What is a rubber U-shaped seal ring?

The rubber U-shaped seal ring is a sealing element with a unique structure and excellent performance, which is widely used in reciprocating motion sealing scenarios in the industrial field. The following is an analysis from four dimensions: core characteristics, technical parameters, classification and selection, and application advantages:

1. Core characteristics
Dynamic sealing performance
The initial seal is achieved by elastic pre-compression of the U-shaped lip. Under the action of pressure, the lip and the sealing surface fit tightly to form a self-enhanced seal.
The single lip form has no effect on heavy loads and piston rod bending. The double lip form forms a lubricating oil film in the sealing gap and can withstand sudden loads.
Pressure and temperature adaptability
Working pressure range: 0-40MPa (typical value), the maximum pressure limit is 35MPa, suitable for high-pressure environments.
Working temperature range: -30℃ to +120℃ (general type), fluororubber material can be extended to -30℃ to +110℃ (high temperature resistant type).
Material and structure
Basic materials: rubber (such as nitrile rubber NBR), polyurethane TPU, fluororubber FKM, etc.
Enhanced structure: The cloth-type U-shaped seal ring uses fiber cloth to enhance its anti-extrusion ability; the balanced design (double seals on the inner diameter and outer diameter) is equipped with a support ring to prevent flattening or distortion under high pressure.
2. Technical parameters
Key dimensions
Gap between the pressure ring and the lip: 1.6-3mm (at least 25% of the lip thickness), ensuring free entry of system fluid and realizing the self-tightening principle.
Transverse hole of the vertical web of the pressure ring: used for pressure balance to avoid local pressure deformation of the seal ring.
Motion performance
Reciprocating speed: ≤0.5m/s (typical value), suitable for low-speed to medium-speed reciprocating motion.
Friction resistance: The friction force is small in the low-pressure range, the movement is smooth, and the energy consumption is reduced.
3. Classification and selection
Classification by use
U-shaped ring for shaft: used for piston rod sealing to prevent hydraulic oil leakage.
U-shaped ring for hole: used for sealing the inner wall of the hydraulic cylinder to isolate the high-pressure and low-pressure chambers.
U-shaped ring for both hole and shaft: taking into account the sealing of the piston and piston rod to simplify installation.
Selection basis
Media type: Hydraulic oil, emulsion, etc. need to choose oil-resistant materials (such as NBR); high temperature or chemical corrosion environment needs to choose fluororubber FKM.
Pressure and temperature: Fluorine rubber materials are preferred in high-pressure environments (≥25MPa); high-temperature resistant rubber is required in high-temperature environments (≥100℃).
Movement speed: High-speed reciprocating motion (＞0.5m/s) requires polyurethane materials with stronger wear resistance.
IV. Application advantages
Easy installation
Integral structure, no complex adjustment is required, and installation can be completed by pressing directly into the sealing groove.
Easy to disassemble and replace, reducing maintenance costs.
Economical efficiency and reliability
Low manufacturing cost: simple structure, high efficiency of mass production.
Long service life: wear-resistant and corrosion-resistant materials extend the replacement cycle and reduce maintenance frequency.
Multi-scenario adaptability
Hydraulic system: piston and piston rod seals of hydraulic cylinders, hydraulic valves and other components.
Pneumatic system: dynamic seals of equipment such as cylinders and pneumatic valves.
Special working conditions: Sealing requirements in harsh environments such as high temperature, high pressure, chemical corrosion, etc. (such as fluororubber material).