Scubapro O-ring Sizes

[Zung]

Just curious, what did you get for the HP o-ring? Originally, it's supposed to be a 2-010 Duro 85 EP.

 

[dpwheeler]

Using MMC's Polyurethane

 

[redacted]

One caution with polyurethane - they may not stand up to the test of time as well as Viton or other materials. About 5 years ago I bought a package of 100 urethane -010, duro 90s online (oringsusa) and I threw the last of them in the trash this last weekend. They had all become brittle and cracked when you tried to install them. The problem actually showed up a year or so after I bought them but it was only a few that were bad at first. I do believe I just got a bad (old) batch as I do have some urethan o-rings from Parker that are over 10 years old and still seem fine. I have also noticed urethane o-rings in older scubapro regs often come out brittle. That is, they often come out in pieces although some were still working (sealing) even though they were brittle. I went to urethane when I had IP stability problems with some Mk10s using new viton o-rings which I suspect had to do with friction between the piston stem and the HP o-ring. The urethane seemed to reduce the problem compared to Viton. I am now going back to Viton in inb my 1sts with larger diameter piston heads and retiring my Mk10s. I have seen a few that leaked pretty badly from piston o-rings but not so badly that it could be expected to endanger the diver - they still mostly sealed although they crumbled on removal (many pieces). I have not had any fail in my regs (not sure which of my regs have them) but I have gone through my wife's, daughter's and granddaughter's regs to make sure there were no urethane piston o-rings from my bad batch in theirs.

Also, what happened to the price of viton vs. EPDM? It used to be that the biggest difference in those materials was that Viton was 2 to 3 times the price of EPDM (somewhat offset by the longer shelf life of viton). M-C prices seem to consistently have viton as somewhat less expensive than EPDM and often packaged in more favorable (smaller) quantities for DIYers.

 

[Zung]

I just checked my stash of MMC 010 PU 90 that's 1 year old, and they're still good: white-ish, and not any harder than the VT 90's I have.

I'll report back in 2015

 

[Couv]

I had very similar experiences as Awap with supposedly new PU o-rings even though my o-rings came from at least two different sources. The odd thing is that a few of the PU o-rings I removed from older regulators still seemed quite supple when I replaced them. I'll look through my "used" bag later and if I still have any of them, I'll check them to see if they have deteriorated since removal and report back later.

 

[halocline]

I was part of the same order from oringsusa. It is too bad, because the 90 duro PU o-rings definitely improved the IP consistency of my MK5s and MK10s. I still have a few good ones, but most have I'm going to talk with oringsusa next time I order and see if they have any explanation. But, I'm also going to EPDM for a while, maybe viton on the MK10s.

 

[Couv]

Update: I looked at the 4 polyurethane o-rings I have in my used stash and all pass inspection. (Two piston head and two SPG spool) They were removed from eBay purchased regulators and SPGs so their ages are not known. I'm reasonably sure they are over 5 or 6 years old coming out of MK 10. An interesting item to note is that none the used PU o-rings I have in my serviceable/used stash are of the higher (>80) durometer type. Like Viton, I suspect there are several different compound mixtures for PU and that may have something to do with why the piston stem -010 o-rings don't hold up.

One other thing I just realized. I got my new PU o-rings from Awap and Halo, so if you guys ordered them from the same source, all three of us may simply have gotten them from the same bad batch. However, the recommended shelf life of PU is still only 5 years and the last set of aviation grade FKM (viton) o-rings I got have no expiration date.

Later,

Couv

 

[redacted]

One other thing I just realized. I got my new PU o-rings from Awap and Halo, so if you guys ordered them from the same source, all three of us may simply have gotten them from the same bad batch. However, the recommended shelf life of PU is still only 5 years and the last set of aviation grade FKM (viton) o-rings I got have no expiration date.

Later,

Couv

Yes, they are all from my order. I'm sure they were just old to start with. But that is always a risk.

I too have some NOS kits with urethane o-rings and they also look good. I assume that may the benefit of favorable storage conditions. At the other extreme, this picture shows what is left of 2 urethane piston o-rings from a Mk5 that seems to have been stored in an outside building for quite some time. Before I opened it up, I put it on a tank and it did leak quite seriously but not near as badly as I would have expected after seeing the inside.

 

[Zung]

Bro, you got me working! But I have a few I can date with some sort of precision, +/- a couple of years:



Right of the plastic bag, and inside of it are some NOS stuff I liberated from my nephew Jim's stash by the time he worked at an LDS in the mid-nineties, so they're about 15 years old.

Left of the bag are some used stuff I removed from 2 MK10 Plus's serviced by another LDS in 2000, so they're 11 years old. I know for sure the 2 011's near the seats have about a dozen dives before we put them in storage during our baby-sitting break.

All of theses guys are supple and good to go, so the real world shelf life should be at least 10 years, and the ones that crumble are very likely from a bad batch.

 

[Zung]

View attachment 102968

Grilled piston with onion rings and pasley?