ASTM D6595 Method for Wear Metals and Contaminants in Used Lubricating Oils
ASTM D6595 Standard Test Method for Determination of Wear Metals and Contaminants in Used Lubricating Oils or Used Hydraulic Fluids by Rotating Disc Electrode Atomic Emission Spectrometry
14. Report
14.1 Report wear metals and contaminants in mg/kg and to one decimal place for concentrations below 10 mg/kg and in whole numbers for concentrations greater than 10 mg/kg. Report additive elements in mg/kg and in whole numbers up to three significant digits. One determination per used oil sample is the standard industry practice.
15. Precision and Bias
15.1 Precision - The precision of this test method was determined by statistical analysis of interlaboratory results obtained by following this method. A total of 16 laboratories participated in the Interlaboratory Study (ILS) of which 14 sent in data on 11 oil samples analyzed in duplicate. The 11 samples in the ILS were: two used automotive oils, one used turbine oil, one used gear oil, one used diesel oil, one hydraulic oil, one mixture of oil standards, one military oil, and three calibration standards. Two determinations were made on each used oil sample and considered separately. Data is available in a research report.
15.1.1 Repeatability - The difference between two test results, obtained by the same operator with the same apparatus under constant operating conditions on identical test material would, in the long run, in the normal and correct operation of the test method, exceed the values in Tables 2 and 3 only in one case in twenty.
15.1.2 Reproducibility - The difference between two single and independent results, obtained by different operators working in different laboratories on identical test materials, would in the long run, in the normal and correct operation of the test method, exceed the values in Tables 4 and 5 only in one case in twenty.
15.2 Bias - Bias was evaluated by analyzing three samples prepared from calibration standards at the 30 mg/kg, 50 mg/kg, and 100 mg/kg concentrations. The t-test concluded that the bias was insignificant for all elements with the exception of barium at 30 mg/kg concentration, nickel at the 50 mg/kg concentration, and titanium at the 100 mg/kg concentration. The calculated bias values are of lesser significance in used oil trending applications.
16. Keywords
16.1 additive elements; contaminant; disc electrode; emission spectrometry; lubricating oil; RDE; rotating disc electrode spectrometer; rod electrode; wear metal
