The UDI-Type Piston Rod Seal (Universal Directional Integral seal) is a compact, integrated sealing unit engineered for robust and efficient performance in standard to medium-duty hydraulic applications. It combines a primary sealing lip with a built-in anti-extrusion and stabilizing function in a single, directionally oriented component, designed for ease of installation and reliable, long-term service.
Asymmetric, Uni-Directional Lip: Features a single, precision-molded primary sealing lip optimized for the pressure direction (typically from the fluid side), ensuring maximum sealing efficiency and controlled fluid film.
Integrated Anti-Extrusion Heel: A reinforced, wider base section acts as a built-in anti-extrusion device, preventing seal deformation into the radial gap under pressure, eliminating the need for a separate backup ring in many applications.
Stabilizing Body Geometry: The seal body provides lateral support, helping to maintain alignment and reduce the risk of rolling or twisting in the gland.
Monolithic Construction: Manufactured as a single part from high-grade, wear-resistant polyurethane (e.g., AU/EU) or other advanced elastomers, ensuring material homogeneity and reliability.
Excellent Sealing & Leakage Control: Provides reliable, low-leakage sealing across a wide pressure range due to its optimized directional lip design.
Space-Saving Design: The integrated design reduces the number of components in the gland, simplifying assembly and allowing for more compact cylinder designs.
Enhanced Extrusion Resistance: The robust heel section provides superior resistance to extrusion, especially in applications with pressure spikes or large radial clearances.
Good Stability & Service Life: Offers stable performance with low friction and high resistance to wear and abrasion, leading to extended maintenance intervals.
Cost-Effective Solution: Combines multiple functions into one part, reducing overall sealing system cost and inventory complexity.
Pressure Range: 0 – 25 MPa (standard); up to 40 MPa with optimal gland design.
Temperature Range: -30°C to +100°C (dependent on compound).
Surface Speed: ≤ 0.5 m/s recommended for optimal balance of sealing and life.
Media Compatibility: Mineral-based hydraulic oils, HLP fluids, water-glycol (HFC), and some biodegradable oils.
Directionality: Unidirectional – Installation orientation relative to system pressure is critical.
Industrial Hydraulic Cylinders: Presses, machine tools, plastic injection molding machines.
Mobile Hydraulic Equipment: Agricultural machinery, material handlers, compact construction equipment.
General Machinery: Lifting platforms, industrial automation actuators, and standard hydraulic power units.
Applications where space is limited and a reliable, integrated sealing solution is preferred over multi-component stacks.
Direction is Critical: The seal must be installed with the primary sealing lip facing the pressurized fluid side of the system. The open side of the lip typically faces the pressure.
Gland Design: Requires a precision-machined gland with proper lead-in chamfers. The groove depth and width are specific to the UDI profile.
Rod & Piston Finish: A high-quality rod surface (hard-chromed, Ra ≤ 0.2 µm) is recommended for best performance and longevity.
Lubrication: The seal and gland should be lubricated with the system fluid during assembly.
Primarily designed for unidirectional pressure. Not suitable for applications requiring pressure from both sides unless specifically configured in pairs.
For extremely contaminated environments, a dedicated rod wiper/scraper should be used in addition to the UDI seal.
For applications with severe side loads, additional guide rings may be necessary.
Note: The UDI-type seal offers an excellent balance of performance, simplicity, and value for a wide range of hydraulic applications. Engineers should always consult the manufacturer’s detailed technical data sheet for specific dimensional tolerances, material compatibility, and performance graphs related to their operating conditions.
Original source: Hydraulic seal https://www.bszzseal.com/
