Piston seal and rod seal comparison
| Feature | Piston Seal | Rod Seal |
|---|---|---|
| Location | In the groove on the piston | In the gland area at the rod exit of the cylinder |
| Dynamic contact surface | Its outside diameter operates against the inner surface of the cylinder tube | Its inside diameter operates against the rod surface |
| Primary function | To limit fluid transfer between the two sides of the piston | To limit fluid leakage along the rod out of the cylinder |
| Related leakage type | Internal leakage between cylinder chambers | Externally visible leakage on the rod side |
| Key selection information | Piston and tube dimensions, pressure direction, single- or double-acting operation | Rod and gland groove dimensions, pressure direction, surface and oil film |
Where are they located in the cylinder?
The piston seal is located around the moving piston, while the rod seal is located in the stationary gland area where the rod exits the cylinder. The dynamic contact surface of the piston seal is the cylinder tube; the dynamic contact surface of the rod seal is the rod.
Why are their functions different?
Piston seal
A piston seal limits uncontrolled transfer of pressurised fluid from one side of the piston to the other. It plays an important role in limiting internal leakage while the cylinder holds its position under load. The cylinder’s single- or double-acting operation, pressure direction and profile design are considered during selection.
Rod seal
A rod seal limits fluid being carried out as the rod moves. In addition to sealing, the operating balance must allow a controlled oil film to remain on the surface. An excessively thick oil film may result in visible leakage, while an insufficient film may contribute to friction and wear.
The role of guiding elements and the wiper seal
Rod and piston seals should not be evaluated in isolation. Guiding elements carry side loads and help limit metal-to-metal contact and seal compression. The wiper seal helps reduce the ingress of contaminants into the system along the rod.
How can you tell whether it is a piston seal or a rod seal?
- If the product was removed from a groove on the piston, examine the piston seal group.
- If the product was removed from the stationary housing at the rod exit, examine the rod seal group.
- Determine which groove in the cylinder the product came from and which surface it contacts dynamically; this information helps identify the piston or rod seal group.
- State the pressure direction and whether the cylinder is single- or double-acting.
- Provide the rod, piston, tube and groove dimensions separately.
- Do not make a final product selection based only on appearance.
Frequently Asked Questions
Where is a piston seal located in the cylinder?
It is located on the piston, and its outside diameter makes dynamic contact with the inner surface of the cylinder tube.
Which surface does a rod seal contact?
It is located on the rod exit side, and its inside diameter makes dynamic contact with the rod surface.
Can a piston seal and rod seal be used interchangeably?
They are generally not directly interchangeable. Their functions, dynamic contact surfaces, pressure directions and profile designs are different.
What do single-acting and double-acting seals mean?
A single-acting seal is designed mainly for pressure from one direction, while a double-acting seal is designed for pressure from both directions. Final selection must be based on the cylinder’s operating mode and product data.
Related Products
K17 Piston Seal
View product →K35 Rod Seal
View product →K21 Piston-Rod Seal
View product →Related Technical Guides
Let us identify the function of your seal together.
Send a sample photograph, installation location and dimensions to our technical team.