Meg cold diving - QC4 leak

Also it warns not to couple and uncouple single end shut off QC (like QC4) while under pressure?

Hi Tibby,

Since my O-ring catalogue is never far away, here is the info listed within this precious reference:

Fluorocarbon is indicated as having Fair to Poor resistance to cold. :-O

For cold resistance, silicone is the best, followed by Fluorosilicone, Ethylene propylene, Nitrile, SBR, polyurethane,...

The temperature range chart does recommend Fluorocarbon down to -31F or -35C. There could be a tolerance issue with the fittings, although Swagelok tend to be good quality.

z

I am pretty sure that the connectors mounted on the Meg are DESO style.
I also have QC4 connectors on my machine for the external diluent and I couple and uncouple while under pressure (same thing for the QC6 on my BOV) and it has never shown any sign of leaking.

Ok, so it's been stinking cold in my neighborhood lately but this never stopped a respecting diver from diving, right?. This morning we all set out to do an ice/slush dive in a balmy 8degF wheather. It turned out we couldn't get to the water and turned to a local warm water spot instead.
Long story short, when I turned my Meg O2 cylinder on, unit having been sitting in the back of my covered truck bed in ambient temp for a couple of hours, a noisy gas leak hiss made itself present. It turned out it came from the QC4 connector (O2 hose to the head) and the more I moved the fitting/hose the worse it got. I looked inside the female part where the o-ring is and it was there so I figured it's just too rigid from the cold considering it worked fine during the predive check. I decided to keep it disconnected until I got the Meg warmed up a bit in the 90deg F water I was about to dive in (geothermal spring). Sure enough, after it warmed up, the damn QC4 worked just fine even when shaken and abused.
I completed my dive with no more QC4 problems but it makes me think whether the QC would've stopped leaking in 35degF water during the ice dive
in the original plan. I doubt it, but I'm glad I didn't find out under the ice.
A few questions spring to mind:
1) Has anyone experienced this before?
2) Has anyone tried to replace the o-ring inside the fitting? I'm just curious as my Meg is only 4 months old so it shouldn't need a new one yet.
3) Has anyone replaced the QC4 with a different fitting? I'm sure ISC chose the odd QC4 for good reason but it seems cold environment wasn't one.
I will try to figure out how cold it needs to be in order for it to start leaking and post what I learn.
Tibby

Hi

Mine does the same... You move the hose, and it releases some gas. Not effected any of the dives, and I checked on a couple of other Megs that were there and they all seemed to release varying levels of gas when the hose assembly going into the fitting was wiggled. Mine did seem worse though..... Must get it checked soon.

I also had the same problem (male end of QC4 leaking). It would only leak when I touched the QC4 (while connected) and let out a decent amount of gas. If I left it alone it was fine. It happened on 2 separate occasions...Air temperatures when it happened were ~42F and 37F. I used a borrowed head and feed hose this past weekend and it would not leak even when wiggled in similar conditions.

When you moved the hose on the leaky head, did the connection feel a bit more sloppy than on the other head? Mine seems to be pretty loose, even when pressurized. I can move the hose side-to-side a fair amount.
Thanks,
Tibby
PS: Nice avatar!

my meg does the same thing i was ice diving 2 weeks ago and the water temp was 28f before the dive in my truck everything was dry and solid with no movement, after my dive under the ice i noticed that i gently bumped the qc4 conector and it would leak gas if it was wiggled.
after the unit warmed up in my house it was fine.
im wondering if the qc4 connector on the head might be made of aluminium and the connector itself (male end) is steel maby the two metals expand and contract different amounts causing the leak...
it scared me pretty good as my meg was new in november at dema
Eric