Scubapro O-ring Sizes

[Zung]

And here's a consolidated view - Actually, it's the back of a recent Maintenance Kit. There're 2 o-rings I can't find: the 259 is a tank o-ring, and the 317 looks a lot like a 117; it's supposed to mate with the MK11/16/17/18/19, but I can't find it in my MK16/18 schematics; they both use 117 for the HP poppet.

 

[Zung]

I just scored a R290 octo off eBay, so here's the annotated schematic.
These guys (and most likely all of the "R" variants) are totally self-serviceable with awap's magic seat punch and some EPDM 70 o-rings, even though SP says 85 in some places.

 

[Couv]

Duro 70 should be fine for any o-ring in a second stage as there is no high pressure differential.

c

 

[superstar]

I have been using Buna 70's in all my 2nd stages with good results.

 

[Zung]

I know some of you don't like Viton because one person-one time, posted a statement about Viton not holding up to oxygen or abrasion well. He is a deservedly well liked and very knowledgably person on Scuba Board and his opinion carries a lot of weight. However, I suspect he got a bad batch or something else went awry in his experience with them. FKM (Viton) tends to be more consistent from batch to batch in hardness, it usually cost about the same as EPDM, and it's easier to find in duro 90. Google M83248 which is military grade FKM, then /-1 for duro 70 or /2 for duro 90. So a part number for a military grade 90 duro -010 Viton o-ring would look something like this: M83248/2-010


I usually order my o-rings from O-rings,Inc. See this link for FKM duro 90 o-rings http://www.oringsusa.com/catalog/index.php?cPath=21_516_67&osCsid=5n0lvn00i5fg71tjt4lc1e4pk4 <http://www.oringsusa.com/catalog/index.php?cPath=21_516_67&osCsid=5n0lvn00i5fg71tjt4lc1e4pk4>


By the way, like Awap, the only o-ring in a regulator I'm really concerned about getting a 90 duro is the piston stem, but to keep things simple I use them almost everywhere except on the second stage orifice and SPG spool.

c

Cross-linking some very valuable info's from another thread for the sake of completeness.
Now the loop is closed and all o-rings are available off the shelf from the Internet.

 

[jacked_72]

I've found that the 90 duro (the gum variety) from oringusa.com are considerably harder than the ones used in the MK5. When I twisted the -010 that goes into the piston shaft chamber, I couldn't get it to go into the grove. A 70 duro pops right in. When I pulled out the -010 90 duro, it held a bent-up shape. I see from one of the latest charts that were posted an 85 duro is called for. The piston oring also seemed softer than the 90 that I bought, but I don't think it was as soft as a 70 called for in the chart. I suspect that various duros will work. I'm going back to oringusa for selection of different hardnesses.

 

[halocline]

I got a few bad 90 duro polyurethane ones from oringsusa that were pretty brittle; maybe yours were like that. I broke several putting them in. The good ones were some work to get in the groove, but once in, work very well. I'm about to order another batch. Maybe I'll try a slightly lower duro if it's available, I think old SP polyurethane HP o-rings were either 80 or 85.

There is a noticeable improvement in IP consistency at high pressures with those 90 duro PU o-rings.

 

[Zung]

I confirm I pulled some old HP o-rings out of used MK10's that are pretty soft, close to Duro 70's; but I have no way to determine if they were original or not.

By feel, the ones shipped with the official service kits are noticeably harder than the 70's, and on part with the 90's. The official rating is 85, but I doubt if there's any practical difference between 85 and 90.

Then again, Genesis once said he used 70's in that position without any problem, MK10 only; he also said the MK20 would leak.

For me, fitting that o-ring is a nightmare; there are some recent discussions (and butts kicking, my butts ) here.

 

[jacked_72]

Is there any good reason why I couldn't just use viton orings on the piston and for the recessed oring in the groove? I notice that the newer scubapro kits no longer use the clear/amber orings in those positions.

 

[Zung]

couv would say none at all.

Actually the piston crown o-ring is a Duro-70 item which is easy to get; only the -010 inside the body is critical to buy and to fit.

Currently, SP ships a black o-ring with a painted-on red (?) stripe to differentiate it from the other -010's in the kit. It's supposed to be a EPDM 85.