Elastomer compatibility in turbine engine oils
Oil manufacturers face the challenge of developing high thermal stability oils that do not damage elastomer materials in turbine engines, which can lead to leaks and high oil consumption. How can we assess the elastomer compatibility of high thermal stability oils?
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Key Takeaways
- Modern turbine oils need strong antioxidants for thermal stability, but these can sometimes affect elastomer seals.
- ASTO 560 and AeroShell Ascender maintain low elastomer swelling, even at high temperatures, to ensure reliable seal integrity.
- These optimised oils reduce maintenance, enhance safety and improve efficiency for demanding aviation applications.
In a race to meet the ever-increasing demand of modern day turbine engines with higher operating temperatures and higher pressures requirement, oil manufacturers have had to use an effective antioxidant system to develop a high thermal stability oil.
Why elastomer compatibility matters
Now here lies the problem for lubricant development chemists. Some antioxidants can provide excellent thermal stability and low coking propensity, but they can be aggressive to certain elastomer materials used in some engine oil systems. This can result in swelling or deterioration of rubber 鈥極鈥� rings, leading to leaks and high oil consumption. The trick is to find a balance with an additive system that provides excellent thermal stability, but is fully compatible with elastomer materials in the engine.
Elastomer compatibility testing
In an elastomer compatibility test in SAE AS5780, oils are tested for 24 and 120 hours at a temperature of 200藲C and tested for the percentage weight change. For the more aggressive testing of 120 hours, the below results showed that a competitor鈥檚 High Performance Capability (HPC) oil has about twice the swelling rate compared to ASTO 560 and AeroShell Ascender on Viton GLC seals.
| Fluorocarbon (Viton A), % swell change after 24 hours | Fluorocarbon (Viton A), % swell change after 120 hours | LCS Fluorocarbon (Viton GLC), % swell change after 24 hours | LCS Fluorocarbon (Viton GLC), % swell change after 120 hours | |
|---|---|---|---|---|
| SAE AS5780 HPC limit | 11% max | 15% max | 12% max | 20% max |
| Competitor鈥檚 HPC oil | 9.5 | 11.5 | 8 | 15 |
| AeroShell Ascender | 9 | 10 | 6.5 | 8 |
| AeroShell Ascender | 7.5 | 9 | 6 | 8 |
After eight days of embrittlement testing, the Viton A o-ring tested in the competitor鈥檚 HPC oil has developed cracks, indicating that it may not be able to maintain the required seal effectiveness:
AeroShell Ascender: Passed
Competitor鈥檚 HPC oil: Failed
AeroShell Turbine Oil 560: Sealing rings in excellent condition throughout, including this oil spray nozzle:
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