ASTM D7412 Standard Test Method for Condition Monitoring of Phosphate Antiwear Additives in In-Service Petroleum and Hydrocarbon Based Lubricants by Trend Analysis Using Fourier Transform Infrared (FT-IR) Spectrometry
10. Procedure
10.1 Collect a background spectrum according to the procedure specified in Practice D7418.
10.2 Differential Trend Analysis Only - Collect the absorption spectrum of a reference oil sample according to the procedure specified in Practice D7418.
10.3 Collect the absorption spectrum of an in-service oil sample according to the procedure specified in Practice D7418.
10.4 Data Processing - All data are normalized to a pathlength of 0.100 mm according to the procedure specified in Practice D7418.
11. Calculation
11.1 Calculation ofPhosphate Antiwear Value:
11.1.1 Procedure A (Direct Trend Analysis) - Phosphate antiwear value by the direct trending method is calculated from the oil sample spectrum using the measurement area and baseline points listed in Table 1. Fig. 1 illustrates the area used in the measurement of phosphate antiwear additives in the spectrum of diesel crankcase oil.
11.1.2 Procedure B (Differential Trend Analysis) - Phosphate antiwear value by the differential trending method is calculated from the differential spectrum using a minimum peak height and a two-point baseline (Table 1), giving negative values as the amount of phosphate antiwear additives in the in-service oil relative to that in the reference oil progressively decreases. Fig. 2 illustrates the band used in the measurement of phosphate antiwear additives in the differential spectrum of diesel crankcase oil.
11.2 Sample Carryover - To ensure the minimum amount of sample-to-sample cross-contamination or carryover, either a minimum volume of the subsequent sample or a solvent rinse is used to flush out the previous sample. The efficacy of the flushing protocol may be assessed by consecutively analyzing a used oil sample having a low phosphate antiwear level (L1) and an oil having a high phosphate antiwear level (H1) followed by a second run of the oil sample having a low phosphate antiwear level (L2) and then calculating the percent carryover (PC) as follows. The calculated PC should be <5 %.
PC = [(L2 - L1)/H1] x 100
where:
L1, H1, and L2 = the values measured for phosphate antiwear additives (using the parameters given in Table 1) for the samples run in the indicated sequence.
