O2 and O-Rings

[kidspot]

I'm in the middle of putting together a fill whip and wanted quick disconnects so I could change between DIN and O2 fittings, but all the ones I can find use Buna-N O-rings ... I can clean them and use O2 compatible lube, but should I also swap out the O-rings for viton (I don't have dimensions yet, so I can't order them)

Here are the QD's in question...

http://www.mcmaster.com/nav/enter.asp?partnum=6537K11&pagenum=242

btw - I believe these are the same ones referenced in the Oxy Hackers guide...

Aloha, Tim

 

[BigJetDriver]

I'm in the middle of putting together a fill whip and wanted quick disconnects so I could change between DIN and O2 fittings, but all the ones I can find use Buna-N O-rings ... I can clean them and use O2 compatible lube, but should I also swap out the O-rings for viton (I don't have dimensions yet, so I can't order them)

Here are the QD's in question...

http://www.mcmaster.com/nav/enter.asp?partnum=6537K11&pagenum=242

btw - I believe these are the same ones referenced in the Oxy Hackers guide...

Aloha, Tim

Tim,

The short answer is simple. If your whip will see O2 under pressure at a concentration above 40%, you are going to have to use either Viton or EPDM (although there is some arguemnt, Viton is preferred), and an O2 compatible grease such as Christolube.

 

[redacted]

I'm in the middle of putting together a fill whip and wanted quick disconnects so I could change between DIN and O2 fittings, but all the ones I can find use Buna-N O-rings ... I can clean them and use O2 compatible lube, but should I also swap out the O-rings for viton (I don't have dimensions yet, so I can't order them)

Here are the QD's in question...

http://www.mcmaster.com/nav/enter.asp?partnum=6537K11&pagenum=242

btw - I believe these are the same ones referenced in the Oxy Hackers guide...

Aloha, Tim

That talks about those QDs having buna "seals". I suspect thay may not be talking about o-rings, but rather seats like are found in an Air2 connector. They are basically a washer shaped seat. You may have to buy appropriate material and punch out your own seats. The good news is M-C has both the sheets of material and the punches.

 

[kidspot]

That talks about those QDs having buna "seals". I suspect thay may not be talking about o-rings, but rather seats like are found in an Air2 connector. They are basically a washer shaped seat. You may have to buy appropriate material and punch out your own seats. The good news is M-C has both the sheets of material and the punches.

ahh - I just "assumed" it meant o-rings ... maybe I should PM OxyHacker and ask what he did ...

If nothing else I'll just use more teflon tape for awhile instead ...

Tim

 

[kidspot]

Found the answer on Page 15 of the Oxygen Hackers companion - There is very little difference between nitrile and viton when not in direct contact with O2 for prolonged periods of time. So it just needs to be clean and use Crysto-lube ... Can't believe I overlooked that whole section (I've only read the book cover to cover 3 or 4 times now )

Tim

 

[mer]

The aviation industry uses buna in o2 applications, the down side is that it breaks down quicker in an O2 environment than viton or EDPM. All of these o-ring materials will burn if you get the adiabatic heating out of control.

Don't try this at home, kiddies, but I used "whatever" for o-rings now, clean them and lube with christo.

 

[DA Aquamaster]

Found the answer on Page 15 of the Oxygen Hackers companion - There is very little difference between nitrile and viton when not in direct contact with O2 for prolonged periods of time. So it just needs to be clean and use Crysto-lube ... Can't believe I overlooked that whole section (I've only read the book cover to cover 3 or 4 times now )

Tim

Nitrile is the approved material for aviation O2 systems and the FAA in general tends to be very concerned about fires, explosions etc so I have not really followed the trend of being religeously zealous about not using nitrile o-rings. I'll use EPDM o-rings if they are available, but I won't have a fit if I ocassionally cannot locate a suitable replacement for a properly cleaned and lubed nitrile o-ring in an application where it is not continuously exposed to high percentages of O2 that would create a potential for faster than normal deterioration.

I am not a fan of viton as, in my experience, it does not wear all that well in dynamic applications, but it works great for tank neck o-rings and that is one area where continuous exposure is a given.

Nitrile, EPDM or Viton will all burn at some point so the emphasis in my opinon needs to be placed on proper operation to prevent any source of ignition. For example in a fill whip, you would not want to have a high flow rate through the hoses and fittings and then suddenly stop it, as the mass of the gas going through the line will create a fair amount of heat if it comes to a sudden stop. So slowly opening and closing the valves is important regardless of the material used.

 

[redacted]

ahh - I just "assumed" it meant o-rings ... maybe I should PM OxyHacker and ask what he did ...

If nothing else I'll just use more teflon tape for awhile instead ...

Tim

I may not have thought that thru very clearly. While a seat may work in an LP applications, I would expect an HP QD would work better with an o-ring seal.

 

[oxyhacker]

The seals in those QDs are indeed just O-rings, and (as I am pretty sure is mentioned in the text) are very easy to remove and replace, so you can order up whatever flavor O-ring you like and replace the ones that come with the fittings.

 

[kidspot]

Thanks for taking the time to reply - you are right the text does mention that and after reading through that section again I found it answered this very question for me ... next time I'll read it first (again) I think... I'm travelling for a week, so I'm gonna go over it again and hopefully start doing my own blending next month. I'm just waiting for the last of the parts for assembling my fill whip to arrive (needed one more NPT to DIN adapter) and my lp tanks to get back from hydro, plus gotta build my O2 analyzer (parts coming in the mail too)... I'm so looking forward to picking up my first cylinder of oxygen from the gas company

Aloha, Tim