Turning air off after equipment assembly

[highdesert]

So on the dive boat two weeks ago, as we're up and moving towards the dive platform to begin our dive, the young fellow
in front of me turns and says, "Hey, turn my air please".

As I turn his air on I ask, "why is it off ?...

He replys, "I always turn it off, after I turn it on... and we've been diving so long, we don't need to do Pre-Dive safety checks anymore"...

I just smiled at him, shook my head and said, "Oh Really" ???

So what does this incompetent diver do when he asks another equally incompetent diver to turn his air on, and if for some reason his air was already on, and the person he asks turns the valve (incorrectly) the only direction it'll move, which is off? Oopsie ...

 

[Diver0001]

Really, this IS a real issue if you go diving in Egypt and dive ops cover this in their "on the way to the jetty" information, yet it happens EVERY day that someones tank goes *POP*HIIIIZZZZZZZZZZZZZZZZZZZZZZZZ* because they forgot to depressurize

Seems preferable to have this happen on the boat. If you turn on the pressure just before getting into the water then for the first few minutes of the dive the pressure will be higher then normal, meaning that the chance of this happening under wtaer is also higher than normal. yymv

I believe that what Tigerman is saying is accurate but it's more of an argument for using DIN valves than it is for depressurizing after setting the kit up.

R..

 

[WB2GLP]

All the way on?
All the way on 1/2 turn back?
All the way on full turn back?

Why worry when the Deckhand will turn it OFF for you before you jump off the boat?

Sorry, just being facetious.

Now for the real question: Does anyone else do the dodge and spin when a deckhand reaches for your valve as you head toward the platform?

 

[GrumpyOldGuy]

I never suggested turning the tank on after you go in, I suggested turning the tank on and checking you have air and then turn off and DEPRESSURIZE the system. 2 minutes before jump time is not the time to find out you geared up on a half used or empty tank..

The point I was trying to illustrate with the very specific example of air readings was just how much of a difference that temprature makes. When it makes that much difference in a larg container, imagine what it does to a smaller, more easilly heated one..

No, generally the o-ring you dont blow by depressurizing dont blow when you turn on the tank just before you jump - unless of course you skipped attaching and testing the first stage when setting up the rest of the gear - then you can bet your ass skipping that part is gonna bite you in the ass and make everybody wait while you fix it..

On a 200 bar tank (which it'll drop back to not long after you splash) 250 bar is already WAY above working pressure, why would you need to let it sit and heat up more, pressurized to "test your o-rings" thats gonna blow just as much if theire brand new in those conditions?

Blowing the o-ring just after I splash would be fine, when youre 15 minutes into the dive and down at 20-30 meters its kinda inconvenient...

What you said was "after you submerge" the pressure drops, I pointed out this is well after you have turned the air back on and hit it with the extra pressure from the heated tanks.

The point that the smaller container of gas would show a higher pressure increase than a larger tank is not supported by physics. Both start out with the same pressure, both get hit with a similar rise in temperature, both have the same type of gas. Thus both will have a similar amount of over-pressure. Sitting out in the sun and hot air provides nice even heat. Perhaps if you have a painted black tank you might have a point.

Lastly, I don't buy the a new o-ring on a good seat is going to blow at 15% above rated pressure, yoke or DIN. They a built to go well over that. That's why they work fine on high pressure tanks (3500 on a steel tank is the same pressure as an overheated 3000 AL tank, basic physics. You may have a defective o-ring, an older one, an imperfect seat or alignment (yokes are touchy) that lead to failure. Your heat and excess pressure may contribute to the issue and accelerate the failure process for sure. I admit your babying them will extend their life, but its not a test. I test my gear above water because I don't want it to fail under water. Red neck common sense. Its a different strategy (testing vs extending life) and maybe you found in your case you prefer one over the other. I made a different choice.

I see an episode of Myth Busters on the horizon

 

[redacted]

Part of my gear check during set-up is turning gas on ato check pressure and then off and leave it pressurized to check for leaks. I may or may not bleed if off. I always check that gas is on before I jump. I do not object to crew members checking my gas. I just always check it again.

 

[Tigerman]

Seems preferable to have this happen on the boat. If you turn on the pressure just before getting into the water then for the first few minutes of the dive the pressure will be higher then normal, meaning that the chance of this happening under wtaer is also higher than normal. yymv

I believe that what Tigerman is saying is accurate but it's more of an argument for using DIN valves than it is for depressurizing after setting the kit up.

R..

The pressure from the tank dont seem to be a problem, the pressure that gets even more increased due to the air trapped in the lines, much smaller volume and much more easilly heated and thus expanded and increased pressure is the problem..

I do see people every week Im down there that "know better" and dont follow the advise to depressurize and they get the problems as well and then they go "wtf, I just changed that o-ring"..
Really, I DO preferr taking the advice of people who dive there every day all year over "being smart about it"..

When people who WORK under those conditions and have done a few thousand dives there goes "damn, Ive never seen THAT before" when an o-ring blow under water and their first reaction when an o-ring blow on the boat is "WHO didnt depressurize" it pretty much says everything about the odds to me..

 

[brnt999]

All the way on?
All the way on 1/2 turn back?
All the way on full turn back?

Why worry when the Deckhand will turn it OFF for you before you jump off the boat?

Sorry, just being facetious.

Now for the real question: Does anyone else do the dodge and spin when a deckhand reaches for your valve as you head toward the platform?

In this day and age, when we can put a man on the moon and manufacture diving computers that can tell you everything except when to take your next bowl movement, why don't we have a tank valve that we know for certain when it is on or off. I have thought about it and come up with an invention. It consists of a hole, a cotter pin, and a piece of wire. When you turn the wheel on a air tank to the on position it exposes a little hole in the shaft. You stick the cotter pin thru the hole. The piece of wire attaches the cotter pin to the tank so it doesn't get lost. The cotter pin prevents the wheel from being closed. I have read where cave divers rubbing the valve on the cave roof can accidentally close the valve. The cotter pin would prevent this from happening. If the cotter pin is in the hole you know the valve is on. If the cotter pin isn't in the hole there is a good chance the valve is off. So how about it? Can I patent this and make a million dollars?

 

[divealaska]

The most compelling reason to turn off and purge for me is to avoid the mishap of the regulator getting jarred and causing a freeflow of your gas. The equipment concerns are unfounded. Prior to your dive, you should do a valve check every time. Even when the well-meaning dive master comes along and checks my valve, I reach back and double-check again. Ideally, you'll develop the ability to reach your valve even while diving and this concern becomes less pronounced.

 

[Ayisha]

Now for the real question: Does anyone else do the dodge and spin when a deckhand reaches for your valve as you head toward the platform?

Yes, I do avoid the deckhand checking my valve due to having DM's turn it off inadvertantly a couple of times.

If they do touch it, I just reach back and check it myself before jumping in.

 

[-hh]

Don't you guys fill the bladder before jumping off a boat? If the air was off, wouldn't you notice the power inflator didn't work?

it depends on the dive plan. Some sites are live drops done negative. Other times, you're moored and you prefer to have your UW camera handed down into you (less hardware risk).

I do a half-way. After mounting I close the valve and blip/pulse the inflator to drop the manometer to just over 100bar.
This serves a multiple role. I always ensure at least some air in my BC, I test that the inflator isn't sticking and I leave enough air in the system to serve as a leak check on the way out. There is also no danger that I will look at my gauge, see it full and assume the valve is open.
I've been doing this routine for many years and it serves me fine.

this is my routine too. I usually do a buoyant entry for my camera, and when doing my final checks, if the pressure isn't where I left it, there's a leak ... And seeing a "low" gage will trigger if I happened to have somehow forgotten to turn it back on.

In this day and age, when we can put a man on the moon and manufacture diving computers that can tell you everything except when to take your next bowl movement, why don't we have a tank valve that we know for certain when it is on or off. I have thought about it and come up with an invention. It consists of a hole, a cotter pin, and a piece of wire. When you turn the wheel on a air tank to the on position it exposes a little hole in the shaft. You stick the cotter pin thru the hole. The piece of wire attaches the cotter pin to the tank so it doesn't get lost. The cotter pin prevents the wheel from being closed. I have read where cave divers rubbing the valve on the cave roof can accidentally close the valve. The cotter pin would prevent this from happening. If the cotter pin is in the hole you know the valve is on. If the cotter pin isn't in the hole there is a good chance the valve is off. So how about it? Can I patent this and make a million dollars?

Such a product already exists - its a replacement tank handle with IIRC a red/green colored stripe on it that is exposed based on on/off.


-hh