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A question: What happens, chemically, when that 1% of O2 is introduced to make your mix 39% to 40%? Does the nitrogen/oxygen change form? What does actually happen to make this instability take place? Could it be that 40% is just an arbitrary number someone pulled out of their ass like the 130' "sport diver limit"? With this trick of yours, the cascade loaded with 39%, who are you trying to fool? The various gov agencies? The divers? Yourself? If you believe so strongly in the 40% rule, why don't you, for the sake of the children, throw in an extra safety margin and put 35% or 33% into your cascade system? I mean what if the gov made a mistake (imagine that!) and the actual percentage that nitrox suddenly becomes volatile is 38.2345% I mean you may be endangering children as we speak! Rather than acting like sherlock holmes and trying to spoof your customers by bleeding off gas (what bullshit, if you ever did that to me, I would never darken your door again) why dont you have the rules posted and test the 02% of every tank that enters your shop which has more than 0psi in it. If you feel so strongly about the rules, would this not be the right thing to do? If you say that it would be too burdensome to do this, is what you are saying that profit is more important than the lives of your customers? How hypocritical! Or could it be that deep down you know these rules are pretty much bullshit and you are just going through the motions? Jim On 8/15/97 3:27 PM Ted Green wrote: > > CAUTION! > The following post was written by a dive store owner, gas >blender instructor, Trimix diver, and opionated SOB. > >Certain parts of this post may be found to be objectionable. Minors, >women and other people who may object to your use of profanity, >should be asked to leave the room. > > > > > > > > > > > > > For the last couple of months I have been reading an excessive >amount of whining posts concerning o2 cleaning, gas fills, and >labelling. I have held my key board as long as I can, and now I going >to tell you the way it ought to be! I have broken this up into a >couple different sections; read what ever you want. > >1. Labelling >2. Switching gases, Air, Nitrox below EAN 40, and Trimix >3. Gas Blending, mixes with an FO2 below 40% >4. EAN 41 and above, and Argon >5. Air top offs, and dive shops >6. Duct tape residue > > >1. Labelling: The purpose of labelling a tank is to identify the > contents of the tank. In the USA, the compressed > gas industry labels all tanks whether it's Propane > for your gas grill, Oxygen for your cutting torch, > or Helium for your balloons. Ownership of the tank > makes no difference. Your Propane tank for your > gas grill and the Propane tanks at the gas > supplier have the same neck contents label. The > reason the tank is labelled is not for gas > supplier, he knows it's a Propane tank by the > style of tank and the valve, but for anyone else > who MIGHT come in contact with the tank. All scuba > should be required to have a neck label; white > background for Air, green for Nitrox, orange for > Trimix, brown for Argon, etc.. Teach all divers at > the entry level what the different labels mean, so > they can be responsible for not using the wrong > tank by accident. Make the labels generic (cheap) > and easily removable for when the contents changes > or the label becomes illegible. Allow space on > Nitrox and Trimix labels for variables such as FO2, > FHE2, etc.. This would not be tough or expensive, > and would keep almost everyone happy. Remember, > the label is not only there for you, but for any > one else who Might come in contact with the tank. > >2. Gas switching: Many gas suppliers change the contents in their > tanks simply by changing the neck label and > sometimes repainting the tank. Here is how and why > it is done. Some gases are lumped into a common > family and do not conflict with others in that > family. An example would be Helium and Argon. Both > gases are inert, they don't react to each other, > they both are used as shield gas in welding, they > leave no residue in the tank, and they use the same > type of tank and the same CGA 580 valve. Also in > this family is Argon CO2 ( a combination of Argon > and Carbon Dioxide ) and Stargon ( a combination of > Argon, Carbon Dioxide, and Oxygen ). All these gases > Come in the same type of tank with the same CGA 580 > valve. Sometimes gas suppliers run low on one type > of tank and have to convert tanks from a different > type of gas mixture to the one they are short of. > The Compressed Gas Association even has guide lines > for doing this. In some cases it's as simple as > changing the neck label! We should be able to do > this for bottom mixes and travel gases with an FO2 > below 40%. You ask," Do you expect us to oxygen > clean all scuba tanks!". The answer is no. Read the > section on Gas Blending. > >3. Gas Blending: Dive stores and other facilities who sell Nitrox and > Trimix with an FO2 below 40%, should be required by > law to fill your tank without exposing your tank and > valve to an FO2 of 40% or greater! It's easy, safe, > fast, and how my store fills Nitrox below EAN 40 and > Trimix. Here is how I do it. The store has a cascading > bank of EAN 39. How the EAN 39 is produced is not > important. Once you have EAN 39 you can put it any > scuba tank without Oxygen cleaning that scuba tank > ( almost everyone will agree with that ). > To make nitrox with an FO2 of 39% or below, simply > base the tank with Premix ( EAN 39 ) and top with air. > This is simple, and requires no Oxygen cleaning of > customer tanks. Trimix is almost as easy. Base the > tank with Helium, add Premix ( EAN 39 ) to raise the > FO2, and top with Air. This is also simple, and > never exposes the customers tank to an FO2 greater > than 39%. All that's required to do this as opposed > to partial pressure filling in the customer's tank > is 10 or more high pressure Oxygen clean storage > bottles. If it's your business, make the investment, do > it right, and reduce your risk. If all stores would > do it this way, blending gas would be a lot simpler > and all we would have to do is change the contents > label on the neck of the tank. > >4. EAN 41 and above, and Argon: Tanks that are for EAN 41 and above > are few and far between. The average technical diver > probably owns two. There appears to have been some > objective testing done by departments of the US > government and members of The Compressed Gas > Association that indicate a need for Oxygen cleaning > above 40%. To date, there have been no objective > scientific tests done to indicate that there is no > need for Oxygen cleaning, or that the level at which > Oxygen cleaning is not required should be raised > above 40%. Until such time as these tests are done, > get your deco tanks cleaned and STOP WHINING! > Argon bottles, since they don't contain a breathable > gas and there have been documented cases of near > fatalities when people have tried to breath off these > bottles mistakenly, should be more boldly labelled and > probably painted brown to avoid confusion. This > shouldn't be any big deal, since most Argon tanks are > very small and generally only used for drysuit inflation. > >5. Air top offs, and dive shops: When a customer brings in a tank for > an Air fill, we blow some gas off and watch his expression > to see if it changes. When a diver bring in a tank that he > has based with either Oxygen or Helium, he has imposed > an unreasonable liability on me. My store is liable for the > mixture in that tank regardless of the fact that I didn't >put > the Oxygen or Helium in the tank. Lets face it, most of > you clowns who play this game have no formal gas > blending training, accurate gauges, or even own an Oxygen > analyzer. You all are your own worst enemy! My advice > to the stores in North Carolina who have to deal with > these type of clowns, is two blow a couple hundred > pounds out of each tank before you fill it. If the > customer screams, empty their tanks all the way, and > then throw the clown out of your store. For those of > you who go to N.C. and can't get the mix you want > from the dive shop, do what I have done since > 1982. I bring all my gas with me. I started diving > Hatteras N.C. in 1982 before there was a dive shop > there. The choice was either the portable compressor > or enough tanks for four days of diving. Even now, > when we go dive the "Clark" or the "Monitor" we still > have to bring all our gas because nobody pumps Trimix > down there. Finally, if you keep bringing all your > gas with you and making a point of telling the owner > of the store why he is not getting your business, maybe > he will change when he sees there is enough demand. > For those of you who don't have enough tanks to do > this, borrow some from your friends. Whatever you > decide to do, please......STOP FUCKING WHINING! > >6. Duct tape residue: I have found that an Oxygen Acetylene torch > works real well when turned up high, for removing duct > tape residue...............just kidding. > > Ted >Ted Green (owner) >Tidewater Aquatics (Dive Store) >Salisbury Maryland USA >TDI IT #029 >SSI MI #178 > >The world contains but three types of people: > 1. Those who make things happen. > 2. Those who watch things happen. > 3. Those who wonder what happened. >-- >Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. >Send list subscription requests to `techdiver-request@aquanaut.com'. -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send list subscription requests to `techdiver-request@aquanaut.com'.
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