johndiver999
Contributor
My favorite oring discussion.
It's true static oring don't need lube, trouble is there is a big misunderstanding of the definition of what a static oring is.
Most believe that once it's in place and does not move (or the parts around it) while in place it's static, the rub here, if you forgive the pun, is to meet the definition of static, the oring can never move against it's mating surfaces. During installation , hose orings move in a spiral rotation while being installed, at that time they are in fact dynamic and need lube. You have to dig deep in the Parker manual but this is discussed (or at least it was years ago). Many will argue that they have not lubed hose orings for years and it worked. No doubt this is true but odds are there was still some remaining lube, it only takes a little, or they got lucky.
Then there is the movement the oring does as it transitions from it's non-sealed state to it's sealed state.. This is discussed in the thread referenced above, you will see the how the oring moves in it's groove while being pressurized, this movement also needs to have some lubricant to prevent binding.
The only true dynamic oring in scuba that I can think of is the tank to valve interface. The oring is pressed into a groove then pressed straight on to the flat surface in the tank., or vise versa depending if it's DIN or yoke.
I don't understand the bolded comment. Why isn't that o-ring subject to torsional forces as it is screwed down? Why is it materially different than a port plug on a first stage? I always lube that one. I think it may help with corrosion as well.