What Types of Seals are Used in Hydraulic Cylinders?

Before going to see about the types of seals used in the hydraulic cylinder, first, we will get to know a clear picture of the hydraulic cylinder and its working. The term fluid power is an essential factor for the working of a hydraulic cylinder.

A hydraulic cylinder is a linear actuator used to push or pull a load or selectively resist motion under load, by means of fluid pressure.

Hydraulic Cylinder and It's Part

Fig. Hydraulic cylinder and its parts

Hydraulic Seal:

Hydraulic seals are playing a significant role in the function of a hydraulic cylinder. So, one must know why seals are used and their types. Hydraulic seals are intended to prevent the fluid used by a machine from leaking to the external environment. Hydraulic seals’ role contributes to the prevention of environmental contamination, energy saving through improved machine operating efficiency, and machine safety.

There are two main types of hydraulic seals in the system, Static Seals and Dynamic Seals.


    They seal between components fixed together without relative motion or a seal not subjected to any movement when pressurized.

Examples: O-ring, Backup Ring, and Wiper seal.


     They seal between components in relative motion or a seal that is subjected to axial and/or radial movement when pressurized.

Examples: Rod seal, Piston seal, and Wear ring.

Hydraulic Cylinder Seal Types


Piston Seal:

    Piston seal acts as a barrier and prevents fluid from passing the piston – essential for controlling the cylinder motion or maintaining the position when at rest.

Rod Seal:

    Rod seal acts as a pressure barrier and keeps the operating fluid inside the cylinder. It regulates the fluid film, which extends with the surface of the piston rod – essential to inhibit rod corrosion and lubricate the wiper seal and rod seal itself. It accepts the lubrication film back into the cylinder when the rod retracts.

Buffer Seal:

Buffer seal will protect the rod seal from the fluid pressure peaks over system pressure and acts as an internal excluder to keep system contaminants such as metal particles, from damaging the rod seal.

Wiper Seal:

Wiper seal will exclude contaminants from entering the cylinder assembly and the hydraulic system. It accepts the lubrication film back into the cylinder when the rod retracts

Guide Ring (O-ring):

    The guide ring prevents metal-to-metal contact between components, and it will react to the radial load caused by side loads on the cylinder assembly. It keeps the piston rod and piston accurately centered in the cylinder assembly.