8. Sampling
8.1 Obtain a sample of the liquid to be tested in accordance with Test Method D923. Record on the label of the sample container identification of the device from which the sample was obtained, the date, and temperature of the sample at the time of collection. Prior to starting the test, the sample shall be inspected for the presence of moisture, sludge, metallic particles, or other foreign matter. If the sample shows evidence of free water, the dielectric breakdown test should be waived, and the sample shall be reported as unsatisfactory.
8.2 The dielectric breakdown voltage of liquids may be seriously impaired by the migration if impurities through the liquid. In order that a representative test specimen containing the impurities may be obtained, invert and swirl the sample container several times before filling the test cup. Rapid agitation is undesirable, since an excessive amount of air may be introduced into the liquid. Immediately after agitation, use a small portion of the sample to rinse the test cup. The cup shall then be filled slowly with the liquid to be tested in a manner that will avoid entrapment of air. It should be filled to a level not less than 20.3mm or 0.8in. above the top of the electrodes. In order to permit the escape of air, allow the liquid to stand in the cup for not less than 2min and not more than 3min before voltage is applied.
