Diving myths taught for safety?

[Carl_F]

Also - another myth I hear frequently....

"Open your valve all the way - and then turn it back an eight to a quarter turn - to prevent damaging the valve or freezing it open..."

Meh - it's a lousy idea. It tends to lead to confusion about the valve status - and it isn't needed in modern scuba valves - but some habits die hard.

Bjorn

Actually it's a great idea and something the Navy and many power plants teach for valves in general. A quarter turn shut allows you to check the valve for open and have positive indication of open. (The valves on tanks do not have backseats which would be the valve type to leave full open.) If the valve is stuck and you check in the open & closed position but it's actually suck, which position is it in? Plus with temperature changes a non-backseat valve full open can get stuck full open (though the typical temperature changes experienced in a dive environment would not result in stuck open valves.)

But, hey, I'm a Navy trained engineer so something's are ingrained forever.

Carl

 

[maniago]

Actually it's a great idea and something the Navy and many power plants teach for valves in general. A quarter turn shut allows you to check the valve for open and have positive indication of open. (The valves on tanks do not have backseats which would be the valve type to leave full open.) If the valve is stuck and you check in the open & closed position but it's actually suck, which position is it in? Plus with temperature changes a non-backseat valve full open can get stuck full open (though the typical temperature changes experienced in a dive environment would not result in stuck open valves.)

But, hey, I'm a Navy trained engineer so something's are ingrained forever.

Carl

Its a great idea for valves that spend a long time of their life in the same open position. Works good for sink valves and toilet valves too. But not really necessary for valves that are routinely exercised, and in the case of our scuba valves open for an hour. In anycase, for positioning I use the XS valves with the Vindicator handle. No more guessing whats open or closed. Worth the few extra pennies IMHO.

 

[Frosty]

your BP/W will push you face down on the surface and drown you.

Actually in a rescue situation i did notice my Pseudowing did tend to push me face down when I was the "victim"

 

[bl6394]

Actually it's a great idea and something the Navy and many power plants teach for valves in general. A quarter turn shut allows you to check the valve for open and have positive indication of open. (The valves on tanks do not have backseats which would be the valve type to leave full open.) If the valve is stuck and you check in the open & closed position but it's actually suck, which position is it in? Plus with temperature changes a non-backseat valve full open can get stuck full open (though the typical temperature changes experienced in a dive environment would not result in stuck open valves.)



But, hey, I'm a Navy trained engineer so something's are ingrained forever.

Carl

Carl - with respect to your training - I strongly disagree. Evaluating the two risks: the risk of a valve becoming frozen in an open position versus the risk of becoming confused and diving a partially or mostly closed valve.

Weighing the likelihood and importantly the consequences of each event:

Stuck Valve Risk: with modern K-valves that have not been abused - the likelihood of a frozen open valve is pretty remote. In the event that it did freeze open - the consequence for a recreational diver is a minor inconvenience. They will have to drain the cylinder before they can remove their reg - but then the cylinder is off for repair - and the diver can proceed with their next dive. A tech diver may have a more serious issue - but will hopefully be self reliant - or have a team member capable of assisting them if they are having a catastrophic failure requiring valve shutdown underwater.

Partially Closed: The path to failure here is to become confused about either how much one should open the valve - or worse yet getting turned around and making the mistake of FULLY CLOSING THE VALVE and then opening it back up a quarter turn! The consequence of this is a valve that may breath at the surface - but at depth could become increasingly difficult to breath - leading to panic. In my experience, the likelihood of this failure is substantially higher than a stuck open valve. I recall a tech instructor teaching a solo class who became confused when manipulating my manifold and turned off all of my valves (including the isolator) by mistake while I was doing a mask off drill. It was annoying - but not catastrophic. I'd assert that Recreational divers are even more inclined to get turned around and crank the valve the wrong way. If they fully shut it off - its pretty obvious. But if they turn it off and then crack it open - it sets up a diver for a nasty surprise. I would argue this is a lot more common than the freezing of a valve. The consequences are also much more severe. Hence - this is a scenario - I would argue - it would be preferable to avoid.

I'm not a Navy trained engineer, nor do I have specific experience with the valves you may manipulate in the course of your work. However, in this case - the practice of leaving a K valve partially open to protect against freezing the valve - is not sound. In my training and experience as an engineer - it's important to realize when to use a pattern - and when it no longer applies.

Bjorn

 

[swimmer_spe]

Carl - with respect to your training - I strongly disagree. Evaluating the two risks: the risk of a valve becoming frozen in an open position versus the risk of becoming confused and diving a partially or mostly closed valve.

Weighing the likelihood and importantly the consequences of each event:

Stuck Valve Risk: with modern K-valves that have not been abused - the likelihood of a frozen open valve is pretty remote. In the event that it did freeze open - the consequence for a recreational diver is a minor inconvenience. They will have to drain the cylinder before they can remove their reg - but then the cylinder is off for repair - and the diver can proceed with their next dive. A tech diver may have a more serious issue - but will hopefully be self reliant - or have a team member capable of assisting them if they are having a catastrophic failure requiring valve shutdown underwater.

Partially Closed: The path to failure here is to become confused about either how much one should open the valve - or worse yet getting turned around and making the mistake of FULLY CLOSING THE VALVE and then opening it back up a quarter turn! The consequence of this is a valve that may breath at the surface - but at depth could become increasingly difficult to breath - leading to panic. In my experience, the likelihood of this failure is substantially higher than a stuck open valve. I recall a tech instructor teaching a solo class who became confused when manipulating my manifold and turned off all of my valves (including the isolator) by mistake while I was doing a mask off drill. It was annoying - but not catastrophic. I'd assert that Recreational divers are even more inclined to get turned around and crank the valve the wrong way. If they fully shut it off - its pretty obvious. But if they turn it off and then crack it open - it sets up a diver for a nasty surprise. I would argue this is a lot more common than the freezing of a valve. The consequences are also much more severe. Hence - this is a scenario - I would argue - it would be preferable to avoid.

I'm not a Navy trained engineer, nor do I have specific experience with the valves you may manipulate in the course of your work. However, in this case - the practice of leaving a K valve partially open to protect against freezing the valve - is not sound. In my training and experience as an engineer - it's important to realize when to use a pattern - and when it no longer applies.

Bjorn

The stuck valve thing is more related to the Steam valves. As a Marine Engineer in the Navy, if they are not backed off slightly, good luck moving it.

If the practice of backing off slightly is wrong, why do they teach it?

 

[Robert Gillcash]

Partially Closed: The path to failure here is to become confused about either how much one should open the valve - or worse yet getting turned around and making the mistake of FULLY CLOSING THE VALVE and then opening it back up a quarter turn! The consequence of this is a valve that may breath at the surface - but at depth could become increasingly difficult to breath - leading to panic.
Bjorn

If the buddy check is done properly, i.e. breathing a few hard breaths off the reg, that will show a partially opened valve. A closed valve is indicated by the SPG needle dropping rapidly to zero. A partially open valve is indicated by the SPG needle dropping then going back up. If your valve is open all the way or even turned back a bit, the needle will not move. (I teach this during the first buddy check at poolside, by turning off a students air and having them breath, then cracking the valve until it shows full again. A few breaths shows something is not right. Then I open the tank fully and show the difference.)
If you do this every time before you enter the water, the chances of going in with not enough air are reduced to virtually zero.
Added: When I teach this, I open the valve all the way and then just every so slightly turn it back just a bit, so it's not jammed open. Too many times I've had to really fight to open valves on the rental tanks because they are closed SO tightly. And the same happens all the way open. Some of these young students (20 year old Marines) are so strong and don't realize how much they are opening or closing the valve.

 

[The Chairman]

Unless it's a back seat valve, I will almost always back it off a bit from full open. Why? It makes easy to tell if the tank is on or not. If the tank valve is tight, then it is closed. If it is loose, then it is open. I don't back it off much, maybe an eighth of a turn... just enough to keep it loose. Once I open my valve, I don't want anyone else to touch it. I have right and left sided valves on a few tanks since I side mount. My favorite are often used to back mount singly since they are 130s. They are even indicator valves showing red when closed and green when open. I have had them turned off by deck hands twice. Why? Because it's pointing in the wrong direction and they get confused.

 

[DCBC]

I believe that any diver shouldn't dive beyond their "safe diving envelope." As you gain experience this envelope increases. A diver can gradually expand this envelope until he hits a wall where his current training/experience is insufficient to move forward. An example of this is overhead environments. At this point the diver needs to be mentored by someone with that experience, or take additional training with an instructor.

Regardless of how much training and experience one has, there are still walls that cannot be crossed. Some of these are dictated by fitness, age and personal choice.

The type of diving someone elects to do, is up to that individual. Can you dive without being certified, or taking any training whatsoever? Yes. Can you dive air to 300 FSW? Yes. Can you enter a Cave without proper equipment and training? Yes. Actually, you can do anything you elect to do. Are actions like these recommended? No they're not.

The majority of all divers lack experience in one area or another. Caution is not just warranted for new divers, but us all. We need to ascertain our personal safe diving envelope and nurture its growth how we see fit. It's recommended that we apply good judgment. We should not be overly quick to criticize the choices of others, but carefully examine our own.

 

[DaleC]

Valve all the way on - air.
Valve all the way off - no air

Valve backed off a bit - maybe almost all the way on, maybe all the way off, maybe restricted flow at depth, maybe not; in any case, needs a secondary action to confirm... let me add that to all the other things you are learning today. All to solve what?

I dive J valves from the early 60's all the way through to convertible thermo DIN's and haven't had one stick yet. And, as Bjorn states, if one did, the biggest risk is that I would need to bleed the tank to remove the reg. The risk to teaching new divers to back the valve off is having them die when they can't get enough air at depth.

If that happened, I want to hear the instructor justify their valve theory rationale to the family.
"Hey, at least the valve isn't stuck".


When I look at risk mitigation I K.I.S.S.

 

[bl6394]

The stuck valve thing is more related to the Steam valves. As a Marine Engineer in the Navy, if they are not backed off slightly, good luck moving it.

If the practice of backing off slightly is wrong, why do they teach it?

Good question - PADI doesn't anymore.

Reviewing my son's PADI OW Manual from 2010 - in Chapter One - page 59 - the following direction is given to setting up your tank: "While holding the SPG away from you, open the valve all the way gently."

Likewise - in my PADI DM slate (2011 version) - Predive Safety Check - The following direction is given during the check: "Valve turned on all the way?"

Maybe someone from the other agencies will chime in too.

Cheers,


Bjorn