![]() A black sticky paste with a well-defined (sharp edge) periphery is cause for serious concern. A dark or brownish stain in the center of the spot could be due to disrupted dispersancy and soot coagulation, a common consequence of glycol contamination. When a drop of lubricant contaminated with glycol is placed on the chromatographic paper, the soot particles can be agglomerated due to dispersant depletion and will not travel. Glycol contamination can also form destructive “ oil balls” and additive precipitation when thermally aged in crankcase lubricants. Coolant contamination forms acids in crankcase oil affecting soot dispersancy, even at low soot loading. When the oil drop is deposited on the chromatographic paper, soot particles will travel easily and the chromatogram will show a translucent gray color (Figure 2).Īureole formation (incorrect injection condition)ĭetecting glycol using the blotter spot test can be difficult because of the coolant’s effects on a lubricant’s dispersancy. If the additives are doing their job, soot particles will be small and finely suspended in the lubricant. When the oil drop is deposited on the chromatographic paper, the larger particles will not travel with the base oil and will form a black spot from the point of deposition. Once this occurs, the oil’s viscosity increases. The technician compares the chromatogram with the respective standard and reports the condition in the data sheet.Įxcessive soot contamination or extended drain intervals cause the dispersant additives to deplete and the soot particles to agglomerate, forming larger particles. It also reduces variability in intensity and color. The white light provides uniform light, which is important during interpretation. Send oil sample to laboratory for exception testing if necessary.Īfter six hours of developing, the chromatogram is placed on a box light and examined for soot and coolant (glycol) (Figure 1). Inspect chromatogram with UV light for fuel dilution.Ĭompare chromatogram with standard comparator. ![]() ![]() ![]() Let chromatogram develop an additional 18 hours (for a total of 24 hours) before analyzing for fuel dilution. Let chromatogram develop for six hours (soot and glycol).Ĭompare chromatograms with standard comparator. Place one drop of oil on the mark of chromatographic paper.ĭeposit excess oil from the sampler into the waste oil container. Shake sample vigorously by hand for one minute. In both cases, consistency must be maintained to ensure that data from each sample can be compared.Įach sample was prepared and analyzed according to the following procedure and schedule: The blotter spot test is a two-step process, namely sample preparation and sample analysis. ![]()
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