Dangerous psychology- Diving beyond one's training

[flots am]

We HAVE had a yoke connection come loose on an open water dive, though. The student involved had not gotten the yoke settled properly in the ring, and although it apparently sealed well enough that no one heard it leaking pre-dive, it did come completely loose underwater, and occasioned an air-share. If you think about the mechanics of the systems, the only thing holding the yoke reg in place is a little pressure from the screw and the sealing of the o-ring.

A yoke connection goes on finger-tight, however once pressurized it becomes extremely difficult to turn the screw. I don't think I've ever seen (heard) a student who has been able to unscrew the yoke from a fully pressurized system with the valve on, although someone tries every few weeks.

It's actually a pretty solid connection, although I wouldn't use it anywhere the knob could be confused for a valve knob, banged on an overhead or anyplace there might be lines floating around.

flots.

 

[fjpatrum]

A yoke connection goes on finger-tight, however once pressurized it becomes extremely difficult to turn the screw. I don't think I've ever seen (heard) a student who has been able to unscrew the yoke from a fully pressurized system with the valve on, although someone tries every few weeks.

It's actually a pretty solid connection, although I wouldn't use it anywhere the knob could be confused for a valve knob, banged on an overhead or anyplace there might be lines floating around.

flots.

That was the point I was trying to make... it's very difficult to even loosen the knob under pressure. I've seen yokes banged though probably not with significant force and they simply don't dislodge that easily. I would dare say, especially in an open-water situation, if it came loose it wasn't properly seated to begin with, but that doesn't make the logic of removing the chance any less valid. Thank you all for sharing your experiences and the information.

 

[MXGratefulDiver]

A yoke connection goes on finger-tight, however once pressurized it becomes extremely difficult to turn the screw. I don't think I've ever seen (heard) a student who has been able to unscrew the yoke from a fully pressurized system with the valve on, although someone tries every few weeks.

It's actually a pretty solid connection, although I wouldn't use it anywhere the knob could be confused for a valve knob, banged on an overhead or anyplace there might be lines floating around.

flots.

You don't need to unscrew it ... in fact, you couldn't even if you wanted to. But all it takes is a momentary jarring that knocks the flat side of the reg out of alignment with the flat side of the tank valve ... at which point the o-ring will deform, and most likely extrude a bit, and the seal will be broken. Since the o-ring is only captured by the air pressure pressing it against the two flat surfaces, all it takes is a bit of uneven surface area to make it deform. I witnessed this happening once with someone who swam underneath a piling and bumped the piling with their regulator ... and they didn't hit it very hard at all ..

... Bob (Grateful Diver)

 

[watercooled81]

Both a Yoke and a Din could come off, being knocked off, knocked losen. Nothing is guaranteed. However Din is safer then yoke as its less likely to happen. As pointed out in many of these comments, its all about reducing risk. Now if you are in a large cave with 3 to 4 meters of head room you could get away with a yoke if you hug the bottom. Again a DIN would be safer as it allows a grater range of error. However if you do that you will stire up more silt then being mid point, which will kill viz.

If you are cave diving in caves only a meter high, then the only yoke you should be carrying is the one you found on the cave floor from the last diver!!!

Best place to learn to cave dive is the uk, if you can cave dive here, where getting to a cave is a logistical nightmare in itself, getting through tiny gaps with less then a meter viz you can dive anywhere.......

As pointed out, there are many cave diving courses out there, but do your research on thr instructor and school......

 

[MXGratefulDiver]

That was the point I was trying to make... it's very difficult to even loosen the knob under pressure. I've seen yokes banged though probably not with significant force and they simply don't dislodge that easily. I would dare say, especially in an open-water situation, if it came loose it wasn't properly seated to begin with, but that doesn't make the logic of removing the chance any less valid. Thank you all for sharing your experiences and the information.

You don't need to loosen the knob, or dislodge the yoke. All you need to do is momentarily create a difference in angle between the two metal surfaces that the o-ring sits between ... the air pressure from your tank will do the rest by moving the o-ring until those distances are equal again. That deforms the o-ring and breaks the seal.

... Bob (Grateful Diver)

 

[nimoh]

Both a Yoke and a Din could come off, being knocked off, knocked losen. Nothing is guaranteed. However Din is safer then yoke as its less likely to happen. As pointed out in many of these comments, its all about reducing risk. Now if you are in a large cave with 3 to 4 meters of head room you could get away with a yoke if you hug the bottom. Again a DIN would be safer as it allows a grater range of error. However if you do that you will stire up more silt then being mid point, which will kill viz.

If you are cave diving in caves only a meter high, then the only yoke you should be carrying is the one you found on the cave floor from the last diver!!!

Best place to learn to cave dive is the uk, if you can cave dive here, where getting to a cave is a logistical nightmare in itself, getting through tiny gaps with less then a meter viz you can dive anywhere.......

As pointed out, there are many cave diving courses out there, but do your research on thr instructor and school......

thanks for the info, although I would argue having to go through tiny gaps with less than one meter of viz would make it the worst place to learn to cave dive, but very interesting cave diving after learning.

 

[boulderjohn]

A yoke connection goes on finger-tight, however once pressurized it becomes extremely difficult to turn the screw. I don't think I've ever seen (heard) a student who has been able to unscrew the yoke from a fully pressurized system with the valve on, although someone tries every few weeks.

We used to tell students that it was not possible to unscrew the yoke with the system pressurized. We stopped saying that when a student did it. I was on the other end of the pool when it happened. I almost went through the ceiling.

 

[xyrandomyx]

We used to tell students that it was not possible to unscrew the yoke with the system pressurized. We stopped saying that when a student did it. I was on the other end of the pool when it happened. I almost went through the ceiling.

Where's that student when you need one of those stubborn jars opened?

 

[kotik]

Now that proves a point-- you don't even have to be in the water for those things to nearly kill you.

Note to self: never challenge someone with doing the impossible, if it's the case that them accomplishing the impossible will result in a large chunk of metal careening around a room I inhabit.

 

[mala]

yokes are yesterdays technology.

wake up and come to the 21st century.