They doubled my o-rings on my high pressure line

[12th Man]

While in Belize diving last Jan my o-ring on my high pressure line into my 1st stage broke. I went to get my o-ring kit out of my bag and inadvertently left it in the hotel. The dive master I've got o-rings said I'll fix it and took it below. A few minutes later he came back and said you're good to go. I connected up to the tank turned on the air and no issues, not that I was expecting any.

Flash forward seven months. Wife and I are getting ready for a long weekend to go diving in Fl with sharks. I decided to convert my Aqua Lung 550i inline dive computer to a quick disconnect. Got the kit for AL which included a new high pressure hose. I took the old hp hose off of the first stage and low and behold there were two o-rings . They were a bit undersized and snug. My guess was the dive master didn't have the correct size, put two that were just a bit too small and called it even.

I've done probably 15 dives since he replaced them. I can't say I've ever seen that trick done. It's worked fine! Thoughts on what the dive master did and has anyone else ever done this?

 

[UCFKnightDiver]

Interesting, never heard of or seen that before. I would be more worried if it was on a low pressure hose as a huge leak there would not be good. If your high pressure hose goes, it's not as big of a deal, as the hole the gas is coming out of is super tiny. So while the pressure in a high pressure hose is super high, the volume of air that can be released is not.

 

[rsingler]

From an engineering standpoint, it's a perfectly acceptable kludge. The seal is made by jamming the oring material simultaneously against the two faces of the parts that need be sealed. If you do it with liquid that then hardens, or two orings to fill a gap, or the proper o-ring, it's all the same to the equipment. As a temp fix.
That said, using the wrong seal makes you more at risk for extrusion. My bigger worry in this case is that the two orings were not only slightly small, but also too soft. Typically (with a few exceptions like Poseidon), HP seals are engineered to require Duro 90, which is harder and less prone to extruding down the tiny gap between components. If the DM had to use two orings, I suspect the outer one at least was Duro 70, since he was able to stretch it over the other one. That's more prone to failure unless the two components have very small machining tolerance.

 

[rmssetc]

I took the old hp hose off of the first stage and low and behold there were two o-rings . They were a bit undersized and snug.

Sounds like you're describing two o-rings of the same size, in-series (stacked) on the HP hose, meaning they are effectively a thick o-ring of a smaller diameter than stock.

If the DM had to use two orings, I suspect the outer one at least was Duro 70, since he was able to stretch it over the other one. That's more prone to failure unless the two components have very small machining tolerance.

It sounds like you're envisioning two o-rings of different sizes, in concentric circles, meaning they are effectively a single "height" along the axis of the hose, and potentially a larger diameter than stock.

 

[12th Man]

both o-rings were the same size in series, just slightly smaller in diameter than the one on the new HP hose from AL.

 

[wnissen]

That's scary, I never considered that as a reason to have my own o-rings in a save-a-dive kit.