Which Hydraulic Seals to Use: UN vs DHS PU Seals

When sourcing seals for hydraulic cylinders, many purchasing managers and design engineers need to tell the difference between UN and DHS polyurethane seals. UN and DHS are commonly used together, but they perform separate sealing tasks.

UN PU Seal: Standard U-cup piston rod seal. It is the primary sealing element, responsible for keeping hydraulic oil inside the cylinder. With excellent wear and extrusion resistance, it stops fluid leakage along the piston rod under high pressure.

DHS PU Wiper Seal: Double lip dust wiper mounted at the cylinder head. One lip scrapes off mud, dust and grit from the moving piston rod. The second lip wipes residual oil film. It prevents external contaminants entering the cylinder and protects the main UN seal from premature damage.

Made of PU (polyurethane), both seals have great wear resistance for mineral hydraulic oil applications. This UN + DHS combination is widely adopted in construction machinery and industrial hydraulic equipment.

We supply UN and DHS PU hydraulic seals in a wide range of standard sizes. Custom dimensions can be produced to fit your cylinder groove requirements.

Important note: PU seals perform best at moderate temperatures. They are not suitable for continuous high-temperature working environments.

Contact us for catalog, sizes, samples and bulk order support for your hydraulic sealing projects.