Valve Stuck On Al80 Tank

[rmediver2002]

http://www.adp.fsu.edu/pics/PENPC021122/31.html

We do a few vip's a year over here...

Rubber mallet has been working fine for the last decade, make sure you shut the valve first (less pressure applied to stem this way), it does not take much force to break the seal.

One item on lubricating threads... Be careful about using excesive lub on them, as the tank heats up (usually laying down in the sun) the lubricant can melt and run down the inside of the tank. This residue will discolor and hold any type of contamination or oxide in the tank. You may end up cleaning your tank more often but that is not a bad thing right!!

Jeff Lane

 

[Mverick]

I always wondered why people would hit the valve handle with a rubber mallet?????

Good way to ruin the valve. I'm sure you do alot of VIP's. But it's still taking a chance with someone else's tank. If you're fine with replacing the valve if you damage it they I guess it's OK. But I'd still take it to someone who would use a wrench.

Good mechanics use the proper tools. Bad mechanics use a Hammer.

I've been in the Bad mechcanics side on things also. But not on my tank valves. I don't pop them with my hand either..

So what is the reasoning to use a hammer instead of a proper sized wrench?

In my VIP class I brought 2 tanks with loose valves. I watched around 5 people start to cock there arm back to pop my valve. I corrected everyone of them before they smacked that handle. I even had a PSI inspector tell me it was OK as there was little chance for damage. When I asked if he was willing to pay for the valve if damage occured. He decided I was right.

Just use a wrench. $10 wrench or a $55 DIN valve. I'll buy the wrench. Heck, I only put them on hand tight anyway.

 

[rmediver2002]

Most of the time nothing more than a twist of the wrist is required to remove a valve, if it is especially snug then a light tap with a rubber mallet removes the valve.

If inexperienced or complacent people begin to use the mallet every valve or by default hit every valve with a great deal of force they will eventually damage a valve.

If they do damage a valve it will damage the stem, a new stem is < $2 for most valves.

I am not saying using a wrench is wrong here but to say your going to ruin a valve using a hammer is incorrect...

Jeff Lane

 

[Mverick]

Yep,
My valves twist off easy. That's why I only put them on hand tight. No wrench to tighten them. And never a Rubber mallet.

"""If inexperienced or complacent people begin to use the mallet every valve or by default hit every valve with a great deal of force they will eventually damage a valve."""

That statement is exactly right. And around 90% of the tank jockies will smack the valve with a mallet or the palm of there hand. And around 90% aren't carefull..


"""If they do damage a valve it will damage the stem, a new stem is < $2 for most valves."""

Yep, and that valve would be nice on your tank. If you would ruin the stem on my valve I'd expect a new valve. You could keep the old one with the replaced stem.


"""I am not saying using a wrench is wrong here but to say your going to ruin a valve using a hammer is incorrect..."""

With a tank jockey using a mallet or you or me. There is a chance to bend the stem. With a wrench. There is no chance.

Why not use the wrench...

 

[rmediver2002]

Your right using a wrench is the right thing to do.

p.s. no one should be using a wrench to tighten down a straight thread (o-ring sealed) valve

Jeff Lane

 

[pescador775]

A tank valve is no different from thousands of other O ring designs for various connectors and bulkhead fittings. The military especially favors O ring connectors (AN fittings) for aircraft and all high pressure systems. All of these have torque specs requiring a wrench. The same is true for tank valves. Manufacturers set specific torque values for their valves which can only be set with a wrench. Nonsense, like hitting with mallets, is not a recommended practice but the valves themselves are fairly well idiot proof. They will usually seal with little effort. However, if metal to metal contact is not made some salt may build up under the valve's machined surface causing corrosion under the valve. Also, the valve will only be secure if the tank is pressurized. If the valve on an empty tank is accidentally bumped or twisted a new O ring may be necessary. Rings which have taken a set will often leak when retightened.

 

[C_C]

"no one should be using a wrench to tighten down a straight thread (o-ring sealed) valve"

As Pescador states, manufacturers have torque specs for valves in scuba cylinders. As far as I know...all current (new) valves use o-rings.

Follow the specs, use a torque wrench to install. Use at least a 15" adjustable end wrench for removal with the cylinder secured in a padded restraining device.

C_C

 

[rmediver2002]

http://www.catalinacylinders.com/valvescuba.html


Hand tightening of the valve should seat the valve completely on the cylinder (i.e. no gap between the valve and the cylinder). If there is still a gap between the valve and the bottom of the cylinder lightly tap the valve handle with a rawhide or rubber mallet to seat the valve completely. If you decide to seat the valve using a torque wrench, following are recommended torque values by Catalina Cylinders and the CGA:


Thread Designation Catalina Cylinders
Recommended Torque CGA C-6.1
Maximum Torque
.750 - 16 UNF 50 lbf-ft 60 lbf-ft
¾ - 14 NGS (NPSM) 80 lbf-ft 100 lbf-ft

 

[bhapps24]

I'll start off by thanking all for the tips. When i picked up the cylinder from the LDS with the valve still stuck on it showed signs of a wrench being used (the flat spots were rounded where the wrench would go). I brought it home and tried the ideas given with no success. So I got my large plumbing monkey wrench figuring it was already mared(couldn't make it much worse) and put it on the base of the valve and could not free it(just rounded more). At that point I decided to go with a new valve not concerned about damage put the wrench smack dab in the middle and whacked hard with a 5lb hammer. 1st whack it came of the tank and ruined the valve. I'm going to take the tank to a different LDS and have them make sure the threads are still ok and not ruined from overtighting not salt intrusion. I'm just hoping it will be just a valve now and not a tank. Thankfully I still have two good tanks to keep diving with.
Thanks you are all gods

 

[pescador775]

Sounds like the valve was not too tight after all, just snug. The manufacturer recommends 80 lbft which is about the same torque as an engine head bolt. If the tank had been tightly torqued as recommended by Catalina the valve should have still been easily removed using a chain vise and 18" monkey wrench. Personally, I don't quite use 80 lbft but should that much torque be used the valve would still not be as difficult as you describe, especially if it had been lubed. It might be instructive to note that the valve and tank neck can withstand these 80-100 torque levels easily but the valve handle and stem are not designed to be banged around. Still, since the stem is partially protected by the main casting it can survive some abuse. A secondary concern is the valve seat. If the hammer blow is not exactly right, torque can be applied to the valve handle causing it to overtighten.