Tank valve opening procedure

[MikeFerrara]

In the sport diving side the 1/4 turn from full open is most common,,,,

Not any more. PADI teaches full open and PADI is the way the world learns to dive.

in the tech side of diving full open is the method usually taken. I prefer full open.

Well, if you want to find out how to do a thing, go to those who know.

 

[LI Diver]

Lately I've seen some references to different opinions about the best procedures for opening tank valves. The traditional belief is that you should open the valve all the way till it stops and then back a quarter turn. More recently some are suggesting that it is better to simply open the valve all the way.

The argument for backing off the valve is that the valve is susceptible to damage if it were to be struck in exactly the wrong way while all the way against the stop.

The argument for opening the valve all the way involves the possibility for human error. Apparently it has been documented a few times that people have made the mistake of turning the valve all the way closed then opening it a quarter turn. At the surface the regulator breathes correctly and the pressure gage shows full. As the diver descends however, the valve may not be open enough to supply the increased air demand at depth. This can cause an immediate out-of-air condition or just very hard breathing.

When I took my certification several years ago our instructor taught the traditional technique but mentioned that the subject was under debate and explained the arguments both ways.

I lean toward having the valve either fully open or fully closed to minimize the chance of human error. My understanding is that newer tanks generally have rubbery valve handles that reduce the chance that an impact will damage the valve.

Is there a consensus on this matter now?

Please advise.

Pete Dudley
Albuquerque, New Mexico, USA

It's funny I was told years ago at at welding school that all high pressure tank valves had double seated valves. One that seated when the valve was closed (which is normal) and one to seat when valve is fully open,so that tank pressure is not being sealed in strictly by the valve stem seal/packing.I'm going to look for a cut away view of a scuba valve. BTW I turn on all the way and close 1/4 turn out of blind faith in my instructors But keep my eyes open for bubbles (they are usually coming out of the DM's tank!)

 

[Charlie99]

One reason for the traditional method of opening valves is that in an operating plant it puts valves in a condition such that you can manually check their position without affecting the operation of the plant.

To manually check a valve without affecting anything, you simply try to close the valve. A closed valve doesn't move. An open valve will close slightly, but you don't rotate it enough to affect the flow. A fully open valve stuck against the backseat will not rotate easily when you try to close it, and may leave one with the incorrect assumption that it is closed.

 

[SStrecker]

I agree with MikeFerra. I was taught the quarter turn back technique, back in the 1970s, but there does not seem to be any critical reason to do so anymore. Therefore, I prefer to dive with the valve all the way open.

 

[daniel f aleman]

Obviously, it doesn't really matter which system is used for diving. Although I agree with Charlie99's scenario in general, and I turn back a quarter...

 

[DandyDon]

Except that if it's all the way closed you'll know it. If it's all the way closed and then turned on part of a turn you may not until you have trouble getting gas or reach back and check...and of course many divers can't reach their valves.

Saw this happen to a lady as she descended into the Belize Blue Hole. The second mater checked her tank, which was already open - closed it all the way by mistake, then opened it enough that she had air pressure down to 60 or 80 ft. We had a lot of problems with that mate.

All the way open or back just a hair, please - not 1/4 or 1/2 turn.

 

[Wayward Son]

A good reason why I want people to keep their grubby mitts off my gear.

 

[Darnold9999]

Taught the full on 1/4 turn back in the 70's as well. Had a rental tank a couple of months ago. If you turned it full on with too much enthusiasm you needed pliers to take it off full on. Don't know hwat caused it, however I do wonder what is inside the valve that prevents the valve from screwing out all the way. Made a point of checking that the valve was a 1/4 turn from full open and treated it with kidd gloves. probably should have got another tank.

 

[Whatgoesdown]

One reason for the traditional method of opening valves is that in an operating plant it puts valves in a condition such that you can manually check their position without affecting the operation of the plant.

To manually check a valve without affecting anything, you simply try to close the valve. A closed valve doesn't move. An open valve will close slightly, but you don't rotate it enough to affect the flow. A fully open valve stuck against the backseat will not rotate easily when you try to close it, and may leave one with the incorrect assumption that it is closed.

This is what I was told way back when. If a diver reaches back over their head and can move the valve easily in either direction, they remembered to open it and won't waste any more time in an OOA situation trying to "open" a valve that is already open fully.

When I put the tech gear on, I open all the way. However, I check my gear and my buddy's on land, then again at the surface at bubble check time, we both check our valves during the descent, during the dive etc. Different discipline!

 

[matt_unique]

Full open, then close just a pinch. This way you know instantly when doing a valve drill (or the real thing) if the valve is open or closed.

Never let anyone touch your valve once you have opened it and checked your breathing system. Avoid it like the plague.

--Matt