Understanding Hydraulic Seals
Hydraulic seals are components designed to contain pressurized fluid, prevent leakage, and help protect hydraulic equipment from contamination. They are used in hydraulic cylinders, construction machinery, manufacturing equipment, and many other industrial applications.
The right hydraulic seal depends on the equipment design, operating pressure, temperature, fluid compatibility, movement, and dimensions of the sealing area. EPM supplies standard and custom hydraulic sealing products for a variety of needs.
Common Types of Hydraulic Seals
Different seals perform different functions within a hydraulic system. Understanding their purpose can help you identify the right type of component for your application.
Rod Seals
Rod seals help prevent hydraulic fluid from leaking along the cylinder rod as it moves in and out of the cylinder.
Piston Seals
Piston seals help maintain pressure between the piston and cylinder bore, supporting the operation of hydraulic cylinders.
Rod Wipers
Rod wipers remove dirt and other contaminants from the rod surface as it retracts, helping protect the internal components of the hydraulic system.
Guide and Wear Rings
Guide and wear rings help guide the piston or rod, reduce metal-to-metal contact, and manage side loads within a hydraulic cylinder.
O-Rings
O-rings are ring-shaped seals used in static and certain dynamic applications to help prevent fluid leakage. Their suitability depends on the application and material.
Backup Rings
Backup rings support O-rings in applications where pressure could force the O-ring into a clearance gap. They help reduce the risk of seal extrusion.
How to Choose the Right Hydraulic Seal
Selecting a hydraulic seal involves more than matching its dimensions. The seal must also be suitable for the equipment and its operating environment.
When identifying a hydraulic seal, consider the following:
- Dimensions: The shaft or rod diameter, bore diameter, groove dimensions, and available installation space.
- Operating pressure: The system pressure and any pressure fluctuations during operation.
- Temperature: The normal operating temperature and any temperature extremes.
- Fluid compatibility: The hydraulic fluid or other substances that contact the seal.
- Movement: Whether the application involves reciprocating, rotating, or stationary sealing.
- Material: The seal material's compatibility with the operating conditions.
If you do not know all these specifications, an existing part, part number, photograph, or equipment model may help EPM determine what information is needed.
Standard vs. Custom Hydraulic Seals
Standard hydraulic seals are often suitable when an existing product matches the application's dimensions and operating requirements. Custom seals may be worth considering when a standard component is unavailable or does not meet the required specifications.
EPM offers standard and custom sealing solutions. For custom requirements, provide available drawings, measurements, a sample part, and information about the equipment and operating conditions.
Learn more about EPM's reverse engineering service or explore the Sealing Gallery for examples of sealing products.
Frequently Asked Questions About Hydraulic Seals
What does a hydraulic seal do?
A hydraulic seal helps contain pressurized fluid, prevent leakage, and maintain separation between components in hydraulic equipment. Different seal types perform different functions, including sealing moving rods and pistons and excluding contaminants.
What is the difference between a rod seal and a piston seal?
A rod seal prevents fluid from leaking where the piston rod exits the cylinder. A piston seal forms a seal between the piston and the cylinder bore. Both are important to hydraulic cylinder performance, but they seal different interfaces.
What materials are used for hydraulic seals?
Hydraulic seals can be made from materials such as polyurethane, nitrile rubber, fluorocarbon rubber, PTFE, and other engineered materials. The appropriate material depends on factors including fluid compatibility, pressure, temperature, friction, and wear.
How do I identify a replacement hydraulic seal?
Start with the original part number, equipment manufacturer and model, and seal dimensions. Photographs, drawings, or a physical sample can also help with identification. If the specifications are unknown, contact EPM for assistance.
Can hydraulic seals be custom manufactured?
Custom hydraulic seals may be available when standard products do not meet an application's requirements. EPM offers custom sealing solutions and reverse engineering services. Contact the team with your specifications or sample part to discuss your needs.
When should a hydraulic seal be replaced?
Signs that a seal may need inspection or replacement include fluid leakage, visible damage, abnormal wear, or loss of system performance. The cause should be assessed before selecting a replacement, since incorrect installation, contamination, and unsuitable operating conditions can contribute to seal failure.
Need Help Finding a Hydraulic Seal?
EPM can help you explore standard and custom sealing options for your application. Have your part number, dimensions, equipment details, or a photograph ready if available.
U.S. Toll-Free: 800-659-5050
Local & International: 770-389-0501
Edited 10/13/2026
