Why isn't there a tank valve-open marking?

[Bob DBF]

The only 100% sure way to do it is a breath check right before entry - breathe it and see if the needle moves on your SPG.

Unless you breathe several times quite fast and forcefully, you may not see any deflection with a tank that has the valve 1/2 turn open. I maintain control of my tank valve so that no one helps me after I have it opened.


Bob

 

[Dan]

When would you see a valve being closed counter clockwise? Even all valves at home, which I use everyday are closed clockwise. Whoever turned your valve open clockwise had probably won the Darwin Award, like some of the guys up there in Mt.Everest, who reduced the oxygen flow by turning the valve counter-clockwise, which was actually turned up & increased oxygen flow & eventually running out of oxygen on the way down (from what I read in the book "Into Thin Air")

This is one convention that is truly worldwide.

There are some nuts & bolts that have to be tightened counter-clockwise for safety reason. For example my electric Craftsman Edger with its blade rotating clockwise. To keep the blade from flying off from the axle due to loose locknut, the locknut is tightened counter-clockwise, so it'll always stay there & self tightening whenever I use it, which is once a week in 10 months out of a year, here in South Texas. It worked fine for more than 20 years.

 

[The Chairman]

However, don't open a valve "like crazy" or it'll be sticky open which is annoying if you have to shut it down.

Shenanigans. Clean, relube the shaft and replace that #10 O-ring every time you VIP the tanks to keep that valve turning easy.

 

[RainPilot]

The Quarter Turn That Kills

Some thoughts on the matter

 

[Dan]

The Quarter Turn That Kills

Some thoughts on the matter

This is to close the valve all the way & open quarter turn, which is pretty much very close to shut off the valve, a stupid idea. It is NOT the same as open the valve all the way and do a half or quarter turn or 1/8 turn clockwise (closing direction), which is to me is pretty much wide open if you look to the valve curve of pressure drop vs number of turn graph.

 

[RainPilot]

This is to close the valve all the way & open quarter turn, which is pretty much very close to shut off the valve, a stupid idea. It is NOT the same as open the valve all the way and do a half or quarter turn or 1/8 turn clockwise (closing direction), which is to me is pretty much wide open if you look to the valve curve of pressure drop vs number of turn plot.

hey Dan

The issue arises when someone has turned the valve completely closed, thinking it was open, then a 1/4 turn or 1/2 turn back. This allows the user to breathe from the tank up to a certain depth then nothing, like what happened to Sheck Exley.

If the tank is turned all the way, then either you can breathe or you cant. No dangerous middle ground. Obviously watching the SPG while taking a few breaths may help identify, but I cant tell you how often I watch divers on the boat turning a tank valve all the way, a little back and then a few breaths without checking the SPG. If someone had turned the valve on before they got to it, they could easily have closed then opened it a bit.

 

[Dan]

I see your point now. I guess those guys have never turn on a faucet at home. LOL.

I don't know how many turns needed to open the scuba tank (never bother to count). But if you see a typical valve curve above, whether the curve is linear or square root or whatever, once you are in completely open (or closed) position, a half turn (10% less of stem opening, if it takes 5 turns to completely open), a quarter (5% less of stem opening) or 1/8 (3% less of stem opening) doesn't make any difference.

 

[RainPilot]

I think that especially for new divers, all the tons of new unfamiliar equipment etc etc as well as nerves over diving kind of short circuit some of the "common-sense" centre of the brain. How many times have you seen a diver doing something where you just "couldn't even" and they are pretty clever outside the boat?

Even speaking for myself, when I open some valve / faucet / bolt etc I will try the conventional way first, if no joy I might turn it the other way just to check. If that then seems to work and I can get air (after the 1/4 turn open again)....

We have a saying in flight training, the student's IQ is inversely proportional to the rotational speed of the propeller.

I think new (and not so new) divers have the same thing going on for quite some time. Myself very much included.

 

[rx7diver]

Due to the occasional apparent confusion about which way to turn tank air valves to open them, and the possibility of air being turned off by inept dive boat crew, etc, why isn't there some universal labeling standard to show which way to turn a valve on?

It would seem relatively simple to have an arrow molded into all valve handles, and the arrow points in the direction of Open / On.

This way even if for some reason a valve is breaking the standard CCW-open method, it's obvious just by looking at the arrow direction what needs to be done.

Javik,

Maybe a better (the best?) solution is for a diver to be able to turn on/off his own gas even when he/she is fully kitted up and diving. He would reach back over his right shoulder with his right hand, grab the valve knob, and turn the valve on/off as required. (Note: He might have to first loosen his BC straps and/or reach back with his left hand to the bottom of his tank to push his tank up a bit to make reaching his valve a bit easier.) This approach works no matter when the valve became closed inadvertently, no matter who closed the valve mistakenly. Fundamentals!

Safe Diving,

rx7diver

 

[Caveeagle]

....Finally, last solution: be responsible for your own safety and don't let someone else touch your gear.

You may not have a choice, or even be aware when a crew member 'checks' your valve. I have observed a crew member that was in the habit of helping divers to the back of the boat (rough water), and would stabilize the diver by holding the diver bay the tank, and would check the valves for 'open' at the same time. I saw this several times on that trip.

If that useless guy that checks valves before you jump in from a boat goes "Oh, your valve was closed, I opened it", I know I'd go back, sit down, take the tank off and check it myself again.

Why do you have to sit down and tank your gear off to check the valve? I like to double check my valves position just before I go in, and am in the habit of putting my hand on the knob as I test breath by regs.

couple more thoughts....

*I suggested this on another thread, but I like the idea of some sort of "Remove Before Flight" tags to be put on closed valves. I know this is not full proof, but an easy way for me to keep track of valve status.

**Its not uncommon to have sets of singe tanks know with mirrored (left/right) valves for use in sidemount. These paired sets often get used for singe tank dives around my area. The valves are still 'Left-to-open, Right-to-close', just like any other valve, but I have observed divers get confused by this. I think it was because the diver was thinking more about the direction of rotation relative to the "front" instead of "clockwise" rotation of the valve. Just another thing to consider that could confuse the situation.