O2 Cleaning of Tanks

[Iguana Don]

A tank flash or explosion is not gonna have any impact on the dive shop's rep. If you follow the guidelines, "correct vip", "correct hydro date" and "suitable for nitrox". If it explodes what good are all the certs anyway. Just because somebody has their tank o2 cleaned, is no guarantee it is still clean when you go to fill it. The only way to prevent this is to o2 clean a tank before every fill.

It seems funny to me, PSI keeps extensive records on tank explosions. You haven't given any for the o2 flashes, except to say you have to "dig".

All this being said I will just have to say we agree on disagreeing.

Nuff said

ID

 

[blacknet]

Hello,

How about those flashes that occur with COMPRESSED AIR? You telling me they don't exist?

Little boy goes to the doctor and said "doc, my arm hurts when I do this with it", dr replies "well don't do that"

Lesson here is these things will happen and the only 100% prevention is don't do it. Any time you fill or blend you are running a risk, question is getting those odds in your favor. This means doing YOUR homework and learning the how/when/where/what/etc.

As for reports there's been numerous reports.

Ed

 

[Warhammer]

I've watched this thread with great interest and I must say I agree with Don here. Blacknet, you keep refering to these reports, well let's have them. Like Don, I'm a "show me" type guy, and I like bonifide proof. Show me one instance of a tank exploding and/or a fire due to any nitrox mixture of 50% or less in any scuba tank and/or regulator that was properly cleaned/prepared for the mix it was recieving.

 

[The Chairman]

Hey ID,Warhammer, Blacknet and all...

The point of contention was NEVER about tanks. The Lizzard and I never disputed that TANKS should be cleaned... it was the "rest of the crap" that "should be" 02 cleaned to comply with (take your pick) the %23.5, or the %25 rule. We do not cuncur that the %40 rule is "Dead Wrong" (don't even care WHAT the Navy said). ID was simply pointing out that many tanks are probably NOT completely O2 clean after only a fill or three.

ID correct me if I am wrong, (you'll do that anyway) but we never indicated that tanks should not be cleaned. Only that the %40 rule has been validated by many many divers on many many dives.

And Warhammer, I DO agree with you on the "showing of these reports" attitude. I have heard a few URBAN LEGENDS about tank explosions, flashes, and I don't discount that they might happen. But MOST of these "reports" are heresay and are only told (and re-told) for their shock value. Heck, we can start a rumor that your head could explode if it weren't O2 cleaned. We can even refer to some vague reports... But, I sure wouldn't believe even ME without seein' them thar reports!

 

[Lost Yooper]

I've personally seen more "evidence" that you can get away without O2 cleaning anything (if done carefully and correctly) than "evidence" of real life O2 fires. The key is the "carefully and correctly" part and is why I wouldn't advocate that dive shops be lenient in requiring O2 cleaned equipment. Liability in todays age is on the ludicrous side, and anything less than 100% safe is unacceptable for them. However, even in the lawsuit filled world of the conservative dive industry, the 40% rule is accepted as safe.

For those filling their own tanks and such, you have to evaluate real life vs laboratory evidence, and then evaluate your own level of acceptable risk. There seems to me to be a whole lot more risk in simply jumping in the water with scuba, driving to the harbor, or walking across the street than worrying too much about O2 cleaned equipment. Considering the type of diving I do, O2 cleaning doesn't rank very high on my list of foremost concerns. Since I have no choice, for the time being, but to get my O2 fills at a shop, I conform to the established rules -- for the most part anyway .

It seems to me that if these fires were happening often, we would hear about them on these boards from time to time. We hear of diving fatalities/injuries all the time, but no fires. I've done some digging and have only found two instances of fires. One was a from a Titanium reg that had a poor alloy for O2 exposure (which had been exposed for about 2 years to 80% O2), but was O2 cleaned. That reg was recalled, if I recall correctly. The other was from a guy was filling O2 too quickly and had a brief fire. Neither incedent was fatal. I'm sure there are others out there, but I haven't found too many, and I certainly haven't heard of any fatalities. If there are, I want to see the reports because this is a very interesting topic for me.

Take care and fill slowly.

Mike

 

[omar]

A point that is overlooked here is the continuous blending method that was pioneered by Dr. Morgan Wells, former director of NOAA. The early versions used a length of coiled garden hose into an oilless compressor to mix 32% Nitrox. Subsequent iterations have resulted in continuous blenders that will work with mixes up to 40% into ANY compressor with no problems (the caveat is that the mix be homogeneous). If there is proper filtration on the end such as a hyper-pure filter, then the mix will not “contaminate” a cylinder cleaned for oxygen service. Systems that have a typical filtration system can also be used, but the hydrocarbon content MAY be higher than what is recommended for oxygen compatible air. NOAA developed this method to save time and money for it’s diving program and to provide an additional measure of safety for divers by reducing the nitrogen content of the mixes.

The continuous blending method is now being used for blending of Trimix as well. It is only a matter of time before PADI becomes part of this.

What NOAA says for their work:
NOAA OXYGEN SPECIFICATIONS
Appendix "D" NOAA Nitrox Diving and Decompression Tables. High pressure storage cylinders, SCUBA tanks, regulators, and all high pressure transfer equipment used with pure oxygen or with nitrox mixtures containing more than forty percent oxygen must be cleaned and maintained for oxygen service.

omar

 

[blacknet]

Hello,

Another was from a guy in florida who was filling a nitrox tank with air. Don't have all the details but the gas was AIR and it went up.

Warhammer, if you want all the 'show and tell details' then please contact rainreg, he has all the details you'll ever need.

Ed

 

[Warhammer]

I was refering more to any "02" caused fires with 50% and below mixes, than anything else. I just threw the tanks and explosion into the mix to broaden the scope. I've yet to hear of any incidents of any fires and/or explosions caused by any mixture of 50% or less, when used according to the generally accepted 40% rule. Does anyone know of any confirmed case? If so, I'd love to find out more about it.

Personally, I think the 40% is good enough for me and that's rule I'll keep following until it's proven unsafe. I won't change my practices simply because the Navy has changed theirs. Going by the 23.5% or 25%(don't recall which it was) rule, like Don, I can't see why you would need to O2 clean the regulator, if not the BC, drysuit, and any other gear that will come into contact with the nitrox. What's the difference? I'd think that my BC's bladder is far more likely to contain oils and/or grease than my regulator. But that's just my opinion. And as most of you already know, going by the old rules, the only reason you would ever have to even O2 clean a tank is if you'd be filling that tank using the partial pressure blending method. Using any other method, it's generally accepted to be safe to not O2 clean the tank.

Back to the original question....Can someone post the exact procedures used for O2 cleaning of tanks? I've been told Simple Green works, as well as 409. I've also been told that that practice is dangerous, and that you need an agregate, like glass beads, and a special chemical to properly O2 clean a tank. Don't know who's correct, but my best guess is it depends on who you ask.

 

[Lost Yooper]

The dive shop up here uses a detergent issued by the DOT, I believe. Do-it-yourselfers use things like simple green and flush thoroughly with water and dry the tank quickly and thoroughly.

Mike

 

[svs3]

Since one seems to want to post any links to studies. Here's one that on topic.

http://www.dnax.com/new_nav/table_nasa.html

Now back to your regularly scheduled show.

Sam