STP214

    The Evaluation of a Direct Emission Spectrographic Method for the Analysis of Used Lubricating Oils

    Published: Jan 1957


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    Abstract

    The metals in a used lubricating oil may occur as additives which have been put into the oil to give it certain desired properties, as the products of wear between moving parts, and as contaminants. The determination of these metals is of interest for a number of reasons. Calcium barium, zinc, phosphorus, and potassium are among the additive elements commonly encountered, and a knowledge of their concentrations will frequently give information about the depletion rate of the additive and, in some cases, of a change in the brand of make up oil. Silicon is usually associated with dust and may be indicative of poor air filtration, while the presence of boron and chromium, which are often used in the cooling water as inhibitors, may mean coolant leakage. Iron, lead, copper, tin, cadmium, aluminum, chromium, nickel, and silver are components of the engine and its bearings; their presence is an indication of engine wear. Sometimes the appearance of a specific element can pin-point the area of wear. For example one manufacturer uses silver only in the wrist-pin bushings, and the appearance of silver in the oil uniquely indicates difficulty in this location. Lead, copper and tin may also mean bearing trouble. Some manufacturers, however, employ lead flashing on many of their new parts, and in these engines the level of lead in the lubricating oil means very little. The emission spectrograph is an ideal instrument for detecting these metals because of its high sensitivity and its ability to determine a large number of elements simultaneously. Procedures in which the oil sample is ashed prior to analysis are often lengthy, and this paper will concern itself primarily with methods in which the oil is sparked directly. The first direct excitation technique to achieve prominence was the quenched electrode procedure of Calkins and White (1). This method was extensively studied by a Subcommittee on Emission Spectroscopy of the American Petroleum Inst. (API) (2). A number of petroleum laboratories participated in a cooperative project, and while it was found that this method was applicable to new oils of known base stock and additive type, it was discovered that it could not be applied successfully to used oils or to oils of unknown base stock and additive type.


    Author Information:

    Perkins, W. D.
    Research Chemists, Shell Oil Co., Martinez, Calif.

    Miller, J. R.
    Research Chemist, Shell Oil Co., Wood River, Ill.

    Moser, J. H.
    Research Chemists, Shell Oil Co., Martinez, Calif.


    Paper ID: STP46907S

    Committee/Subcommittee: D02.04

    DOI: 10.1520/STP46907S


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