O-ring blows underwater

[travelingpat]

We've all seen a tank try to imitate a jet pack when the o-ring breaks and high pressure air blasts out while setting up the gear. I was diving last weekend when my buddy's o-ring blew six minutes into the dive. It's pretty spectacular underwater! We were only 8 meters down, doing a liesure dive, so it was simple to do an ascent to the surface. What surprised me was that while the tank was emptying, he was still able to breathe through his regulator. I had my octopus in my hand, ready to give it to him, but he didn't need it.

Is this a common occurance? It seemed pretty unusual to me.

Pat

 

[H2Andy]

hmmm... i wouldn't say common, but it does happen, especially with rental tanks (they get a lot of wear and tear)

one time, while walking back from a dive, my primary hose somehow disconnected from my second stage (which was clipped to my harness) and started whipping about like a snake. took me a second to grab a hold of it (didn't poke my eye out) and my buddy ran over and turned off my tanks. the noise was something awful

weird stuff happens =)

 

[Gary D.]

A yoke nut that isn't properly seated is generally the cause for that as is a dried out or cut O-ring.

Gary D.

 

[andydiver06]

Blown O ring I did happen to me once at a depth of 6 m. The noise is awful and might scare some of the fellow divers. But there was nothing to worry much about I could breathe and came up safely. From 170 Bar the tank pressure came to 120 bar in one minute. A blown O ring at say 30 m and anything less than 100 bar might be a problem.

 

[rawls]

Yep...Funny how such a small polymer can cause a great big problem u/w. Luckily you and your friend were shallow and you had the clarity of forethought to be on top of things by having your alternate ready.

There is a useful little practice called checking your tank's o-ring before you dive.
You may want to remind your friend of this.

 

[drbill]

Yikes, that "blows."

One of the reasons I dive DIN.

 

[philmayer]

Is this a common occurance? It seemed pretty unusual to me.

It's not unheard of, but it's pretty unusual. All of the o-ring failures I've seen have been pre-dive. And they're not always tank rings. On our trip to Belize last year we had 4 different people with o-ring failures, all in their equipment. One of those failures was mine -- the ring on my LP inflator hose failed. Less than a dozen dives after annual service too.

 

[lifeisfullofgooddives]

I have never had it happen to me...but then again I always check the o-rings on rental tanks....and change them out if they look questionable.

 

[Marek K]

it does happen, especially with rental tanks (they get a lot of wear and tear)

And I think that's the thing about yokes. I've had my share of o-ring failures, all pre-dive, and all with yokes and rental tanks. The o-rings are on the valves, and (like H2Andy says) they can get a lot of abuse or just neglect if they're rental tanks. Plus, yoke o-rings tend to be a lot more exposed to damage (and abuse) on the valve.

With a DIN, the o-ring is on the first stage, which I think tends to be generally taken care of better than a tank valve -- if only because more people own their own regulators than tanks. We always cap them and take care of them. And, at least in North America, owners of DIN equipment are on the average more experienced and/or may be more conscientious.

I'm not a technical expert, and I know I'm gonna get flamed... but I really don't think there's anything mechanically inferior with a yoke vs. a DIN, as far as the o-ring. People keep saying that DINs are superior because the DIN o-ring is "captured." But I don't buy that. I think a yoke o-ring, in good shape, that's not already damaged or extruded, in a fitting that mates correctly, is just as reliable; it's "captured" just fine by the flange on the first stage orifice. Maybe better. (See my pitiful attempt at a diagram, attached. Somebody correct me if I'm wrong... if I don't understand the definition of "captured o-ring"? Or how a yoke fitting seals?)

A yoke just can't take as high a pressure as DIN; but it's not because of the o-ring design. It's because at extremely high pressures, the two yoke arms tend to straighten and break the seal. But at 3,000 psi, the margin of safety with a yoke is pretty high.

We dive with DINs, but that's because of where we live.

--Marek

 

[captain]

There is no reason for an O ring to blow if the O ring is good and the regulator and valve are properly assembled and there is no damage to the regultor or valve sealing surface. The only times I have ever had an O ring blow is when I failed to properly install the regulator on the valve. All blew when I turned on the tank.