XS Scuba manifolds with engravings vs HOG manifolds without.

[olphart]

Why is it that normally intelligent people seem the think that O2 is explosive? It is not. It is necessary for combustion and supports it, but if there is no fuel there is no combustion. The Heat, O2, Fuel triangle has to be complete to have a fire. Basic physics

 

[Scared Silly]

More recently, Thermo brand PRO DIN/K 200-bar Nitrox SCUBA valves have been tested by an independent laboratory as meeting the CGA V9-2002 valve standard for use with oxygen. The Thermo 300-bar DIN only SCUBA valve, because of the higher pressure, cannot pass the oxygen test portion of the GCA V9-2002 standard and thus is now only available labeled as "Air Only".

May I ask why you believe that it's just a case of "covering ass" and not that there is a real danger in using high O2 content gases with non-O2 compatible & O2 clean parts? In every other industry the threshold for O2 compatible/clean equipment is 25% O2.

You missed the point. The 200 and 300 bar valves are the exact same valve sans two threads (5 vs 7 threads). Theoretically those two threads are there so that a regulator that can not handle 300 bar is not attached to the cylinder. A modern din regulator has 7 threads.

Now explain this fact to me. A 200 bar valve is 2900 psi but I can put it on a 3000 psi (207 bar) cylinder and partial pressure fill it. Take that same valve and add 2 threads so it is a 300 bar valve and though rated to 4300psi and put it on the exact same 3000 psi cylinder and magically it is air only.

I have a better idea lets call the 300 bar valve a 7 thread valve with a working pressure of 200 bar and the 200 bar valve a 5 thread valve with working pressure of 300 bar. Damn, left is right and right wrong, the sky is green and grass blue. The world is upside down and she's gonna blow. Run Henny Penny, run Henny Penny.

Sarcasm aside I would have to dust off my engineering and do some calculations but I am willing to bet that the 200 bar and 300 bar designations are a bit of a misnomer to say the least when it comes to their actual rating. And if you want to do the calculations the DIN fitting is:

5/8” 14TPI BSP

 

[Dr. Lecter]

Why is it that normally intelligent people seem the think that O2 is explosive? It is not. It is necessary for combustion and supports it, but if there is no fuel there is no combustion. The Heat, O2, Fuel triangle has to be complete to have a fire. Basic physics

Why is it that this subject invariably brings out someone who thinks they're being clever by pointing this out to an audience largely better read on the subject than they are?

No, O2 is not explosive (or even flammable) and, as anyone with basic reading comprehension would see, nobody in this thread said that it was. However, pressurized tanks of O2 may well explode...particularly when an O2 fire occurs in/near them.

 

[olphart]

Why is it that this subject invariably brings out someone who thinks they're being clever by pointing this out to an audience largely better read on the subject than they are?

Why is it that this, or any subject invariably brings out some self important "expert" who thinks he's being clever by making hostile remarks? I'm surprised that you are so well versed in my reading habits, but then, you seem to be supremely knowledgeable about everything else.




No, O2 is not explosive (or even flammable) and, as anyone with basic reading comprehension would see, nobody in this thread said that it was.

Poor writing on my part, and a non sequitur to the direction the subject was headed I suppose. I hadn't meant that anyone in this thread had made such a claim, though I see that the way my post was worded certainly implied that.



However, pressurized tanks of O2 may well explode...particularly when an O2 fire

Ya think? Now who's stating the obvious?

 

[WarrenZ]

Once ignition occurs the hoses fittings and even the tank itself can become fuel.

 

[kr2y5]

I have a better idea lets call the 300 bar valve a 7 thread valve with a working pressure of 200 bar and the 200 bar valve a 5 thread valve

A brilliant suggestion. It seems that in practice, the choice of one valve over the other has little to do with their pressure rating. Some people, like myself, find the presence of those 2 additional threads aesthetically pleasing, whereas others feel inconvenienced by the need to make an extra turn when putting a regulator on.

 

[DiveGearExpress]

Now explain this fact to me. A 200 bar valve is 2900 psi but I can put it on a 3000 psi (207 bar) cylinder and partial pressure fill it. Take that same valve and add 2 threads so it is a 300 bar valve and though rated to 4300psi and put it on the exact same 3000 psi cylinder and magically it is air only.

It's not magic, it's science. The valve is not considered suitable for oxygen service unless it can pass the oxygen gas section of tests exactly as described in the CGA V9 standard for valves. That 7 thread DIN valve is described in the DIN standard as being suitable for cylinders with test pressures up to 450 bar. Take 120% of the maximum pressure that the valve might see and then pressurize the valve (as fast as possible) with ultra pure five nines oxygen that has been pre-heated to adiabatic combustion temperature. Thus subjected to the conditions of the test, if the valve catches on fire, the valve fails the test and the valve is not considered suitable for use with oxygen. The Thermo brand Nitrox 5-thread PRO DIN/K valve will pass, and the 7-thread DIN valve will not.

I doubt it's possible to make a chrome plated brass SCUBA valve that can pass at such high pressure as required by V9 for the 7-thread DIN valve, it would likely need to be made of Monel. Fortunately, we can't arbitrarily change the conditions of the test to suit our needs by just lowering the test pressure of the valve to the service pressure of whatever cylinder we choose. The process to safely effect change is to join the CGA, establish engineering qualifications and credentials to help convince all the other members to change the V9 standard or establish another standard for something more reasonable for the recreational dive industry.

In the US, suppliers have a legal obligation to warn about the hazards associated with their products (scuba and otherwise), and they generally do a good job. Properly warned, we are free to just ignore these safety related issues and do as we please, there is nothing about SCUBA valves that physically prevents their use with oxygen. The reality is that is exactly what is happening. But don't think that what we might be doing with pure oxygen in diving is no more risky than handling air, in fact the handling of pure oxygen in scuba is significantly higher risk than in other industries. The issue of Nitrox handled as pure oxygen is questionable, given the long history of safe handling of nitrogen-oxygen mixtures in diving, but that ship has sailed and US law says Nitrox is to be handled as oxygen. Thus the DOT says you can't put 40% Nitrox in a 3300psi service pressure aluminum scuba cylinder. We can do it, but we are not going to get someone else to accept responsibility. Ignorance is bliss.

---------- Post added June 24th, 2015 at 10:39 AM ----------

Two days ago I bought a Worthington al40. The shop owner had the intention to put in an etched thermo valve in it. Luckily he put the valve in my hands before actually screwing it into the tank. While in my hands I noted that the new valve has clear lubrication on the threads and the tank neck o ring. This lubrication felt more like silicone grease and nothing like Christo.

The Thermo valves have always been a lubrication free design. Chances are the valve threads were lubricated by the shop owner themselves.

 

[tomfcrist]

If the engraved manifold were all I could source I'd buff out the "Air Only" and have them stripped and re plated.

Tobin

I like thermo valves...they unfortunately come with the 40% Nitrox premixed only etching in them. I just "un" etch them....no need to re plate it...anyone with half a clue will know why I did it. They can look at the inspection sticker and see that the tank AND the valve are cleaned yearly.

I had an acquaintance of mine actually get pissed off at a shop owner because a tank he ordered came with one of these valves...as if it was the shop owners fault.

 

[cool_hardware52]

I like thermo valves...they unfortunately come with the 40% Nitrox premixed only etching in them. I just "un" etch them....no need to re plate it.

I have a close working relationship with a local plater, no reason for me not to....

Tobin

 

[eelnoraa]

May I ask why you believe that it's just a case of "covering ass" and not that there is a real danger in using high O2 content gases with non-O2 compatible & O2 clean parts? In every other industry the threshold for O2 compatible/clean equipment is 25% O2.
.

Because you don't need any O2 clean parts for recreation nitrox up to 40%. Also, why would anyone mark "air only" permanently on metal if o-ring and lube, replaceable items, are the only thing that keep you from using O2?