Pneumatic applications

NBR 70 Shore A handles dry and lightly oiled air without trouble and is the cheapest choice. Choose PU (polyurethane, ~90 Shore A) when the stroke is fast and frequent or the cylinder works in a dusty environment — PU resists abrasion better and lasts longer under dynamic motion.

In pneumatics the forces are lower than in hydraulics, so low friction and smooth cylinder start-up matter. The O-ring is usually fitted with a thin film of rubber-compatible lubricant (silicone or PTFE grease for NBR). For lubrication-free systems, choose PU or special low-friction compounds.

NBR holds continuously up to about +100 °C, but with oiled hot compressor air its service life is shortened. For higher temperatures or more aggressive conditions, choose FKM (Viton®), which handles up to +200 °C. Always check compatibility with the compressor oil type as well.

The most common are metric O-rings with a 1.5–4 mm cross section depending on the cylinder bore. When replacing, measure the inner diameter and cross section of the original ring, or send us the cylinder type (Festo, SMC, Airtac) together with that measurement — and we will find the equivalent.