O-Ring Groove Design & Working Pressure Reference Guide｜Sizes, Compression & Material Selection
O-Rings are critical components for sealing applications in hydraulic, pneumatic, and fluid systems. To ensure proper sealing performance and service life, correct groove design and working pressure tolerance must be carefully considered. This guide summarizes standard O-ring sizes, groove dimensions, and maximum pressure ratings by material and hardness.
🔧 O-Ring Design Factors
Effective sealing depends on:
O-Ring size (Inner Diameter & Cross Section)
Groove dimensions (width, depth, and squeeze ratio)
Operating pressure (static or dynamic)
Material hardness (Shore A)
Chemical compatibility (fluid or gas type)
📐 Common O-Ring Sizes (AS568 Extract)
| AS568 # | ID (mm) | CS (mm) | Groove Width (mm) | Recommended Squeeze |
|---|---|---|---|---|
| 010 | 5.28 | 1.78 | 2.34 ~ 2.54 | 15–30% |
| 112 | 12.37 | 2.62 | 3.25 ~ 3.40 | 13–25% |
| 214 | 20.29 | 3.53 | 4.32 ~ 4.50 | 12–22% |
| 325 | 57.00 | 5.33 | 6.55 ~ 6.80 | 10–20% |
✅ Proper squeeze ensures sealing without overcompression.
💡 Max Working Pressure by Material & Hardness
| Material | Hardness (Shore A) | Max Pressure (No Backup Ring) | With Backup Ring |
|---|---|---|---|
| NBR | 70 | ≈ 5 MPa | Up to 20 MPa |
| EPDM | 70 | ≈ 4 MPa | Up to 15 MPa |
| FKM | 75 | ≈ 7 MPa | Up to 25 MPa |
| HNBR | 80 | ≈ 8 MPa | Up to 30 MPa |
👉 Use backup rings for pressures over 10 MPa or in dynamic motion.