TECHNICAL
O-Ring Engineering
🧮 Design Calculator 📐 Groove Design 🔍 Failure Analysis 🔧 Installation 🧪 Material Selection

O-Ring Size Calculator

Calculate groove dimensions, compression ratios, and design parameters for optimal O-ring performance. Professional engineering calculations with ±0.002" precision.

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Groove Dimension Calculator

Calculate optimal groove dimensions for static and dynamic O-ring applications based on AS568 standards.

Calculated Groove Dimensions

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Compression & Stretch Calculator

Calculate compression ratio, stretch percentage, and stress factors for optimal sealing performance.

Calculated Compression & Stretch

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Engineering Guidelines

Static Applications

  • Compression: 15-25%
  • Stretch: 1-5%
  • Fill Ratio: 70-85%
  • Surface Finish: 16-32 μin Ra

Dynamic Applications

  • Compression: 10-20%
  • Stretch: 2-8%
  • Fill Ratio: 65-80%
  • Surface Finish: 8-16 μin Ra

High Pressure

  • Compression: 20-30%
  • Back-up rings recommended >1500 PSI
  • Extrusion gap: 0.003-0.005"
  • Shore A durometer: 75-90

High Temperature

  • Reduced compression: 10-18%
  • FFKM materials recommended >400°F
  • Increased clearances for expansion
  • Consider thermal cycling effects
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O-Ring Failure Mode Engineering Calculations

Extrusion Failure Calculations

Maximum Gap Calculation Formula

G = 0.1 × P^0.5
G = Maximum gap (mm), P = System pressure (MPa)

Application Examples:

  • 10 MPa pressure → Maximum gap 0.32mm
  • 50 MPa pressure → Maximum gap 0.71mm
  • 100 MPa pressure → Maximum gap 1.0mm

Prevention Design Measures

When P > 15 MPa, back-up rings are mandatory. Recommended materials: PTFE (low temp) or PEEK (high temp), thickness = 0.6-0.8 × CS.

Compression Set Prediction

Arrhenius Lifetime Prediction Model

t = A × e^(E/RT)
t=Lifetime (hours), A=Frequency factor, E=Activation energy (J/mol), R=Gas constant, T=Absolute temperature (K)
NBR Material Parameters:
E = 65,000 J/mol
A = 1.2 × 10^8
FKM Material Parameters:
E = 85,000 J/mol
A = 2.8 × 10^9

Real-World Lifetime Prediction Examples

NBR 70A at 80°C Operating Conditions:
• 15% compression ratio: Expected lifetime 45,000 hours (5.1 years)
• 20% compression ratio: Expected lifetime 32,000 hours (3.7 years)
Every 5°C temperature increase reduces lifetime by 50%
💡 Engineering Recommendation: Apply 2-3x safety factor in actual design
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Professional Engineering Formula Library

Contact Stress Calculations

Hertz Contact Theory

σ = 0.418 × √(E × P × δ / R)

σ = Maximum contact stress (MPa)

E = Elastic modulus (NBR: 5-15MPa, FKM: 8-25MPa)

P = Contact pressure (MPa)

δ = Compression deformation (mm)

R = Contact radius (mm)

Safe Design: σ < 0.7 × Tensile Strength

Sealing Pressure Calculations

Minimum Sealing Pressure

P_seal = k × P_system + P_0

k = Safety factor (Static: 1.5, Dynamic: 2.0)

P_system = System working pressure

P_0 = Initial sealing pressure from pre-compression

P_0 Calculation:

P_0 = E × ε × (1-ν) / [(1+ν)(1-2ν)]

ε=Compression strain, ν=Poisson's ratio (rubber≈0.5)

Recommended Compression: 15-25% (Static), 8-15% (Dynamic)

Thermal Expansion Compensation

Thermal Expansion Coefficient Correction

ΔL = α × L × ΔT

Material Thermal Expansion Coefficients (×10⁻⁵/°C):

NBR: 15-18
FKM: 12-15
EPDM: 16-20
Silicone: 20-25

Groove Design Corrections:

Width allowance: +2% × ΔT/100°C

Depth allowance: +1.5% × ΔT/100°C

Critical: Consider differential expansion between material and groove

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