Introduction to O-RingsO-rings are elastic rubber sealing rings with a circular cross-section, and are one of the most commonly used sealing elements worldwide. Due to their simple structure, low cost, and reliable sealing performance, they are widely used in various static and dynamic sealing applications.
Core Characteristics
| Characteristic |
Description |
Advantages |
| Simple Structure |
Monolithic structure with no connecting parts |
Easy installation and high reliability |
| Reliable Sealing |
Self-sealing under pressure and medium action |
Zero leakage in static sealing |
| Wide Applicability |
Suitable for static, reciprocating, and rotary sealing |
One specification for multiple uses |
| Low Cost |
Molded production with high efficiency |
Significant cost advantage for large-scale applications |
| Diverse Sizes |
Inner diameters from a few millimeters to several meters available |
Meets various size requirements |
Material Selection
| Material Type |
Characteristics |
Suitable Media |
Temperature Range (°C) |
| Nitrile Rubber (NBR) |
Good oil resistance, excellent overall performance |
Petroleum-based oils, water |
-30~100 |
| Fluoroelastomer (FKM) |
High temperature and chemical resistance |
Acids, alkalis, solvents |
-20~200 |
| Silicone Rubber (VMQ) |
High and low temperature resistance, good elasticity |
Hot air, steam |
-60~200 |
| EPDM Rubber (EPDM) |
Good weather and ozone resistance |
Hot water, steam |
-40~120 |
| Polyurethane Rubber (PU) |
Wear resistance, high mechanical strength |
Hydraulic oil, lubricating oil |
-30~80 |
Performance Parameters Table
| Performance Indicator |
NBR |
FKM |
EPDM |
VMQ |
Test Standard |
| Hardness (Shore A) |
50~90 |
60~90 |
50~90 |
30~80 |
ASTM D2240 |
| Tensile Strength (MPa) |
10~25 |
10~20 |
10~15 |
4~10 |
ASTM D412 |
| Elongation (%) |
100~600 |
100~300 |
100~500 |
100~800 |
ASTM D412 |
| Compression Set (%) |
15~30 |
10~25 |
15~30 |
20~40 |
ASTM D395 |
Groove Design Key Points
1. Static Sealing Groove:
· Compression ratio: 15~25%
· Fill ratio: 65~85%
· Surface roughness: Ra ≤ 3.2 μm
2. Dynamic Sealing Groove:
· Compression ratio: 10~15%
· Fill ratio: 70~90%
· Surface hardness: HRC ≥ 35
3. Groove Size Standards:
· Follow AS 568A, ISO 3601, etc.
· Consider thermal expansion and swelling allowance
· Reserve installation chamfers
Selection Guide
1. Working Condition Analysis:
· Medium type and concentration
· Operating temperature and pressure
· Motion type and speed
2. Material Selection:
· Chemical compatibility first
· Match temperature range
· Consider cost factors
3. Size Determination:
· Select according to standard sizes
· Consider installation space
· Confirm compression amount
Installation Precautions
1. Pre-Installation Inspection:
· Confirm O-ring specifications
· Check for surface defects
· Clean sealing surfaces
2. Installation Tools:
· Use dedicated installation tools
· Avoid sharp tools
· Use guide sleeves
3. Lubrication Requirements:
· Apply compatible lubricant
· Avoid using mineral oil for silicone products
· Ensure lubricant is compatible with the medium
Application Fields
1. Hydraulics and Pneumatics: Hydraulic cylinders, pneumatic cylinders, valves
2. Automotive Industry: Engines, transmissions, braking systems
3. Mechanical Equipment: Pumps, compressors, reducers
4. Electronics and Electrical: Connectors, waterproof sealing
5. Medical Devices: Syringes, infusion equipment
Common Failure Modes
1. Installation Damage: Scratches, cuts
2. Compression Set: Elasticity failure
3. Chemical Corrosion: Swelling, aging
4. Extrusion Damage: Excessive pressure
5. Thermal Aging: Cracking, hardening
O-rings, as simple and effective sealing elements, can meet most sealing requirements through reasonable material selection, groove design, and correct installation. Their economy and reliability make them indispensable basic sealing components in mechanical equipment. Understanding the characteristics and application ranges of different materials is key to ensuring the sealing effectiveness of O-rings.
