REFRIGERATION LUBRICANTS
REFRIGERATION
TERMINOLOGY
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ANILINE
POINT F
Is
the minimum temperature at which aniline (aromatic dye) and
oil sample are completely soluble. The test apparatus heats
aniline and sample until miscible, then cools until liquids
separate. Temperature at separation is aniline point.
Low
aniline points were once considered to indicate tendency of
oil to swell rubber seals. High aniline points were once considered
to indicate tendency of oil not to soften or swell seals. Much
controversy associated with significance of aniline point.
AROMATICS
%
Aromatics
are the unstable portions of the oil. Napthenic oils have higher
percentages of aromatics than paraffinic oils. A food grade
white oil has 0% aromatics. Percentages of aromatics present
is associated with Aniline Point.
COLOR
"L
1.0" means less than one. Numbers are determined by comparison
with a color chart. A value of "5" would indicate
a very dark oil.
CONRADSON
CARBON %
Measure
of coke remaining after oil is evaporated and partly burned
at atmospheric pressure. Useful in selecting lubricant for
refrigeration compressors.
COPPER
STRIP
Polished
copper strip exposed to oil at 50 C (122 F) for three (3) hours.
Low numbers best. Test important because of importance of copper
in refrigeration systems.
DIELECTRIC
STRENGTH KV
A
measure of the electrical insulating properties of petroleum
oils. Test has value in determining dryness of oils. Values
above 25 KV are considered satisfactory.
FIRE
COC, F
Above
test is continued to higher temperature where oil continues
to burn in cup when flame is removed.
FLASH
COC, F
Measured
tendency of oil to give off flammable vapors when heated. COC
(Cleveland Open Cup). Oil is heated in cup of tester. Small
flame dipped in cup causes "flash" but burning does
not persist.
FLOC
POINT F
A
mixture of oil and refrigerant is chilled and observed at 1
F intervals until a distinctly flocculent material is observed.
This is the floc point.
GRAVITY
API
Measures
weight or density.
Specific
Gravity
INTERFACIAL
TENSION
Components
with lowest surface tension will concentrate in the surface
of the oil. As an oil oxidizes with the organic acids produced
are concentrated at the surface and lower the interfacial tension.
This test is sometimes used on place of total acid no. To indicate
deterioration of the oil. High numbers are good. A value of
15 would indicate the oil is no longer suitable.
POUNDS
PER GALLON
Weight
at 60 F.
POUR
POINT
Oil
is chilled. As oil cools container is removed at 5 F intervals
and tilted. Pour point is lowest temperature at which any movement
of the oil can be observed.
REFRACTIVE
INDEX
The
ratio of velocity of light in sample of oil to velocity of
light in a vacuum. Measurements are taken at 25 C. Refrigeration
oils should have values between 1.45 and 1.51.
SEALED
TUBE % - R-22
A
mixture of oil and R-12 and a steel catalyst is heated at 175
C. At the end of the test the amount of R-22 formed by reaction
of oil and R-12 is determined. The smaller the quantity, the
more stable the oil.
SPECIFIC
GRAVITY
Compares
density of oil with water, with both liquids at 60 F.
SULFUR
%
Sulfur
can occur naturally or come from additives. Excess amounts
can cause corrosion.
TOTAL
ACID NO.
Milligrams
of potassium hydroxide to neutralize gram of oil sample.
VISCOSITY
A
measure of resistance of oil to flow. SUS is the abbreviation
for Saybolt Universal Seconds. The numbers are seconds required
for 60ml of oil to flow through a short tube. Usually measured
at 0 F and 210 F.
VISCOSITY,
CS
"CS" (sometimes
cSt) is the abbreviation for CENTI-STROKES. This is a measure
of kinematic viscosity and measurements are taken in a capillary
viscometer. Kinematic viscosities are sometimes taken in 100
F and 210 F (37.8 C and 98.9 C) and some manufacturers use
40 C and 100 C (104 F and 212 F). Kinematic viscosities are
considered to be more accurate and results can be obtained
more rapidly.
VISCOSITY
INDEX
The
rate at which the viscosity of an oil increases as it is chilled,
and decreases as it is heated. When the index was established,
an index of "100" was the oil that changed the most.
VI is determined by measuring viscosity at 40 C and computing
from ASTM D-2270 formulate.
WATER
PPM
The
lower the better. Most refrigeration oils have a moisture well
below the specification when it leaves the refinery.
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