Valve O2 Rating

[redt1de]

So I have decided I will be picking up a Luxfer AL40 to sling when I dive locally. My go to source for stuff is DGX when I don't want to drive out to my LDS. I was taking a look at the tank/valve package provided by DGX here: Aluminum SCUBA Tanks - Dive Gear Express and I noticed the fact that the valve is only rated for pre-blended mixes up 40% O2. Have a question or two...

If I want a 38% blend, and it is not banked, I suppose most shops fill it partial pressure. Will they fill the tank in the package above via partial pressure? The marking on the neck of the valve leads me to be the answer is no.

I dont intend to immediately use the tank for blends north of 40% O2, but if I can't get a fill via partial pressure that limits where I can get gas and my mix potentials. However, I do plan to transition to tech once I fill the log book a bit further.

Feeling like I should just order that tank, no valve, then buy one of their other valves that is O2 clean/compatible: DGX Premium Cylinder Valves - Dive Gear Express . What do you think?

 

[teknitroxdiver]

I'm not sure where you're reading that. This is what their page says:

According to our suppliers, their Nitrox Ready products are compatible with oxygen and factory cleaned for oxygen service with compressed gases in excess of 23.5% oxygen.

So their tanks marked 'nitrox ready' (all of them) are good for 100% oxygen, which would include partial-pressure blending.

 

[redt1de]

I'm not sure where you're reading that. This is what their page says:



So their tanks marked 'nitrox ready' (all of them) are good for 100% oxygen, which would include partial-pressure blending.

I agree, the cylinders are repped and cleaned as O2 ready. I am asking about the valve itself. Clicking on the picture of the Thermo Pro valve shows this picture: http://cdn.divegearexpress.com/media/gas/thermo/Thermo_Valve_Insert-640a.jpg which is marked "40% MAX OXYGEN PREMIXED." So in partial pressure, O2 hits the valve prior to the cylinder, I would assume that I would want this piece to be O2 clean as well. "40% MAX OXYGEN PREMIXED" to me is 40% or less blend, which by the "40% rule" the blender treats as basic air...so if banked its fine. But my question is based on partial pressure, therefore the blender is dropping pure O2 first into the cylinder via the valve which by my read based upon the marking is not O2 compatible. So can I fill that cylinder (or any O2 clean cylinder) with that valve via partial pressure? Or in theory pure O2? Maybe I am over analyzing this...

 

[teknitroxdiver]

I agree, the cylinders are repped and cleaned as O2 ready. I am asking about the valve itself. Clicking on the picture of the Thermo Pro valve shows this picture: http://cdn.divegearexpress.com/media/gas/thermo/Thermo_Valve_Insert-640a.jpg which is marked "40% MAX OXYGEN PREMIXED." So in partial pressure, O2 hits the valve prior to the cylinder, I would assume that I would want this piece to be O2 clean as well. "40% MAX OXYGEN PREMIXED" to me is 40% or less blend, which by the "40% rule" the blender treats as basic air...so if banked its fine. But my question is based on partial pressure, therefore the blender is dropping pure O2 first into the cylinder via the valve which by my read based upon the marking is not O2 compatible. So can I fill that cylinder (or any O2 clean cylinder) with that valve via partial pressure? Or in theory pure O2? Maybe I am over analyzing this...

Hmm, sure enough. I'd give em a call. Strange that they would brag on their cylinders being O2-clean and put non-cleaned valves on them. As they are marked, you're right, the valves are not suitable for partial pressure blending.

 

[rjack321]

NO scuba valve is rated for O2 use by the manufacturer. None, zero, nada. CYA...

They are all fast opening by design, with nylon seats (also not technically O2 compliant) and both attributes are no-no's as far as commercial gas industry standards for O2 use. That said, there are no alternatives, and "up to 40%" valves are as hydrocarbon free as they can be so they are used in O2 service anyway.