Tank Neck O-Ring

[ngray]

Just bought some used tanks from a charter captain. When I picked them up, he did a visual for me, which I watched. Only thing of note was that when he filled one off a whip from a full tank, the valve leaked where it mated with the neck. All he did was give the valve a good clockwise whack with his hand to tighten it up, then checked each of the other tanks. Curious, and not knowing any better, I asked if the valves should be tightened with a wrench, as it took one to remove the valves. He said no. It's also worth mentioning that as he vis'd each tank, he replaced each neck O-ring with a new, greased one.

Fast forward a few days later. I gave a few of the tanks to a guy who was going in on the tanks with me, and he took them to Ginnie, where he was diving with his family. When he got them filled there, something real odd happened. He said that the "O-Ring was sticking out of the neck, where the tank and valve meet". Obviously, it was not holding air. He paid the Ginnie shop to do a new vis, and they replaced the O-Ring. No problems from there on out.

Freakier (sp?), on one of the other tanks, his sister did her 2nd dive into the main spring at Ginnie, entering with 1500psi, got to 50ffw, and breathed the last breath from the tank. Her buddy was further than some ajoining stranger, whom she shared with to the surface. She said she heard/saw no bubbles.

Barring the fact that the person I gave the tanks to wants to take all the tanks back, sit them in the seller's front yard and knock the valves off with a sledgehammer, I'd really like to know what might have caused this. I don't know much about tanks, I'm buying my first set after my first year of diving. I'm guesssing:
1) Wrong O-Ring
2) Valves weren't tight enough
3) In the process of mounting the reg, a little ccw 'twist' was applied.
4) O-Ring shouldn't have been greased
5) All newly installed valves are susceptible to unseating until they 'corrode in' a bit
6) Valve should've been installed with locktite

I'm discounting 1, because I saw it installed, and it fit perfect. Looks about 3/16" thick. 2 seems unlikely. and is counter to my own clockwise hand-banging on the valves before I left the seller's place. 3 on is are uneducated guesses.

Do I have a right to be upset? Should I take them back? Should I have another lds re-vis all of them?

 

[ngray]

and breathed the last breath from the tank.

clarification. she breathed the TANK'S last breath. she's fine. just pissed.

 

[Ontario Diver]

All he did was give the valve a good clockwise whack with his hand to tighten it up, then checked each of the other tanks.

This is pretty standard. A lot of people overtighten valves. The valve should be about 60 ft/lbs.... which for most people is finger tight followed by a whack from the palm of the hand.

he vis'd each tank, he replaced each neck O-ring with a new, greased one.

It is correct procedure to install new O-rings on every visual inspection. The are usually not greased however. Maybe a bit of christolube on the threads of the valve but not on the oring.

"O-Ring was sticking out of the neck, where the tank and valve meet".

Ummmm that would be a problem. It is called an extruded O-ring and happens when the pressure in the tank pushes the o-ring out. This can happen if the oring is the wrong size, if the oring seat is dirty/cracked/broken, or if the tank valve is the wrong type or installed incorrectly.

I'm guesssing:
1) Wrong O-Ring
2) Valves weren't tight enough
3) In the process of mounting the reg, a little ccw 'twist' was applied.
4) O-Ring shouldn't have been greased
5) All newly installed valves are susceptible to unseating until they 'corrode in' a bit
6) Valve should've been installed with locktite

1) possible if the o-ring was too large it may have been ripped during tightening.
2) Possible but it sounds like it was done right.
3) Doubt it. Hard to do when there is 3000 PSI in the tank. The internal pressure makes it darn hard to move the valve. (I've tried!)
4) Yes.
5) Not true.
6) No, No, No.... Do not use loctite. Please.

Do I have a right to be upset? Should I take them back? Should I have another lds re-vis all of them?

Yes you have a right to be upset. If the tanks are steel, they should be revised, especially the one that was breathed down to nada. You want to ensure that there is no rust or water in the tanks.

If I was going to check the tanks, I'd check around the top of the valve thread area. There is something like a little step or lip and the o-ring fits inside of it. It is called the o-ring seat. Check to make sure that the o-ring seat is not broken or dirty.

If the tanks are aluminum, I would take all of them into a good LDS and buy a handfull of orings. Get some 3/4 tank o-rings and get some of the orings that fit in the valve head (yoke) or captured o-rings if you have DIN. Get the LDS guy to show you how to install them and put them into your Save-a-DIVE kit.

This is a simple issue but tanks are simple things. Just darn important that things are done right. Take them into a store and get them looked at.

 

[Lemonade]

Looks like same problem with both tanks. I bet it was two wrong size o-rings.

 

[Drew Sailbum]

An extruded o-ring is unlikely unless the fitting was not properly tightened.

It sounds you were dealing with a few tanks, and that one might have accidentally not been properly tightened down.

 

[Ontario Diver]

Looks like same problem with both tanks. I bet it was two wrong size o-rings.

Yeah. He probably confused his 7/8UNF Genesis style orings with his 3/4NPS .

I know I do.

<Grin>

Actually they were probably too big and being lubed would not have helpe either.

 

[pescador775]

Here we go again. Sixty foot pounds, sic (pound feet) is a lot of torque and is not a 'whack'. Not even close. Tighten that valve with a wrench until metal to metal contact is felt. A good tighening will be about 40 pound feet. Yes, if you go by the book it should be 60 but I have found that this is unnecessary. The O ring will not extrude. A little grease is fine, just a little. The people that 'whack' valves are wacked, IMO. Noted the O ring size comments. Possible but the ring for 7/8 fine is smaller than the standard 3/4 straight pipe thread.

A valve under pressure cannot be twisted, CCW or otherwise. However, when valve has been whacked and tank is empty the valve can come loose when being handled, carried by the valve. This will not happen to a valve tightened with a wrench.

This is pretty standard. A lot of people overtighten valves. The valve should be about 60 ft/lbs.... which for most people is finger tight followed by a whack from the palm of the hand.



It is correct procedure to install new O-rings on every visual inspection. The are usually not greased however. Maybe a bit of christolube on the threads of the valve but not on the oring.



Ummmm that would be a problem. It is called an extruded O-ring and happens when the pressure in the tank pushes the o-ring out. This can happen if the oring is the wrong size, if the oring seat is dirty/cracked/broken, or if the tank valve is the wrong type or installed incorrectly.




1) possible if the o-ring was too large it may have been ripped during tightening.
2) Possible but it sounds like it was done right.
3) Doubt it. Hard to do when there is 3000 PSI in the tank. The internal pressure makes it darn hard to move the valve. (I've tried!)
4) Yes.
5) Not true.
6) No, No, No.... Do not use loctite. Please.




Yes you have a right to be upset. If the tanks are steel, they should be revised, especially the one that was breathed down to nada. You want to ensure that there is no rust or water in the tanks.

If I was going to check the tanks, I'd check around the top of the valve thread area. There is something like a little step or lip and the o-ring fits inside of it. It is called the o-ring seat. Check to make sure that the o-ring seat is not broken or dirty.

If the tanks are aluminum, I would take all of them into a good LDS and buy a handfull of orings. Get some 3/4 tank o-rings and get some of the orings that fit in the valve head (yoke) or captured o-rings if you have DIN. Get the LDS guy to show you how to install them and put them into your Save-a-DIVE kit.

This is a simple issue but tanks are simple things. Just darn important that things are done right. Take them into a store and get them looked at.

 

[Ontario Diver]

Here we go again. Sixty foot pounds, sic (pound feet) is a lot of torque and is not a 'whack'.

This is the problem..."Whack" is very subjective. It is a tap, not a full out "bash" Way too many tanks are over torqued. On older tanks, 40 foot pounds may not be enough. YMMV.

 

[NINman]

I know that when my buddy inspected my pony he did excatly what Ontario Diver does, with the excemption that he used a tourque wrench. Couse you might use a tourque also, but just didn't mention it.

 

[MAK52580]

My guess is that either the o-ring was the wrong size, or the tank valve was crossthreaded. This may be the case as occasionally it will seem as of the valve is screwed in properly but isn't. This could result in some bubbling out, or the o-ring protruding on one side when pressurized.

I would definitely bring the tanks back to the shop, explaining the problem, seeing if you can get your money back or more likely store credit for your pain and suffering and make sure the person that did the VIP never inspects your tanks again.