ASTM D6786 Test Method for Particle Count in Mineral Insulating Oil
ASTM D6786 Standard Test Method for Particle Count in Mineral Insulating Oil Using Automatic Optical Particle Counters
12. Report
12.1 Report the average of the particle count runs as the cumulative number of particles per mL >4, >6, >10, >14, >21, >38, and >70 µm (c). The “(c)” after the size indicates that the particle counter was calibrated using ISO 11171. These particle sizes correspond approximately to >2, >5, >10, >15, >25, >50, and >100 µm for particle counters that were calibrated with the old ISO 4402 calibration standard. If only one particle count run is analyzed, report the results of the single run.
12.2 Optionally, also report the ISO solid contaminant code corresponding to the number of particles per mL >4, 6, and 14 µm (c), as prescribed in ISO 4406:1999.
13. Precision and Bias
13.1 The precision of this test method is based on an Interlaboratory Study of D6786 - Particle Count in Mineral Insulating Oil Using Automatic Optical Particle Counters - conducted in 2006-2007. Each of eleven laboratories tested four materials (in triplicate); covering seven particle size ranges to determine the intralaboratory and interlaboratory precision of D6786.
13.1.1 Repeatability - Two test results obtained within one laboratory shall be judged not equivalent if they differ by more than the "r" value for that material; "r" is the interval representing the critical difference between two test results for the same material, obtained by the same operator using the same equipment on the same day in the same laboratory.
13.1.2 Reproducibility - Two test results should be judged not equivalent if they differ by more than the "R" value for that material; "R" is the interval representing the difference between two test results for the same material, obtained by different operators using different equipment in different laboratories.
13.1.3 Any judgment in accordance with statements 13.1.1 or 13.1.2 would have an approximate 95 % probability of being correct.
13.1.4 Results from the Interlaboratory Study are summarized in Tables 1-4. Data for the larger particle sizes were omitted because the small number of particles present did not produce good statistical results.
13.2 Bias - At the time of the study, no certified reference material suitable for determining bias was analyzed; therefore no statement on bias can be made from this data.
14. Keywords
14.1 optical particle counter; particle count; particulate contamination