Tank Notice

This is in no way intended to be a flame as I have used similar tanks with no problems for years. But,

Two weeks ago I bought two Worthington X7 HP 100 steel tanks from my LDS and had them filled with nitrox for my upcoming offshore trip. I dropped them off at my parents' house since we'll be departing from there. This morning as my dad (also a dm) was leaving for work he heard a hiss coming from one of them. He put his ear up to the valve (Thermo) and noticed it came from the valve/neck connection, not from an accidentally opened valve. So I called the LDS who thinks mine may have been among a batch of tanks produced a year or two ago in which they tried a new purple seal between valve and tank which have been shown to be faulty/badly designed.

So I have to get the tanks from my parents place (1 hr away), bring them back to the LDS who said they have replacement seals and will take care of it and get me new fills and VIPs, as the tanks will likely be bled dry.

I was pretty upset since if my dad didn't happen to hear the hiss, this could have happened in the middle of a trip or in the middle of a dive. I figured I'd share so people are aware of this possibility.

Just to offer that "glass is half-full" perspective, I hope you're tempering your upset with the fact that your Dad did notice the problem now, so that you didn't end up finding your tanks empty while setting up for a dive.

It's inconvenient to get it fixed now, but at least you didn't lose your dive trip because of it. It sucks there's a problem, but it's great that it was caught ahead of time. Be happy about that last part.

L_A_S:

So I called the LDS who thinks mine may have been among a batch of tanks produced a year or two ago in which they tried a new purple seal between valve and tank which have been shown to be faulty/badly designed.

So I have to get the tanks from my parents place (1 hr away), bring them back to the LDS who said they have replacement seals and will take care of it and get me new fills and VIPs, as the tanks will likely be bled dry.

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Sounds like your LDS is stepping up and taking care of them. Sounds like a LDS that deserves a plug here.

I had a bunch (6) of Catalina tanks start slow leaks at the oring between the valve and tank this year. My new LDS spotted it when filling them in a water bath - previous LDS filled without water. The leaks may have been there awhile and I just wrote off the 2800/2900psi starting pressure as short fills.

I honestly do not know if I was to blame (not rinsing the tank enough) or if the orings were somehow defective. In any case with new orings and a lack of salt water immersion (moved to Amarillo TX) the issue has resolved.

L_A_S:

This is in no way intended to be a flame as I have used similar tanks with no problems for years. But,

Two weeks ago I bought two Worthington X7 HP 100 steel tanks from my LDS and had them filled with nitrox for my upcoming offshore trip. I dropped them off at my parents' house since we'll be departing from there. This morning as my dad (also a dm) was leaving for work he heard a hiss coming from one of them. He put his ear up to the valve (Thermo) and noticed it came from the valve/neck connection, not from an accidentally opened valve. So I called the LDS who thinks mine may have been among a batch of tanks produced a year or two ago in which they tried a new purple seal between valve and tank which have been shown to be faulty/badly designed.
.

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It's real easy to see when the tanks were made. The manufacturer date/month is stamped on the tank as the initial hydro. just look and see.

question is if your LDS has known about this for a year or two, why didn't they check the tanks before they sold them to you to see if they were affected? (in theory it would have been real easy to notice a purple seal when they did the initial VIS or installed the valve? (the valves come shipped off of the tank.)).

chances are these tanks have been sitting at your LDS for all that time.

All cylinders are shipped to your LDS without the valves installed. This is to avoid hazmat issues and added costs in shipping. Your LDS then installs the oring and the valve on the cylinder.

IF the valve is not torqued to the proper specs it could cause a gap to form between the cylinder neck and valve. This in turn would cause the oring to extrude out the gap and fail. The color of the oring has no bearing on anything, you can order orings in any color you want.

Thanks for that further information, these are the first tanks I own (previous steels were all rented). I just mentioned the seal color because they seemed to think that particular purple batch may have been bad. The tanks are currently still at my parents place so I can't check the date, I can post it next week if anyone's interested. When I called for price and availability before buying they told me they aren't in high demand, so they quite likely had been in the store for a while. I'm looking forward to learning something when I watch them take it apart and inspect it.

As for the plug, it's Waterworld Inc in Durham NC, extremely helpful and personable, which might explain their longevity.

I have heard the same "purple o-ring" issue before.

On an aluminum tank the recess for the o-ring is milled into the tank neck and is more or less square in cross section and provides surfaces for the o-ring to seal. On a steel tank this recess is more of a cone shaped shoulder so the anlges and seatign surfaces are a bit different.

However in either case, when the valve is installed properly, the valve comes into metal to metal contact with the tank neck and fully contains the o-ring. If there is no gap between the metal surfaces, there will be no extrusion of the o-ring and it will not leak as it is fully supported.

The theory behind the "purple o-rings leak" allegation is that the material was softer and more prone to extrusion. That was probably true in some cases, but only when combined with a poorly installed valve that was not quite tight and allowed a gap for the o-ring to extrude.

That said, it makes sense to not use them as they are a bit less tolerant of less than perfect mating surfaces than other slightly harder o-rings.

fppf:

The color of the oring has no bearing on anything, you can order orings in any color you want.

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Completely UNTRUE. orings are designated different colors to the make up of the oring (silicone, rubber, teflon mix, etc) and how hard or soft they are. Different colors are designed for different temps and different chemicals. green are typically ac to combat pag oil yellow is another form of oring to combat pag oil but higher temps. Purple can handle oils and synthetic oils in extreme temps like inside a volvo 13 or 16 litre engine. a black oring would fall apart after a short time as that is just a standard rubber oring. i know these real well as i use them everyday in my job. so color does mean something. There are still more colors that i have no clue what they are for. there are red, orange, brown which i know in a medical setting are used for anything with oxygen, etc etc. My guess would be that they were trying the purple because of the high temp and resistance to most chemicals.

I agree with Aaron that color often means something - but it is not what you could call "standardized" across industries.

For example in the scuba world viton o-rings are usually brown but sometimes green. Nitrile o-rings are black. EPDM o-rings are also black and have a stripe painted on them to differentiate them from nitrile o-rings. Yellow paint is commonly used on 90 duro EPDM o-rings and white paint on 70 duro EPDM o-rings. Other materials are rarely if ever encountered on scuba equipment. Resistance to sustained high temps and resistance to hydrocarbons are not really issues. Resistance to O2 and ignition temp in an O2 environment are relevent concerns and the materials used reflect that.

In the past Scubapro used all sorts of colors to denote specific sizes and applications but has moved away from that to the standard industry markings noted above, probably for cost savings. But if I wanted to order a run of pink o-rings for my new Larry 3000 regulator, I could probably get them in a variety of materials and hardnesses as there are no o-ring standards police that would forbid it.

Personally I am not 100% sure what the composition was of the purple o-rings. I used them when they were around and never had issues - but I am very careful about valve/tank compatitbility and assembly. Now I seldom see them any more which says something.