Tank leak...this can't be good

[String]

Any proof to back up the fact that rubber mallets do not do the job adequately? Any incident statistics to back up that claim?
Or do you just sell spanners or involved with a tank business?
We're not talking about randomly battering a valve in a random place with a hammer here.

 

[captain]

A rubber hammer is OK but I use it on the end of a wrench on the valve not on the valve itself.

 

[GrumpyOldGuy]

The following is my actual experience, take it for what you want.

1) I moved from NH (diving s/w) to Amarillo TX almost 3 years ago. When filling in a water bath, the local LDS notices several of my tanks with slow O-ring leaks. He nicely drained the tanks, cleaned the surfaces and replace the o-rings. He also suggested that maybe salt crystals had formed under the o-rings and I needed to clean my gear better. Note: I am not exactly a new diver, but I did not argue and took his advice.

2) About 6 months later, the same tanks leaked. Same story, cleaned and replaced the o-rings.

3) A few months later, one of the same tanks leaked. Same story.

The interesting part of the story is after moving TX, these tanks have been used exclusively used in fresh water for the last 3 years. They have had 2 VIPS since the move, several changes of O-rings, etc.. I rent tanks for diving in salt water (CA & NH). So salt crystals are not present. He uses a wrench to snug down the valve and only uses the mallet to break a stuck valve loose. I watched him mount the valves, he was very careful in his procedure, cleaned everything, used a tiny bit of lube. He has 30+ years in the business and seems to know his stuff.


So, I honestly do not have a good explanation of what caused the leaks. He does torque the valve down a wee bit more than before. Maybe the surface has an imperfection neither one of us could see that under 3,000PSI allowed a very slow leak.

 

[SDAnderson]

Any proof to back up the fact that rubber mallets do not do the job adequately? Any incident statistics to back up that claim?

The only evidence I am going to offer of a connection between leaky neck o-rings and the common practice of using a rubber mallet to install the valve is anecdotal. This is repetitive but you summed it up quite nicely, I think:

Cause:​

Rubber mallet is all you want for a tank.

Effect:​

Its not that uncommon for neck o-rings to leak especially in new tanks.

New cylinders, with their smooth glans, normally have better seating surfaces for the o-ring than old, beat up cylinders. Heck, they come from the factory with a plug in them designed to keep crud out and to protect the glans. When cylinders leak at the valve/neck joint, it's rarely because of problems with the glans and almost always because the connection wasn't sufficiently torqued. The reason new cylinders tend to leak is because the installer isn't adjusting his technique/protocol to account for the new threads and then checking his work to make sure he achieved a seal. The new threads are fresh and tight and it takes more torque to close the gap and make the seal than it will after the threads have worn a bit. If you're too lazy/inexperienced/uncaring/poor to use a tank clamp and a wrench, you'll have to be very (impossibly?) good with a mallet to be able to vary the force used.

Everybody is afraid to put too much torque on the valve for fear of damaging the threads but, in reality, both the cylinder and the valve are nearly as tough as nails. You don't want to use any more force than necessary but maximum torque for most AL80's is 100 foot pounds/135 newton meters, a pretty hefty value. The valve itself (plated brass) is able to handle at least half again that value. You shouldn't need to get that high but if the joint is leaking you definitely want something more precise than a hammer.​

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We're not talking about randomly battering a valve in a random place with a hammer here.

Actually, yes, you are. The notion that "just a couple of whacks" from a rubber mallet produces anything other than a widely (and wildly) variable torque value is, well, nonsensical. If you're thumping the valve hard enough with a hammer, rubber or otherwise, getting it to seat properly means you have to worry about the side-effect of bent and broken valves. Whacking produces a "damned if you do, damned if you don't" situation.​

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Or do you just sell spanners or involved with a tank business?

Cute. Nope, I don't sell spanners. Yep, I do service tanks. Lots of them for lots of years. That may not qualify me as an expert (though I am a qualified instructor teaching others to service and inspect cylinders) but it has given me an opportunity to learn a little something here and there. I'm just passing along some of what I've learned, YRMV. I'm at least marginally more qualified than the usual cyber-expert, however.

It's just better to use a wrench. If you're going to use a mallet, do like the captain does, use it on the wrench. Save the Whack-A-Mole games for the carnival.​

 

[Saudi-Diver]

How about dismantling the valve having a quick look at the seating, O ring and re torquing it up to the manufacturers settings, that all ways seems to work for me. If the O ring is flat or marked in any way throw it away its pennies. I hate it if I am diving and have a leak. Never usually happens unless I am diving rental tanks.

 

[sealark]

The reason rubber mallets were used was old US divers valves had a round flange. People would use a wrench on the regulator seat and screw the seat up. Best way for todays modern valves is use wrench and hit end with mallet. On heavely used old tank make sure the top surface is flat where the valve meets the tank.

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[captain]

The reason rubber mallets were used was old US divers valves had a round flange. People would use a wrench on the regulator seat and screw the seat up. Best way for todays modern valves is use wrench and hit end with mallet. On heavely used old tank make sure the top surface is flat where the valve meets the tank.

Sent from my DROIDX using Tapatalk[/QUOTE

You don't screw up the regulator seat if you use the right wrench and put it on the valve correctly according to whether you are installing or removing the valve.