Question about my new steel tank (new to me).

[Brett Hatch]

Now I have the grammar police on me.

Even on SB there is no scuba police. But grammar police -- haha, nice try, it's still the Internet

 

[dead dog]

Even on SB there is no scuba police. But grammar police -- haha, nice try, it's still the Internet

If you read it right you would have seen it was a spelling mistake not a grammar mistake.

 

[rnln]

Hi Brett,

Reading the whole topic again, I am not sure if I understand this correctly. Is there anywhere on the tank saying that it is Nitrox rating? The shop already filled the tank with air, does it mean the Nitrox rating is already voided?

Also, both tank and valve said 2400 psi, so it only can be filled with 2400 psi now?... do I have to change the valve with higher pressure rating to be able to fill with 2640psi?

Thanks everyone again

First off, I am not an expert on gear or gas mixes, not a tank filler, and not instructor of any kind. Just a guy with a nitrox cert who owns my own tanks. My understanding is that:

If the tank passes VIP, then you can put air from any shop in there, and it will work and be perfectly safe. Since the tank is safe for nitrox, it will be safe for air. However if you want to use it for nitrox in the future, you will want to ensure that your fill operators put O2 clean air in the tank. If they put regular air in it, it may contain some contaminants which will void the nitrox rating. These contaminants aren't unsafe to breathe, but they are a fire hazard around high-O2 gas mixes (such as 100% O2).

If you want to learn more about this, I would highly recommend that you take a nitrox course. It's maybe 50 pages of reading, plus a 2-hour in-person course with some hands-on experience with tanks, analyzers, etc. Typically no dives required, and very cheap.

 

[Brett Hatch]

Hi Brett,

Reading the whole topic again, I am not sure if I understand this correctly. Is there anywhere on the tank saying that it is Nitrox rating? The shop already filled the tank with air, does it mean the Nitrox rating is already voided?

Hi rnln,

Again, I'm not an expert here of any kind, so take the following with a grain of salt.

So let's first talk a bit about what a nitrox rating is. It is the absence of a certain set of chemicals which are a fire hazard in the presence of a gas with a high percentage of O2. In particular, some of these chemicals are commonly used to lubricate some air compressors used to fill scuba tanks. So if your tank is O2 clean one day, and then you fill your tank with such a machine, the tank may take on some of these chemicals and no longer be safe for high-O2 fills. However, there are also many common compressors used for air fills which will NOT pollute your tank with these chemicals.

O2-cleanliness therefore is not really a property of the tank itself, it's a property of the contents of the tank. Compare this to hydrostatic testing, which is a measurement of the actual metal of the tank. So you won't find an embossed stamp (like the hydro stamps near the neck) on the tank claiming a nitrox rating, because it's not a permanent thing. However, there may be something more temporary stating that the tank was cleaned for nitrox ("O2 clean"). For example, my tanks have a different-colored visual inspection sticker that says it was O2 clean at the time of the inspection, as well as a 6-inch green-and-yellow sticker that goes around the tank. These stickers are commonplace among rec divers in my area, but are not necessarily universal.

It's important to note that these markings on my tank don't actually say anything about the O2 cleanliness of the tank. The stickers should be an indication to any operator NOT to fill my tank from an air compressor that utilizes the no-no lubricants. But I have no guarantee that any random operator will understand and respect these issues -- one day, some bozo could come along and fill it off the wrong type of compressor. At that point, the tank will no longer be O2 clean, and no longer safe for nitrox fills, but will still have nitrox stickers on it! So I am careful with who I let fill my tanks, and avoid shady businesses and would especially never ever get a fill from a place like a paintball store or a car mechanic or anything else.

These topics are covered in much more detail (and by actual experts) in any nitrox course. I would highly recommend taking such a course.

I'll leave your pressure-related questions to other posters. Since I don't have LP tanks and they are not very common in my area, I do not have very good information there.

 

[Scared Silly]

Reading the whole topic again, I am not sure if I understand this correctly. Is there anywhere on the tank saying that it is Nitrox rating?

Look at the visual inspection sticker. If it has a box checked that says that is was inspected to the appropriate standards OSHA/CGA and suitable for enriched air service then you can fill it with NITROX which may be banked or from partial pressure blending. Otherwise you will find a box checked that it can be filled only with plain ole air.

Now a days one can sometimes find a third box which is NOT an industry standard and just made up BS that says it is "Suitable for premixed NITROX" First, there is no such thing as premixed NITROX. Second there is no such industry standard.

The shop already filled the tank with air, does it mean the Nitrox rating is already voided?

Depends on the quality of the air, if it was plain ole air (Grade E) then yes technically the cylinder is no longer suitable for NITROX until it has been re-inspected. If the air was modified Grade E or similar then it is fine.

Also, both tank and valve said 2400 psi, so it only can be filled with 2400 psi now?... do I have to change the valve with higher pressure rating to be able to fill with 2640psi?

You do not have to change the value or the really the burst disk as they are based on the working pressure. For a 2400 psi cylinder it is a 4000 psi burst disk.

 

[rnln]

So the scuba shop can easily screws you by not inspecting for OSHA/CGA and suitable for enriched air and pumping in OLE grade E air. ummm...
Thanks

 

[Brett Hatch]

So the scuba shop can easily screws you by not inspecting for OSHA/CGA and suitable for enriched air and pumping in OLE grade E air. ummm...
Thanks

No respectable shop would do this. But yes, it's possible.

 

[rnln]

I just check the VIP sticker. It doesn't say anything about what type of air, It only says inspected interior/exterior for rust and such. Another sticker sticker does said this tank was clean such and such from manufacture for enriched air... I guess this is the manufacture sticker. Also, the biggo yellow/green band on top saying Nitrox is gone. I am going to ask them on this.
Thanks.

 

[Brett Hatch]

Sure. From what you described, my best guess is that the tank was O2 clean when it was manufactured -- both my tanks had similar stickers on them when I purchased them brand-new). But subsequently it was not necessarily kept O2 clean, and very well may have been filled with grade E air. You'll need to have it O2 cleaned before you can fill it with nitrox. This isn't a big deal, but can be costly. For example, one shop near me charges $125 for O2 cleaning + VIP (vs $20 for VIP only). Shop prices vary, of course.

If you haven't bought the tank yet, maybe you can leverage this to bargain down the price a bit.

Best of luck.

 

[rnln]

The tank is bought with nitrox ready. The PO always use Nitrox, he said. The new shop VIP it already, and I already have it back with me. The new sticker doesn't say it's enriched air compatible and the big yellow Nitrox band is gone. I guess they assume I don't need nitrox and pump in OLE air, not clean air. (I didn't not mention with the shop that I will get into Nitrox in the future).
If this is true, it means the shop just ruined the Nitrox capable and it will cost me $125 in the future to get that nitrox grade back?
Question is if I have to do O2 cleaning every time I do VIP, or the O2 cleaning is only need to be done once if I keep up with using clean air?

hehe, the price is way too low to be bargained. I was grabbing it as soon as I can