FED-STD-791D
Method 3433
September 30, 1986
COMPATIBILITY OF SYNTHETIC AIRCRAFT
TURBINE LUBRICANTS WITH SILICONE RUBBER
1. SCOPE
1.1 This method is used for determining the compatibility of synthetic aircraft turbine
lubricants with a standard silicone rubber composition representative of commercial seal
materials. It determines the extent of deterioration of a silicone rubber standard by the
lubricating fluids.
1.2 Advanced synthetic lubricant fluids for aircraft turbine engines with modified
additive systems must be compatible with materials of construction used in aircraft engines
particularly with silicone rubber seals. This test was devised to reveal rubber seal-lubricating
fluid compatibility problem areas.
2. SUMMARY
2.1 This method provides a procedure for exposing silicone rubber test specimens to the
influence of synthetic lubricants under definite conditions of temperature and time for purpose of
measuring the resulting deterioration by noting the changes in physical properties before and
after immersion in the test liquid.
3. SAMPLE SIZE
3.1 Approximately 500 mL of the lubricant to be tested.
4. REFERENCES, STANDARDS, AND APPARATUS
4.1 References.
4.1.1 U.S. Air Force Specification bulletin 539, Standard Elastomer Stocks.
4.2 Apparatus
4.2.1 Oven, gravity convection, 121 1C (250 2F).
4.2.2 Beakers, tall-form, heat resistant, 600 mL.
4.2.3 Suspension device, glass, for holding test rubber specimens
4.2.4 Hook, stainless steel, for suspending test rubber sheets from balance.
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