Scubapro O-ring Sizes

[Zung]

I don't do EAN, so I have no problem with Buna-N, but a lot of people here swear by PU for the HP ring, so I ordered a bag just to see. Btw the "Millable Gum" is PU (polyurethane).

SP has reverted back to EDPM for whatever reasons, maybe cost; I've got 3 recent kits that come with those black rings with a red/brown stripe.

 

[superstar]

Zung, sorry about spelling your user name with a J in my previous post, no offense intended. I missplaced my reading glasses and I do not type well wearing my bifocals.
Thanks for the o-ring link.

 

[superstar]

mattboy, where did you and Awap ordered the 90 duro o-rings from?

 

[halocline]

oringsusa.com

 

[superstar]

A few years ago I replaced every o-ring in my mk5 with 70 duro buna-n's. This reg has been on two dive trips plus two seasons of local diving and still works perfect.

 

[Zung]

Zung, sorry about spelling your user name with a J in my previous post, no offense intended. I missplaced my reading glasses and I do not type well wearing my bifocals.
Thanks for the o-ring link.

No prob
From what I heard, MK5's & MK10's are very tolerant of the HP o-rings. The 2 that I removed recently are SP "originals" that look a lot like PU (whitish, semi-transparent) and they are very soft, a lot softer that the Duro 90's I have, so I assume they're 70.

 

[redacted]

No prob
From what I heard, MK5's & MK10's are very tolerant of the HP o-rings. The 2 that I removed recently are SP "originals" that look a lot like PU (whitish, semi-transparent) and they are very soft, a lot softer that the Duro 90's I have, so I assume they're 70.

My understanding is that Scubapro switched to the plastic washers and o-ring design because of extrusion problems with the Mk5/10 design. But the problem may just be that manufacturing tolerance were not be held as tightly 25 years ago so there may be a lot of variance item to item.

 

[Zung]

awap, you mean tolerances were better 25 years ago or the other way around?

I think ease of service could be a factor for the change. I did it 4 times so far on my MK10's, and I'm still scared to death at the idea of poking some sharp pointy thingies at those o-rings. Maybe SP got tired of replacing free of charge bodies that are destroyed by careless tech's.

 

[Zung]

MILLERJE asked for it, so here's the D400, but I have no data on the square-ring, 11-014-212.
Anyone cares to proof?

 

[halocline]

A few years ago I replaced every o-ring in my mk5 with 70 duro buna-n's. This reg has been on two dive trips plus two seasons of local diving and still works perfect.

I'd be willing to bet that if you measure the IP at 3000 PSI supply pressure and 500 PSI, you'll find at least a 10 PSI difference. Then if you removed the 010 70 duro buna-n from the HP piston spot and replaced it with a 90 duro polyurethane, then re-did the IP test, you'd find much less difference in IP between full tank and low tank pressure. How much difference this makes in actual diving is certainly debatable, especially if you're using a balanced 2nd stage.

But for me, it's worth using the higher duro PU o-ring in that spot, mostly because working on the regs is a hobby and I'm a real stickler for the way they perform. I also anticipate that the 90 duro PU o-ring will last longer on average in that spot. Yours might be working fine for years, but if you had 100 MK5s, and put 70 duro nitrile (buna-n) o-rings in the HP piston spot, and another 100MKs with 90 duro PU o-rings, you'd see a difference in how long they go without leaking.