Info WARNING: LP leak with Omni-Swivel on Atomic M1!

[rsingler]

I had a customer bring in an M1 set for biennial service. He noted parenthetically that on a recent dive he had "foamy" air bubbles intermittently appearing between the hose nut and the regulator. A little hose twist, and the issue would disappear. I figured that maybe the hose end o-ring got sheared during a hose change, and a simple o-ring switch would take care of the problem. Service was uneventful, as the reg was in good condition. I changed the hose o-rings with the kit o-rings and also disassembled and serviced the Omni-Swivel 2 which he used at the second stage end, using the Omni-Swivel service kit. Testing went just fine, and no leaks when submerged. I reattached the Omni-Swivel to his 60" primary hose, and to my surprise, it leaked!

As with most mis-adventures, this problem was an alignment of holes in the Swiss Cheese. Here we go:

As you can see, the M1 differs from the rest of the Atomic Fleet in part because of an extra thick heat sink barrel nut. Where the T2 has a 9.74mm nipple, the M1 is restricted to 8.37mm by the thick nut.

Atomic also has a fairly generous chamfer on the inside of the barrel to prevent o-ring shear on hose attachment:

Finally, Omni-Swivel has a deep sealing o-ring placement, compared with (for example) a DGX standard hose end:

as well as the Atomic hose that comes with the M1:

Consequences? (See next post)

 

[BoltSnap]

Consequences? (See next post)

Where is it? We are waiting!!!

 

[rsingler]

Here's your standard hose-to-reg construct.
A barrel nipple screws into a hose nut with an internal sealing o-ring on the hose end shaft.

The hose nut screws tight against the second stage (actually against the barrel nut), so the hose shaft and sealing o-ring can rotate inside the barrel. In fact, most hoses will shift in and out in the barrel after tightening, anywhere from 0.25-1.0mm.

Now add in the extra large barrel nut on the Atomic M1, and couple it with a large chamfer at the end of the barrel:

When the hose is pushed in after tightening the hose nut, no problem!
But let the hose twist and pull out a hair during a dive, and bingo! The hose end o-ring is just barely sealing, and occasionally leaks.

The solution was to just switch to a standard (slightly shorter) Atomic barrel nut from the heat sink nut when the Omni-Swivel is used. If my diver decides to go ice diving and needs the heat sink? He should probably sacrifice the Omni-Swivel on this reg.

(Oops! The jam nut is facing the wrong way in the pic. My bad!)

I'll let Atomic and Omni-Swivel know, but I ain't expecting much. Since Atomic uses common barrels among models (excepting materiel), I wouldn't expect them to change over this, though a shorter chamfer is probably not a bad idea. That's just wasted sealing surface, IMO. That thick sealing nut makes sense from a heat radiation standpoint, but if the Omni-Swivel nut loosens even a little with that barely engaged center post o-ring, we're talking a HUGE and rapid gas loss.

As for Omni-Swivel, having such a deep o-ring land on that center barb is also part of the problem, IMO.

 

[lexvil]

Where is it? We are waiting!!!

It would appear that the consequence was your not waiting for his next post

 

[lexvil]

Just when you think there is a “standard” standard someone comes along and changes things. The Omni is a pretty good heat sink in its own right, I liked the old M1 nut/sink better than this new type.

 

[BoltSnap]

It would appear that the consequence was your not waiting for his next post

I am just always so eager and in great anticipation and excitement for Rob's posts

 

[BoltSnap]

Atomic barrel nut

This is what Atomic calls, jam nut?

 

[rsingler]

This is what Atomic calls, jam nut?

Yes, the jam nut.

Well, I submitted a contact form to Atomic Aquatics with a reference to this thread. We'll see if anything comes of it.

To my pleasant surprise, when I reached out to OmniSwivel International, the owner's wife handed him the phone! We just spent a pleasant 15 minutes discussing the issue, and I'll be sending him the analysis for his consideration. Apparently he also did a similar modification of the AGA omniswivel to allow military technicians to reach the seal with a curved pick. I guess no one has taught them how to use a double-hook pick. In any case, something might actually happen at that end. We'll see...

 

[Gone for diving]

Looks to me that its Atomic that mess up!!

Machine the nut down or counter bore it and don't make a huge chanfer.

If it was mine it would be in the lathe.

Or if you don't want to touch the reg, shorten the omi swivel nut, on the face.

 

[Jimchris]

I've experienced the same with my M1s, namely with aftermarket hoses made offshore. Changed hoses and the problem went away (at least in my case).