2nd-stage swivel failure in Cenote Cristalino, Mexico - 06-Nov-2010
I started diving just over 2 years ago on 26-Aug-2008. Today, 06-Nov-2010, was my 353rd dive, 41st since 26-Aug (year anniversary), and 95th of 2010. It was my 90th cave dive after having completed full cave. I have had a couple incidents where I had to assist another diver but this is the first case where I was the one with a fairly significant issue. Perspective.
Today was the last day of 8 days of diving - all guided - here in Mexico caves. It has been a great week of diving including the Blue Abyss via Pet Cemetery, Xunaan Ha, and more - a different cave every day. Today began with my pick-up at 8:15am in Playa del Carmen. We headed out to Cenote Cristalino after picking up the gear and tanks and so on. I'm writing this to share some experience. I don't know if anyone will take anything away from this or not but the hope is that there's at least one little tidbit.
I've been diving sidemount all week to further work on getting comfortable with sidemount. Gabriel of Advanced Diver Mexico has been my guide.
I'll fast-forward ahead to the incident. Gabriel was leading the dive. We completed 2 jumps and were at about 23 minutes into our dive when all of a sudden I heard something "pop." I hear a fairly significant "free-flow" of bubbles on my right and immediately reached to shut off my right tank while signalling to Gabriel (though I later found out he didn't see my signal but heard me coughing). It's a good thing I had so many simulated free-flows during my full cave. The problem got a little worse because the free-flow continued. Gabriel had already reached me (we stayed pretty close to each other in the caves the entire week - it was a good pairing for me) and saw that it was actually my left side having issues. He shut off my left valve. Unfortunately, since I was slightly flustered at this point, I didn't it yet realize it but had 2 regulators I couldn't breathe from - both valves were now off. The visibility was quickly going south due to the percolation caused by the free-flow. We both maintained our buoyancy and both had touch contact with the line. I signalled to Gabriel that I'm out of air and I grabbed one of his regulators. I had already taken in some water (hench the earlier coughing) and admit I started to get a bit nervous. It isn't a good feeling to be taking on water and feel like you have no air 23 minutes inside a cave.
Ok, so now I have Gabriel's reg and he has one and he checks his pressure seeing that he has plenty of air and we both signal thumbs-up and "ok" to exit immediately. After a few metres, he asks again if I'm ok and he maintains touch contact with me (to say "hey buddy, I'm here with you and we're going out together") - this was very good. Then he checks my right regulator/valve and turns it on slowly and pushes the reg at me. I accept cautiously but breathe and all is ok. I had plenty of gas - well over 2,000 psi at 30' with only about 20 minutes to the exit to go. So, I'm with my right tank/regulator again and we make an uneventful, smooth exit cleaning up our jumps and communicating often - as we did all week.
After surfacing, Gabriel told me it was my frickin' 2nd-stage swivel and not a valve, which I originally thought. I looked at it (we're still in the water fully kitted up) and saw the o-ring protruding from the middle of the swivel. He tightened it right there on the surface and It is interesting timing since I saw a recent thread on the swivels. It was a simple matter of the screw loosening a little. It was enough....
So, a few hours later (I deliberately waited), I wonder some things...in my current sidemount configuration, I heard the free-flow on my right side. This could *easily* be confusing since the left bottle 2nd-stage swivel is on my right side and my long-hose 2nd-stage is on my right side. This was the first in the problems here. I switched off right because I heard it on right. Gabriel uses a double short-hose configuration which keeps the 2nd-stages separate. It looks clean and also would have avoided this problem.
Of course I have to think about whether or not I want to continue to use the swivel. I dive fairly often in between my travels and I'm pretty conservative and watch my gear closely. I get it serviced when it's supposed to be and pretty carefully check it when kitting up. It is not possible to systematically check every possible failure point. I understand the desire to remove them when possible. I'm going to think about this for a while but while I'm considering, I'll probably use right angles. Wayne @ Amigos told me that if one of my swivels fails and I die, he doesn't want me coming back there to complain about it. Very Wayne :) ...
There are some things I could have done different. One of the most important things is that we communicated and he responded quickly and calmly. This could have turned into an ugly situation and been a real vacation spoiler.
I have a forced break from caves for a while as I'm flying out tomorrow to New Jersey then back to BrasÃ#l and around South America before going back to the States. I'm not sure if I'll dive in December as planned.
Swivels: the good the bad and the ugly.
This is Cave Diving Woman's man posting, so I guess I am Cave Diving Man? I am a design engineer, EE & physicist by occupation when I am not diving, so o-rings and seals are the stuff of my life. Here's the simplified story:
1) All swivels add one or more dynamic seals (typically an o-ring moves against a rigid & hopefully smooth sealing surface), so they are prone to wear out and leak eventually (if you don't periodically lube the o-ring, preferably using silicone or an oxygen compatible grease intended for continual movement, and keep the mating surface clean and polished to prevent corrosion build up and abrasion), but no more than the typical seal at the end of a second stage regulator hose anyway. So the chance of a failure just increases linearly with the number of such seals in line. If/when they do leak they tend to give early warning by bubbling a tiny bit at first which then gets progressively worse over time, so the failure is very rarely catastrophic unless you ignore it and don't do any maintenance even after you get the warnings. Botttom line is if you do not need a swivel don't use one as it is an additional failure point, but if you do need it, e.g. for a short hose feeding from the LHS tank for a right handed second stage in sidemount rig without neck wrapping, then go ahead, but use the right kind.
2) The good: a fixed angle right angle or 45 degree swivel only typically adds one dynamic seal. The other internal seal that is typically employed in the assembly is static and has very low risk. Good (though somewhat difficult to get and rather expensive) examples of this kind of swivel are the Scubapro 45 degree type which are also very compact (or there are more available and lower cost right angle versions available from Trident). I've never seen one of this type fail, and they are used extensively and successfully in technical applications.
3) The ugly: the second class of swivels are very similar to the first but are formed from a solid metal sphere with an oulet union port that screws in to one side either at right angles or 45 degrees from the inlet port. This kind are OK, available and inexpensive, but they are rather bulky and I have seen that the outlet port can come loose (loctite threadlock can fix this problem), so I tend to avoid them. Another even uglier class of swivels are the type more recently found on some second stages that have a ball joint with a limited solid angle cone to swivel through. This type not only rotates the seal but allows it to translate across the surface of the sphere, which is much more likely to result in abrasion of the o-ring, especially if any corrosion occurs, so I recommend against using this type.
4) The bad: this class of swivel look spherical like the previous type and have the apparently attractive feature of swiveling to any angle, but they achieve this by having two internal concentric o-rings sandwiched between two hemispheres held together with a screw through the middle. I warn against using this type. It adds multiple failure points including 3 dynamic seals, but most seriously if the central screw comes loose the failure can be catastrophic as the two hemispheres will separate enough for the o-rings to escape the retention grooves, so instantly you get all leak and no air delivered. If you feel you must use this type make sure the central screw is captured tight and retained in place using loctite/permatite or similar cyanacrylate thread locking adhesive. better still just avoid them.
Neil Benjamin
