Hello,
Some clarification
How does a regulator (being downstream and all) contaminate a tank?
Say you have a contaminant in the loop and you turn high pressure on that it will hit against the wall and could cause a fire. It has happened before. Or you put some contaminants on the valve from your regulator then you have shop A fill the tank and the next tank they fill will get the contaminant in their system.
Why clean the first stage and hoses, but not the second stage? If the pressure drop through the first stage is sufficient to reduce the combustion risk to acceptable levels, then why do the hoses need to be O2 clean?
Well the cleaning standards states all high pressure (anything over 200 psi) must be o2 cleaned, since your intermediate pressure is under this there is 1/2 the regulator that technicaly needs to be cleaned. Since you can not clean half the first stage you clean the whole unit and the hoses connecting to the unit. Once the gas flow reaches the second stage it's considered low pressure
Does the ANDI standard for fills require the fill station operator to investigate the O2 status of a divers regulator, as well as his tank?
This is just a CYA procedure that will help save your life. You can't trust just anyone that comes into the shop with a said 'o2 clean unit' and think it's 100% clean, you don't know how it's been treated, stored, cared for, handled or cleaned, or when it was cleaned for that matter. Or what method it was cleaned in. You have alot of yahoo's out there who thinks just using simple green is all there is to o2 cleaning.
I don't know about the standards but where I fill my tanks at I show them my tank log book. In this log book I list everything that was done to the tank, who filled it, their signature, the date, the mix and what method was used. I also have the same for my regulator. BTW I use DIN exclusively on my nitrox setups because I don't want some yahoo to goof and put their non-o2 clean regulator on my tank or put my o2 clean reg on their tank. Just another safeguard.
Will they accept an O2 prepped regulator from, for instance, Apeks without further inspection/cleaning/upgrading or is in-store service required?
Shops will see alot of 'o2 clean' crap that is actually that, crap. They are running a huge risk by filling your tank so I can understand all the safeguards. One shop in particular gave me the 3rd degree about filling my tank so I picked up the phone and called my buddy rainreg who took care of the situation. My tank was filled and not to my specifications so I won't be using that shop again.
Even if you look at apeks they will tell you to have the regulator o2 serviced BEFORE using it, even tho it's 'o2 clean'
Also, do the more limiting standards that ANDI requires have anything to do with their "SafeAir" which is mixed as high as 50% O2 instead of the usual 40% limit for recreational nitrox?
Basicaly when they partial pressure blend you are working with o2 HIGHER than 200 psi and thus requiring o2 cleaning. Even if you look into the noaa manual you will find reference to cleaning *ALL* mixtures over air that exceeds 200 psi.
Also note the current edition of the NOAA manual contains alot of errors, ranges from simple math errors, table errors, false data, and so forth. After a long conversation with the production manager at NTIS I was informed there is another publication in the works to correct the many errors that has been found and to update the outdated information in the manual.
Basicaly from my observation and experience, when in doubt o2 clean it. This may be abit drastic but I personaly would rather be safe than sorry. O2 cleaning is rather cheap, economical and cost effective and does *NOT* need to be recleaned yearly. Personaly I don't see what all the hype is about not doing the cleaning.
Ed
