Hydraulic applications

For common HLP/HLPD mineral oils, NBR 70–90 Shore A is the standard. For higher oil temperatures or long service life, choose HNBR. For fire-resistant HFD-R fluids (phosphate esters, Skydrol), do not use NBR — there, depending on the fluid type, EPDM or FKM is the right choice.

An O-ring on its own, without support elements, seals reliably up to roughly 100–150 bar. Above that, add a back-up (anti-extrusion) ring made of PTFE or POM and choose a higher hardness (90 Shore A) so the rubber is not extruded into the gap. For dynamic rods and pistons, accurate groove geometry also matters.

Yes. A static seal (flange, plug) is more forgiving — a standard O-ring is enough. For a dynamic seal (moving rod, piston), hardness, surface finish, and abrasion resistance are critical; an O-ring is often combined with a back-up ring, or PU is chosen for greater mechanical resistance.

Extrusion results from a combination of high pressure, a large gap in the groove, and rubber that is too soft. The fix: a harder material (90 Shore A), the correct gap for the pressure, and adding a back-up ring. If you are unsure about the groove geometry, send us the dimensions — we help free of charge.