Quarter Turn Back

[Ledznvrdead]

Can anyone tell me the theory in turning the tank valve a quarter turn back after opening it all the way.

 

[JRScuba]

Can anyone tell me the theory in turning the tank valve a quarter turn back after opening it all the way.

That is the same with any valve.
If you open the valve all the way it might seize in that position and be hard to close after a period of time. This is what I learned about water, steam, gas, etc, faucets. Another thought is turning the knob full on will make it hard to close and possibly damaged the valve.

That's the best explanation I can come up with. I'm sure someone will have a better technical reason.

 

[IaDiverJ&L]

Can anyone tell me the theory in turning the tank valve a quarter turn back after opening it all the way.

So your Buddy or Dive master, etc ,can check to see if you have your valve on All the way. If it was tight All the to the Left (open) someone might make a mistake to see if it was open or closed. You just need a little play.

 

[StSomewhere]

That is the same with any valve.
If you open the valve all the way it might seize in that position and be hard to close after a period of time. This is what I learned about water, steam, gas, etc, faucets. Another thought is turning the knob full on will make it hard to close and possibly damaged the valve.

That's the best explanation I can come up with. I'm sure someone will have a better technical reason.

That's a very good explanation.

Ledznvrdead, the problem I have is with the 1/4 turn part. A quarter turn may be too much for some valves and not nearly enough for others. "Turn it back to where it first no longer grips" works better in all instances.

 

[Rick Inman]

If you open the valve all the way it might seize in that position and be hard to close after a period of time.

I'm told the older valves would, but the newer valves won't.

I open my valve all the way so there is no doubt that it is open.

I try to keep the DMs away from my valves for safety's sake.

 

[knotical]

similar thread here:
http://www.scubaboard.com/showthread.php?t=91704

 

[Bob3]

I agree with JRScuba, I've done the pipefitting & steamfitting thing in shipyards, paper mills, processing plants, & etc.
Some styles of valves need to be backseated to prevent stem leakage but the valves used on scuba tanks aren't one of them.

I try to keep the DMs away from my valves for safety's sake.

yeee haw! How many folks have had their regs unscrewed (or tanks turned off) by folks "helping out"?

 

[JRScuba]

I'm told the older valves would, but the newer valves won't.

I open my valve all the way so there is no doubt that it is open.

I try to keep the DMs away from my valves for safety's sake.

As far as diving goes, the 1/4 turn is probable a safe way to go. The one time a DM ( not all ) goes to open your valve he/she might think it is stuck closed and Try REAL HARD to open it. Then you will really be in DEEP SNEAKERS.

I treat all valves the same way, leaves no room for mistakes.

Murph's Law Pervails.

 

[Dive-aholic]

I'm told the older valves would, but the newer valves won't.

I open my valve all the way so there is no doubt that it is open.

I try to keep the DMs away from my valves for safety's sake.

I can't even count how many times the DM and I have gone back and forth with that. DM goes around checking valves, turns it back a 1/4 turn. I fully open it. DM does another check and turns it back a 1/4 turn. I fully open it. I've thought about bringing duct tape with me to tape it fully open!

 

[Rick Murchison]

You haven't lived until you've had a valve get jammed open. I mean jammed to the point that the stem shears when the pipe wrench is used to try to close it. A major PITA. Been there, done that, don't want to ever do it again.
I say open the valve all the way and back it off a hair. (a quarter turn is fine)
Rick