ASTM D3455 for compatibility of construction material with insulating oil
ASTM D3455 standard test methods for compatibility of construction material with electrical insulating oil of petroleum origin
4. Apparatus
4.1 Sample-Handling Apparatus:
4.1.1 Oven, forced-draft, adjustable to 100 +/- 1°C, and a drying oven, adjustable to 105 +/- 5°C.
4.1.2 Glass Containers, 1-L, fitted with glass or aluminum foil covers.
NOTE 1 - Other materials have been found to be suitable as covers.
4.2 Sample-Testing Apparatus:
4.2.1 Tensile Strength - As specified in appropriate test method.
4.2.2 Hardness - As specified in appropriate test method.
4.2.3 Dimensional Change - Micrometer and caliper.
4.2.4 Weight Change - Analytical balance.
5. Preparation of Test Specimen
5.1 Test specimen size shall be such that the ratio of surface area to oil volume is four times as large as the ratio encountered in normal use in electrical equipment unless there is some special reason for using a different ratio (Note 2). Some suggested ratios are as follows:
5.1.1 If the test specimen can be measured, no less than 52 cm2 are used with each 800 mL of oil.
5.1.2 If the test specimen is insoluble in oil and the surface area cannot be measured, the test specimen shall be used in the amount of 1 % by the weight of the oil.
5.1.3 If the material is soluble in the oil, the test specimen shall be used in the amount of 0.5 % by the weight of the oil.
5.1.4 Varnishes and materials used as dip coatings shall be cured on aluminum foil or paper known to be compatible with insulating oil. They should be tested at a ratio of 14 g or approximately 1300 cm2 of surface area per 800 mL of oil.
5.1.5 Core steel and core-steel coatings shall be tested at a ratio of 3100 cm2 for each 400 mL of oil, for transformer applications. A realistic core steel ratio for regulators is 5000 cm2 of surface area per each 400 mL of oil.
5.1.6 Gasket materials shall be tested at a ratio of 65 cm2 surface area per 800 mL of oil.
5.1.7 Wire enamels shall be tested at a ratio of 1300 cm2 of surface area per 800 mL of oil.
NOTE 2 - There are certain materials in electrical apparatus where the suggested ratios of material to oil are impractical; when this condition exists, the ratio shall be reported.
5.2 Caution must be taken in obtaining and preparing the test specimen to ensure that it is representative of the material as supplied by the manufacturer. Do not handle with fingers.
5.3 Pre-dry all solid materials for 16 h in an oven at 105 +/- 5°C. Use care when testing specimens which are comprised of paper or applied to paper to limit damage to the paper from drying in an air circulating oven. It is recommended that such components be dried and impregnated in a vacuum oven as outlined in Practice D2413, Section 9.1.1, to reduce the effects of oxygen on the paper.
5.4 Remove the test specimen from the oven and place in a 1-L jar with 800 mL of approved insulating oil (Note 3), meeting all the limits required for new oil. Bubble dry nitrogen through the oil for approximately 10 min, and place the cover on the jar.
NOTE 3 - An approved oil is one that meets the requirements of Specification D3487, or an oil specified by the material purchaser.
5.5 Prepare a reference oil specimen from 800 mL of the approved oil alone as a control for each group of specimens tested.
6. Conditioning
6.1 Place the covered glass jars in an oven at 100 +/- 1°C for 164 h.
6.2 Remove the jars from the oven and cool to room temperature.
