O-ring obfuscation

[JB]

I believe this link will get you to the main O-ring Handbook page with several downloading options:

O-Rings, Materials, Metric, Inch, Groove Dimensions

Thanks, great resource. Just wonder why they list Viton as having the best abrasion resistance, and the Parker manual list it as having poor abrasion resistance?? This is too hard to make any sense of.

@JB: AFAIK, there are 2 different sizes for the "external" o-ring on a DIN-configured first stage: -111 = smaller size (e.g., Apeks), -112 = standard size (e.g., Aqualung, Scubapro, etc.). I recommend keeping both sizes in your save-a-dive kit.

AFAIK, the o-rings on port plugs and hoses that screw into the LP (3/8 UNF) and HP (7/16 UNF) ports on a first stage are standard sizes: -010 = 3/8 UNF, -012 = 7/16 UNF.
Bear in mind that some first stages have one slightly larger LP port (1/2 UNF). The port plug and hose (or adapter fitting) which screw into this larger LP port take a -013 o-ring.

That is exactly my point, I also believed that they were standard, until I checked the service manuals of the different brands, and clearly 3 different sizes are specified by different manufacturers, Oceanic use 9xx sizes not 0xx. Don't forget the 614 for some DIN fittings as well, the only one I know for sure that uses this size is Beuchat, but people have posted here in frustration when neither the 111 nor 112 seems to fit their DIN fitting, I suspect they needed the 614.

I suppose what got me started is that the true specs are not readily available, and when I walk into a dive shop, they eyeball the their o-rings and pick the best fit. They don't refer to a database to see what is specified for that particular reg. Probably just use 010, 012, 112/111 for everyone. I suppose when we try and sort out which o-ring it is we measure and pick the closest BS-0xx, 1xx or 2xx forgetting that there are also 4xx, 5xx, 6xx, 8xx and 9xx sizes to chose from as well as metric. While this is probably not that critical in these external applications it could be internally.

Here's a link to the other sizes. Downloads - O-ring size charts, fep/pfa encapsulated O-rings and seals, Premium O-ring cords, Hirschmann catalogues | O-rings | Rubber washers | Rubber gaskets | Rubber mouldings | Rubber extrusion (common inch sizes)

 

[Zung]

Zung, is that a Scubapro specification, where do they specify these things? I was not aware that you could get EPDM harder than Sh80. (Certainly can't make Sh90 out of EPDM)...

Yes it is. There's a extensive thread contributed by awap and others where we reverse-engineered nearly all of SP's o-rings.

EPDM over 70 are hard to get retail. I think I saw them at the O-ring Store but the cost is prohibitive. But then Scubapro could get any weird specs they want if they buy in bulk.

The thread abovce also discuss alternatives. For the hoses and the port plugs, Viton works well, and Nitrile too, and that's what I use.

 

[Bubbletrubble]

I suppose what got me started is that the true specs are not readily available, and when I walk into a dive shop, they eyeball the their o-rings and pick the best fit. They don't refer to a database to see what is specified for that particular reg. Probably just use 010, 012, 112/111 for everyone. I suppose when we try and sort out which o-ring it is we measure and pick the closest BS-0xx, 1xx or 2xx forgetting that there are also 4xx, 5xx, 6xx, 8xx and 9xx sizes to chose from as well as metric. While this is probably not that critical in these external applications it could be internally.

The typical diver doesn't have the patience and know-how to replace that many o-rings on his regs. For the most part, he'll deal with the "external" o-rings: yoke tank valve face, DIN o-ring, port plug o-rings, and hose o-rings. Those are the ones that the dive shop will carry. The shop won't usually sell "internal" reg o-rings to one of their customers. If a customer wants those, he'll probably have to purchase an official overhaul kit and measure the o-rings using some calipers. At least that's what DIYers do. As Zung pointed out, that's what a number of helpful folks here on SB have done.

I agree that it would be nice to have the exact specs of all the o-rings in official reg overhaul kits listed by the manufacturer on the Internet. Obviously, the manufacturers have this info, but they are loathe to release it since divers would then source the o-rings elsewhere at a much lower cost.

 

[knotical]

A couple of other info sources:

Oxygen Compatible O-Rings, Lubricant and Tools - Dive Gear Express

http://www.parker.com/literature/ORD 5700 Parker_O-Ring_Handbook.pdf

 

[Zung]

From my point of view, o-rings don't fail that often: I've seen maybe 3-4 extruding out of some rented tank valves, that's way less than 1%. One time my inflator hose let out a stream of tiny bubble; I opened it up, and the o-ring was broken, but it still sealed, more or less; and that's probably 10 years of service.

When I travel, I carry a small baggy of assorted o-rings I remove when I service my regs. I've never got to use a single one.

 

[scubamikey]

I know it's an old thread, but I've been going crazy trying to figure out why I have such a hard time finding the correct DIN o-ring for my Zeagle Flathead VI regs. This really helped and now I have more options to try.