Originally Posted by
DaveReidUK
Then I stand corrected.
I've come across plenty of hydraulic actuators in my career, just none with seals that were remotely O-shaped, but clearly I was wrong to rule out their existence.
As long as the O-shaped seals aren't loaded beyond their specifications, no problem, think about aspects like lubrication, cleanliness, deformation, load forces, sheering, etc.
The issue arises, when O-rings are being used in a presumed "static" situation and contamination of the sealing areas happens, then a "vibrating" static situation, will result in the contamination working itself into the sealing and leaking will start (including damaging the seal material itself). This is typically something to be expected, when the 2 sides of a seal are attached to different "fixed" mountings: The seal starts moving, the contamination works itself into the seal and the leaking starts.