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KR Seal PU NBR Combined Piston Seal For Hydraulic Cylinder
- Category： Piston seals
- Temperature: -35 - +110℃
- Material: PU, NBR
- Color: blue
- Application: hydraulic cylidner
- Product description：
KR Seal is a two-piece double-acting combined piston seal designed according to ISO7425-1 standard. It consists of a wear-resistant PU sliding ring and an elastic NBR energizer ring. The internal rubber ring provides continuous pre-tension, which automatically compensates for wear and ensures stable sealing performance during reciprocating movement.
5.0
design customization
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1. Description
KR seal is a two-piece double-acting piston combined seal, originally developed in accordance with ISO 7425-1 standard, widely used for hydraulic cylinder pistons.
It consists of a wear-resistant polyurethane sliding ring and an elastic preloading O-type back-up ring. The elastic ring continuously pushes the PU sliding ring against the cylinder bore to achieve reliable bidirectional sealing.
2.Structure
2-component assembly:
- Outer sliding ring: PU
- Inner elastic energizer: NBR
No separate anti-extrusion back-up ring required for normal working conditions.
Technical Parameters
- Maximum working pressure: ≤ 300 bar
- Max reciprocating speed: ≤ 0.5 m/s
- Working temperature: -35℃ ~ +110℃ (short-time peak: 125℃)
- Standard medium: Mineral-based hydraulic oils
- Sealing type: Double-acting (bidirectional piston sealing)
Features & Advantages
- Excellent dynamic and static sealing performance, low leakage
- Compact axial width, saves installation space on pistons
- Polyurethane sliding ring delivers outstanding wear resistance
- Automatic wear compensation via elastic energizer, long service life
- Integrated anti-extrusion design under standard clearance
- Easy assembly for one-piece piston design
Limitations
- Not suitable for high-speed reciprocating motion
- Standard NBR version is incompatible with high temperature and special hydraulic fluids
- Not recommended for working pressure over 300 bar
Typical Applications
- Light construction machinery hydraulic cylinders
- Agricultural machinery cylinders
- Vehicle steering cylinders
- Piston-type accumulators
- General industrial medium-pressure hydraulic cylinders
- Low-speed hydraulic equipment requiring strict leakage control
Size Marking Rule
Format: Outer Diameter × Inner Diameter × Groove Width (D × d × L)
Common groove width series: 3.2 / 4.2 / 6.3 / 8.1 / 10.5 mm
Optional Custom Materials
- FKM energizer: For high temperature & chemical resistant working conditions (-20℃ ~ 180℃)
- Polyether-based TPU sliding ring: Optimized low-temperature resistance
Installation & Machining Requirements
- Cylinder bore surface roughness: Ra ≤ 0.2~0.4 μm
- Groove side surface roughness: Ra ≤ 1.6 μm
- Groove corner radius R ≤ 0.3 mm; sharp edges are forbidden
- Chamfer lead-in is necessary during installation to avoid cracking the PU ring
Comparison: KR / OK / KDAS Seal
| Item | KR Seal | OK Seal | KDAS Seal |
|---|---|---|---|
| Structure | PU sliding ring + NBR energizer | POM sliding ring + NBR energizer | PU + NBR + double anti-extrusion rings |
| Max Pressure | 300 bar | 500 bar | 400~700 bar |
| Max Speed | 0.5 m/s | 1.0 m/s | 1.0 m/s |
| Main Usage | Compact low-speed medium-pressure cylinder | Heavy hydraulic system, higher pressure | Super high pressure, large clearance heavy machinery |
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