Hydraulic Cylinder Seals and Sealing Systems
The sealing system decides leakage, friction and service life of a hydraulic cylinder. Piston seal, rod seal, guide band and wiper must match pressure, temperature and fluid. This guide shows how to choose the right design and material for your application with confidence.
View hydraulic cylindersWhich seals sit inside a hydraulic cylinder?
A hydraulic cylinder seals at several points. The piston seal separates the two pressure chambers, the rod seal keeps oil inside the cylinder, and the wiper keeps dirt and water off the retracting rod. Guide bands centre piston and rod so the seals never run on metal. Only the interplay of all elements gives a tight, long-lasting system.
Which seal material fits your fluid and temperature?
The material sets temperature range, fluid compatibility and service life. NBR is the standard for mineral oil at moderate temperatures. FKM (Viton) handles higher temperatures and aggressive fluids but costs more. Polyurethane offers high extrusion resistance under pressure, and PTFE compounds run with low friction and dry starts. Always check the approval for your specific hydraulic oil.
- Check the operating and peak temperature of the oil, not just the ambient air.
- For fire-resistant or biodegradable fluids, obtain the maker's material approval.
- For high pressure choose polyurethane or a seal with a back-up ring against gap extrusion.
How do I match seal, pressure and speed?
Pressure, piston speed and surface finish decide the right design. High pressures need back-up rings against extrusion, high speeds need a low-friction seal with a good oil film. A rod surface that is too rough or too smooth ruins any seal early. Match the selection to your load profile.
At high pressure plan a back-up ring, or the seal is forced into the gap.
Compare cylindersFrequently asked questions
How do I spot a failed rod seal?
By visible oil drops or a puddle under the cylinder and a heavily wetted wiper area. A very thin oil film on the rod, in contrast, is normal and serves lubrication.
Can I just swap an NBR seal for an FKM one?
Only if the housing dimensions and the approval for your oil match. FKM tolerates more heat and aggressive fluids but costs more and is less flexible in the cold. Check temperature range and fluid compatibility before swapping.
Why does my new seal last only a short time?
The most common causes are a damaged or wrongly finished rod surface, contaminated oil, or gap extrusion under high pressure without a back-up ring. Check the surface, oil cleanliness to ISO 4406 and the pressure load.
Find the right sealing system
Our hydraulics specialists help with design, material and housing dimensions for your cylinder.
Vetted selection
Recommendations from maker data and field values.
Fluid-compatible
Material matched to oil and temperature.
Long service life
Wipers and oil cleanliness clearly explained.
Expert advice
Hydraulics specialists support your selection.