FED-STD-791D
Method 350.2
September 30, 1986
EVAPORATION LOSS OF LUBRICATING GREASES AND OILS (HIGH TEMPERATURE)
1. SCOPE
1.1 This method describes the test procedure and apparatus for the determination of
evaporation loss of lubricating greases and oils for applications where evaporation loss is a
factor. Evaporation loss data can be obtained at any temperature in the range 99 to 538C (210
to 1,000F).
2. SUMMARY
2.1 The method consists of heating the oils or greases in containers vented with 2 L/min
of air in order to determine the percentage evaporation loss of the lubricant.
3. SAMPLE SIZE
3.1 Approximately 20 g of the grease or oil to be tested.
4. REFERENCES, STANDARDS, AND APPARATUS
4.1 Evaporation cell and attachments conforming with the dimensional tolerances
indicated in Figures 6 and 7. Other structural details are given below.
4.1.1 The body and cover of the cell shall be constructed of stainless steel and air-heating
coil also of stainless steel.
4.1.2 The sample cups (recommended maximum weight 200 g each), hood, eduction
tube, and orifice shall be constructed of stainless steel. A suitable material is an alloy steel
conforming to grade S, type 304, of ASTM A204. To facilitate removal and separation of the
cup and hood for inserting the sample and weighing, The sample cup shall be threaded to the
hood and this in turn to the eduction tube of the cover. The cover of the cell shall be made air-
tight.
4.2. Air supply system, capable of supplying to the cell the required flow of air free of
mechanically entrained particles. A 61.0-cm (24-in) length of 12.7-cm (5-in) diameter pipe,
reduced to 2.54-cm (1-in) diameter at each end, packed with glass wool at each end, and filled
with a suitable drying agent has been found satisfactory for filtering and drying. Means must be
provided for filling the drying and filtering tube.
4.3 Heating blocks of cast aluminum with evaporation cells and air coils cast within.
The heating block shall be heavily insulated and equipped with sufficient electric heating
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