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!
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 RingsTypeLocationFeaturesO-ringStatic 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 pressureV-combo sealsHigh-pressure piston rod sealsMulti-layer stacking (3–5 segments); high pressure resistance (>70 MPa), anti-extrusionWiper sealOuter end of piston rodScrapes dust/oil from the rod surface; first barrier against contaminationGuide/wear ringBoth sides of pistonPrevents metal-to-metal contact; reduces friction and eccentric wear (keeps piston centered)III. Material Selection & ComparisonCommon materials must meet four criteria: oil resistance, pressure resistance, temperature resistance, wear resistance.MaterialPropertiesApplication ScenarioNitrile (NBR)Excellent oil resistance (mineral oil); cost-effective; temp: -30°C~120°CLow/medium-pressure jacks (O-rings/U-rings)Polyurethane (PU)Superior wear/extrusion resistance; high pressure tolerance; poor hydrolysis resistanceHigh-pressure piston seals (U/V-rings)Fluororubber (FKM)High-temp resistance (-20°C~200°C); chemical/fuel corrosion resistance; expensiveHigh-temp/special oil (e.g., aviation)PTFE (Teflon®)Ultra-low friction; chemical corrosion resistance; requires rubber elastomer supportGuide rings, high-speed sealsIV. 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 valvesVI. 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!
Post time: Aug-12-2025