Seals play an important role in hydraulic cylinders—they contain the fluid and prevent the leakage of fluid between components. They fall into two main categories: dynamic and static. Dynamic seals are used in between parts that are in relative motion. The seals for a rod sealing system protect the dynamic reciprocating motion for the piston rod and head. The dynamic reciprocating motion between the piston and cylinder bore is another area of a hydraulic cylinder that uses dynamic seals.
Static seals are used between fixed components. In a hydraulic cylinder, static seals are typically employed between the piston and the piston rod, and between the head and cylinder bore tube.
The following is a list of dynamic seals and the special function each has in relation to cylinder performance:
Piston seals
- They function as a pressure barrier.
- They prevent fluid from passing the piston and are essential for maintaining the position at rest and controlling the motion of the cylinder.
Rod seals
- They are a pressure barrier and maintain the operating fluid inside the cylinder.
- The rod seal regulates the fluid film, which extends with the surface of the piston rod. This is important to prevent rod corrosion, lubricate the wiper seal, and lubricate the rod seal itself.
- Rod seals also accept the lubrication film as it comes back to the cylinder upon retraction of the rod.