Implementación y verificación del método ASTM D4052-22 para la determinación de densidad, relativa y gravedad API en aceites industriales en un laboratorio de planta de lubricantes

Abstract

Accurate density determination is fundamental in the lubricant industry for quality control, logistical operations, and regulatory compliance. Digital oscillating tube densimeters standardized by ASTM and ISO provide accurate and traceable results. However, international standardization does not automatically guarantee reliable results, as specific operational conditions require local experimental verification. This work verified the implementation of the ASTM D4052-22 method for determining density, relative density, and API gravity in industrial oils, evaluating precision, accuracy, and uncertainty according to ISO/IEC 17025:2017. The methodology included (i) experimental design with two analysts performing measurements on different days with replicates per material following ISO 5725-2, (ii) evaluation of seven materials (certified reference materials, Group II base oils, and formulated lubricants) in the range 0.859-0.881 g/cm³, (iii) statistical analysis using two-factor ANOVA, (iv) accuracy evaluation using t-test comparing with certified values, and (v) uncertainty estimation according to GUM methodology. The results demonstrated that the method operates 9-28 times below the ASTM repeatability limit (0.00016 g/cm³) and meets intermediate precision criteria. Biases were statistically significant but within acceptable limits (±0.0006 g/cm³). The analysis revealed that bias constitutes the dominant source of uncertainty, contributing 96% of the combined variance, while intermediate precision contributes <2%. Control limits and charts were established for continuous monitoring. This study provides evidence of technical capability to generate traceable and reliable results, meeting ISO/IEC 17025:2017 requirements. Keywords: method verification, density, measurement uncertainty, ISO/IEC 17025, industrial lubricants