FED-STD-791D
6.3.13 Remove the oil sample and steel specimen by carefully breaking the test cell.
This may be accomplished by scribing a mark around the test cell near the top and applying a hot
wire to the scratch mark. (See Note 5).
6.3.14 Remove the steel specimen with forceps, wash with a stream of toluene from a
wash bottle to remove oil then dip in two successive warm toluene washes and a final dip in
warm acetone. Wipe with lint-free tissue and air dry. Weigh to the nearest 0.1 mg. Using a 20X
microscope, carefully examine each steel specimen and note any evidence of pitting or etching
either above or below the liquid level.
6.3.15 Inspect the tube for insolubles and gum deposits.
6.3.16 Determine the viscosity at 37.8C (100F) of both the original lubricant and the
lubricant after exposure to heat in accordance with ASTM D 445.
6.3.17 Determine the neutralization number on both the original and heated lubricant in
accordance with ASTM D 664.
7. CALCULATIONS
7.1
-
Percent viscosity change = V 2 V 1 * 100
V1
where:
V1 - viscosity, Initial
V2 - viscosity after test
7.2 Total Acid Number change = N 2 - N 1
where:
N1 - Total Acid Number, Initial
N2 - Total Acid Number after test
B-A
Change in weight of the steel specimen in mg/ cm2 =
7.3
12.96
where:
B - Metal weight before test in mg
A - Metal weight after test in mg
8. REPORTING
8.1 The report shall include the following:
147
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