Apeks O2 clean question

[randy88k5]

I have an Apeks DST 1st with an AT20 2nd that I am considering making into a deco bottle regulator. This will be its primary function, and maybe be a vacation regulator for single tank diving. Haven't decided on that yet. I am looking at getting parts kits from DRIS for the regulator, but it does not say O2 clean on the package. I am planning on using between 50% and 80% for deco gas. Will the standard kits work? Do you know if Apeks has another kit specifically for high O2 applications?

 

[Bubbletrubble]

The o-rings in Apeks kits are composed of EPDM, which is an O2-compatible material.
Tribolube 71 and Christolube MCG111 are suitable O2-compatible lubricants.
If you want to set up your reg to be O2 clean, I highly recommend purchasing Vance Harlow's Oxygen Hacker's Companion.
The book should answer any questions you might have about making your gear O2 clean.

 

[SDAnderson]

Apeks doesn't sell an O2 compatible service kit, at least not in the US.

We see a lot of regulators and tank valves each year, only a few of them have had serious burns but it isn't all that uncommon to find out that the root cause of the complaint, "My regulator/cylinder is leaking" ends up with an ablated seat.

Using EPDM or Viton o-rings in high-O2 environments is a good idea but if you still end up using a Teflon seat, well, that's the hot spot that most people tend to ignore. Then there is the whole how do you clean/know if it really is clean issue.

Personally, I've used Apeks regulators for MOD20 and MOD70 bottles for years and have rarely had problems. Note that I didn't say never had a problem.

Bonus Points: The answers to these questions will help illuminate the problem and point the way toward a solution:

1. What is the partial pressure of oxygen in a cylinder filled with 100% to 3000 psi?
2. What is the partial pressure of oxygen in a cylinder filled with EAN80 to 3000 psi?
3. What is the partial pressure of oxygen in a cylinder filled with 100% to 2500 psi?
4. Why do you suppose the suppliers only fill their oxygen bottles to ~2500 psi?

Oxygen suitability claims often have more to do with lawyers than science, but that doesn't mean you shouldn't have a solid understanding of the physics - and protocols - involved.

 

[Bubbletrubble]

@randy88k5: reefraff makes an excellent point about O2-cleaning the tank and tank valve as well. The Oxygen Hacker book offers suggestions on how to do this.
Apeks reg overhaul kits sold in the U.S. are not certified for use with >40% O2 scuba mixes right out of the package. It would make sense to prep all of the parts to be O2 clean and handle them properly prior to installation if an "O2 clean" reg is the goal.

On a side note, you might want to check whether you really have a DST 1st stage.
AFAIK, in the U.S., the AT20 currently comes stock with a US4 (non-swivel) 1st stage, which is not environmentally sealed.
In other countries, I believe that the AT20 comes stock with a UST (swivel turret) 1st stage, which is not environmentally sealed.
That being said, it's certainly possible that you have a DST.
FYI, if the first stage lacks a rubbery hydrostatic diaphragm, then it isn't environmentally sealed.

 

[randy88k5]

Reefraff, thank you for the explanation. I have a good handle on the physics and mechanics of it, but I am still learning.

BubbleTrouble, I am beginning to get into regulator and valve servicing. I have taken a few classes and have the Regulator Savvy Book. I have the Harlow book on my wishlist. I have an ultrasonic to help get the parts really clean. I have a tube of Christolube, which I have been using on all my orings. I want to do it correctly. Thanks for the advice.
The regulator is a DST 1st with ATX50 and AT20 2nds. I was going to use the ATX50 on another overbalanced 1st stage when I come across one. I just couldn't see putting a balanced 2nd stage on a deco bottle.