7. Adjustment and Care of Electrodes and Test Cup
7.1 Daily Use - At the beginning of each day's testing examine the electrodes for scratches, pitting, and contamination. If pitting or scratches of the disk faces are found, examine the electrodes in accordance with 7.4 for the proper sharp edge and then polish in accordance with 7.5. For severe problems resurfacing may be required. The gap shall be reset in accordance with 7.2. Clean and prepare the cup in accordance with 7.3.
7.2 Electrode Spacing - The spacing of the electrodes during tests is 2.54mm(0.100in.). The adjustment is made with a standard round gage of 2.54mm(0.100in.) more or less 1.0% or 0.100 more or less 0.0005 in., or fat steel "go" and "no-go" gages having a thickness of 2.53mm and 2.55mm or 0.0995 and 0.1005 in., respectively. Recheck the spacing following any disturbance of the cup or electrodes and at operation in the beginning of each day's testing. Use the same gage size when conducting comparative tests.
7.3 Cleaning - Wipe the electrodes and the cup clean with dry, lint-free tissue paper or a clean dry chamois. It is important to avoid touching the electrodes or the cleaned gage with the fingers or with portions of the tissue paper or chamois that have been in contact with the hands. After adjustment of the gap spacing, the cup shall be rinsed with a dry solvent. A low-boiling solvent should not be used as its rapid evaporation may cool the cup, causing moisture condensation. If this occurs, the cup should be warmed slightly to evaporate any moisture before use. Take care to avoid touching the electrodes or the inside of the cup after cleaning. Flush the cup using part of the sample. Fill the cup with a specimen from a sample with a known breakdown voltage. Make a voltage breakdown test as specified in this test method. If the breakdown voltage is judged in the proper range for the sample with a known breakdown value, the test cup is prepared for testing other samples. If a value lower than expected is obtaied, flush or clean the cup as necessary until test results meet the expected value for the known sample.
7.4 Electrode Edge Verification - Using a 0.010-in. (0.254-mm equivalent), radius gage5 or an optical comparator, verify that the radius of the edge of the electrode, on the gap side,is less than 0.010in.(0.254mm), verify the face of the electrodes are at 90°more or less 1°to the side edge of the electrode. If the edge radius is no greater than the value specified and the sides are at 90°, the electrodes are satisfactory for continued use. Check the disk in at least four locations for each criteria. If the radius exceeds the tolerance or the edges are not at 90°, the electrodes shall be resurfaced to the specified values.
7.5 Polishing of Electrodes - When examination of electrodes shows minor scratching or pitting,the electrodes should be removed from the test cup and polished by buffing with jeweler's rouge using a soft cloth or soft buffing wheel. (Resurfacing may be necessary in order to remove deep pit marks or edge damage.)Care must be taken in resurfacing or in polishing to ensure that the electrode faces remain perpendicular to the axis and the edges' radius does not exceed the value specified in 7.4. All residue from the buffing must be removed before the electrodes are reinstalled in the test cup. This can be accomplished by repeated wiping with lint-free tissue paper saturated with a suitable solvent (such as petroleum ether), followed by solvent rinsing or ultrasonic cleaning. After the electrodes have been reinstalled in the test cup, clean and adjust spacing in accordance with 7.2 and 7.3.
7.6 Storage of Test Cup - When not in use, the cup, if used for referee tests, shall be stored filled with a new, dry, filtered liquid of the type being tested, and tightly covered.
