FED-STD-791D
4.4 Jacket. Glass or metal, water tight, of cylindrical form, flat bottom, about 12
cm in depth, with inside diameter 0.9 to 1.2 cm greater than the outside diameter of the
test jar.
4.5 Disk. Cork of felt, 0.6 cm in thickness of the same diameter as the inside of
the jacket.
4.6 Gasket. A ring gasket, about 0.5 cm in thickness, to fit snugly around the
outside of the test jar and loosely inside the jacket. The purpose of the ring gasket is to
prevent the test jar from touching the jacket.
4.7 Bath.
A cooling bath of a type suitable for obtaining the required
temperatures.
5. MATERIALS
5.1 CAUTION: SOME MATERIALS ARE TOXIC AND HAZARDOUS. The
chemical materials listed in this section must be handled carefully. Federal Test Method
10000, Material Handling Safety Precautions, is a reference which lists all toxic and
hazardous materials cited in FTMS 791. The synonyms, life hazard, flammability,
handling and storage precautions, emergency treatment and measures, and spill practices
of each chemical are explained.
5.2 Six reference oils. Information concerning the availability of the reference oil
may be obtained from USA Belvoir Research, Development, and Engineering Center,
ATTN: STRBE-VF, Ft. Belvoir, VA 22060-5606.
6. PROCEDURE
6.1 Shake oil sample well and pour into six sample jars to 3.2 cm mark and one
sample jar to the 7.5 cm mark. Add a reference oil to each of the six sample jars to the
7.5 cm mark.
6.2 Mix the oil thoroughly and heat to 46C in a water bath.
6.3 After the oils reach room temperature, observe and record the color and
evidence of separation.
6.4 Determine and record the pour point of each oil.
a. Maintain the temperature of the cooling bath at -1 to 2C. Support the jacket,
containing the test jar, firmly in a vertical position in the cooling bath so that not
more than 2.5 cm of the jacket projects out of the cooling medium.
b. Starting at a temperature 12C above the expected pour point remove the test jar
from the jacket carefully and tilt it just enough to ascertain whether there is a
movement of the oil in the test jar. Take a test thermometer reading when the
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