Cylinder valves seal only when fully open or fully closed?

[visor_down]

Hi
Another gas Q from me!
I have always had the valve on the bottle fully open or fully closed as I was told that they only seal in the fully open or closed position, is this the case with hobby bottles with the handscrew on top? Or can you just undo them a turn without any issue?
Cheers

 

[Wendelspanswick]

Its bad practice to fully open a gas bottle valve as:
It takes too long to close the valve in an emergency.
Its possible to jam the valve open if too much force is used.
If you wind the valve fully open so it jams and the next operator comes along to check the bottle and they give the valve a gentle twist they can be fooled into thinking the valve is closed.

We had a ham fisted apprentice who was found with a pair of Stilsons on an Oxygen bottle, trying to open the valve which he moaned had been closed too tight, turned out the valve was already wide open, left in that position by him the night before!

The normal practice is half to one complete turn open.

 

[Bill Edwards]

Just undo them a little, whatever the valve. I tend to go with a 1/4 turn, as cylinders keys often hit the regulator and it should be left where it's quick to turn off if something goes wrong. I use bottles with a handwheel on top, I don't take these to more than 1/2 a turn, anything more really isn't needed.

 

[chevy2]

I normally use one of those small cylinder keys with just the square in one end,
Keep it at about the 4 o'clock position when closed and about the 8 o'clock position when open,

this way a quick glance at the key position will let you know if its on or off regardless of whether the regulator is showing any pressure,

I find half a turn or so of the key is enough for adequate flow.

 

[gordon stephenson]

I remember reading on an American forum about the posters question,Maybe it's the USA bottles that need opening fully to a top seal

 

[edd]

I was taught the same thing, oxy/inert bottle fully open, flammable gasses 1/4-1/2 a turn.
I still do it this way, not sure if it is right mind!

 

[Bill Edwards]

There really is no point in opening any of them any more than you need to let the gas flow!

 

[backpurge]

1/4 to 1/2 turn is enough to fully open