Semi-Solids
Table of Contents
Physical & Chemical Properties

Semi-solid contaminants are generally oxidation and/or thermal polymerization products, carbonaceous material, micro-organisms, or oil/ additive/water reaction products, and fragments of elastomers. In lubricated systems, these and other small particulates contribute to sludge, which collects and plugs pipes, pumps and orifices possibly leading to oil starvation. Dirty and discolored oil is a sign of the presence of these materials.

If there are oxidation products present, they can be measured by an increase in TAN, pentane-toluene insoluble's, IR spectrums, or the amount of filter residue. With the exception or IR and pentane-toluene insoluble's, these tests do not necessarily measure the actual lubricant degradation products, but rather the presence of a semi-solid material, and the evaluator makes a judgment on the source.

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