Repeated O-Ring failure

[PEIDiver]

My normal dive buddy has been having a rather frustrating problem with o-rings failing on almost every dive. The first four or five times we figured the o-rings must have been nicked or dirty. However, the last dozen or so times, we've started to suspect the yoke fitting on his first stage. Is it at all possible that his first stage isn't applying even pressure across the o-ring causing the seal to fail?

Anyone else ever have this problem? Would there be any solutions?

Thanks,
Steve

 

[Goldminer]

I would suggest getting a good quality magnifying glass or loupe and having a very close look at the part of the yoke/reg that seals against the o-ring. Look for tiny nicks or scratches. I know from my days in plumbing that even a tiny scratch on the seat in a water valve will tear up a washer very quickly. And that is at low pressures not the 3,000 psi you are talking about.

Also check the valve for nicks. You may be damaging the o-ring when you insert it.

 

[nickjb]

It does sound like a problem with the reg but... Is your buddy fitting the reg on the tank properly? You should hold the reg against the o-ring then tighten the knob, not tighten the reg onto the o-ring. Also be careful not to over tighten. The air pressure holds everything tight, not the knob.

HTH
Nick

 

[Conch]

make sure you aren't tightening down the yoke THEN moving it from one side to the other to adjust the hose placement. If the 1st stage is ground against the oring while the yoke is tight, this will shear the orings. A good way to see if it is sheared is to look at it and see if it looks like it is splitting in two pieces.

If that isn't the problem, maybe there is defect in the tank valve. Some regs will have a problem seating on the older valves.

 

[mddolson]

I noticed you're in PEI.
I'd consider that a little out of the way, so there's another possibility.
Where are your o-rings coming from?
Standard off the shelf o-rings are A-70 durometer unless otherwise specified and are only rated to 1500 psi. They will extrude through the clearance between the regulator and valve seat no matter how tight you crank the knob.
The o-ring on your valve-regulator seat should be A-90 durometer.
I'd ask your supplier where he gets his o-rings.
It's common to order 0-rings from industrial supply houses in bulk since it's cheaper that way, but if you don't specify A-90, they ship A-70 hardness.
Pinch the o-ring between your finger nails, you can tell the difference between a good one and soft one.

Mike D
:blfish:

 

[Wendy]

I had this problem when I borrowed a tank from a friend of mine once before. He must have dropped the tank on the the valve at some point. Whenever I hooked the firststage up to the valve, about 5 mins later the o-ring would blow out. The o-ring wasn't damaged though. The firststage wasn't sitting right against the valve and the o-ring would start to work its way out. Check your valve and make sure that's its not damaged.

 

[PEIDiver]

Thanks for the replys folks. I'll pass on all your advice to my buddy, but it's really starting to look like it's the reg. He has been setting things up correctly and the problem has stopped since he started using a rental reg. As far as the o-rings go, they should be good, he's even blown out the silicon ones that come with the valves.

Thanks again,
Steve.

 

[Norm]

I've seen this happen several times down through the years too!

 

[Techniciany]

Hello

Make sure that the replacement o-rings you are using are the correct size and that they have not been crossed over with metric or the reverse. A good biology microscope will help you see the surface areas of your regulator parts and you may find a slight scratch in the metal which is not visible by the naked eye is your problem. Are you ajusting the Ip correctly?. sometime over pressurising the ip to high at first than bringing back down can cause o-ring fatiqe and failure.

Good luck let us know how things turn out.

Technician

Diving Technologies

 

[Rick Murchison]

to the most likely source of repeated o-ring failures. But if it's happening on more than one tank and only on one regulator, I'd suspect the brass seat on the regulator was warped in a tank fall rather than the tank valve. To check, take a metal ruler and lay it across the face of the regulator valve seat and look all around the edge to see if it's flush. My bet is you're going to find a little space on one side - the source of the problem. It's a common cause of what you describe; a replacement valve seat should be a standard item at your LDS.
Rick