Lubricant and Seal Material Compatibility
Compatibility guidelines for lubricants with common seal and O-ring materials including NBR, FKM, EPDM, silicone, and PTFE elastomers.
Lubricant-seal compatibility is critical for preventing leakage and ensuring seal longevity. Incompatible lubricants cause seals to swell, shrink, harden, or soften, leading to failure.
Common Seal Materials
NBR (Nitrile, Buna-N)
- Most common industrial seal material
- Good with petroleum products
- Temperature range: -40°C to +100°C
- Incompatible with PAG and phosphate esters
FKM (Viton, Fluoroelastomer)
- Premium seal material for demanding applications
- Excellent high-temperature capability (-20°C to +200°C)
- Good chemical resistance
- Higher cost than NBR
EPDM (Ethylene Propylene)
- Excellent for water-based fluids
- Good for phosphate esters
- NOT compatible with petroleum products
- Temperature range: -50°C to +150°C
PTFE
- Widest chemical compatibility
- Very broad temperature range (-200°C to +260°C)
- Higher friction than elastomers
- May require energizer for sealing pressure
Evaluating Compatibility
When changing lubricants, consider:
- Volume change: Swelling >25% or shrinkage >5% typically problematic
- Hardness change: Softening indicates degradation
- Tensile strength: Should retain most of original strength
- Elongation: Excessive reduction indicates brittleness
Compatibility Testing
For critical applications:
- Immerse seal material sample in lubricant
- Hold at operating temperature for 72-168 hours
- Measure volume change, hardness change
- Compare to baseline and acceptance criteria
Special Considerations
Biodegradable Lubricants
Many biodegradable esters are aggressive toward NBR. FKM or HNBR seals may be required.
Food-Grade Lubricants
NSF H1 lubricants use restricted base stocks. Verify compatibility—don’t assume food-grade equals seal-safe.
High-Temperature Applications
Seal compatibility often decreases at elevated temperatures. Use temperature-specific compatibility data.
Compatible Combinations
| Seal Material | Compatible Lubricants | Application Notes |
|---|---|---|
| NBR (Nitrile) | Mineral oil, PAO, most greases | Most common industrial seal material |
| FKM (Viton) | Mineral oil, PAO, synthetic esters | High temperature, chemical resistance |
| EPDM | Water-based fluids, PAG, phosphate esters | Not for petroleum-based |
| PTFE | Nearly all lubricants | Widest chemical compatibility |
| Silicone | Mineral oil, PAO, some synthetics | Wide temperature range, limited load |
| HNBR | Mineral oil, PAO, biodegradable esters | Improved NBR for higher temps |
Incompatible Combinations
| Seal Material | Incompatible Lubricants | Effect | Risk |
|---|---|---|---|
| NBR (Nitrile) | PAG (polyalkylene glycol) | Swelling, softening | High |
| NBR (Nitrile) | Phosphate esters | Degradation | High |
| NBR (Nitrile) | Strong aromatics | Excessive swelling | High |
| EPDM | Mineral oil | Swelling, failure | High |
| EPDM | PAO | Swelling | High |
| EPDM | Most petroleum products | Degradation | High |
| FKM (Viton) | Ketones, amines | Chemical attack | High |
| Silicone | Concentrated acids/bases | Degradation | Moderate |
Notes
- - Always verify compatibility with specific elastomer compound—variations exist within material families
- - Temperature affects compatibility—marginal materials may fail at elevated temperatures
- - Minor swelling (5-15%) may be acceptable; excessive swelling causes failure
- - Shrinkage can cause leakage—equally problematic
- - Additive packages can affect compatibility independent of base oil
Sources
- Parker O-Ring Handbook
- SKF Sealing Solutions Catalog
- Freudenberg Sealing Technologies Material Guide
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