32.1 The initial concentration of the substance in oil, C, is determined using Eq 17 and the partition coefficients given in Table 6. For instance, the hydrogen peak gives an area of 4000 counts, which corresponds to 10 ppm in accordance with the calibration curve that has been plotted. This corresponds to the concentration of hydrogen in the gas phase, CG. The partition coefficient (K) of hydrogen at the equilibrium temperature is 0.074, VG = 5.61 mL and VL = 15 mL. Hence, in accordance with Eq 17:
NOTE 17 - In the previous example, it is assumed that the vial used is from a batch with an estimated average volume of 20.61 mL in accordance with the procedure in 30.1.
32.2 The total volume of gases in a given volume of oil, expressed as a percentage, is obtained by the sum of the individual gas concentrations expressed in parts per million. For instance, the concentrations obtained from Eq 20 for CO2, C2H2, C2H4, C2H6, C3H8, CH4, CO, H2, O2, and N2 are 7300, 94, 248, 27, 8, 19, 813, 21, 9636, and 42123 ppm, respectively. Hence, the total volume of gas:
33. Report
33.1 Report the following information:
33.1.1 Identification of oil sample,
33.1.2 Temperature of oil at time of sampling,
33.1.3 Volume concentration in the oil, for each component gas, expressed in parts per million at 0°C and 760 torr,
33.1.4 The total volume of gases in a given volume of oil expressed as a percentage,
33.1.5 The presence of sizable bubble, and
33.1.6 The test method, (for example, D 3612, Test Method C).
34. Precision and Bias
34.1 A round robin is planned to determine the precision and bias of this test method. An estimate of the repeatability of this test method was obtained from one laboratory by performing the measurement of twelve 15-mL aliquot portions of a sample collected from an open-breathing transformer. The results are given in Table 7. When the accuracy is estimated by one laboratory with dissolved-gas standards of different concentration levels (10, 50, 100, and 175 ppm) prepared in accordance with Annex A2 (no O2 and N2 added), the results show that it is possible to obtain an accuracy better than 10 % per constituent.
35. Keywords
35.1 capillary columns; combustible gases; dissolved gases; gases; headspace; insulating oil; oil; transformer oil