Nitrox cylinder bands
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There are official rules set up by someone without the force of law, like the 23.5% GA rule mentioned earlier, and there is reality. The two are often quite different.
When I bought my first tanks and had them set up for oxygen service, someone else did it, and I then went about having them O2 cleaned every year before learning to do it myself. Then I got some more brand new tanks and valves (Thermo) and did it myself. I read the materials that came with them carefully and discovered that, according to Thermo, their valves cannot be made O2 clean! They cannot be used for anything more than 40%. I was shocked--almost all my valves are Thermo. I was doing this in a shop, and I contacted Thermo through the shop to ask about it We got a vague reply that referenced a carefully worded document that appeared to confirm that rule. I said "appeared" because the wording of the reply and the document clearly implied the following message: "We are just doing this to cover our keisters. We know darn well you are going to ignore this, and go right ahead and do so."
When I bought my first tanks and had them set up for oxygen service, someone else did it, and I then went about having them O2 cleaned every year before learning to do it myself. Then I got some more brand new tanks and valves (Thermo) and did it myself. I read the materials that came with them carefully and discovered that, according to Thermo, their valves cannot be made O2 clean! They cannot be used for anything more than 40%. I was shocked--almost all my valves are Thermo. I was doing this in a shop, and I contacted Thermo through the shop to ask about it We got a vague reply that referenced a carefully worded document that appeared to confirm that rule. I said "appeared" because the wording of the reply and the document clearly implied the following message: "We are just doing this to cover our keisters. We know darn well you are going to ignore this, and go right ahead and do so."
The Chairman
Chairman of the Board
Sure.
Partial Pressure Blending: I put in 418psi of O2 in an O2 clean AL80, top off with air and I should get @ %32.
On The Fly (aka Continuous Gas Blending): I bleed in O2 into a mixer before it gets to my compressor. The tank never sees more than %32 and I have less to worry about.
If a tank only sees one shop, then PP blending is fine. However, once you start traveling, that O2 compatible air that unfamiliar LDS is giving you, just may not be, leaving an oily residue. Back to your home LDS and once they put the O2 in that not-so-clean tank, you now have poison in a bottle. I travel too much, so I never know just how clean that tank really is. After I O2 clean a tank, I simply only indicate that it's NitrOx clean and not O2 clean.
Sorry about my less than standard reference to continuous gas blending RJP. It appears to have caused you some confusion. Thanks for asking for clarification rather than assume I have no idea what I was discussing.
TDI issue a sticker which clearly just says oxygen clean. It appears a LDS issues a sticker which states clearly "cleaned for Nitrox to 40% or oxygen clean to 100%. It is on this basis I would ask ONLY for oxygen clean as clearly both methods are the same. One however limits you to 40% which is really a con if you ask me. If you want your tank clean then its oxygen cleaned, how you use it after that is up to you, <40% or oxygen, its clean for either.
It would appear in OZ anyway in many of the LDS, they clean for Nitrox on the basis of PP fills, rather than pre-blended or Nx stick.
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It would appear in OZ anyway in many of the LDS, they clean for Nitrox on the basis of PP fills, rather than pre-blended or Nx stick.
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I don't think you took the post as it was intended. but to answer a few ?s
No they will not teach the fine points in class. they have liability issues. The comment was made int he spirit of you haveing so many ?'s trhat other than SB you would answer your self with experience and diving with those that actually know what is going on. My point was not being critical of you per se'.
The nitrox class is a all possibilities class not for those that do only banked 32%. My comment of experience and your ?'s was targetted at ,,,like you put it,,,, "PADI's teaching" and the like. You are questioning from comparing curriculum aspects which will vary. What is needed is you diving in the reality and not the utopic of course discriptions to put more of a ,,,, " I my diving I have exerienced xxxxxx aspect" to you inqueries. Then and only then can anyone taylor an answer to the situation you are relating to. Too many want a one answer fits all. the courses are tending to go that way for liability purposes. Because of that,,,, the processes are no longer the best for the specific diving. You pointed out nitrox bands. the rules are the same but the applicatoin for them vary when it comes to new divers seasoned divers and technical divers. For instance All nitrox bottles are sopposed to have a marking on them. but yet techies do not use bands on them. they mark the tanks such as "oxygen 20" Or nitrox 70 or smith 70. The community knows that if it says smith 70 that the tank belongs to some person names smith and it has a gas that is used at a depth of no more than 70 ft (50% O2). oxygen 20 is a gas that when at 1.6 ppO2 has a MOD of 20 ft. 1.6 ppO2 because it is deco gas. The padi nitrox class is very brief on those aspects of gas usage but they do say 1.6 is used and OK to use in decompression situations where activity is non existant, other than that nitrox is also 1.4 ppO2 limited with 1.6 for contingency use. Are classes for nitrox going to teach this to a OW diver. NO. They teach the aspects of the system as will be aplied to new divers. and i say new divers because it is allowed to give an OW and nitrox in the same week. If you want the rest of the story , as Paul Harvey would say, take advanced nitrox which discussed the uses beyond the basic OW use.
Here is an example. One of your threads delt with doing OW in doubles. Probably will never happen. Is it prihibited, possibly not. Do instructors allow people to do it. probably not. Doubles is what you go to when singles will no longer provide the reasources you need and not till after being able to control the single set for some time. Doing doubles for OW is setting the student up for exceeding NDL. The problems with all that weight on you back and rolling ect just can't be dealt with with out the experience of learning to deal with a singles set first. Its kinda of like requireing learning to walk before you run. Do experienced divers dissagree with things. You bet they do. 2 ft 5 ft or 7 ft hose. depends on the dive. Integrated or belt for weight. There is no one right answer. There is a near best action to take given a situation, and there are unlimited situations. Your profile seams to say you are not certified or if so no experience. Why should you not expect people to react to your question's with get some time in the water. Like buoyancy the process can be pretty specific and yet the concept of ballanced rig would negate many of the concerns you have. Only diving will reduce the list of concerns to a coulple of items. You sill never get 100 people commenting on buoyancy and others on set suits and others on fins and others on nitrox policy and leave you with a feelling of satisfaction. With out experience you can not cull out the varied opinions to what is usefull to your preticular diving. All coments may be valid but with ounderstanding (not just from books) you can not help but maake your situation worse from lack of continuity in opinions.
Im the last person to tell you not to ask questions but like I learned in instructor courses there is no stupid question, however there is a lot of bad timing in the asking and answering of questions. when giving an answer that is not supported with primacy you end up giving no answer at all and add confusion.
The 23.5 is from PSI along with the O2 cleaning requirement. Their position or interpretation of the regs say that pure O2 above 50 psi is a hazzard. ( or O2 under 4 ata..... As such 23.5 could be mixed via PP blending. PP blending will result in O2 being under a psi of >50# will exist. Some other reg says any vessel or system handling O2 will be O2 cleaned to be put in service. Now PSI is an agency that functions from the aspect that if you follow their methods and an accident occures you will have the best chance of being found not guilty in a court of law. As with anything everyones interpretaion of hte regs are ging to vary. Psi trains from a legal aspect.
I know of the cave country fill stations and i have no problem with them my self. The feds say federal regulations have the power of law.
Once again this is from the time where <40 treat as air. if it was visualy clean it was good for air and thus gas with content up to 40%. The bands were on tanks that had greater than 40% in them to tell fill shops to allow nothing less than hyperfiltered air in them. Now it is required for 23.5 and above contents. Not for the contents but for the possibility of PP blending to get that contents. The up to 40% punch out is really only good for air now because of that requirement of O2 cleaning for 23.5 gas. The band also says by default you can not put trimix in the tank of any gas that is not nitrox nitrogen oxygen. You can not put argon in a tank with a nitrox band on it. There is no cleaning per se' for 40% content. The sticker means the tank meets the cleaning standards for O2 content of < than or >than 40%. <40 no cleaning required > 40 O2 cleaning. Also usta be,,,,, <40 allowed grade e to be put in the tank, >40 meand nothing but hyperfiltered e or better to be put int he tank.
Yea Kel long ago the congress gave up trying to keep up with how things should be handled, They then said that federal regulations were to be treated as law. In the process to KYA they attempted to make all compressed air subject to this, they backed off cause all gas stations used air to raise lifts and that was cost prohibitive. so they put 21% and found that there are 2 places in N americs that have higher O2 content than 21% sop they settled on 23.5. Many organizations like nasa and other groups adopetd sifferent specs but the 23.5 is what made it to the federal regulations. And that made it law. There is still the argument of whether it is comercial or not. DOT.. for instance a tank does not have to be with in hydro when full to be shipped so long as it was with in hydro when it was filled. The regs i believe say no comercial entity will presure ize a velssel beyond 23.5% at > than 50 psi with out being O2 cleaned. Home compressor fillers are not commercial entities. So is it no wonder that there are so many opinions as what can be done. I wish i had my PSI slide show with the information on it. There was at one time debate on whether an instructor can haul tanks to a site for check out dives as that was part of a comercial venture. some regs say no more than x amount of tanks can be moved or some amount of tanks with a value of 1000 dollars.. Some instructors then has the students transport the tanks to stay below the limit and thus out of the comercial definition. If students carry tanks it is recreational. I wish i still had the source info for all this. PSI gets very defgensive when you ask about these things. They pride them silves in that the feds name PSI as the only authorized inspectors allowed to certify some items because they so closely follow the fed regs. Right or wrong i take their word pretty much as gospel. Do i agree with it not really butr again i am not in the comercial side of things. I do the inspections on my own tanks cause it is cheaper to be a PSI inspector than to pay the fees for the tanks over the 3 year period.
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seeker242
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