Tuning Regulators and O-ring longevity

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nervoustrig

nervoustrig

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Jan 21, 2018
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Just wanted to pose a question to the tuners and DIY guys who do their own repairs. A common failure I see is with the O-ring on the small end (high side) of a regulator spool. What usually happens is the regulator will begin leaking out of its atmospheric vent. Upon disassembly, this particular O-ring is found to have lost all elasticity and just crumbles to bits. Meanwhile the larger O-ring on the opposite end looks and feels fine.

My best guess is it has to do with the repeated adiabatic heating of the plenum refilling, causing the elastomer to rapidly age and harden. Granted, both O-rings are exposed to the plenum air and therefore experience a temperature rise as the pressure recovers. But perhaps the reason the large O-ring doesn't degrade to the same extent is because the big end of the spool is a larger thermal mass that helps absorb away the heat.

Anyway it occurred to me I've seen this failure again and again on Huma regulators and others sharing a similar design but I don't remember ever running into it on a Ninja paintball regulator. Why? Well, the fundamental operation is the same and in some cases the regulators even have similar dimensions so that doesn't seem to be the reason why. But Ninja uses polyurethane O-rings whereas the brittle O-rings always seem to be the more common Buna-N. If indeed that's the relevant difference, it runs counter to the industry data on O-rings, for which polyurethane has the lowest temperature rating of all common elastomers.

Do any of you guys have experience or knowledge that either substantiates or challenges this theory?
 
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Seen the same ... also including the o-ring on seat adjuster.
I don't concur on it being a heat related issue, but more of a Compressive issue of the Higher pressure on the small end of spool than the larger LP side in terms of Regulators.

What ever is the medium / liquid that makes a said Estolimer such as an o-ring able to maintain a pliable state is certainly less so as o-ring shrinks in size.
So if we envision an o-ring like a sponge and subject said sponge to extreme crush which size would loose its captive moisture first ?
It appears the captive medium that keeps an o-ring pliable does not necessarily migrate threw the material as a sponge but is forced to leave it due to the crushing pressure. This can be seen also as Gas molecule incursion as well with o-ring swelling. O-rings are not a solid and as such absorb as well loose Gasses / moisture etc ...
Smaller an o-rings cross section less distance the medium needs to migrate to exit the material. As this medium keeping o-rings material pliable exits the o-ring Plasticizes becoming hard and non pliable.

I've taken enough PCP's & Regs apart that given enough time & Pressure EVERY SINGLE o-ring tip to tail dang near crumbles into pieces upon being removed.
The processes of an o-ring losing pliability over time & pressure is a constant and it so happens that small o-ring get effected before larger ones and does not really matter where in the PCP there located ... IMO
But higher pressure certainly exacerbates this hardening process :cautious:
 
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corny said:
I’ve had lengthy conversation with experienced tuners….who seems to to be of the opinion that most reg need to be rebuilt every 2-3 years.

What was interesting was the opinion that the really high end regs in anshutz, feinverkbau were a lot less troublesome. Mainly because the tolerances to which they are manufactured too.
Click to expand...
AND .... there choice of specialty o-ring materials appearing to be NON industry standard that while sizes are a non issue, material they use can't seem to be found outside OEM replacement.
 
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Sorry Jason,
I have no technical information to add, besides I've also seen this issue on the stem of RAW regulator and now my Huma regulator in my BSA R10.

I accidentally released almost a full 480 cc bottle through both my RAW regulators in late August and both regulators started leaking out their weep holes immediately thereafter. I replaced 1 Buna-N O-ring and (I think) 1 Clear O-ring on each regulator's stem as they were damaged by the extremely cold air passing through. Immediately solved the problem .......... :)

I also had two other regulators over time which needed both Buna O-rings (on stem) replaced as they were simply "old" and hardened. Weeping/leaking air out the regulators weep hole is classic.

Matter of fact waiting right now for these O-rings ordered from Huma last week.

- If anyone knows the sizes of these Huma (regulator stem) O-rings please chime in as I would like fix this issue sooner than later.
 
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Hey guys, thank you for the ideas and comments. I've also been doing some more research and industry sources (Parker O-ring handbook, Hudson design guide, etc.) list the following as the causes for hardening and embrittlement:

1. heat
2. oxidation
3. loss of plasticizers
4. ozone and weather

1. Heat - skipping this one since it's the one I speculated on in the original post.

2. Oxidation - This reason fits with Scott's comments about gas permeation into the material...elevated pressure causes more permeation and presumably more accelerated oxidation. However if that were the case, the reservoir O-rings and the check valve O-ring should harden at a similar rate but they don't. (A lesser point being the small O-ring on the piston does not carry the burden of the full reservoir pressure...it only briefly sees an elevated gradient and then settles to the reduced regulated pressure.)

3. Loss of plasticizers - This one seems to be associated with O-rings in continuous exposure to fluids like solvents that absorb into the elastomer and migrate back out, carrying plasticizers with them. Doesn't seem like it pertains to our scenario. But even if compressed air had some analogous effect where it leeches out the plasticizers, it should cause the other O-rings in the system to deteriorate at a similar rate.

4. Ozone and weather - Similar thoughts as with plasticizers...I don't think ozone and weather are factors that apply to our use. But to the extent they do, the effect should be about the same for all O-rings, not just the one at the end of the regulator spool.

So after considering all 4 factors, I'm still inclined to blame it on heat. Here's what I think is happening. There's a moment immediately after firIng when the plenum pressure drops, the piston leaves the seat and air rushes in from the reservoir, producing a rapid pressure rise (and temperature rise) in the tiny volume at the tip of the piston, where the O-ring in question resides.

And Scott's comment about the O-ring on the adjuster also frequently being hard...that's a good point I failed to mention in the original post. It too resides in this same space so it makes sense that it's getting cooked as well.

I'm going to consider using a different compound going forward and see if the longevity can be improved.
 
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Hi Jason, all of the Huma regs now come with Viton orings on the small side. It was a heat problem. The Viton has extended the service window, but I have seen the Viton act funny when it’s real cold. The cold isn’t much of an issue for most, but sometimes FT matches are in the cold. I still use the buna on mine and remind guys to just replace them every season if they don’t ever want the experience a failure after traveling to a match. Most don’t listen. 😀

Mike
 
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Interesting subject, thanks for posting nervoustrig!

Haven't had any trouble with my regulators (yet) but expect that I'll eventually be doing some service on them. 😐

Guessing that the operating pressure might have some bearing on the temperatures being experienced by the regulator o-rings. I've had a pair of HW100 PCPs (.177 & .22) for going on 8 years and the regs are still fine. Reservoir pressure is 200 bar, reg is around 115 bar IIRC.
 
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Vana2 said:
Interesting subject, thanks for posting nervoustrig!

Haven't had any trouble with my regulators (yet) but expect that I'll eventually be doing some service on them. 😐

Guessing that the operating pressure might have some bearing on the temperatures being experienced by the regulator o-rings. I've had a pair of HW100 PCPs (.177 & .22) for going on 8 years and the regs are still fine. Reservoir pressure is 200 bar, reg is around 115 bar IIRC.
Click to expand...

The pressure drop between plenum and HPA reservoir likely increases heat transmission during the shot cycle. So higher power guns with smaller plenums may be more susceptible, lower power / larger plenums less so, at least I think..

-Matt
 
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nervoustrig said:
Just wanted to pose a question to the tuners and DIY guys who do their own repairs. A common failure I see is with the O-ring on the small end (high side) of a regulator spool. What usually happens is the regulator will begin leaking out of its atmospheric vent. Upon disassembly, this particular O-ring is found to have lost all elasticity and just crumbles to bits. Meanwhile the larger O-ring on the opposite end looks and feels fine.

My best guess is it has to do with the repeated adiabatic heating of the plenum refilling, causing the elastomer to rapidly age and harden. Granted, both O-rings are exposed to the plenum air and therefore experience a temperature rise as the pressure recovers. But perhaps the reason the large O-ring doesn't degrade to the same extent is because the big end of the spool is a larger thermal mass that helps absorb away the heat.

Anyway it occurred to me I've seen this failure again and again on Huma regulators and others sharing a similar design but I don't remember ever running into it on a Ninja paintball regulator. Why? Well, the fundamental operation is the same and in some cases the regulators even have similar dimensions so that doesn't seem to be the reason why. But Ninja uses polyurethane O-rings whereas the brittle O-rings always seem to be the more common Buna-N. If indeed that's the relevant difference, it runs counter to the industry data on O-rings, for which polyurethane has the lowest temperature rating of all common elastomers.

Do any of you guys have experience or knowledge that either substantiates or challenges this theory?
Click to expand...
Great topic. I was in the process of rebuilding the regulators on 2 of my Taipan Veterans. Didn't find any crusty orings, but was surprise to see OEM specified poly on the pressurized, dynamic o-rings...

IMO a very related topic is the use of good lubes in this area, such as products from Krytox, Lubriplate, Ultimox, etc vs your normal run of the mill silicone grease....
 
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Very intersting topic indeed, and I think Motorhead and Vana2 are definately onto to something with the pressure they're run at. I have two Huma's that I rebuilt after a couple of years that run at 150 and 165bar, and a Ninja regulator that only runs at 95 bar that has more than twice the years and ten times the shot count through it, that still functions perfectly. I will be interested to see where this thread goes.
.
 
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I replaced my Bulldogs Huma regulator o-rings with polyurethane 90 duro o-rings because about every 3-6 months my Huma regulator would leak out the atmospheric weep hole. I found the same mis-shapened o-ring or both o-rings. I tried Viton and Buna, neither would hold up. Going on a whole year now without a problem with the Polyurethane o-rings.
 
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