Hydraulic seal

A seal keeps hydraulic oil where it should be and keeps dirt out. In a cylinder, piston seals stop oil passing from one side of the piston to the other, rod seals stop oil leaking out along the rod, and the wiper cleans the rod as it retracts.

Seals are chosen for the working pressure, temperature, speed and type of fluid. Worn seals are the most common cause of leaks and of a cylinder drifting under load.