In industrial rotary sealing applications, the single-lip oil seal (single-lip radial shaft seal) serves as a core component for preventing fluid leakage and excluding contaminants under medium-speed, low-pressure conditions. Combining a chloroprene rubber (CR) sealing lip and a metal case, this design delivers a reliable, cost-effective sealing solution. This article comprehensively analyzes its structure, performance, and applications.
I. Structure: Metal Case and CR Lip Synergy
- 1.
Metal Case:
- •Function: Provides rigidity, ensuring dimensional stability during press-fitting and static sealing with housing bore (interference fit).
- •Material: Low-carbon steel (SPCC) or galvanized steel (stainless SUS304 for corrosive environments).
- •Design: L-shaped cross-section; knurled/serrated OD surface or bonded coating (rubber/epoxy) enhances anti-rotation.
- •Edge Rolling: Rolled lip edge anchors rubber, preventing peel-off under pressure.
- 2.
Single-Lip CR Seal Body:
- •Primary Lip: Forms dynamic sealing interface with shaft surface.
- •Interference: Lip ID < shaft diameter (0.2–0.6 mm typical).
- •Contact Width: Narrow sealing band (0.1–0.5 mm) balances sealing and friction.
- •Auxiliary Features:
- •Helical Ribs: Machined on air-side (atmospheric side) surface. Critical for pump-back effect—returns leaking oil to sump. Direction (left/right spiral) must match shaft rotation.
- •Garter Spring: Stainless steel spring (SUS304) in lip groove maintains radial force against shaft eccentricity, wear, or thermal relaxation.
- •Dust Lip (Optional): Secondary lip (no spring) blocks external contaminants (dust/water). Strongly recommended for construction/agricultural equipment.
- •Core Material: Chloroprene Rubber (CR):
- •Oil Resistance: Good resistance to mineral oils, lubricants, hydraulic fluids (better than NR; slightly inferior to NBR).
- •Weather/Ozone Resistance: Excellent (superior to most general elastomers).
- •Temperature Range: **–40°C to +120°C** (continuous); short-term to 150°C.
- •Flame Resistance: Self-extinguishing (chlorine content).
- •Water/Weak Chemical Resistance: Good.
- •Mechanical Properties: Strong tensile strength, abrasion, and tear resistance; moderate compression set.
II. Key Advantages & Applications
- 1.Cost-Effective: Simple tooling + low-cost materials enable mass production.
- 2.Reliable Sealing: Effective under ≤12 m/s shaft speed and ≤0.5 MPa pressure. Ideal for gearboxes, bearings.
- 3.Environmental Suitability: CR resists UV, ozone, oxidation—ideal for outdoor equipment near motors/transformers.
- 4.Contaminant Exclusion: Optional dust lip enhances protection.
- 5.Typical Applications:
- •Automotive: Transmissions, differentials, wheel hubs, steering gears, water pumps (low-temp).
- •Industrial: Gear reducers, pumps, blowers, conveyor rollers, electric motors, compressors.
- •Appliances: Washing machine bearings, power tools.
- •Heavy Equipment: Hydraulic cylinder rods, axle bearings (with dust lip).
III. Performance Limits
- 1.Max. Temperature: 120°C—Exceeding causes hardening/cracking.
- 2.Min. Temperature: **–40°C**—Higher than silicones/FKM.
- 3.Polar Fluid Weakness: Avoid ketones, esters, phosphate-ester hydraulic fluids, strong acids.
- 4.Swelling Risk: Inferior to NBR/HNBR in EP gear oils or synthetic fluids.
- 5.Pressure Limit: ≤0.5 MPa—Higher pressure distorts lip.
- 6.Speed Limit: ≤12 m/s—High speed increases friction/heat.
IV. Selection Criteria
- 1.Shaft/Housing Bore: Match dimensions per ISO/GB standards.
- 2.Media Compatibility: Confirm compatibility with oils/greases. Avoid fuels/polar solvents.
- 3.Temperature: Ensure peak ≤120°C; below –30°C risks brittleness.
- 4.Shaft Speed: Calculate speed v=60,000π×D×n m/s (D: mm, n: rpm).
- 5.Environment: Select dust lip version for dirty/wet conditions.
- 6.Installation Prep:
- •Shaft: Chamfer ≥15°×1 mm; hardened surface; roughness Ra 0.2–0.8 μm; hardness ≥30 HRC.
- •Bore: Tolerance H7/H8; chamfered edges; roughness ≤ Ra 3.2 μm.
- •Tools: Use sleeves/arbors—never hammer directly! Lubricate lip/shaft before fitting.
V. Installation & Maintenance
- 1.Pre-install Check: Inspect seal/shaft/bore; verify spring direction (left-hand spiral for CW rotation).
- 2.Lubrication: Apply system oil/grease to lip/shaft.
- 3.Press Direction: Apply force only to metal case back—never on rubber lip!
- 4.Mounting Speed: Press evenly at controlled speed.
- 5.Post-install Test: Hand-rotate shaft to confirm smooth operation.
- 6.Leak Monitoring: Minor initial weep is normal (oil film formation); persistent drips indicate failure.
VI. Failure Analysis
| Failure Mode |
Root Cause |
| External Leakage |
Lip wear/cracking, shaft damage, improper install, housing loose, overpressure |
| Lip Burn-Dry |
Excessive friction (misalignment, overspeed), reversed helical ribs |
| Lip Torn/Flipped |
Incorrect install, insufficient shaft chamfer, brutal mounting |
| Case Corrosion/Loosen |
Wet/corrosive environment, uncoated metal case |
| Rubber Swelling |
Media incompatibility, excessive heat (>120°C) |
Conclusion
The CR single-lip metal-cased oil seal is an economical standard for sealing mineral oils/greases in medium-speed applications (–40°C to +120°C). Its metal case ensures robust installation, CR lip balances sealing and environmental resistance, while the helical ribs provide active sealing. For dusty/wet environments, the dust-lip variant is essential. Always respect material/temperature boundaries—upgrade to HNBR/ACM/FKM for extreme temperatures, high speeds, or aggressive media. Precision installation and maintenance are critical for long-term reliability.
[DLSEALS kindly Reminder] Sealing issues? Turn to DLSEALS! As a sealing component manufacturer, we specialize in customizing sealing components, providing a full range of services from design, research and development, production, testing, and more. If you have more information you'd like to know, feel free to contact us directly. DLSEALS's product experts are dedicated to serving you!
