Chemical Analysis of Commercial Lubricating Oils Used in Mining Equipment in Plateau State

Lubricating oils used in heavy mining equipment in Plateau State, North Central Nigeria, are subject to degradation through oxidation, thermal breakdown, and contamination with metal wear particles during service, and their timely replacement is critical for equipment reliability and contamination prevention. This study applied chemical analysis to characterise the condition of used lubricating oil samples collected from tin mining equipment in Plateau State, comparing used oil properties against new oil baselines and established change-out criteria. Forty used oil samples from hydraulic systems, diesel engines, and gearboxes were collected at defined service intervals. Chemical tests performed included kinematic viscosity at 40 and 100 degrees Celsius, viscosity index, total acid number, total base number, oxidation and nitration by infrared spectroscopy, water content by Karl Fischer titration, and elemental analysis for wear metals and contaminants by inductively coupled plasma spectroscopy. Viscosity degradation exceeding 25 percent of new oil values was recorded in twelve engine oil samples, indicating lubricant breakdown requiring immediate change. Total acid number increases above 2 mg KOH/g were observed in 35 percent of hydraulic oil samples. Iron and lead wear metal concentrations indicated abnormal bearing wear in six equipment units. Water contamination above 0.2 percent was found in five gearbox samples, consistent with seal failure. These results validate the application of used oil analysis as a predictive maintenance and environmental management tool for mining operations and recommend routine oil analysis programmes for all mining operators in Plateau State.

Keywords: used oil analysis, lubricating oil degradation, wear metals, mining equipment, Plateau State