Sealing Rings: The Lifeline and Safety Guardian of Hydraulic Jacks

Jack seal

Sealing rings are the core components of hydraulic jacks, directly determining their sealing performance, pressure-bearing capacity, and service life. Below is a detailed breakdown of key knowledge about sealing rings:

I. Core Functions of Sealing Rings

1.Prevent Hydraulic Oil Leakage
• Ensure hydraulic oil does not leak from the sealed oil circuit, maintaining stable pressure (basis of Pascal’s Law).
2.Block External Contaminants
• Prevent dust, moisture, etc., from entering the hydraulic system, avoiding oil contamination and part wear.
3.Reduce Friction Loss
• Some seals (e.g., guide rings) minimize hard friction between metal parts, extending piston/cylinder life.

II. Types & Locations of Sealing Rings

Type	Location	Features
O-ring	Static seals (end caps, valve block interfaces)	Low cost, high elasticity; fills gaps via compression (seals tighter under high pressure)
U-ring (lip seal)	Dynamic seals (piston, piston rod)	Lip structure automatically tightens against the cylinder wall under pressure; low friction at low pressure, enhanced sealing at high pressure
V-combo seals	High-pressure piston rod seals	Multi-layer stacking (3–5 segments); high pressure resistance (>70 MPa), anti-extrusion
Wiper seal	Outer end of piston rod	Scrapes dust/oil from the rod surface; first barrier against contamination
Guide/wear ring	Both sides of piston	Prevents metal-to-metal contact; reduces friction and eccentric wear (keeps piston centered)

III. Material Selection & Comparison

Common materials must meet four criteria: oil resistance, pressure resistance, temperature resistance, wear resistance.

Material	Properties	Application Scenario
Nitrile (NBR)	Excellent oil resistance (mineral oil); cost-effective; temp: -30°C~120°C	Low/medium-pressure jacks (O-rings/U-rings)
Polyurethane (PU)	Superior wear/extrusion resistance; high pressure tolerance; poor hydrolysis resistance	High-pressure piston seals (U/V-rings)
Fluororubber (FKM)	High-temp resistance (-20°C~200°C); chemical/fuel corrosion resistance; expensive	High-temp/special oil (e.g., aviation)
PTFE (Teflon®)	Ultra-low friction; chemical corrosion resistance; requires rubber elastomer support	Guide rings, high-speed seals

IV. Common Causes of Seal Failure

1.Aging/Cracking
• Long-term exposure to heat/ozone hardens rubber, losing elasticity (NBR degrades rapidly >120°C).
2.Extrusion Damage
• Overpressure or excessive gaps force seals into metal crevices (high-pressure applications require anti-extrusion rings).
3.Wear/Scratches
• Oil contamination, piston rod rust, or scoring (scratches >5µm can breach seals).
4.Improper Installation
• Overstretching causes permanent deformation; burrs in seal grooves damage lips.

V. Maintenance & Replacement Guidelines

1.Regular Inspection
• Check for oil leaks (oil droplets on the rod = main seal failure); weak lifting may indicate internal leakage (piston seal damage).
2.Cleaning & Protection
• Retract the piston rod after use; release pressure during storage.
3.Professional Replacement
• Replace seals in sets matching OEM size/material; use dedicated tools (avoid forceful squeezing).
4.Lubrication Requirements
• Apply hydraulic oil to seals during assembly (dry friction burns lips).

⚠️ Warning: Hydraulic oil leaks/seal failure may cause:
• Sudden load drops (Danger!)
• Insufficient system pressure (fails to lift)
• Contaminants jamming hydraulic valves

VI. Technological Trends

• Composite Seals: e.g., PTFE coating + rubber base (low friction + high elasticity)
• Smart Monitoring: Embedded sensors detect abnormal pressure/temperature in seals.
• Long-life Materials: Hydrogenated nitrile rubber (HNBR) with temperature resistance up to 150°C.

Though small, sealing rings are the "lifeline" of hydraulic jacks. Proper selection and maintenance significantly enhance reliability—especially in automotive repair and heavy machinery, where safety redundancy is paramount!

[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!

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Sealing Rings: The Lifeline and Safety Guardian of Hydraulic Jacks

​I. Core Functions of Sealing Rings​

​II. Types & Locations of Sealing Rings​

​III. Material Selection & Comparison​

​IV. Common Causes of Seal Failure​