Hydraulic Piston Seals

Hydraulic piston seals are installed in the piston groove and seal the dynamic interface between the moving piston and the cylinder bore. In double-acting cylinders they must retain pressure on both sides of the piston as it extends and retracts. In single-acting cylinders they seal against pressure from one direction only. Piston seals directly affect cylinder efficiency, leakage, friction and positional accuracy, making profile and material selection critical for hydraulic system performance. IDU is a common metric U-cup piston seal designed for piston bores and seals on the outer diameter. ODU is the rod-type counterpart used in rod glands. Both energize under pressure to increase sealing force. KDAS is a popular composite piston seal consisting of an NBR (or FKM) sealing element, POM guide/anti-extrusion rings and TPU/TPE support rings assembled into a single groove. This design provides bidirectional sealing with low friction and excellent pressure capability without separate backup rings. For low-friction or high-pressure applications, Glyd rings and step seals use a PTFE-bronze sealing ring energized by an O-ring. These are common in servo-controlled cylinders and precision machinery where stick-slip must be minimized. OK and SPGW are additional composite profiles used by specific OEMs and in heavy-duty mobile equipment. Our piston seal range covers bore diameters from 16 mm to 500 mm in TPU, NBR, FKM and PTFE-bronze materials. We supply standard IDU, KDAS, Glyd ring, OK and SPGW profiles as well as custom designs from drawing or sample. For each application we verify groove dimensions, pressure rating, fluid compatibility and expected cycle life.