ASTM D2225 Test Methods for Silicone Fluids Used for Electrical Insulation
PHYSICAL METHODS
6. Color
6.1 Significance - The chief significance of color as applied to silicone fluid lies in the fact that if the fluid is colored, some degree of contamination exists that may affect the physical, chemical, and electrical properties of the fluid.
6.2 Procedure - Determine the color in accordance with Test Method D2129.
7. Flash and Fire Points
7.1 Significance - The flash and fire points of a silicone insulating fluid indicates the limit to which the material may be heated, under the specified test conditions, before the emitted vapors form a flammable mixture in air. Unusually low flash or fire points for a given product may indicate contamination.
7.2 Procedure - Determine the flash and fire points in accordance with Test Method D92.
8. Polychlorinated Biphenyl Content
8.1 Scope:
8.1.1 Test Method D4059 - describes a quantitative technique for determining the concentration of polychlorinated biphenyls (PCB's) in electrical insulating liquids.
8.2 Definition:
8.2.1 PCB concentration - is normally expressed in units of parts per million (PPM) on a weight by weight basis. Standard chromatograms of Aroclors 1242, 1254, and 1260 are used to determine the concentration of PCB in the sample.
8.3 Summary of Test Method - Following dilution of the sample in a suitable solvent, the solution is treated to remove interfering substances. A small portion is then injected into a packed gas chromatographic column where the components are separated and their presence measured by an electron capture or halogen-specific electrolytic conductivity detection. The method is made quantitative by comparing the response of a sample to that of a known quantity of one or more standard Aroclors obtained under the same conditions.
8.4 Significance and Use - United States regulations require that electrical apparatus and electrical insulating fluids containing PCB be handled and disposed of through the use of specific procedures as determined by the PCB content of the fluid. The results of this test method can be useful in selecting appropriate handling and disposal procedures.
9. Pour Point
9.1 Significance - The pour point is important as an index of the lowest temperature to which the material may be cooled without seriously limiting the degree of circulation of the fluid.
9.2 Procedure - Determine the pour point in accordance with Test Method D97.
10. Refractive Index
10.1 Significance - The refractive index is often useful for the detection of some types of contamination and for the identification of the molecular makeup of the various types of silicone insulating fluids.
10.2 Procedure - Determine the refractive index in accordance with Test Methods D1807.
11. Specific Gravity
11.1 Significance - Silicone insulating fluids are usually sold on a weight basis. The values for the specific gravities must frequently be known to calculate the volume of fluid present at any given temperature.
11.2 Procedure - Determine the specific gravity in accordance with Test Methods D1481 or D4052 and Practice D1298.
12. Volatility
12.1 Significance - High values may indicate contamination of the silicone with other organic materials, inadequate removal of volatile components, or contamination with a depolymerization catalyst.
12.2 Procedure - Determine volatility in accordance with Test Method D4559.
13. Viscosity
13.1 Significance - The viscosity of a silicone fluid is important during the process of impregnation.
13.1.1 At operating temperatures the viscosity of a silicone fluid is a principal factor affecting heat transfer by convection flow of the fluid.
13.2 Procedure - Determine the viscosity in accordance with Test Method D445. The kinematic viscosity may be converted to absolute viscosity in accordance with Test Method D2161.
