Do I really need Oxygen compatible grease to assemble the loop?

[Cio]

Mostly bc I’m curious if this is taught elsewhere: Can you think of a non-loop hose manner to also validate this negative? Non sound based

Other than adding a vacuum gauge (totally unnecessary) , no.

 

[Akimbo]

why bother with o2 lube on the other o-rings?

For what it is worth, I concur.

For other readers:
There is a great deal of folklore and FUD (Fear, Uncertainty and Doubt) around O2 cleaning and compatibility that dates back to the NASA/Apollo 1 and NEDU (Naval Experimental Diving Unit) fires in the late 1960s.

Although the chemistry of fire is well understood and combustion points can be calculated, the practicality of being fully aware of all the variables in the O2 fire triad is between challenging and impractical. As a result, the tendency is for recommendations to be hyper-conservative due to unknown or unforecastable variables and partly for simplicity for rules of thumb.

Info - Oxygen Fires

Document Name: Flammability in Unusual Atmospheres Part 1 - Preliminary Studies of Materials in Hyperbaric Atmospheres Containing Oxygen, Nitrogen, and/or Helium Author: J. E. Johnson and F, J. Woods, Naval Research Laboratory See the attached file: Flammability in Unusual Atmospheres.pdf File...

scubaboard.com

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SAFETY WARNING

This does not mean you can use axil grease instead of a grease suitable for Nitrox or disregard potential ignition sources in the loop like short circuits.

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Here are three recent posts that may help explain Oxygen fire safety to other readers a little more fully:

Slow Opening O2 valve

We're looking for some slow opening oxygen valves for our bottles. We bought the slow opening valves from DGX but in my opinion they still open too fast at first (when compared to say a standard CGA valve). I know that Hollis also has slow opening valves, any feedback?

scubaboard.com

Slow Opening O2 valve

I should also add that the opening action of the Nautec O2 valve is practically binary in type. Either it immediately opens or closes. You need a fine gradual opening action for use with O2, like a needle valve, and the AP are so much better in this regard.

scubaboard.com

Slow Opening O2 valve

I should also add that the opening action of the Nautec O2 valve is practically binary in type. Either it immediately opens or closes. You need a fine gradual opening action for use with O2, like a needle valve, and the AP are so much better in this regard.

scubaboard.com

 

[JMBL]

M3S recommendation concerning the Triton rebreather : use only O2 grease on all o-rings. Silicon might damage them.

That's how I've bee trained at least.

 

[GiraffeMarineSalvage]

M3S recommendation concerning the Triton rebreather : use only O2 grease on all o-rings. Silicon might damage them.

That's how I've bee trained at least.

Another thing to keep in mind on using O2 compatible grease according to manufacturer recommendations is risk/reward ratio and reducing risks of human error:

In grande scheme of things it is a trivial economic cost (in my opinion fully offset by convenience and one less thing to buy) vs potentially catastrophic consequences. Eliminating risk of human error transferring non-O2 compatible grease to area that absolutely needs 02 compatible grease may be worth considering.

 

[Superlyte27]

Remember that a silicone grease on a silicone oring (like the optima) will cause the oring to swell.

 

[DiverDiverRUOK]

Mostly bc I’m curious if this is taught elsewhere: Can you think of a non-loop hose manner to also validate this negative? Non sound based

I teach to pull a negative after flushing unit down to .21 (Dil flush if using air dil for example). Then, during negative test, po2 readings should be ~.19 due to lower pressure inside the loop.

If negative is holding, this should remain stable.

If you notice po2 creeping back up to .21 that indicates a possible leak. This can also be accomplished watching the mV of the cells, but watching po2 is simpler I think.

This, of course, in addition to the visual and auditory clues of a good negative check.

 

[tbone1004]

Another thing to keep in mind on using O2 compatible grease according to manufacturer recommendations is risk/reward ratio and reducing risks of human error:

In grande scheme of things it is a trivial economic cost (in my opinion fully offset by convenience and one less thing to buy) vs potentially catastrophic consequences. Eliminating risk of human error transferring non-O2 compatible grease to area that absolutely needs 02 compatible grease may be worth considering.

the only thing that absolutely needs O2 compatible grease is the first stages being used with high O2 concentrations *though admittedly to keep it easy I O2 clean all of my first stages*, and the SPG spool o-rings on the same first stages. There is nothing on the LP side that needs it, and there is very little on a CCR that isn't actually at ambient pressure, only the Dil and O2 inlets are at IP, everything else is ambient and doesn't care whether or not it's O2 compatible.

 

[tbone1004]

Remember that a silicone grease on a silicone oring (like the optima) will cause the oring to swell.

fact, made worse when the unit is hot right after a dive. I have to wait an hour or so for my unit to cool down for it to come apart easily

 

[Cio]

Remember that a silicone grease on a silicone oring (like the optima) will cause the oring to swell.

Doesn't apply to me but is the exact type of info I was looking for, thanks for the info.

 

[davehicks]

Doesn't apply to me but is the exact type of info I was looking for, thanks for the info.

Lots of camera, strobe, and housing O-rings are silicone. For camera gear I only use tribolube. For my KISS rebreather (aside from the 1st stages), I only use silicone.