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 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.
“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.
Measure of coke remaining after oil is evaporated and partly burned at atmospheric pressure. Useful in selecting lubricant for refrigeration compressors.
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.
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.
Above test is continued to higher temperature where oil continues to burn in cup when flame is removed.
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.
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.
Measures weight or density. Specific Gravity
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.
Weight at 60 F.
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.
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.
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.
Compares density of oil with water, with both liquids at 60 F.
Sulfur can occur naturally or come from additives. Excess amounts can cause corrosion.
Milligrams of potassium hydroxide to neutralize gram of oil sample.
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.
“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.
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.
The lower the better. Most refrigeration oils have a moisture well below the specification when it leaves the refinery.
