Another o-ring question

[Freeflyer]

Hi all,

once again I'm picking your collective brains on my purchases. I'm about to move to Brunei and, having used the board here to decide on my apeks regs that I recently purchased I'm now building a stock of spares to take with me.

I've been reading the threads on o-rings (lot's of discussion for something so small) and have a list of sizes that I need, and the website of air-oil for ordering. Just needed to ask a final couple of questions about sizing/materials and whether I understand certain terminology correctly.

What exactly is the tank neck? Is that where the valve screws into the actual tank itself, or is it the face that the first stage goes up against on the valve. Can't imagine needing a lot of those if it's the former, as I don't tend to be the one taking the valves off (I hope)

I was planning to get primarily viton rings, as they're cheaper from air-oil than buying nitrile elsewhere. I'm then setup for whether I dive air or basic nitrox mixes. The exception to this would be taking a stock of valve o-rings (where the first stage mates with the tank valve, I think this is what's labelled as std. tank yoke 2-014) as those seem to be the most likely rings to get damaged regularly. A stock of nitrile for when we're diving air (most likely out there) would probably be worthwhile, as there's no point using up the viton stock if you know you're on air, and most of the tank valves I've seen on holiday dives tend to be a bit roughed up.

Do you find that o-rings fail with any regularity? I was thinking of taking a stock of 20 rings in each size (we have two sets of everything for my wife and I) and then an extra 20 nitrile valve rings. I thought that this should last me for a good while. We'll be in Brunei for 3 years and plan to dive a couple of weekends each month, possibly more.

Should I get 70 or 90 duro on the nitrile rings?

Could you comment on whether I have all my terminology correct please, and on the duro rating.

Many thanks,

Justin.

 

[Genesis]

I would get EPR instead of Viton.

Just as good on the oxygen compatability, and Viton has pretty poor abrasion resistance - that's its bugaboo - while EPR doesn't have that problem.

EPR is almost as cheap as Nitrile, and much cheaper than Viton.

I go through a LOT of the -010s, as they are extremely common in both first and second stages. I'd take more of those than anything else, with a balance on the rest of them.

Note that the big problem on self-rebuilds and repairs is NOT O-rings - its seats. Those are specific to each brand/model of reg - if the seat is ok it can be reused, but its one wear part that DOES wear out and when it fails you NEED a new one.

 

[LUBOLD8431]

Yeah, all the Apeks kits are EPDM (EPR) orings, and you get everything you need to overhaul the reg. A few of the other sizes should keep you going for a while. 003 for pressure gauge spindle, 010 for second stage hose end, 011 for LP hose end, 012 for HP hose end, 014 for K valve FACE seal, 214 for tank neck (just above threads on valve). Those are the most common, and you should have a good stock of these. I would go with the EPDM if you can get them. Durometer is usually 90 for EPDM.

 

[Genesis]

Air-oil's EPR are all 70 duro - they do not stock 90s (I've asked them - they can get them, but you won't like their minimum order quantity!) The only place I've had trouble with 70s is on the SP Mk20/25s on the HP (small) piston ring - the bushing system wants a harder O-ring in there and will leak with the 70s.

The MK10s and such have been fine with 70s in the same place, but they don't use the bushing system.

 

[Freeflyer]

I wasn't thinking about buying o-rings for the overhauls yet. I've just ordered Vance's book, and the regs are brand new so I have a year or so to read and learn. I'd probably buy the kits for the overhaul from somewhere online so that I know I have the right stuff for that.

What I'm looking for are o-rings for the saveadive kit. ie, the ones that are likely to be damaged and are found on the valve face seal, and the ends of the high and low pressure hoses etc. I didn't think of epr for those, is there a reason that viton is the common option for nitrox as opposed to epr, if the epr is that much cheaper?

Thanks for the help, it's great to be able to learn all this and not rely on someone else to sort/fix things.

J.

 

[LUBOLD8431]

Well, for Aqualung and Apeks regs, they use EPDM for use with Nitrox. All of their orings are now EPDM, not viton. Many companies are making the switch from viton to epdm for nitrox and high O2 use environment. You will see that EPDM is becoming the preferred oring for nitrox use over viton.

Also, in my above post, I mentioned all of the most common orings for a save a dive kit...

And, yes, I would get the EPDM, not nitrile or buna. If they only have 70 duro, that will do.

 

[Genesis]

The reason for the EPDM preference is that Viton has horrible abrasion resistance. In static applications this doesn't make a difference, but in dynamic applications it DOES.

Things like the O-rings on the end of LP hoses at the 2nd Stage, etc are all dynamic connections - and there, EPDM is far superior to Viton.

EPDM is also cheaper than Viton.

The reason for people using 90 duro in Viton is that Viton has such horrid abrasion resistance that the softer duros in Viton will get ripped to shreds in short order; 90s avoid this to an extent. But too-hard O-rings will sometimes fail to seal properly!

 

[Freeflyer]

I have an order going in to air-oil for epdm o-rings, loads of them and at a really cheap price. Can't believe 3c an oring for most sizes.

Cheers,

J.

 

[Genesis]

You're beginning to understand the "big rip" at the LDS..... (and some of the manufacturers too) when it comes to parts...

 

[lmorin]

I have an order going in to air-oil for epdm o-rings, loads of them and at a really cheap price. Can't believe 3c an oring for most sizes.

Cheers,

J.

The order was for standard yoke o-rings between the valve and first stage? Where did you place the order and what did you give as specifications for the o-rings?