Proposal of Lubricant Maintenance by Monitoring Peroxide Value

Abstract

This preliminary study on the maintenance of industrial lubricants for chemical plant investigated appropriate maintenance through condition monitoring of the lubricants, in particular autoxidation of base oil as the major degradation process. Changes in chemical and physical properties caused by the autoxidation of hydrocarbons were considered in terms of reaction sequence. The roles of antioxidants for maintaining the quality of lubricants were also considered. The reaction mechanism suggested the importance of antioxidants in lubricants during service. Therefore, a new method to diagnose consumption of antioxidant was required. Organic peroxides are reactive species generated during the autoxidation of hydrocarbons at the initial stage and can be quantitatively analyzed by iodometric titration. The peroxide value (POV) is proposed as a new parameter to monitor conditions of lubricants. The POV trace was examined by a model oxidation test of lubricant in the laboratory. Subdivided addition of antioxidants to lubricant before an increase in POV was found to prolong the lifetime of the lubricants. POV in lubricants for compressors in chemical plant was monitored during the regular maintenance process for two years. Increased POV was observed during machine operation. Oil refill reduced the POV of the lubricant to some extent. Changes in total acid number (TAN) of lubricant were closely related to change in POV, whereas other parameters such as viscosity, insoluble contaminants and water contaminants seemed independent of the changes in POV. The utility of the POV trace depended on the conditions of machine operation, but provided early diagnostics of lubricant degradation in some cases.

Reducing Friction and Wear of Tribological Systems through Hybrid Tribofilm Consisting of Coating and Lubricants

“…However, change of properties in AW (anti-wear) additive is caused by oxidation. To prevent oxidation, addition of antioxidant is required [8]. What is worse is that too much AW additive causes more wear on steel surfaces than without any AW additives [9].…”