O-ring experiment

[diveprof]

Yeah, I struggled a bit getting them on the larger nipple. Practiced words not normally in my vocabulary Failure rate for me is about once in 3 years or so. That was why I was thinking "just get the spool with the viton o rings" from:
HP Spools "Stems"
This is an example of the tool for o ring placement I found:
O rings Installer Tool | eBay

---------- Post added at 05:58 PM ---------- Previous post was at 05:55 PM ----------

I was able to get a duro 90 on my spool using a DIY tool I made. I used the plastic tube inside an old ball point pen. Just cut off a 4" piece and heat it in the middle with a cigar lighter while pulling on the ends to draw it to a tapered point in the middle. Cut it in the middle with scissors then heat the other end and push a tapered object in the end to flare it. I was able to get the "O" rings on fairly easily, but if I make another I'll try and find an object that will give a more gradual flare.

Actually tired something like this, but it still wan't "big" enough for the nipple.

 

[redacted]

I'm not convinced 90 duro is the way to go unless you are experiencing extrusion problems. I believe increasing the hardness increases the force of friction at the dynamic surface.

 

[Couv]

Master,

I am not convinced either-hence the experiment. Those o-rings see high pressure on one side and ambient pressure on the other. That's why I wanted to give 90 duro a try. The last two o-rings in that application I had fail were actually cut in half. I'm thinking first they extruded causing a leak, then when the hose/spg was removed they were cut.

I'll admit, I have no idea how long those o-rings were installed (could be > 20 years) as that is a part of my kit I have a tendency to ignore, but I promise to be better.

Couv

 

[redacted]

Master,

I am not convinced either-hence the experiment. Those o-rings see high pressure on one side and ambient pressure on the other. That's why I wanted to give 90 duro a try. The last two o-rings in that application I had fail were actually cut in half. I'm thinking first they extruded causing a leak, then when the hose/spg was removed they were cut.


I'll admit, I have no idea how long those o-rings were installed (could be > 20 years) as that is a part of my kit I have a tendency to ignore, but I promise to be better.

Couv

Cut in half like a big O and little O or cut in half like the O became two Cs? Sounds like some really old o-rings rather than extrusion damage. I would expect extrusion to eventually cause pieces of the o-ring to separate and result in a leak rather than an complete break. The spool o-ring faliures I have seen were the fizz leak where it looked like the o-ring was damaged by salt deposits on the sealing surface. And a few where the spool was stuck in the gauge or hose by those deposits. A real good cleaning and a couple new, easily installed 70 or 75 duro o-rings and all is well.

 

[Couv]

Cut in half is a bad description. I should have said cut-as no longer an O and now a C. Yes, I've seen quite a few fizzy fittings over the years and a simple o-ring replacement was all that was needed, as you said, probably salt crystallization. But the last couple of failures were a bit different in that the o-rings were cut, not just abraded or worn. But I guess it is also possible they simply broke when the spool was removed.

 

[axxel57]

Since more than three years I’m using the nitrile Buna 90 o-rings for the spools of my customers. According to my experiences they last way much longer than the Buna 70s.
I have equipped hundreds of spools with those o-rings and they work very well. It is almost impossible to install them on the bullet nose type spools, even with the installation bullet. You would have to stretch the o-rings (role them up and down, but not too much up))carefully on the installation bullet for a while, than it might work.
Usually I broke two or three o-rings before finally being able to install one, so finally I equipped those with the Buna N 70.
It’s working easy after some practice on the shouldered and the standard spools. As Couv shows correctly you might find some shouldered spools with a ‘big’ head, but those are usually older models.
Actually I went recently back to install the Buna N 70 o-rings on the spools of my clients (at least on the diving school regulators), because the failure of the those o-rings marked mostly the time for the service. Since the o-rings last at least six to eight months ( using the regs every day or almost every day), I would get them in average about once every nine months to one year for service.
The way the regulators are used and wasted here, I found that this is not often enough, even if they still work. For example too often the orifice (hard seat) in the first stage body (MKII) is damaged by minerals (sooner or later enters water the 1^st stage) and has to be replaced.
So with the Buna N 70s I expect the regulators to get back to me every five to eight month months in average.
Please don’t comment on the system how operators here control their regulator service routine, I’m already happy that they finally agreed to not touching (repairing ) the regulators, but sending them to me when anything is wrong ( which is usually the spool o-ring first).
Thanks for reading…….

 

[Zung]

... Since the o-rings last at least six to eight months ( using the regs every day or almost every day)...

Very good data point: that's about 200+ dives, so replacing the o-rings every other service makes sense.
Sadly, with our current run rate of about 50 dives/year, that's 4 years. :depressed:

 

[Couv]

Hi Axxel57,

Thank you for your input. Just to be sure I understand, you have found the higher duro seals to be more dependable than the softer ones, right? But like me, you found the higher duro seals difficult to install on the spools with large ends.

Next question: Have any of you found any gauges or hoses where the T type spool would not work? Is there any combination of hose/spg/spool that will not work? I thought I had such a case, but removing the spool and then re-installing it seem to fix a jamming problem. (Screwed the hose on and found the SPG would not swivel unless the hose fitting was only finger tight.)

c

 

[axxel57]

Hi Couv

Exact, the Buna N 90 last longer, but are harder or not at all to install (bullet nose type spool).
As far as I remember does the shouldered type spool ( T type) not fit into the SPGs of UWATEC, I think it started leaking. And definitely doesn't the UWATEC spool fit in almost all other types, because it is longer than the usual ones ( at least the ones produced in Europe) and causes what you described as the jamming problem.
I think I met also some other SPGs or HP hoses where the shouldered type spool did not fit, but it's rare and I don't remember which brand they were. Next time I stumble over one, I will note that and keep you posted.