not to dive
on each trip. Each diver enters the water with only suit and weight
belt. He is then kitted up by the others before his dive and de-kitted
by them after his dive. He then leaves the water and gets handed a
warm drink. The surface support is responsible for making sure that
everything is okay once the divers reach their decompression stops.

Alan

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