Info Scuba Cylinder Valve Installation

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I currently have ChristoLube MCG 111-5g - but these doubles are gonna be mostly for air service. Maybe Nitrox (<40%) - but probably 95% of the fillings are gonna be air.
Is it okay for me to use this lube for air service tanks?

ChristoLube MCG 111 is fine up to 100% oxygen. The reason these more expensive lubricants are used is to prevent Oxygen fires/explosions. Lots of material will ignite at higher O2 percentages and pressures, 40% Nitrox for example, that won't on air. Technically you could use 10w-40 on pure Nitrogen (not recommended). If 100% of the time your doubles were filled with air you could use Dow Corning Molykote 111 (or equal).

Does this make sense to you?
 
Akimbo, thanks for the quick reply!

Problem is that I don't have "Dow Corning Molykote 111 (or equal)" right now. I'd have to order it online etc, which would postpone things a bit. If this is something that I should do - then that's fine - of course.
My question was whether I can use the ChristoLube MCG111 on these air service tanks since that's the lube that I have right now.
My assumption is that if it's good for 100% oxigen - it should be fine for 21% (air) though probably a bit of an overkill. Also its more expencive etc - again - fine by me right now since I have only one doubles set to put together, so I don't need a ton of it.
So yeah - I generally understand the difference in theory - was just wondering if there are any technical problems or downsides (or maybe reasons why not-to) in using ChristoLube MCG111 in regular air service steel tanks valves. Again, not because I'm streatching the subject here, it's just because that's the only lube I have in my shop right now.
 
@Kovach

I guess I wasn't clear.
  • You should use your ChristoLube MCG111 (or equal) because your doubles will have greater than 21% Oxygen (air) about 5% of the time.
  • You can use ChristoLube MCG111 to lubricate O-rings for gases from pure Nitrogen or Helium up to pure Oxygen -- including air.
  • You should not use Dow Corning Molykote 111 (or equal) anytime the gas mixture will have more than 21% Oxygen.
You do not need to buy any different lubricant, you can use ChristoLube MCG111 on all your diving breathing systems. It is a little expensive to lubricate O-rings on your underwater light but it is fine to use ChristoLube there too.

Technically your doubles are not "air service tanks" because you plan to use Nitrox about 5% of the time and the highest oxygen level is the determining factor. It doesn't matter if you plan to use Nitrox 1% or 99% of the fills, the fact that even one fill will be more than 21% oxygen dictates using ChristoLube MCG111 (or equal).
 
@Akimbo

Thank you very much and sorry about the small misunderstanding there.
Now everything is perfectly clear and I really appreciate the help.
 
@Akimbo

Thank you very much and sorry about the small misunderstanding there.
Now everything is perfectly clear and I really appreciate the help.

If I wasn't clear enough for you then that means than a lot of other divers reading this would also be confused. My apologies and thanks for helping me get it right.
 
Very informative, thank you!
 
A lot of great information in this discussion, but respectfully we must disagree with the opinions expressed that recommend lubrication, especially in regards to use with oxygen. Keep in mind our perspective is from the point of view of best practice regarding safety, because so many of our customers are actually using very rich oxygen mixtures.

The benefit of using lubrication during installation of valves in SCUBA cylinders is debatable. In our own research, we can't find any objective basis for recommending lubrication with properly maintained SCUBA tanks where the valve is removed and O-ring replaced on a periodic basis. Professional Scuba Inspectors (PSI) says in their manual Inspecting Cylinders - 5th Edition that "threads with O-ring seal do not require a lubricant." O-ring suppliers tell us that lubricating static O-rings, such as the neck O-ring, causes more problems than any dubious benefit it might provide. While oxygen compatible lubrication of threads and O-rings in SCUBA valves and cylinders is probably harmless under ideal conditions, it also has no clear benefit.

Generic cylinder and valve maintenance guides rarely address the specific nature of the SCUBA industry, especially in regards to Nitrox applications. Since the valve, O-ring and cylinder manufacturers in any assembled SCUBA tank are all different, it's commonplace to hear conflicting recommendations regarding use of lubricant. Our suppliers do agree that nearly all installation, sealing and removal problems are caused by improper technique and over-tightening the valve into the cylinder, not the absence of lubricant. Some local dive shops intentionally avoid all lubricant, some use it very sparingly and others use it liberally. The bottom line is that lubrication use in this SCUBA application seems to be a matter of opinion, not science.

Lubrication, even oxygen compatible lubrication, is not considered best practice for cylinders and valves used with medical oxygen or industrial oxygen. That's because while oxygen compatible lubricants might have higher temperatures of ignition than hydrocarbons, they can still serve as fuel in the kindling chain of an oxygen fire. Any lubricant will attract and retain contaminates, plus there is the significant risk that an incompatible lubricant might be applied. In our opinion, legitimate oxygen safety concerns outweigh the questionable benefits espoused by those recommending lubrication in Nitrox SCUBA cylinder and valve applications.

Based on oxygen handing best practices and advice of industry experts, Dive Gear Express currently does not recommend and does not use any form of lubricant, including oxygen compatible lubricant, with our Nitrox Ready SCUBA valves and cylinders.
 
To elaborate on our recommendation against lubrication in SCUBA valve and cylinder Nitrox applications:

(1) The proposed benefit of lubrication of threads is based on using a dielectric to reduce galvanic action. However, this is unlikely to be a serious concern in properly maintained SCUBA cylinders where the valve will be removed on a periodic basis. In our own experience with literally thousands of valve removals, the SCUBA valves that are difficult to remove (where the cylinder is completely empty) are a result of being grossly over-torqued in to the cylinder during installation not the absence of lubrication. I don't recall ever having a problem removing a valve that any of our staff had previously installed the year before.

(2) O-ring manufacturers generally don't recommend lubrication of their O-rings where the application is "static", that means wear due to movement is minimal. The neck seal in a SCUBA tank certainly falls within that description. In our own experience with literally tens of thousands of fluorocarbon 90 durometer AS568-214 O-rings, use of a proper material and hardness O-ring along with correct installation technique obviates the necessity of lubrication to make a seal. Conversely some years ago, we observed a problem in some aluminum tanks where the O-ring had been generously lubricated with silicone based lubricants that there would be tiny "fizzing" leaks at the neck. Once we removed the valve, cleaned the neck groove and replaced using a V90 O-ring the leaks disappeared and did not ever reappear as long as we were the only ones doing subsequent inspections. It's very possible the neck leaks were due to failure to clean the residue of previous lubrication, or excessive lubrication, but we eventually concluded the lubrication was in some way causing these tiny leaks we would observe at the valve neck interface of aluminum cylinders.

(3) During discussions regarding use of lubrication in cylinders and valves intended for use with pure oxygen, experts were universal in their condemnation of any such practice. Even the lubrication manufacturers themselves were reluctant to recommend their oxygen compatible lubricants in high pressure compressed oxygen gas applications, especially in oxygen breathing gas systems such as those found on aircraft. (The various experts we talked to were clueless about SCUBA but seemed to be knowledgeable about ABO applications.) Oxygen compatibility means the material properties are resistant to degrading in oxygen rich environments, it does not mean they won't burn. While oxygen compatible materials typically have higher temperatures of ignition than hydrocarbons, nearly all oxygen compatible lubricants and O-rings can still serve as fuel in the kindling chain of an oxygen fire. An unwelcome side effect of oxygen compatibility is when the materials do burn, their combustion byproducts can be extremely toxic gases. I have personally experienced this in which I was uninjured as result of a small oxygen fire, but incapacitated by the toxic gases generated from the PTFE. The use of oxygen compatible materials does not eliminate the need to always follow best practices for oxygen handing, including avoiding contamination and opening valves slowly.

(4) When PST sold their high pressure 3442 psi steel scuba cylinders, they arrived from the factory with the Thermo Pro DIN/K valve already installed. PST did not use any form of lubricant, and during all the years we sold PST cylinders I don't recall the absence of lubricant ever causing any problem.
 
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O-ring suppliers tell us that lubricating static O-rings, such as the neck O-ring, causes more problems than any dubious benefit it might provide.

That is inconsistent with the recommendations I have received from Parker Hannifin engineering support, the US Navy, NASA, and every manufacturer of components rated for HP Oxygen systems. I agree that excessive and improper lubrication of gas service O-rings can create their own problems. The function of the very thin film of lubrication on a Scuba neck O-ring is to minimize stress on the O-ring during the rotation required to install the valve in addition to normal movement during pressurize and depressurize cycles.

There are countless static a dynamic O-rings in high pressure service on submarines, military and commercial saturation diving systems, and in industrial gas plants all over the world that specify that O-rings should be properly lubricated. I suppose that assuming people installing Scuba valves are not competent enough to use proper lubricants and techniques is a justification for leaving them dry. However these people should not be trusted to service static and dynamic O-rings inside valves and first stage regulators either; which do require lubrication according to the manufacturers. I suppose we will have to respectfully disagree.

BTW, congratulations on running a truly exceptional operation.
 
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